A NEW ARCHAIC CETACEAN FROM THE 
OLIGOCENE OF NORTHWEST OREGON 
Douglas Emlong 
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J. ARNOLD SHOTWELL, Director 
Museum of Natural History 
University of Oregon 
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addressed in care of the Museum of Natural History, University of Oregon, Eugene, Oregon 
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. 
A NEW ARCHAIC CETACEAN 
FROM THE OLIGOCENE 
OF 
NORTHWEST OREGON 

A NEW ARCHAIC CETACEAN 
FROM THE OLIGOCENE 
OF 
NORTHWEST OREGON 
by 
DOUGLAS EMLONG 
Bulletin No. 3 
Museum of Natural History 
University of Oregon 
Eugene, Oregon 
October 1966 

1 
A NEW ARCHAIC CETACEAN FROM THE 
OLIGOCENE OF NORTHWEST OREGON 
by 
DOUGLAS R. EMLONG 
Research Associate University of Oregon 
Museum of Natural History 
ABSTRACT 
Intensive search by the author, in marine Oligocene formations of Oregon has resulted in the discovery of a 
very interesting cetacean skelton. This animal possesses so many distinctive features that it seems appropriate 
to propose a new family, the Aetiocetidae for its reception. 
Although this mammal possessed a functional dentition, and bears some resemblance to cetaceans be· 
longing to families Agorophiidae, Patriocetidae, and Microzeuglodontidae, its total compliment of dissimi-
larities from known cetaceans indicates that it is well differentiated from these families. 
Many features appear to be definitely antecedent to those developed on members of the suborder Mysti-
ceti. If it were not for the presence of functional teeth on this mature specimen, this cetacean could easily be 
placed in the suborder Mysticeti. 
No morphological obstacles exclude this cetacean from mysticete lineage. Because of its lack of similarity 
to cetaceans referred to the Odontoceti, and the presence of several critical archaeocete affinities which are 
not retained on any known odontocete skull, this cetacean is referred to the suborder Archaeoceti. 
INTRODUCTION 
The cetacean described in this report was 
discovered in March 1964 by the author who 
excavated and prepared the remains during the 
rest of that year. 
Fossil marine mammals described from Lin-
coln County, Oregon, include Desmatophoca 
oregonensis Condon ( 1906), Desmostylus hes-
perus Marsh ( 1915), and Cophocetus orego-
nensis Packard and Kellogg ( 1934). 
In coastal Oregon no marine mammal re-
mains complete enough for familial allocation 
have been described from formations older 
than the Astoria Formation of middle Miocene 
age. Only fragmentary vertebrae from Oligo-
cene formations of Oregon have been men-
tioned in previous reports (Packard and Kel-
log 1934). 
The specimen described here is apparently 
the first archaic cetacean to be named from pre-
Miocene deposits of the Eastern Pacific region. 
The upper Oligocene Yaquina Formation, in 
which this cetacean occurred, may be approxi-
mately correlative in age with the Aquitanian 
Stage of Europe. Sediments of this age near 
Lintz, Austria have yielded the remains of the 
archaic cetaceans Patriocetus ( Abel 1913), 
and Agriocetus (Abel 1913), which bear some 
resemblance to the cetacean described in this 
report. However, close examination reveals 
features which exclude these Austrian cetaceans 
from familial relationship with this new dis-
covery. Comparison with the Eocene cetacean 
A rchaeodelphis ( Allen 1921 ) as well as Mio-
cene cetaceans also reveals familial dissimi-
larities. 
I am deeply indebted to Dr. J. A. Shotwell, 
University of Oregon, and to Dr. Remington 
Kellogg, U. S. National Museum, for their 
technical advice and critical review of this 
manuscript, and for their generosity in supply-
ing reference material used in preparing this 
paper. Without their assistance, I would have 
been unable to complete the study. 
I am also much indebted to Mr. Parke D. 
Snavely, Jr., U. S. Geological Survey, for 
generously supplying geological data and ad-
2 BULLETIN, MUSEUM OF NATURAL HISTORY, UNIVERSITY OF OREGON No. 3 
vice in the preparation of this manuscript, and 
also to Dr. Edward Mitchell, Jr. for suggestions 
and advice extremely useful in my studies and 
in my evaluation of the cetacean here described. 
OCCURRENCE 
The cetacean skeleton described in this re-
port occurred in place in the upper part of the 
Y aquina Formation of late Oligocene age 
( fig. 1) . The specimen was obtained from a 
bedrock exposure about one mile south of the 
mouth of Beaver Creek, and one-half mile 
north of Seal Rock State Park, Lincoln County, 
Oregon (fig. 2) (UO Loe 2503). The locality 
is covered by beach sand during most of the 
year but winter storms occasionally remove the 
sand to expose the Oligocene bedrock. Two 
small creeks, about a hundred yards apart, 
enter the ocean at this point. The specimen was 
found about fifty feet no:rth and 150 feet west 
of the mouth of the smaller creek, which is the 
most northerly. 
The Yaquina Formation at this locality con-
sists of fine-grained gray sandstone alternating 
with layers of siltstone and medium-grained 
light-gray sandstone. Thin layers of mussel 
shells and other mollusks are present, as well 
as beds of carbonized wood, thin seams of coal, 
and a few concretions containing T eredo-
bored wood. About one-quarter of a mile south-
ward toward Seal Rock the lower part of the 
Yaquina Formation is exposed. This part of 
the formation consists of massive coarse-
grained micaceous sandstone that also contains 
wood fragments. This sandstone is exposed in 
ribs which rise about five feet above beach 
level, even during the summer months. 
The Yaquina Formation was named by Har-
rison and Eaton ( 1920), and further described 
by Schenck ( 1927), and Vokes, Norbisrath and 
Snavely ( 1949). Most recently it has been re-
ported on by Snavely and Wagner (1964). The 
type section of the Y aquina Formation is ex-
posed along the Yaquina River, six miles north 
of the locality of interest in this paper. The 
lithology of the formation in both regions is 
SERIES STAGE 
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Figure 1. Generalized composite stratigraphic sec-
tion of Tertiary rocks exposed in the Newport em-
bay.ment, Oregon, showing the stratigraphic po-
sition of the new cetacean discovery (From Snave-
ly and Wagner, 1964, p. 7) 
' 
1966 EMLONG : A NEW ARCHAIC CETACEAN 3 
rather similar. Vokes, and others ( 1949) 
found a large number of mollusks that indi-
cate a latest Oligocene age, and suggests that 
the Y aquina is correlative with the Blakely 
Formation in Washington. The Y aquina For-
mation rests disconformably, or with little if 
any angular discordance, upon the upper mem-
ber of the Toledo Formation of middle Oligo-
cene age. 
The Nye Mudstone, which conformably over-
lies the Yaquina Formation and is of early 
Miocene age, has been described from its type 
area at Yaquina Bay by Harrison and Eaton 
( 1920), Schenck ( 1927), Vokes and others 
(1949), and most recently by Snavely and 
others ( 1964). The contact between the Nye 
Mudstone and the Y aquina Formation is ex-
posed near the mouth of Beaver Creek at the 
base of the sea-cliff a little less than one-half 
mile north of the cetacean locality ( fig. 1). 
This contact strikes southwest, and is offset by 
small faults in several places. The contact is 
visible west of the type locality at times of 
extreme minus tides, but is normally below 
tide level. 
SYSTEMATIC DESCRIPTION 
suborder ARCHAEOCETI 
Aetiocetidae new family 
Definition: A toothed whale with the rounded 
apex of the supraoccipital, not thrust forward 
to the level of the postorbital projections of the 
frontals. The ascending process of the maxil-
laries over-rides the frontal in a V-shaped man-
ner. The postero-ventral portion of the maxil-
laries under-rides the ventral anterior ends of 
the frontals. The dorso-ventrally thin plate of 
the infraorbital process extends outward 
slightly beyond the outer edge of the orbit. The 
jugal horizontally over-rides this plate on its 
outer edge. This relationship is maintained to 
the posterior termination of the maxillary plate 
located behind the level of the center of the 
orbit. The nasals are long. The posterior por-
tion of the jugal is wedged between the median 
external surface of the zygoma and the ventral 
surface of the frontal. 
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Figure 2. Map showing the location of the new ce-
tacean discovery and its relation to geologic for-
mations ( Geologic contacts from Vokes and others, 
1949) 
Only the genus Aetiocetus is presently as-
signed. 
The new family Aetiocetidae differs from 
known members of the family Agorophiidae, 
Abel in the following major features: Zygoma 
with strongly attenuated anterior extremity 
which projects forward beneath the postorbital 
projection of the frontal. Jugal firmly wedged 
between external (lateral) surface of zygoma 
and postorbital projection of frontal. Posterior 
portion of elongate jugal extends well behind 
level of anterior termination of zygoma. Infra-
orbital process of maxillary with strongly de-
veloped lateral extension which extends to 
outer edge of frontal, contacting jugal laterally. 
Dorsal posterior portions of maxillaries nar-
row markedly. Palatines, pterygoids, carina of 
vomer carried far posteriorly, roofing over 
choanae. Molars and premolars single rooted. 
4 BULLETIN, MUSEUM OF NATURAL HISTORY, UNIVERSITY OF OREGON No. 3 
Aetiocetus differs from the Patriocetidae 
Abel in these major characteristics: Lack of 
lateral projection of parietal, supraorbital 
processes of frontals project outward at right 
angles from relatively narrow inter-temporal 
region, maxillaries overspread median surface 
of frontals. Alveoli shallow, single, large. 
Aetiocetus also differs from members of the 
Patriocetidae in the same general features of 
the zygoma, jugal, infraorbital process of the 
maxillary, the teeth, and posterior ventral 
cranial region which were mentioned as char-
acteristics that differentiate the new family 
from the Agorophiidae. 
Aetiocetus differs from the Microzeuglo-
dontidae in these major characteristics: Dorsal 
posterior terminations of maxillaries over-ride 
median surface of frontals, nasal bones elon-
gate, rostrum broad, maxillaries very thin 
dorso-ventrally near external edges, posterior 
caudals relatively thin antero-posteriorly, third 
molar present in the maxillary. The Aetioceti-
dae differ from the Microzeuglodontidae in 
the same general features of the zygoma, jugal, 
infraorbital process of the maxillary, teeth, 
and posterior ventral cranial region mentioned 
in comparison with the Agorophiidae and 
Patriocetidae. 
TYPE GENUS: Aetiocetus gen. n. 
AETIOCETUS COTYLALVEUS 
gen.n. et sp. n. 
GENOTYPIC SPECIES: Aetiocetus cotylalveus 
sp. n. 
HOLOTYPE: University of Oregon, Museum of 
Natural History No. 26351, (Emlong collec-
tion No. 218). 
The holotype consists of a skull in an excel-
lent state of preservation, lacking a portion of 
the right side of the braincase, right exoccipital, 
squamosal, and tip of right supraorbital proc-
ess of the frontal; it is otherwise complete, and 
remarkably well preserved; 39 vertebrae, com-
plete, or nearly so; whole, or portions of 23 
ribs; 6 detached teeth, and two teeth in place 
in the premaxillary; two sternal bones; two 
chevrons, all from one individual. 
The skeleton was embedded in fine-grained 
sandstone with the right side of the braincase, 
and the ends of several ribs exposed. The skull 
and ribs were washed away from the almost 
completely articulated vertebra column before 
burial. The skull was upside down. The de-
tached teeth were embedded in matrix below 
and behind the skull. The distal caudals were 
about four feet below the surface of the bed-
rock. The bones were highly silicifi.ed and suf-
fered no decomposition before burial. 
DIAGNOSIS: Generic diagnosis same as species. 
cies. Rounded apex of supraoccipital not thrust 
forward to the level of the postorbital projec-
tions of the frontals. Supraorbital processes of 
the frontal extend outward at right angles to 
the shortened, moderately narrowed intertem-
poral region. The ascending process of the 
maxillaries over-rides the frontal in a V-shaped 
manner, narrowing posteriorly. It closely re-
sembles the ascending process on cetothere 
skulls. The posterior ends of the maxillaries do 
not closely approximate the outer edge of the 
orbit. The postero-ventral portion of the maxil-
laries under-rides the ventral anterior ends of 
the frontal, forming a well developed infra-
orbital process. A dorso-ventrally thin plate of 
this process extends outward slightly beyond 
the outer edge of the orbit, and this plate is well 
separated from the under surface of the frontal. 
The jugal horizontally over-rides this plate on 
its outer edge. This relationship is maintained 
to the posterior termination of the maxillary 
plate, located behind the level of the center of 
the orbit. This feature is unique among typical 
Cetacea, and resembles the Archaeoceti. The 
rostrum is broad at the antorbital notches, at-
tenuated distally. The posteriormost alveolus 
is located anterior to the level of the preorbital 
angle of the frontal. The alveoli are shallow 
and large and extend to the outer edge of the 
maxillary and premaxillary. The nasals are 
long, the nasal cavity is located anterior to the 
level of the preorbital projection of the frontal. 
The zygoma have a very narrow anterior termi-
1966 EMLONG: A NEW ARCHAIC CETACEAN 5 
nation. The anterior termination under-rides, 
and closely approximates the outward flaring 
postorbital projection of the frontal. The pos-
terior portion of the jugal is firmly wedged 
between the zygoma and the postorbital projec-
tion of the frontal. The posterior termination of 
the jugal projects well behind the level of the 
anterior end of the zygoma. The vomer has a 
prominent posterior ventral longitudinal ca-
rina. The pterygoid fossa is well developed. 
The palatines are narrow and elongate posteri-
orly, and broad anteriorly. The posterior proc-
ess of the periotic is elongate. All teeth are 
single rooted. Small accessory cusps are pres-
ent on the molars and premolars. The neural 
spines of the lumbars are short vertically and 
broad antero-posteriorly. The neural arches 
are very low on all vertebrae, and very broad 
on the cervicals and anterior dorsals. The an-
terior dorsals have short, heavy, rounded 
diapophyses. The transverse processes on the 
lumbars and the anterior caudals are very 
broad antero-posteriorly. A shelf is present on 
the outer portions of the transverse processes 
of the ninth and tenth lumbars, and the first 
and second caudals. At least fifteen pairs of 
ribs were present. 
SKULL 
DORSAL VIEW: When the skull is viewed dorsally, 
one's attention is immediately directed to the antero-
posterior shortness of the braincase. The transversely 
broad parietals slope forward , and downward to 
meet the frontals , which have thrust backward, 
shortening the intertemporal region, which is con-
siderably depressed below the level of the posterior 
median portions of the parietals. The frontals extend 
backward farther on the dorsal surface of the inter-
temporal region than they do on the lateral surfaces 
of this region. The median frontal-parietal contact 
lies 35 mm anterior to the apex of the supraoccipital, 
and the parietals extend about 35 mm farther for-
ward on each lateral wall of the intertemporal re-
gion, closely approximating the roots of the supra-
orbital processes of the frontals, which project out-
ward at right angles to the moderately narrowed 
intertemporal area. 
The supraoccipital shield is crescentic in shape. 
A small, narrow ridge extends downward for 24 mm 
from the apex of the supraoccipital shield, and a 
slight median occipital ridge extends for 31 mm 
posterior to the apex of the supraoccipital. The 
supraoccipital shield is much elevated above the 
intertemporal region, but does not extend forward to 
the level of the outward flaring postorbital projec-
tions of the frontal, or the frontal-parietal contact. 
The lambdoid crest slightly overshadows the pos-
terior surfaces of the parietals. The entire braincase 
is constructed of dense, thickened bone. 
The frontals slope outward and backward to form 
the supraorbital processes. The outward flaring post-
orbital projections of these processes curve down-
ward, and over-ride the anterior ends of the zygo-
matic processes of the squamosal. The medial an-
terior exposed surface of the frontal is slightly con-
cave near where it is over-ridden by the maxillaries. 
The temporal fossa are irregularly oval, small in 
relation to the size of the skull, and shortened 
antero-posteriorly. The left temporal fossa measures 
82 mm transversely, and 74 mm antero-posteriorly. 
(The transverse measurement is from the zygoma-
frontal contact to the dorsal root of the frontal. The 
antero-posterior measurement is from the zygoma-
frontal contact to the posterior edge of the fossa 
formed · by the squamosal). The oblique measure-
ment of this fossa is 102 mm (from the posterior end 
of the fossa to the dorsal root of the frontal) . 
A slight ridge marks the squamosal-parietal con-
tact. Inside the posterior portion of the transversely 
thin zygoma, the squamosal forms an anteriorly 
deepened trough, which is bounded by the lambdoid 
crest posteriorly, and the temporal fossa, anteriorly. 
The maxillaries, premaxillaries, and nasals have 
overridden the median anterior region of the frontal, 
and although the telescoping of these bones is not 
greatly advanced, the basic mysticete arrangement is 
clearly present. The convex hump, which comprises 
the ascending process of the maxillaries, premaxil-
laries, and nasals has the characteristic anteriorly 
broadened V-shape of the cetotheres. This contrasts 
with most primitive odontocetes. These archaic ceta-
ceans have maxillaries which override the frontal, 
and rather than narrowing toward their posterior 
borders, run close and nearly parrallel to the outer 
edge of the orbit. This condition seems to have begun 
to develop even on the skull of the primitive odonto-
cete Archaeodelphis patrius Allen ( 1921). The maxil-
laries of Aetiocetus cotylalveus terminate at about 
the level of the center of the orbit. They are very 
narrow at this point. Anteriorly, they gradually 
broaden. Their inner borders become more elevated 
above their outer borders. The outer borders then 
curve outward around the lachrymal. 
The relatively large, transversely elongate lachry-
mal is wedged between the preorbital angle of the 
6 BULLETIN, MUSEUM OF NATURAL HISTORY, UNIVERSITY OF OREGON 
No. 3 
Figure 3. Dorsal view of the skull, AETIOCETUS COTYLALVEUS 
1966 EM LONG: A NEW ARCHAIC CETACEAN 7 
Figure 4. Dorsal view of the skull, AETIOCETUS COTYLALVEUS, indicating rel.ative positions of bones of the 
skull 
8 BULLETIN, MUSEUM OF NATURAL HISTORY, UNIVERSITY OF OREGON No. 3 
Abbreviations used in illustrations of the skull, 
Figs. 4, 6, and 7 
Al. 
ant. f. 
ant. n. 
Bo. 
c. 
exoc. 
f.ov. 
Fr. 
Ju. 
La. 
1. pr. 
Max. 
m.e.a. 
Na. 
Pa. 
pr.p. 
pgl. 
Pmx. 
Pt. 
pt. f. 
soc. 
sor. pr. 
Sq. 
ty. 
v.pt. 
v. 
zyg. 
alispheonid 
antorbital foramina 
antorbital notch 
basioccipital 
occipital condyle 
ex occipital 
foramen ovale 
frontal 
jugal 
lachrymal 
lateral protuberance of basioccipital 
maxillary 
groove for external auditory meatus 
nasal 
parietal 
posterior process of periotic 
postglenoid process of squamosal 
premaxillary 
pterygoid 
pterygoid fossa 
supraoccipital shield 
supraorbital process of frontal 
squamosal 
tympanic bulla 
vaginal process of pterygoid 
vomer 
zygomatic process of squamosal 
frontal and the postero-external angle of the maxil-
lary. The dorsal portion of the posterior external 
angle of the maxillary is elevated above the lachry-
mal, and forms a ridge which diminishes inwardly. 
This ridge forms the antorbital notch. The anterior-
external portion of the lachrymal projects outward 
for 10 mm beyond the posterior external angle of 
the maxillary, on the left side, and is clearly differ-
entiated from it at this point. The inner border of 
the left lachrymal lies 4 7 mm inside the outermost 
projection. As was previously mentioned, a promi-
nent ridge forms the antorbital notch. The external 
posterior ventral edge of the thin rostral tooth-
bearing maxillary is concealed from a dorsal view 
by a portion of this ridge. This ridge becomes less 
pronounced inwardly, and the maxillary rises toward 
its contact with the premaxillaries near the level of 
the posterior end of the nasal cavity. Just anterior to 
this point two small round antorbital foramina are 
present. On the right side, they are only 3 mm apart. 
The larger, innermost one is 8 mm in diameter, and 
lies 6 mm external to the maxillary-premaxillary 
suture. Anterior to these foramina, the maxillaries 
descend, then flatten, becoming slightly convex. They 
are dorso-ventrally compressed, their outer edges are 
very thin, measuring 1-2 mm on the average at the 
outer edge. They do not thicken rapidly inwardly, 
but remain thin inside the level of the alveoli, and 
then gradually thicken toward the maxillary-pre-
maxillary suture. They much resemble the same 
bones on cetothere skulls, except for the presence of 
alveoli. Dorsally, a groove is present at the maxillary-
premaxillary contact. Anteriorly, the maxillaries 
gradually narrow in transverse diameter, and termi-
nate at a point 251 mm anterior to the level of the 
antorbital notch. 
The posterior ends of the nasals and premaxil-
laries terminate slightly behind the level of the pos-
terior ends of the maxillaries. The premaxillaries 
extend forward, and gradually broaden, their outer 
surfaces maintaining even contact with the maxil-
laries for about 70 mm anterior to the posterior ends 
of the premaxillaries. At this point, their outer edges 
become rounded, and the outer dorsal surface be-
comes elevated above the maxillary. At the level of 
the anterior outer terminations of the nasal bones, 
the inner portions of the premaxillaries turn down-
ward and slant inward. 
A peculiar discontinuity is present on each pre-
maxillary. This rift runs anteriorly and outward 
from the inner edge of each premaxillary at the level 
of the outer anterior ends of the nasal bones. The rift 
is about 52 mm long on each premaxillary. The 
surface of the premaxillary anterior to this rift is 
slightly depressed below the surface behind the rift. 
This feature has the same contour on each pre-
maxillary. The adjoining thin maxillaries show no 
evidence of distortion. A slight distortion is present 
on the ventral surface of the maxillaries somewhat 
behind the level of this feature, but has no obvious 
connection to the premaxillary feature. If this feature 
is not the result of distortion, or individual peculiar-
ity, it may be an effect of the telescoping process. 
Anterior to the rift, the premaxillaries broaden and 
remain elevated above the maxillaries. Their inner 
surfaces slope inward steeply, forming the upper 
external borders of the narrow nasal cavity. The 
inward slope of the inner surfaces of the premaxil-
laries gradually lessens anteriorly. At a point 281 mm 
anterior to the level of the right antorbital notch, the 
median surfaces of the premaxillaries join, and a 
prominent ridge is formed. The rostrum narrows. 
and terminates at a point 70 mm anterior to thi~ 
juncture. 
The nasal bones are relatively long, the left one 
measures 125 mm antero-posteriorly, and they are 
narrowest toward their posterior borders. They are 
slightly convex. At a point about 85 mm anterior to 
their posterior ends, their inner borders dip below 
the level of the premaxillaries and curve strongly 
1966 EMLONG: A NEW ARCHAIC CETACEAN 9 
Figure 5. Posterior view of the skull, AETIOCETUS COTYLALVEUS 
downward near their anterior terminations, forming 
the posterior end of the nasal cavity. The outer 
borders of the nasals are level with the adjoining 
premaxillaries for 90 mm, then depress to a much 
lesser degree than do the inward extensions, · and 
terminate 32 mm anterior to the inward extensions. 
The nasal cavity is relatively narrow. The matrix 
was not removed to expose the vomer, as removal 
might damage the skull. A mesorostral gutter extends 
anteriorly from the nasal cavity, and terminates at 
a point 258 mm anterior to the posterior end of the 
nasal cavity. 
From a dorsal view, the occipital condyles are 
rather large, their upper surfaces are far apart, being 
separated 52 mm. 
POSTERIOR VIEW: The posterior wall of the braincase 
is depressed medially, forming a concave 'dish'. To 
either side, slightly above the center of this depres-
sion, a slight protuberance is developed on the brain-
case. The lower border of the left protuberance lies 
33 mm below the edge of the lambdoid crest. The 
lambdoid crest projects backward to some extent, 
over-shadowing the exoccipital. 
The left exoccipital extends outward, and down-
ward. However, the outermost angle does not project 
downward as far as does the surface just external to 
the jugular notch. A sharp, downward projecting 
paraoccipital process is present at this point. The 
jugular notch is rather narrow, measures 5 mm 
transversely, at the posterior base. The inner portion 
of the jugular notch is filled with matrix. A small 
knob projects downward slightly between it and the 
lateral protuberance of the basioccipital. The dorso-
ventral height of the jugular notch from the base of 
this small knob is 12 mm (measurements of jugular 
notch taken externally, on the posterior portion of 
the skull). The deeper, matrix-filled inner portion 
is concealed from posterior view by bone. The ex-
ternal depth of the jugular notch from the ventral 
projection of the paraoccipital process is 35 mm. 
The left lateral protuberance of the basioccipital is 
well differentiated from the surrounding surface. 
The squamosal is not as robust as on cetothere 
skulls. The postglenoid process projects outward 
beyond the level of the outer angle of the exoccipital, 
but does not extend downward below the level of the 
exoccipital. 
The occipital condyles are heavily built, and are 
separated from the posterior surface of the exocci-
pitals by a thin groove. They project moderately out-
ward. Their lower surfaces narrow considerably in 
transverse diameter. The most posterior portion of 
the basioccipital, which separates the ventral sur-
faces of the occipital condyles has been displaced by 
distortion, and shoved slightly upward into the fora-
men magnum. The upper and middle portions of the 
occipital condyles are broadest. The maximum trans-
I 
. 
I' 
1,. 
10 BULLETIN, MUSEUM OF NATURAL HISTORY, UNIVERSITY OF OREGON No. 3 
verse distance across the occipital condyles is 94 mm. 
The maximum vertical diameter of the left condyle 
is 58 mm. 
LATERAL VIEW: The pronounced elevation of the 
rounded apex of the supraoccipital is very distinc-
tive in lateral view. A concave depression is present 
on the parietals, immediately below the apex of the 
supraoccipital. These features may have foreshad-
owed the forward overthrust of the supraoccipital, 
as is seen on most mysticete skulls. The occipital 
condyles project slightly behind the level of the ex-
occipitals. The postglenoid process of the squamosal 
on mysticete skulls is very robust. On this skull, it 
projects rather strongly downward, but is compara-
tively thin antero-posteriorly. Anterior to the post-
glenoid process, the zygoma becomes thinner dorso-
ventrally, measuring 21 mm at the thinnest point, 
90 mm behind the anterior extremity of the zygoma. 
Anterior to this point, the zygoma again thickens, 
and measures 32 mm dorso-ventrally at a point 43 
mm posterior to the anterior end. From here, it 
tapers, and becomes very thin near its termination. 
It is over-ridden for a distance of 25 mm by the post-
orbital projection of the supraorbital process of the 
frontal. 
The postorbital projection of the frontal is quite 
thick. It measures 30 mm dorso ventrally at its pos-
terior extremity. Anteriorly, the dorsal outer edges 
of the frontals become undermined. This condition 
prevails all the way to the outer anterior end of the 
frontal. 
The j ugal is peculiarly constructed. Its posterior 
end lies firmly wedged between the tip of the post-
orbital portion of the supraorbital process of the 
frontal, and the median-external anterior portion of 
the zygoma. Its posterior projection emerges behind 
the tip of the preorbital angle of the frontal, and 
projects outward and backward for 21 mm behind 
the level of the preorbital angle. Anterior to the level 
of the center of the orbit, the j ugal thickens dorso-
ventrally, and contacts the lower posterior edge of 
the lachrymal. The over-all length of the jugal is 
123 mm. 
The maxillaries are compressed dorso-ventrally, 
and the thinness of their outer edges is clearly evi-
dent from a lateral view. The premaxillaries at the 
tip of the rostrum are rather thick dorso-ventrally in 
their median region measuring 31 mm thick at the 
median ridge, 65 mm posterior to the tip of the 
rostrum. 
The alisphenoid appears on the temporal wall of 
the braincase behind the base of the supraorbital 
process. It is triangular in shape, with the apex of 
the triangle projecting downward, touching the upper 
boundary of the pterygoid anterior to, and well above 
the level of the pterygoid fossa. The alisphenoid can-
not be seen on a ventral view of the skull, and its 
ventral projection lies 21 mm above the lower boun-
dary of the temporal fossa on the left side. The pos-
terior boundary of the alisphenoid is the squamosal. 
The alisphenoid is bounded dorsally by the parietal. 
It is depressed on each side of the braincase, and its 
boundaries are well defined on each side of the skull. 
On the left side, the alisphenoid measures 43 mm 
antero-posteriorly, and 29 mm dorso-ventrally. 
The posterior maxillary alveolus is located at the 
level of the antorbital notches, anterior to the level 
of the preorbital angles of the frontals. 
VENTRAL VIEW: A very unusual feature of this skull 
is the shape, and form of the alveoli. Eleven alveoli 
are present on each side of the rostrum. Eight are 
present in each maxillary, and three in each pre-
maxillary. The posterior maxillary alveoli are very 
shallow, roundish, large, cup-like depressions, which 
are deepest on the inner edges. The depth of the 
alveoli gradually lessens externally, and the outer 
edges of the alveoli have no well defined wall, so that 
the depressions merge with the very thin external 
border of the maxillary. Proceeding anteriorly each 
alveolus becomes slightly deeper than the one pos-
terior to it. None of the posterior maxillary alveoli 
were deep enough to firmly hold the teeth. Much of 
the stabilization would have to have been accom-
plished by a firm gum. Anterior to each alveolus, the 
thin outer border of the maxillary and premaxillary 
curves slightly inward. On the surface of the maxil-
lary, just inside the inner edges of the alveoli, a weak 
ridge is developed. This antero-posterior ridge is 
broken, and not pronounced. 
The premaxillary alveoli are somewhat narrowed 
antero-posteriorly, and are slanted outward in an 
obliquely posterior direction. Their antero-internal 
ends are deepened. No well-defined outer wall is 
present on these alveoli, and their outer border is 
formed by the external edge of the premaxillary. 
The first incisor is present in the anterior alveolus 
of each premaxillary. The anterior premaxillary al-
veoli obviously held the teeth in place much more 
firmly than did the posterior maxillary alveoli. These 
characteristics would seem to foreshadow a tendency 
toward the elimination of the teeth. 
The ventral surfaces of the broad maxillaries are 
shaped similarly to these same bones on cetothere 
skulls. Their postero-ventral portions have under-
ridden the frontal. A slight distortion is present on 
the underside of the maxillary at about the level of 
the preorbital angle of the frontal. The posterior 
borders of the infraorbital extension of the maxi!-
' 
.. 
1966 EM LONG: A NEW ARCHAIC CETACEAN 11 
Figure 6. Left lateral view of the skull, AETIOCETUS COTALALVEUS 
12 BULLETIN, MUSEUM OF NATURAL HISTORY, UNIVERSITY OF OREGON No. 3 
laries terminate just behind the level of the center of 
the orbit. 
The inner borders of the maxillaries encircle the 
rounded anterior portion of each palatine. Their 
surfaces are slightly raised above the palatines on 
the anterior portion of this contact, and slightly de-
pressed on the posterior portion of this contact. Pos-
terior to the posterior alveolus on each maxillary, 
an antero-posterior ridge is developed. It measures 
36 mm antero-posteriorly on the left maxillary. This 
ridge extends slightly below the closely approximat-
ing thin outer border of the maxillary, and slants 
obliquely outward in a posterior direction. Anterior 
to the palatines, the medial surfaces of the maxil-
laries become slightly convex. They closely approxi-
mate each other, and conceal the vomer. 
At a point 215 mm posterior to the tip of the 
rostrum, the premaxillaries are exposed to view. The 
inner surfaces of the maxillaries part, and the most 
posterior extension of the premaxillaries is very nar-
row, and slightly concave. Anteriorly, they broaden, 
and become elevated above the encircling maxillaries . 
Well developed antero-posterior ridges are present 
on the surfaces of the premaxillaries at this point. 
These ridges become less pronounced toward the end 
of the rostrum. 
The outer edges of the maxillaries terminate at a 
point 82 mm posterior to the end of the rostrum. 
The anterior ends of the antero-posteriorly elon-
gated palatines are rounded, and somewhat concave, 
medially, just behind their anterior contact with the 
maxillaries. This region is slightly distorted. The 
palatines measure 195 mm, antero-posteriorly, and 
114 mm transversely. Anteriorly the palatines are 
solidly united with each other on their inner margins. 
Posteriorly, the outer edges of the palatines contact 
the ventral inner edges of the pterygoids. The pos-
terior extensions of the palatines form a V-shaped 
termination, divided by a process of the vomer. The 
transversely narrowed posterior ends of the palatines 
are prolonged backward to the level of the anterior 
end of the pterygoid fossa ; much farther backward 
than on any known Eocene archaeocete. This pos-
terior prolongation extends the internal choanae pos-
teriorly, and relates to the backward shift of the 
external nares. A prominent median ventral antero-
posterior carina descends abruptly at a point 125 mm 
anterior to the posterior ends of the palatines. The 
ventral exposed surface of the anterior 87 mm of this 
carina is formed by the median portions of the pala-
tines, and the contact point of the two palatines can 
be seen on part of the slightly distorted ridge. An 
overlying process of the vomer becomes exposed to 
view at a point 41 mm anterior to the posterior ends 
of the palatines. This carina extends backward 25 mm 
behind the posterior terminations of the palatines. 
The posterior end of this carina, behind the posterior 
terminations of the palatines, is a transversely thin 
blade-like structure, and its posterior lower edge lies 
38 mm below the level of the medial surface of the 
basioccipital. From this point, the posterior edge of 
this ridge rises abruptly, and contacts the basioccipi-
tal. 
No definite suture can be seen as the dividing line 
between the hasioccipital, and the basisphenoid. It 
may be concealed by a horizontally expanded plate 
of the vomer which extends outward to either side 
of the longitudinal carina of the vomer, and back 
about to the level of the anterior portion of the 
lateral protuberance of the basioccipital. This plate 
is bounded externally by the vaginal process of the 
pterygoid. The vaginal process of the pterygoid is 
bounded externally by the pterygoid fossa. Anteri-
orly, it is under-ridden by the anterior ventral plate 
of the pterygoid, which is separated from the vaginal 
process, forming a cavity. These features are re-
peated where preserved on the right side. The pos-
terior boundary of this vaginal process is the anterior 
end of the lateral protuberance of the basioccipital. 
The inner surfaces of the anterior ventral portions 
of the pterygoids are slightly depressed below the 
level of the palatines. The outer surfaces of the ptery-
goids turns upward at nearly a 90 degree angle, as do 
the outer edges of the palatines, thus forming the 
inner ventral boundary of the temporal fossa. Pos-
teriorly, the ventral surfaces of the pterygoids 
broaden, extending inward toward the ridge of the 
vomer. The right and left plates of the pterygoid are 
separated from each other 24 mm at the minimum, 
by the narrow posterior extension of the palatines 
which is separated by the ridge of the vomer. These 
ventral plates of the pterygoid are over-ridden by 
the vaginal process of the pterygoids. 
The pterygoid fossa is irregularly oval, with an 
outward extension around the anterior end of the 
tympanic bulla. The left fossa is well preserved. The 
extreme anterior portion of this fossa is concealed 
by the under-riding anterior ventral plate of the 
pterygoid. The pterygoid fossa is bounded inwardly 
by the vaginal process of the pterygoid. The lateral 
protuberance of the basioccipital projects outward, 
meeting the tympanic, forming the posterior end of 
this fossa. The external edge of the fossa is formed 
by the tympanic, and antero-externally, a small por-
tion of the falciform process of the squamosal forms 
the outer wall. The distance between the posterior 
boundary, formed by the lateral protuberance of the 
basioccipital, and the under-riding antero-ventral 
plate of the pterygoid is 42 mm on the left side. The 
distance between the falciform process of the squa-
. 
I· 
1966 EMLONG: A NEW ARCHAIC CETACEAN 13 
mosal, and the inner ventral edge of the pterygoid 
fossa is 33 mm. 
Two distinct levels are present in the region of 
the pterygoid fossa. The posterior portion of this 
fossa is concealed from view by a dorso-ventrally 
thin plate of bone which may be a process of the 
pterygoid. This plate emerges into view above the 
outer edge of the under-riding vaginal process of the 
pterygoid, and extends outward, and is concealed by 
the tympanic externally, and is bounded by the 
lateral protuberance of the basioccipital posteriorly. 
The lateral protuberance of the basioccipital lies 
below the level of this thin plate. This relationship 
is not a result of distortion. A portion of the anterior 
outer edge of this extremely thin plate has been. dis-
placed slightly upward into the cavity of the fossa. 
The cavity of the pterygoid fossa is exposed to ventral 
view on its anterior exposed end. The dorsal roof of 
this cavity appears to be formed by another thin 
process of the pterygoid. However, this cannot be 
determined with certainty. As was already men-
tioned, the anterior end of this cavity is partially 
underlain by the posterior ventral plate of the ptery-
goid. The pterygoid fossa is for accessory air sinuses 
of the inner ear, and is a feature present on mysticete 
skulls. 
The lateral protuberance of the basioccipital pro-
jects strongly downward. The right protuberance is 
eroded away. The left protuberance directs down-
ward, and backward. Its postero-external edge rests 
against the inner edge of the tympanic bulla. It does 
not descend below the level of the exoccipital. It is 
relatively flattened, and broadened, transversely. The 
posterior extension of this lateral protuberance is 
well differentiated from the over-lying surface. The 
distance between the outer edges of the most pos-
terior extension of the right and left lateral protuber-
ances is about 75 mm. The distance between the 
posterior extension of the left lateral protuberance of 
the basioccipital, and the ventral tip of the para-
occipital process is 18 mm. The jugular notch is 
narrow and deep, as was previously mentioned. 
The paraoccipital process projects ventrally, and 
a well marked depression is present just external to 
the downward projection. This depression is most 
strongly developed toward its anterior edge, where 
it contacts the posterior process of the periotic. This 
concavity is for the reception of the stylohyoid. Ex-
ternal to this depression, the exoccipital narrows 
antero-posteriorly, and the posterior process of the 
periotic fits tightly against it, and extends nearly 
all the way out to the external edge of the exoccipital. 
Between the posterior process of the periotic, and 
the posterior face of the postglenoid process, a deep 
transverse channel for the external auditory meatus 
is present. This channel is narrow on its external 
end, and widens inwardly. It is concealed by the tym-
panic just posterior to the posteriorly twisted distal 
end of the processus sigmouleus, and disappears from 
view. The posterior side of this channel curves 
moderately downward, and meets the posterior proc-
ess of the periotic, which extends below this level. 
The channel measures 43 mm transversely to where 
it disappears from ventral view over the tympanic. 
The posterior face of the postglenoid process pro-
jects rather strongly downward, but is relatively thin 
antero-posteriorly, and rolls forward, forming a very 
concave glenoid fossa. This region is heavier than on 
other zeuglodont skulls, but not as thickened as on 
skulls of cetotheres. The distance between the most 
posterior extension of the exoccipital, and the most 
posterior extension of the temporal fossa is 90 mm. 
The distance between the external side of the zygo-
matic arch, and the protuberant portion of the falci-
form process of the squamosal is 78 mm transversely, 
in level with the posterior extension of the temporal 
fossa. The distance between the posterior extension 
of the glenoid fossa and the posterior extension of 
the temporal fossa is 40 mm. 
The transversely thin falciform process of the 
squamosal descends 25 mm below the more level 
surface of the anterior internal portion of the squa-
mosal. This process descends below the level of the 
anterior portion of the tympanic bulla. It is united 
with the pterygoid, anteriorly, forming the outer 
wall of the pterygoid fossa. An inwardly directed de-
pression on the anterior internal portion of the 
squamosal, just external to the anteriormost part of 
the falciform process, appears to be an outer exten-
sion of the foramen ovale. This depression measures 
15 mm antero-posteriorly on the shallow external 
portion, and narrows and deepens near where it runs 
inward over the falciform process, the actual foramen 
being obscured to ventral view by the falciform 
process. The distance between its outer border, which 
is the outer border of the ventral portion of the 
squamosal, and the point where it disappears from 
view over the falciform process is 13 mm. 
The median ventral surface of the root of the 
zygomatic process is concave. The anterior inner 
edge of the zygoma is also concave, medially (an-
terior to the root of the process) . At this area of 
median concavity, the upper portion of the internal 
surface of the zygoma turns moderately inward, and 
the lower (ventral) portion of this inner surface 
slants moderately outward. These features are de-
veloped at the point of maximum dorso-ventral swel-
ling, just posterior to where the zygoma is over-
ridden by the postorbital projection of the frontal , 
and anterior to the level of the posterior extension of 
14 BULLETIN, MUSEUM OF NATURAL HISTORY, UNIVERSITY OF OREGON No. 3 
Figure 7. Ventral view of the skull, AETIOCETUS COTYLALVEUS 
1966 EM LONG: A NEW ARCHAIC GET ACEAN 
J 
J 
J 
ax. 
15 
Figure 8. Ventral view of the skull, AETIOCETUS COTYLALVEUS, indicating relative positions of the bones 
of the skull 
16 BULLETIN, MUSEUM OF NATURAL HISTORY, UNIVERSITY OF OREGON No. 3 
the temporal fossa (root of the zygomatic process). 
The external surface of the zygoma in this region is 
convex, medially. Immediately anterior to the area 
of maximum dorso-ventral swelling, at a point 4 7 mm 
anterior to the posterior extension of the temporal 
fossa, a slightly concave, well differentiated facet 
develops on the ventral edge of the zygoma. This 
antero-posteriorly elongate facet extends all the way 
to the anterior end of the zygoma, and measures 31 
mm antero-posteriorly, and 8 mm transversely, at 
maximum. The anterior end of the zygoma tapers to 
an extremely sharp point. The median external 
(lateral) portion of the zygoma rests firmly against 
the posterior portion of the peculiarly constructed 
jugal. However, the sharply pointed tip of the zygoma 
does not touch the jugal at all, as the terminal ex-
tremity of the zygoma extends below the level of the 
j ugal. No distortion, or defects are present. The dis-
tance between the sharply pointed anterior termina-
tion of the zygoma, and anteriormost contact of the 
zygoma with the jugal is 5 mm. At the level of the 
anterior termination of the zygoma, the jugal slopes 
moderately upward, above this termination, and be-
comes very solidly wedged between the median ex-
ternal (lateral) surface of the zygoma, and the very 
closely approximating postorbital projection of the 
frontal. The jugal extends backward to a point 44 
mm behind the anterior tip of the zygoma, and directs 
obliquely outward, and upward, becoming separated 
from the zygomatic near the posterior end, which 
lies 21 mm behind the posterior extremity of the 
postorbital process of the frontal. 
The jugal measures 13 mm transversely at the 
level of the anterior end of the zygomatic, and be-
comes narrower anteriorly, and posteriorly to this 
point. The jugal is extremely thin dorso-ventrally in 
this region. The distance between the anterior end 
of the zygoma, and the ventral posterior external 
extension of the maxillary is 40 mm. This dorso-
ventrally thin outer plate of the infra-orbital process 
of the maxillary is considerably depressed below the 
ventral surface of the frontal, and represents a very 
early stage in the interdigitation of these bones, al-
though these ventral extensions of the maxillaries 
are located about as far back beneath the frontal as 
they are on the skull of the Lower Miocene cetothere, 
Cetotherium moreni Kellogg (1934). However, even 
on this cetothere, the ventral outer posterior ends of 
the maxillaries actually are mortised on the frontal, 
as is shown on the restorations. On the Aetiocetus 
skull, the j ugal over-rides the outer edge of this thin 
plate of the maxillary, and fits firmly against it. The 
anterior end of the jugal lies 48 mm anterior to the 
posterior outer extension of the maxillary. The jugal 
becomes thicker dorso-ventrally toward the anterior 
end, measures 9 mm dorso-ventrally (left side) at 
the squared extremity, which abuts against the pos-
terior edge of the lachrymal at about the level of the 
preorbital tip of the frontal. The external edge of the 
lachrymal extends outward beyond its contact with 
the jugal. 
The matrix was not removed from between the 
posterior ventral extension of the maxillary, and the 
anterior ventral-surface of the frontal. The posterior 
half of the ventral side of the frontal is exposed, and 
a portion of the ventral channel for the optic nerve is 
partially exposed. Near the point of emergence from 
the optic foramen, which is filled with matrix, the 
shallow channel is relatively narrow. It then widens 
rapidly, and its anterior wall directs obliquely for-
ward, and outward, and is lost to view beneath the 
ventral plate of the maxillary. The distance between 
the posterior edge of the frontal directly posterior to 
this ridge, and the ridge is 45 mm at the point where 
the ridge is concealed from view by the maxillary. 
The dorso-ventral separation of the ventral plate of 
the maxillary from the ventral surface of the frontal 
at this point is 13 mm. These measurements were 
taken at a point 18 mm external to the root of the 
posterior edge of the supraorbital process of the left 
side. The distance from the root of the left supra-
orhital process, and the tip of the postorbital projec-
tion is 85 mm. 
It was not possible to separate the tympanic bulla 
from the skull without risk of serious damage, there-
fore, some of the more diagnostic features of the 
tympanic and periotic are concealed from view. The 
left tympanic is well preserved. It is very large in re-
lation to the size of the skull. It measures 70 mm an-
tero-posteriorly, and 49 mm transversely, at the level 
of the processus sigmoideus. The general shape of the 
bulla resembles that of cetothere bulla in general 
form, and also is somewhat similar to bulla of the 
archaeocete Zygorhiza kochii Kellogg ( 1936). On 
the posterior ventral fourth of the bulla, there is a 
moderately developed median convexity, which be-
comes most pronounced near the posterior edge of the 
bulla. The posterior portion of this convexity slants 
obliquely outward and is bounded inwardly by a 
moderately pronounced antero-posteriorly elongated 
upward hollow. This median upward hollow is best 
developed posteriorly, and extends anteriorly about 
one fourth the length of the bulla. The posterior 
ventral edge of the bulla is continuous with the in-
volucrum, which turns abruptly upward, and slightly 
forward , and is lost to view against the surrounding 
bones. The internal ventral edge of the bulla forms 
an almost straight antero-posterior line. The rounded 
anterior ventral end of the bulla projects farthest 
forward on the inner portion, and the external an-
1966 EMLONG: A NEW ARCHAIC CETACEAN 
TABLE 1 
MEASUREMENTS OF THE SKULL 
Greatest length of skull ( tip of rostrum to posterior end of left occipital condyle 
Tip of rostrum, to apex of superoccipital shield 
Length of rostrum, level of antorbital notches to tip of premaxillaries 
Greatest length of right premaxillary 
Anterior end of left premaxillary, to anterior end of left nasal bone 
Apex of supraoccipital shield to posterior end of left nasal bone 
Greatest length of left nasal bone 
Transverse diameter of nasal bones at posterior end of nasal cavity 
Maximum transverse diameter of nasal cavity 
Distance from posterior end of nasal cavity to anterior end of mesorostral gutter 
Transverse diameter of left nasal bone near posterior end 
Combined width of nasal bones near posterior ends 
Transverse distance between outer margins of premaxillaries at level of anterior ends of nasal bones 
Maximum transverse distance between outer margins of premaxillaries at level of anterior 
terminations of maxillaries 
Transverse diameter of rostrum at level of antorbital notches 
Transverse diameter of skull across preorbital angles of frontals 
Minimum transverse distance across median orbital area of supraorbital processes 
Transverse diameter of skull across postorbital projections of supraorbital processes 
Greatest antero-posterior diameter of left supraorbital process 
Maximum transverse distance between outer surfaces of zygomatic processes 
Distance between outer edges of ascending processes of maxillaries at level of preorbital angles 
of frontals 
Distance between outer edges of ascending processes of maxillaries at their poster terminations 
Transverse diameter of skull between outer margins of exoccipitals 
Transverse distance between outer margins of occipital condyles 
Greatest vertical diameter of left occipital condyle 
Greatest transverse diameter of left occipital condyle 
Transverse diameter of foramen magnum 
Distance from upper margin of foramen magnum to apex of supraoccipital shield 
Vertical distance from ventral carina of vomer to apex of supraoccipital shield 
Greatest length of left zygomatic process, posterior edge of postglenoid process to anterior 
end of zygoma 
Vertical distance from left exoccipital to level of apex of supraoccipital 
Least transverse diameter of intertemporal region, dorsally 
Least transverse diameter of intertemporal region ventrally 
Greatest antero-posterior length of palatines 
Greatest transverse diameter of palatines 
Distance from posterior end of vomer to anterior end of palatines 
Greatest transverse diameter of left pterygoid fossa 
Greatest antero-posterior diameter of left pterygoid fossa 
Maximum antero-posterior length of jugal 
Distance from posterior dorsal termination of left maxillary to tip of rostrum 
17 
mm 
630 
525 
351 
418 
300 
103 
125 
37 
30 
258 
10 
21 
79 
67 
172 
187 
174 
300± 
115 
320± 
128 
47 
265± 
94 
58 
37 
36 
104 
145 
125 
153 
90 
93 
195 
114 
222 
33 
42 
123 
406 
18 BULLETIN, MUSEUM OF NATURAL HISTORY, UNIVERSITY OF OREGON 
TABLE 1 (Continued) 
Posterior ventral termination of left maxillary to tip of rostrum 
Posterior extension of exoccipital to tip of postorbital projection of supraorbital process 
Posterior external edge of left premaxillary to tip of rostrum 
Posterior alveolus of left maxillary to tip of rostrum 
Posterior edge of left occipital condyle to posterior extension of anterior ventral plate of 
left pterygoid 
Anterior end of palatines to tip of rostrum 
Posterior edge of right occipital condyle to posterior end of right palatine 
Antero-posterior diameter of second left maxillary alveolus 
Transverse diameter of second left maxillary alveolus 
Depth of second left maxillary alveolus from ventral inner wall 
Antero-posterior diameter of third left maxillary alveolus 
Transverse diameter of third left maxillary alveolus 
Depth of third left maxillary alveolus 
Transverse diameter of second premaxillary alveolus 
Antero-posterior diameter of second premaxillary alveolus 
Depth of second premaxillary alveolus 
Distance between posterior maxillary alveolus, and posterior edge of glenoid fossa 
Posterior maxillary alveolus to posterior edge left exoccipital 
Posterior ventral extension of maxillary to posterior edge of glenoid fossa 
Maximum antero-posterior width of left lachrymal 
Transverse diameter of left lachrymal 
Dorso-ventral thickness of outer extremity of left lachrymal 
Apex of supraoccipital shield to posterior end of nasal cavity 
Posterior end of nasal cavity to tip of rostrum 
Maximum dorso-ventral thickness of left supraorbital process of frontal at base 
Antero-posterior length of bulla at maximum 
Transverse width of bulla at maximum 
Maximum dorso-ventral thickness of bulla 
Antero-posterior diameter of processus sigmoideus 
Free vertcial height of processus sigmoideus 
Exposed length of posterior process of periotic 
Maximum antero-posterior width of posterior process of periotic 
No. 3 
432 
162 
82 
347 
123 
323 
112 
13 
10 
3 
12 
11 
5 
10 
11 
9 
225 
278 
144 
16 
47 
25 
200 
322 
32 
70 
49 
39 
24 
22 
47 
27 
terior edge curves outward and backward gradually, 
and is bounded by the falciform process of the 
squamosal, which fits tightly against the bulla, and 
extends below the level of the anterior ventral surface 
of the bulla . The anterior ventral end of the bulla is 
relatively wide, and does not have the attenuated 
projection seen in bulla of such archaeocetes as 
Kekenodon onomata Kellogg ( 1936) , or most odon-
tocete bullae. The anterior ventral end of the bulla 
is moderately convex, medially. This median con-
vexity becomes much more pronounced, posteriorly. 
Immediately external to the before mentioned median 
upward hollow, the postero-ventral surface of the 
bulla becomes very convex, and projects downward 
in a protuberant manner. From this ventral con-
vexity, the external ventral surface of the bulla turns 
rather abruptly upward. This upward slope is most 
abrupt on the posterior portion, and becomes more 
gradual anteriorly. The processus sigmouleus is lo-
cated a little less than two-thirds of the way back 
from the anterior end of the bulla on its thin outer 
lip. The processus sigmoideus becomes differentiated 
from the rest of the bulla a little more than half way 
upward from the posterior downward protuberance, 
and the upper portion of this process curves posteri-
orly at nearly a right angle, as well as curving out-
ward moderately. This area is relatively wide, and 
is flattened dorso-ventrally. The anterior edge of the 
1966 EMLONG: A NEW ARCHAIC CETACEAN 19 
sigmoid process curves slightly forward on the upper 
portion, but does not project outward. The antero-
posterior diameter of the processus sigmoweus is 
24 mm, which is unusual according to Kellogg 
(1936), as it exceeds the free vertical height of the 
process, which is 22 mm. This same basic feature is 
present on the tympanic bullae of the archaeocetes 
Zygorhiza kochii, and Dorudon osiris Kellogg 
(1936). The backward curved posterior upper por-
tion of the processus sigmoideus is well differentiated 
from the processus medius on the tympanic of Aetio-
cetus. 
The channel for the external auditory meatus is 
underlain by the processus medius of the tympanic, 
which lies just posterior, and inward from the proces-
sus sigmoideus. The upper edge of the bulla in this 
region is antero-posteriorly rounded, and turns down-
ward. The distance between the posterior projection 
of the processus sigmoweus and the anterior edge of 
the posterior process of the periotic is 11 mm. The 
anterior process of the outer lip fits snugly against 
the thin posterior portion of the falciform process of 
the squamosal. The maximum dorso-ventral thick-
ness of the bulla from the posterior-ventral pro-
tuberance to the uppermost portion of the sigmoid 
process is 39 mm. The posterior process of the peri-
otic emerges into ventral view above the postero-
external end of the tympanic, and is bounded at this 
point by the processus posterius on the anterior edge, 
and by the postero-external portion of the involu-
crum on the postero-internal side. The posterior 
process extends outward and backward, and is firmly 
wedged between the exoccipital and the squamosal. 
It extends outward nearly to the external edge of the 
exoccipital. The outward extension of this process 
seems to be about intermediate in development be-
tween the stage seen on the skull of the archaeocete 
Basilosaurus cetoides Kellogg ( 1936) and that de-
veloped on skulls of cetotheres. The posterior process 
of Aetiocetus is very broad, measuring 27 mm an-
terio-posteriorly at maximum. Its surface is rough-
ened, and a very well developed groove is present 
medially, and extends to the outer edge of the process. 
The maximum antero-posterior width of this groove 
is 10 mm, on the inward portion. The posterior 
process of the periotic extends 4 7 mm outward from 
where it emerges from above the concealing tym-
panic. The anterior edge of this process descends 
11 mm below the level of the adjoining squamosal at 
maximum. 
DENTITION 
Six detached teeth were embedded m the 
matrix surrounding the skull. The posterior 
alveoli of the skull are too large and shallow 
for the placement of the teeth, thus the maxil-
lary teeth were probably held in place mainly 
by a ligamentuous gum. Since the teeth could 
not be placed in the corresponding alveoli, and 
considering the fact that these teeth differ con-
siderably from those of any living, or fossil 
cetacean, their allocation is highly uncertain, 
and must be regarded as tentative. It is assumed 
that all the preserved teeth are from the skull, 
and that none are from the missing mandibles. 
There is virtually no chance that they are from 
any other individual than that which they were 
associated with, as bones are extremely rare 
in this deposit. 
Four premolars, and two molars are repre-
sented by detached teeth. The first incisor is in 
place in each premaxillary. Some of the crowns 
of these teeth are very well worn, indicating the 
maturity of the individual. The crowns of the 
molars and premolars are laterally com-
pressed, but are heavily constructed, and 
equipped with moderately developed accessory 
cusps on both edges. These teeth bear a slight 
resemblance to those of Patriocetus ehrlichi 
Abel ( 1913). However, the roots of the molars 
and premolars of Patriocetus are double, and 
widely divergent near the base, whereas, the 
roots are completely fused on the teeth of 
Aetiocetus. Both these cetaceans had eight teeth 
in each maxillary and three in each premaxil-
lary. 
The single tooth preserved with the skull of 
Agorophius pygmaeus True ( 1907) does not 
bear any close resemblance to teeth of this 
cetacean. No strong inward curvature is devel-
oped in the Agorophius tooth. Inward curva-
ture is strongly developed on the premolars of 
Aetiocetus. The Agorophius tooth appears to 
have been double rooted. 
The left third premolar of this cetacean 
seems to bear some resemblance to the lower 
right third premolar of the zeuglodont Kekeno-
don onamata. The basic shape of the crowns, 
the inward curvature, and the swelling below 
the neck are similar in the two teeth. However, 
the Kekenodon tooth is double rooted. The 
20 BULLETIN, MUSEUM OF NATURAL HISTORY, UNIVERSITY OF OREGON 
other described teeth of Kekenodon do not bear 
any strong resemblance to those of this ceta-
cean. All of the detached teeth of Aetiocetus 
appear to be from the left side of the mouth. 
This cetacean apparently had three molars, 
four premolars, a canine, and three incisors on 
each side of the rostrum which apparently coin-
cides with the upper dentition possessed by the 
early cetacean Patriocetus ehrlichi. 
The first tooth to be discussed appears to be the 
upper third premolar. The crown is considerably 
worn, the posterior edge being worn the most. The 
external surface of the crown is coated with smooth 
enamel. The tooth is curved strongly inward from 
the base of the root .It is slightly bowed antero-pos· 
teriorly, both ends being curved backward, slightly. 
The exact number of accessory cusps on the posterior 
edge of the crown is uncertain, as they have been 
worn greatly. Two very minute cusps are present at 
the base of the crown, and there were two, or three 
better developed ones above these. The anterior edge 
of the crown is less worn. One minute cusp is present 
just above the base of the crown, and three better 
developed ones are clearly visible above the minute 
one. None of these cusps were strongly developed 
when compared to the teeth of most zeuglodonts, 
and squalodonts. All these cusps show some degree 
of wear, the upper one is worn the most. The apex 
of the crown, or main cusp rises 3 mm above the base 
of the uppermost anterior cusp, and it is somewhat 
worn on the internal side. The crown of this tooth is 
rather low, and heavily constructed, when compared 
to the teeth of such cetaceans as Agorophius, or most 
squalodonts. The squalodonts have teeth which gen· 
erally have much more prominent accessory cusps, 
and are generally relatively thinner in diameter 
through the base of the crown. The crown of this 
tooth , although laterally compressed, and not coni-
cal, is rather thick at the base, measuring 6.5 mm in 
external-internal diameter. The tooth measures 10 
mm, antero-posteriorly near the base of the crown. 
The crown is widest slightly above the base. The apex 
of the crown rises 12 mm above the base. The internal 
surface of the crown enamel is sculptured with 
moderately pronounced vertical striations. The ex-
ternal side of the tooth is convex. The internal side of 
the crown is convex antero-posteriorly, but the entire 
internal side of tht tooth is concave relative to either 
end. The neck of the root is narrower antero-posteri-
Pl 
P2 
P3 
P4 
orly than the base of the crown. Both roots have com- M I 
pletely fused. A slight median groove on both the 
external, and internal sides runs from below the neck 
No. 3 
to the base of the root, and bifurcates the extremity Figure 9. Upper teeth of AETIOCETUS COTYLALVEUS 
of the root. The distance from the anterior termina-
1966 EMLONG: A NEW ARCHAIC CETACEAN 21 
TABLE 2 
MEASUREMENTS OF THE TEETH 
Rll Lil 
AP of enamel crown 8 7 
Tr of enamel crown 
AP of root, maximum 13 12 
Tr of root, maximum 
Length root plus crown 
Height of enamel crown 6a 11 
a- incomplete 
tion of the root to the apex of the crown is 28 mm. 
The distance from the posterior termination of the 
root to the apex of the crown is 30 mm. The upward 
indentation of this bifurcation is very slight. The root 
is very swollen below the neck, and expands outward 
most on the posterior edge. The distance from the area 
of maximum posterior swelling, to the posterior base 
of the root is 9 mm. This swelling is to accommodate 
the large alveolus. Only about a third of this tooth 
actually fitted in the alveolus. The external, and in-
ternal surface of the root below the maximum swell-
ing point is pitted, and rugose. Above the maximum 
swelling point, it is relatively smooth. The antero-
posterior diameter of the root at the maximum swell-
ing point is 14 mm. The end of the root is completely 
closed on all the detached teeth. 
The second tooth to be discussed may be the upper 
fourth premolar. It is very similar in shape to the 
upper third premolar. On the anterior edge, two 
minute cusps are present, just above the base of the 
crown. Above these, two worn cusps are present. 
The main cusp, or apex of the crown, projects 3 mm 
above the base of the uppermost anterior cusp. The 
fused double root is similar to that of the previously 
described tooth, except that it is not so strongly 
curved inward, and the root is not quite as swollen 
below the neck. The tooth is slightly bowed antero-
posteriorly. The posterior edge of the crown is worn 
flat. No cusps are preserved but cusps were certainly 
present originally. The groove developed on the ex-
ternal and internal side of the root is similar to that 
described on the root of the third premolar. 
The third tooth to be discussed appears to be the 
first premolar. The crown is narrower, and comes to 
a very sharp point, unlike the two teeth already men-
tioned. The crown curves strongly inward and back-
ward. The posterior edge has a sharp-pointed acces-
sory cusp, just above the base of the crown. The apex 
of the crown is very pointed, and rises 8 mm above 
the lowest, best developed posterior cusp. The an-
Pl P2 P3 P4 Ml M3 
10 9.5 10 10 10 9 
6.5 6.5 6.5 6 5.5 Sa 
12 12 14 12 Ila 8.5 
10 8.5 8.5 9 8 6 
28.5 33 30 28.5 32 19 
12.5 11.5 12 11 11 7 
terior edge is free of cusps, except for a minute one 
just above the base of the crown. The anterior and 
posterior edges of this tooth between the cusps are 
very thin and sharp. The external side of the tooth is 
convex, and the enamel of the crown is smooth. The 
internal side of the crown is concave, and the enamel 
is striated vertically. A slight antero-posterior groove 
distinguishes the crown from the neck on the external 
side. The root is swollen below the neck. The tooth is 
strongly bowed in an antero-posterior direction, both 
ends directed posteriorly, as well as being curved 
strongly inward. The narrowed base of the root 
twists slightly outward, to add to the strange appear-
ance of this tooth. No median grove is developed on 
the root, and no bifurcation is developed in the 
termination of the root. 
The next tooth is considered to be the second 
premolar. The crown is sharply pointed. The crown 
curves strongly inward, and backward. On the pos-
terior edge, three prominent, sharp accessory cusps 
are present. The cusp immediately below the apex 
of the crown is the most prominent. The second of 
these three cusps is worn. The apex of the crown is 
very pointed. It rises 3 mm above the base of the 
uppermost accessory cusp on the posterior edge. On 
the anterior edge of the crown, a minute cusp is 
present. A slightly larger one appears just above the 
minor one. These lie slightly above the base of the 
crown. The distance between the highest anterior 
cusp, and the apex of the crown is 8.5 mm. The 
internal surface of the crown is striated vertically. 
The root is swollen below the neck. Externally, the 
lower portion of the root is flattened antero-posteri-
orly. This lower region is not curved as strongly as 
the root of the previously described tooth, but the 
entire tooth is bowed in an antero-posterior direc-
tion, both ends point in a posterior direction, and the 
tooth also curves inward on either end. 
The crown of the first molar is more laterally 
compressed than the other teeth preserved. The ex-
22 BULLETIN, MUSEUM OF NATURAL HISTORY, UNIVERSITY OF OREGON No. 3 
ternal surface of the crown is slightly curved inward 
near the apex. Both external and internal sides of the 
crown are coated with smooth enamel. Three acces-
sory cusps are present on the posterior edge of the 
crown. These cusps are slightly worn, but were not 
strongly developed. The moderately pointed apex of 
the crown rises 3.5 mm above the base of the upper-
most posterior cusp, and is not worn. On the an-
terior edge of the crown, three very minor cusps are 
present. The two roots of this tooth are completely 
fused. The posterior edge of the root was broken 
away during excavation. The root is broad antero-
posteriorly, and the internal and external sides are 
relatively flat, only slightly convex. No median 
groove is present. The posterior side of the root pro-
jects downward slightly more than the anterior side. 
There is no inward curvature of the root. This con-
trasts with the before mentioned teeth. Also, there is 
none of the antero-posterior bowing in this tooth. 
The sixth detached tooth is probably the third 
molar. It is much smaller than the others. The an-
terior side was badly broken during excavation. The 
crown is very low. Part of the inner side, and the 
anterior edge is missing. The posterior edge is well 
worn. Remnants of one accessory cusp appear on 
the anterior edge, just above the base of the crown. 
The posterior edge of the root is nearly vertical and 
straight-sided. No bowing, or inward curvative is 
present on the root. 
As was before mentioned, the first incisor is pres-
ent in each premaxillary. The left incisor is complete, 
but the crown is bent inward slightly more than it 
should be, by distortion. The root is swollen where 
it is lost to view in the alveolus. It measures 12 mm 
antero-posteriorly at maximum. The neck tapers. The 
crown measures 7 mm antero-posteriorly at the base, 
narrows rapidly, and the upper part of the crown is 
narrow, terminating in a sharp point. The crown 
measures 11 mm high, and the tooth measures 20 mm 
long from where it emerges from the alveolus. Some 
matrix was left on the internal side of the tooth to 
strengthen it. The right incisor is similar to the left, 
except that the upper portion of the crown was 
broken away before internment. 
VERTEBRAE 
The vertebrae column of this individual is 
remarkably complete. Only the atlas, and a 
few caudals are missing. It indicates that the 
total length of the skeleton, including the skull, 
was about twelve feet. 
The vertebral formula of this cetacean ap-
pears to have been: 7 cervicals, 12 dorsals, 10 
lumbars, and 15 (?) caudals. With the excep-
tion of the caudals, little uncertaintly exists in 
this formula. The vertebrae were completely 
articulated from the axis to the ninth caudal, 
and the centra were separated by a half inch, 
or less. The tenth and eleventh caudals were 
deposited forward about a foot, and rested on 
the right side of the anterior caudals, a few 
inches from them.Just how many more caudals 
were present originally with the skeleton is 
highly uncertain, as some cetaceans had a 
number of antero-posteriorly thin terminal 
caudals. 
The epiphyses of all the vertebrae are pres-
ent, and are solidly fused with the centra. These 
vertebrae, particularly the lumbars and caudals 
are very large in proportion to the skull. Aside 
from the unique development of the ninth and 
tenth caudals, most features of the vertebrae 
resemble mysticete vertebrae more closely than 
they do modernized odontocete vertebrae. The 
neural arches are all rather low, and are par-
ticularly low, and transversely broad on the 
cervicals and anterior dorsals. The transverse 
processes of the lumbars are broadened antero-
posteriorly. Neural spines of the lumbars are 
relatively short, are thick transversely, and 
long antero-posteriorly. The distal ends of these 
neural spines are considerably thickened trans-
versely. The tail of this cetacean was very 
powerful. 
The vertebrae are all essentially complete. 
Fragments are missing from a few of the proc-
esses, a few of the neural spines lack the distal 
end, and one vertebrae lacks one transverse 
process. Some of the neural spines, transverse 
processes, and metapophyses have been slightly 
displaced, causing slight discrepancies in their 
measurement. The neural spines of most of the 
lumbar and anterior caudal vertebrae would 
be slightly higher than the measurements show. 
Some of the neural arches are slightly distorted. 
CERVICAL VERTEBRAE 
The cervicals are all free, and distinct. The 
vertebral column was so well articulated in the 
matrix, that the neural arches overlap, and 
1966 EM LONG: A NEW ARCHAIC GET ACEAN 23 
Figure 10. Sixth cervical vertebrae, right, posterior and dorsal views 
separation of some of the vertebrae from the 
matrix would seriously damage them. The 
neural arches are transversely broad, and low. 
The postzygapophyses are rounded at their 
edges, and flattened, transversely. They project 
strongly backward. 
AXIS: The axis is heavily constructed with a broad 
neural canal, which measures 38 mm transversely. 
The transverse processes are short, projecting more 
backward than outward . No foramina are present on 
their surfaces. On most cetotheres, the axis is much 
shorter antero-posteriorly, broader transversely, and 
the transverse processes project outward more. The 
anterior articulating facets of this axis are wide, 
transversely, and flattened toward their outer edges. 
The transverse distance across these facets is 104 
mm. The odontoid process is large, with a median 
ridge running posteriorly into the neural canal. A 
concave depression lies to either side of this ridge. 
The antero-posterior diameter of the centrum, in-
cluding the odontoid process is 64 mm. The post-
zygapophyses are flattened, antero-posteriorly, do 
n.ot project outward beyond the level of the neural 
arch. The dorsal surface of the neural spine is some-
what eroded in places. The anterior end projects 
forward, narrowing at its tip. The posterior end is 
broad, and relatively flat, transversely. On the ventral 
portion of the centrum, posterior to the odontoid 
process, a well marked ridge runs antero-posteriorly. 
The posterior end of this ridge is thickened, and 
bifurcates. The posterior end of the centrum cannot 
be seen, as it rests against the third cervical in the 
matrix. This axis closely resembles the axis of the 
archaeocete Zygorhiza kochii in shape, the only 
noticeable differences being the greater outward ex-
tension of the postzygapophysis on Zygorhiza and 
the presence of foramina on the transverse processes 
of the Zygorhiza axis. 
THIRD CERVICAL: The centrum is relatively thin. The 
neural spine is slightly defaced, and was vestigial. 
The neural arch is the thinnest, antero-posteriorly, of 
all the cervicals. The upper, and lower bars of the 
transverse processes are fused, and rounded at their 
ends. The bases of these processes are concealed by 
matrix and the overlapping processes of adjoining 
24 BULLETIN, MUSEUM OF NATURAL HISTORY, UNIVERSITY OF OREGON No. 3 
cervicals. Just above the base, a vertebra arterial 
canal which perforates the transverse processes is 
partly exposed to view. The fused posterior ends of 
the transverse processes are directed backward. 
FOURTH CERVICAL: The centrum of the fourth cervi-
cal is slightly longer than the third. The distal end of 
the vestigial neural spine is missing. The transverse 
processes project outward and downward slightly 
farther than on the third cervical. The upper and 
lower bars are fused and similarly shaped to those 
of the third cervical. The vertebra arterial foramina 
is exposed on the left process. 
FIFTH CERVICAL: The distal end of the neural spine is 
defaced, but was apparently slightly higher than on 
the preceding cervical. The upper and lower bars of 
the transverse processes are similarly fused, but pro-
ject outward more strongly. Inside the outer extrem-
ity of the fused bars of these processes the anterior 
portion of the lower bar curves more strongly in an 
anterior direction than in preceding processes. The 
centrum is slightly longer antero-posteriorly than. 
that of the fourth cervical. The posterior end of the 
centrum is concave. The median ventral ridge is 
prominent. 
SiXTH CERVICAL: The neural spine is complete. The 
neural arch is much wider transversely and broader 
antero-posteriorly than that of the fifth cervical. The 
postzygapophyses are well developed and extend well 
beyond the posterior edge of the centrum. The upper 
bar of the transverse process is separated by a dis-
tance of 22 mm from the outer edge of the lower bar. 
The upper bar projects most strongly outward and is 
rounded. The end is directed obliquely upward an-
teriorly. The lower bar is elongate antero-posteriorly, 
and pointed on the posterior end. The posterior end 
of the right process projects 33 mm posterior to the 
posterior edge of the centrum. The level of the lower 
bar is much below the ventral surface of the centrum. 
The inner margin of the process is concave dorsally. 
The centrum is quite concave, and rectangular in 
outline. The anterior edge of the centrum is nearly 
round. The vertebrae were separated at this point 
during excavation. 
SEVENTH CERVICAL: The neural spine is twice as high 
as that of the previous vertebra. The neural arch is 
broad transversely. There is no lower bar on the 
transverse process. The transverse process is little 
depressed below the level of the neural arch. It is 
rounded and heavy on its extremity, which projects 
outward and backward. The anterior face of the 
centrum is rounded, and slightly concave. 
DORSAL VERTEBRAE 
The anterior dorsals closely approximated 
each other in the matrix. They could not be 
freed without damage. They have broad, low 
neural arches. The diapophyses are thickened 
and project strongly forward. Well defined 
concave rib facets are present on the heavy ends 
of the diapophyses. The transverse processes 
are developed only on the three posterior dor-
sals and have thickened rib facets at their ex-
tremities. The postzygapophyses of the first 
four dorsals are very broad transversely, but 
become progressively less developed, posteri-
orly. The neural spines of the dorsals are 
broader antero-posteriorly at the base than at 
the top with the exception of the eighth and 
ninth. 
The anterior dorsals are markedly different 
from those of cetotheres, such as Cetotherium 
f urlongi Kellogg ( 1925 A, pp. 35-50). The dor-
sal vertebrae of Cetotherium furlongi all have 
long, relatively flattened transverse processes 
which project outward to a greater degree than 
do the diapophyses of this cetacean. The trans-
verse processes of the dorsals of Pelocetus cal-
vertensis Kellogg ( 1965) also project outward 
more strongly. The diapophyses on the anterior 
dorsals of Aetiocetus project more strongly for-
ward than do those on most cetothere dorsals. 
However, the transverse processes on the three 
posterior dorsals of this cetacean are well de-
veloped, and resemble those processes on the 
same vertebrae of Cetotherium furlongi , and 
Pelocetus calvertensis to a considerable degree. 
The anterior dorsals of Pelocetus calvertensis 
are considerably thinner antero-posteriorly 
than those of the new cetacean. The third to 
seventh cervicals of most cetotheres are rela-
tively thinner antero-posteriorly than those 
cervicals of the new cetacean. The centra of the 
eleventh and twelfth dorsals of Aetiocetus are 
quite elongate antero-posteriorly, and resemble 
the anterior lumbars in general dimensions. 
The neural arches of the anterior dorsals are 
broad, and transversely flattened. The post-
zygapophyses are flattened and rounded at the 
1966 EMLONG: A NEW ARCHAIC CETACEAN 25 
edges. The prezygapophyses of most of the 
anterior dorsals are concealed by the over-
lapping postzygapophyses of the preceding 
vertebra. 
FIRST DORSAL: The centrum is slightly longer than 
the seventh cervical, and is broad transversely. Four 
antero-posterior ridges are present on the ventral sur-
face of the centrum. These ridges are present to some 
degree on each of the first five dorsals. The antero-
superior rib facet is minute, vertically elongate in an 
irregular oval. It is directed slightly backward as 
well as upward. The posterior superior facet is 
almost indiscernible. The neural spine is broader 
antero-posteriorly, higher and thicker than that of 
the seventh cervical, and rakes forward. The distal 
end of the spine is rounded antero-posteriorly. The 
neck of the diapophysis is short, and directed for-
ward. The end is elongate antero-posteriorly, and 
directed downward posteriorly. The articular facet 
for the tuberculum of the first rib is a convex depres-
sion on the median portion of the head of the dia-
pophysis. The lower edge of this convexity slopes 
inward, under the head of the diapophysis. The 
right articular facet measures 15 mm antero-
posteriorly. 
SEy OND DORSAL: The centrum is considerably wider 
than long. The antero-posterior rib facet is larger 
and broader than on the preceding dorsal, but little 
higher. It rakes forward. The neural spine rakes for-
ward. It is broader antero-posteriorly than the pre-
ceding dorsal, but little higher. The neural arch is 
flat, broad, and similar to that of the first dorsal. 
The neck of the diapophysis is long. The articular 
facet for the tuberculum of the second rib is strongly 
concave. It is broad at the top and narrows toward 
the bottom. The left facet measures 18 mm at its 
widest point antero-posteriorly. 
THIRD DORSAL: The centrum is considerably longer 
than that of the second dorsal. The antero-superior 
rib facet is similarly shaped to that of the second 
dorsal, but slightly larger. The posterior rib facet is 
better developed, but still small, and is convex. The 
neural spine is much broader antero-posteriorly than 
in the preceding dorsal, but little higher. It rakes for-
ward. The distal end is thinner transversely than on 
the second dorsal. The neural arch is not as broad 
and is slightly depressed at the base of the neural 
spine. The postzygapophyses are rounded at their 
edge, and project well beyond the posterior end of 
the centrum. The neck of the diapophysis is long and 
projects strongly anteriorly. The articular facet for 
the tuberculum of the third rib is concave, and more 
rounded than on the preceding dorsal. It measures 
22 mm antero-posteriorly. 
FOURTH DORSAL: The neural spine is broad antero-
posteriorly, thin transversely and rakes forward. The 
neural arch is less broad than on the preceding 
dorsal. The centrum is longer, and heavier. The neck 
of the diapophysis is longer, and projects more 
strongly forward. The articular facet for the attach-
ment of the tuberculum of the fourth rib is oval, and 
directed antero-posteriorly. It is concave. The left 
one measures 24 mm antero-posteriorly. 
FIFTH DORSAL: The centrum is heavier, than that of 
the preceding dorsal. A rounded median ridge is 
developed on the ventral side. The antero-superior 
rib facet is diminuitive. The posterior superior facet 
measures 22 mm dorso-ventrally and 9 mm antero-
posteriorly. The neck of the diapophysis is thickened, 
heavy, and directed strongly anteriorly. The facet for 
the tuberculum of the rib measures 25 mm antero-
posteriorly, an.d 20 mm dorso-ventrally. It is rounded 
and concave. The neural arch is less broad trans-
versely than on the preceding vertebrae. The neural 
spine is broader antero-posteriorly, and nearly verti-
cal. The antero -posteriorly elongate postzygapo-
physisial facet faces obliquely downward. The post-
zygapophyses project slightly beyond the posterior 
end of the centrum. 
SIXTH DORSAL: The centrum is nearly the same length 
as the fifth dorsal. The rounded ventral median ridge 
is more distinct. The upper borders of the centrum 
are just below the rib facets and are more concave. 
The anterior and posterior rib facets are both fairly 
small. The distal end of the neural spine is missing. 
The neural spine rakes back1Vard. The neural arch 
is narrower transversely than on the preceding 
dorsal, and directed more upward. The articular facet 
for the tuberculum of the sixth rib is rounded and 
concave. It recedes upward on the lower edge. The 
diapophyses above the articular facet are protuber-
ant, and separated by a groove. They extend forward. 
The postzygapophyses are much narrowed. The right 
articular facet for the tuberculum of the sixth rib 
measures 24 mm, antero-posteriorly. 
SEVENTH DORSAL: The centrum is slightly longer than 
that of the sixth dorsal. Its posterior face is broader 
than the anterior face. The antero-superior rib facet 
is minute, and the posterior facet small. The diapo-
physis is heavy, and shorter, and does not project so 
far anteriorly. The articular facet for the attachment 
of the seventh rib is fairly small and crescent shaped. 
26 BULLETIN, MUSEUM OF NATURAL HISTORY, UNIVERSITY OF OREGON No. 3 
It deepens sharply near its lower border. The right 
articular facet measures 18 mm antero-posteriorly. 
The first pair of metapophyses are present on this 
vertebra. They closely approximate the diapophyses, 
and do not flare strongly outward, but project for-
ward beyond the anterior edge of the centrum. Their 
anterior surfaces are deeply pitted. The distal end of 
the neural spine is missing. The neural spine rakes 
backward. The posterior end of the centrum is 
slightly concave. 
EIGHTH DORSAL: The centrum is little longer than that 
of the seventh dorsal. The anterior end is slightly 
convex. The antero-superior, and postero-superior 
rib facets are both small. The neck of the diapophysis 
is short. The facet for the tuberculum of the eighth 
rib is reduced to a small inden.tation in the end of the 
diapophysis. The metapophyses are slightly further 
separated from the diapophyses and project farther 
forward over the anterior end of the centrum. They 
project much farther anteriorly than do the diapo-
physes. A depression separates them from the diapo-
physes. The neural arch is narrow transversely. The 
neural spine rakes backward. The right articular 
facet for the tuberculum of the eighth rib feasures 
17 mm antero-posteriorly. 
NINTH DOR'SAL: The centrum is longer than the eighth 
dorsal. The posterior end is the same width as the 
anterior end. A small antero-superior rib facet is 
present. No postero-superior facet is discernible. The 
neck of the diapophysis is very short. The articular 
facet for the tuberculum of the ninth rib is similar to 
that on the preceding dorsal. The head of the diapo-
physis is smaller. The lower portion of the crescentic 
articular facet curves strongly inward. The metapo-
physes are somewhat further away from the diapo-
physes. A broad, concave depression separates the 
metapophyses from the diapophyses. The left articu-
lar facet for the tuberculum of the ninth rib measures 
16 mm antero-posteriorly. 
TENTH DORSAL: The centrum is longer than that of 
the ninth. No superior rib facets are present on this 
vertebra. A short, broad transverse process is present. 
These processes are thickened at their extremities and 
each possesses a well-developed rib facet. These 
facets are elongate antero-posteriorly. Just above the 
median portion of these facets, a round convex nob 
is present, which appears to be a weak remnant of 
the diapophysis. Another slight protuberance is pres-
ent at the base of the metapophysis. The metapo-
physes are somewhat broadened transversely near 
their anterior extremities and are greatly elevated 
above the transverse processes. The neural spine is 
Figure 11. Eleventh dorsal vertebrae, left, anterior 
arul dorsal views 
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28 BULLETIN, MUSEUM OF NATURAL HISTORY, UNIVERSITY OF OREGON No. 3 
elongate antero-posteriorly and thickened trans-
versely near the extremity. It rakes backward. The 
left articular facet for the tuberculum of the tenth rib 
measures 39 mm antero-posteriorly, and 21 mm 
dorso-ventrally. 
ELEVENTH DORSAL: The transverse process is longer 
than that of the tenth. These processes are thickened 
at their extremities and a well developed single rib 
facet is present on each process and is antero-pos-
teriorly elongate. The posterior edge of the extremi-
ties of the transverse processes are thickest dorso-
ventrally, the left one measures 23 mm dorso-ven-
trally. The centrum is elongate. A distinct median 
ridge is present on the ventral side. No remnants of 
the diapophyses are present. The metapophyses are 
slightly longer antero-posteriorly, fairly thin trans-
versely. The postzygapophysis projects beyond the 
posterior end of the centrum, no strong facets are 
developed. The antero-posteriorly elongate neural 
spine rakes backward. The left articular facet for the 
tuberculum of the eleventh rib measures 34 mm 
antero-posteriorly, and 16 mm dorso-ventrally. 
TWELFTH DORSAL: The transverse processes are 
longer and thinner, but their outer ends are thickened 
to form a well developed distal articulating facet for 
the twelfth rib. This antero-posteriorly elongate facet 
is less thickened dorso-ventrally than that of the 
eleventh dorsal. The centrum is longer, than that of 
the eleventh. It is also heavier than on the preceding 
dorsals. The metapophyses are slightly longer and 
broader. The neural spine is thicker transversely and 
longer antero-posteriorly. It rakes backward slightly. 
The postzygapophysis does not project beyond the 
posterior end of the centrum. The left articular facet 
for the tuberculum of the twelfth rib measures 35 mm 
antero-posteriorly, and 14 mm dorso-ventrally. 
LUMBAR VERTEBRAE 
The centra of the lumbars progressively in-
crease in length and width. A median ridge is 
present on the ventral side of all the lumbars. 
These vertebrae are all complete, or nearly so. 
Small fragments are missing from some of the 
edges of the neural spines, and the left trans-
verse process is missing from the second lum-
bar. There is a forward projection on the an-
terior edge of the transverse process of each 
lumber. This is most pronounced on the pos-
terior lumbars. This projection is located about 
two thirds of the way out from the root of each 
transverse process. The transverse processes 
are all broad antero-posteriorly. The transverse 
processes of the lumbars, and anterior caudals 
project strongly outward, and relatively little 
downward and backward. 
The metapophyses all project well beyond 
the anterior end of the centra and become 
transversely broader and flatter progressively. 
The neural arches are all low. The neural 
spines are relatively short vertically and very 
long antero-posteriorly. They are much 
thickened at the top transversely, especially 
toward the middle of the series. The first four 
neural spines are longest antero-posteriorly 
near the base. The postzygapophyses are 
weakly developed, but are present on all the 
lumbars. The best developed ones are little 
developed, and project only very slightly be-
yond the posterior edge of the centrum. Distinct 
facets are not present on any of the lumbar 
postzygapophyses. 
FIRST LUMBAR: The transverse processes show no evi-
dence of rib facets. Their outer edges are smooth, 
rounded antero-posteriorly, and thin dorso-ventrally. 
The pedicle of the neural arch is short, as it is on all 
the vertebrae. The neural spine is broad antero-
posteriorly, and transversely thick at the distal end. 
The distal end is almost triangular in profile. It is 
highest medially. The neural spine rakes slightly 
backward. 
SECOND LUMBAR: The left transverse process is 
broken off near the root. The right transverse process 
is widest at the level of the broad anterior projection, 
about two-thirds of the way out from the root. The 
neural spine rakes slightly backward, and is rounded 
antero-posteriorly at the distal extremity. 
FOURTH LUMBAR: The distal end of the neural spine 
is wide transversely. It measures 11 mm wide at 
maximum. 
FIFTH LUMBAR: Similar to the fourth lumbar it shows 
progression in dimensions. The neural spine rakes 
backward slightly. The median longitudinal carina 
on the ventral side of the centrum is pronounced, 
and is sharp in the middle portion, as well as toward 
the ends of the centrum. 
SIXTH LUMBAR: The neural spine is nearly vertical, is 
much thickened transversely at the distal end, and is 
1966 EMLONG: A NEW ARCHAIC CETACEAN 29 
Figure 12. Sixth lumbar vertebrae, right, posterior and dorsal views 
30 BULLETIN, MUSEUM OF NATURAL HISTORY, UNIVERSITY OF OREGON No. 3 
very broad, antero-posteriorly. The transverse proc-
esses are much broadened, antero-posteriorly, espe-
cially toward the extremities. 
SEVENTH LUMBAR: The neural spine of this lumbar is 
thickest transversely of any lumbar. It measures 18 
mm transversely. The neural spine rakes forward 
slightly. The transverse process is the longest in the 
vertebral column. 
EIGHTH LUMBAR: The relatively high neural spine 
rakes backward slightly. The transverse processes are 
shorter than on the seventh. 
NINTH LUMBAR: The neural spine rakes forward. The 
transverse processes are shorter, but still broad 
antero-posteriorly. A shelf is present on the posterior 
half of their outer edges. This depression is about 
6 mm wide and 42 mm antero-posteriorly. It is not 
bounded by an outer wall, and is located external to 
the anterior projection of the transverse process. The 
centrum is the longest in the series. 
TENTH LUMBAR: The neural spine is less elongate 
antero-posteriorly and its anterior edge is higher 
than its posterior edge. It rakes forward, and is 
thinner transversely at the top than the preceding 
lumbars. The centra of the posterior lumbars are 
very large and heavy. The posterior end of the 
median ventral ridge bifurcates, forming two minor 
protuberances which are separated by a thin groove. 
This bifurcation is very weakly developed. It is un-
likely that this vertebra is the first caudal, as the 
chevron facets of the first caudal are very well de-
veloped. The first caudal has no median ventral ridge, 
its ventral surface is rounded. The transverse proc-
esses of the tenth lumbar possess a well marked de-
pression, or shelf on their outer extremities. This 
depression is most pronounced on the anterior por-
tion of the extremities and is 12 mm wide at maxi-
mum. It measures 55 mm antero-posteriorly at the 
internal edge and dwindles in width on the posterior 
end. This depression is located external to the broad-
est part of the transverse process. 
CAUDAL VERTEBRAE 
Eleven caudals were present with the skele-
ton, all but the last two were articulated. These 
caudals are very large and heavy in proportion 
to the size of the skull. The vertebrae are all 
complete or nearly so. The metapophyses of 
the anterior caudals are extremely well devel-
oped. They project far beyond the anterior end 
of the centrum and are broad and flat trans-
versely. They are best developed on the first 
three caudals and progressively reduce in di-
mensions toward the posterior end of the series. 
The neural spines of the caudals progressively 
shorten, are broad antero-posteriorly and are 
broader at the top than at the bottom. 
FIRST CAUDAL: The chevron (haemapophysial) facets 
located on the posterior ventral end of the centrum 
are well developed, project downward strongly and 
are separated by a depression. Two small projections 
are present on the anterior ventral end of the cen-
trum. The transverse processes are shortened, broad 
antero-posteriorly toward their outer edges and a 
projection is present on their anterior extremities. A 
distinct depression, or shelf is present about two-
thirds of the way out from the base of these processes. 
It measures 24 mm wide and 58 mm antero-pos-
teriorly at its internal edge. The inner edge of this 
depression is located internal to the broadest part of 
the transverse process. The sides of the centrum are 
quite convex medially above the roots of the trans-
verse processes. The neural spine rakes forward and 
is highest toward the anterior edge of its extremity. 
It is not transversely thickened greatly at the top. 
SECOND CAUDAL: The transverse processes project 
less strongly forward at their anterior edges than do 
those of the first caudal. The external portions of the 
transverse processes of the first and second caudals 
are depressed below the inner regions. This shelf 
reaches a transverse width of 43 mm posteriorly on 
the right transverse process, becomes less wide, an-
teriorly, but extends all the way across the process at 
a point about two-thirds of the way out from the 
base. The depression measures 57 mm, antero-pos-
teriorly, at its internal edge, located inside the 
broadest part of the transverse process. The median 
surface of the centrum is rather concave above the 
transverse processes. This condition is more pro-
nounced than on the lumbars, and is well developed 
on all of the first eight caudals. The chevron facets 
on the posterior ventral surface of the centrum are 
even larger than those on the first caudal. The neural 
spine is much shorter than that of the first caudal, 
and is more elongate, antero-posteriorly. The cen-
trum is slightly shorter than that of the first caudal, 
although there is no really marked shortening of 
these centra, until the ninth caudal is reached. 
THIRD CAUDAL: The transverse processes are shorter, 
and much less broad, antero-posteriorly. They do 
not rake strongly backward and no shelves are pres-
1966 EMLONG: A NEW ARCHAIC CETACEAN 31 
Figure 13. First caudal vertebrae, left, anterior and dorsal views 
32 BULLETIN, MUSEUM OF NATURAL HISTORY, UNIVERSITY OF OREGON No. 3 
ent distally. The chevron facets are very pronounced. 
The neural spine is shorter, but is as broad antero-
posteriorly as that of the second caudal. The median 
ventral surface of the centrum is rather concave. 
FOURTH CAUDAL: The transverse processes are 
markedly reduced and their sharply pointed ends 
rake strongly forward. The antero-posterior length 
of the base of the right transverse process is 45 mm. 
No foramina are present on the transverse processes 
of any of these caudals. The chevron facets are pro-
nounced. Two prominences are also present on the 
anterior ventral end of these caudals. A roundish 
depression is present on the median ventral surface 
of this caudal and is bounded to either side by a 
ridge. This feature is pronounced from the fourth to 
the eighth caudal. The centrum is slightly shortened. 
FIFTH CAUDAL: The transverse processes are further 
reduced and their sharply pointed ends rake strongly 
forward, beyond the anterior end of the centrum as 
do those of the fourth caudal. The right process 
measures 61 mm from the posterior edge of the root 
to the curved anterior extremity and 39 mm at the 
base of the process antero-posteriorly. The chevron 
facets progressively reduce in dimension posteriorly 
along the caudals, but are still large on the fifth. The 
metapophyses are reduced and progressively dimin-
ish in dimensions toward the end of the series. The 
neural spine is shorter and thin transversely . 
SIXTH CAUDAL: The transverse processes are reduced 
to an antero-posteriorly directed ridge on the sides 
of the centrum. This ridge is thickened and pro· 
tuberant at the anterior end. On the fourth through 
the eighth caudal, the median area of the centrum 
between the underside of the roots of the transverse 
processes and the ridges which bound the ventral 
depression is concave to a pronounced degree. The 
neural spine is low and rounded antero-posteriorly 
at the top. 
SEVENTH CAUDAL: The ridge, which is the remnant 
of the transverse process, extends the full antero-
posterior length of the centrum, as it does on the 
sixth caudal, and is best developed on the anterior 
end. The chevron facets project to within 10 mm of 
the anterior projections. 
EIGHTH CAUDAL: Only a slight ridge marks the rem· 
nants of the transverse process. The anterior end of 
this ridge is slightly enlarged. The ridge extends the 
full length of the centrum. The fourth to eighth cau-
dals are slightly concave on their anterior ends. 
These caudals have centra which are slightly convex 
Figure 14. Fifth caudal vertebrae, left anterior and 
dorsal views 
1966 EMLONG: A NEW ARCHAIC CETACEAN 33 
Figure 15. Ninth, tenth, and eleventh caudal vertebrae right views 
on their posterior ends. The metapophyses are re-
duced to minor eminences which do not project be-
yond the anterior end of the centrum. The top of the 
neural spine is missing, but the spine is very reduced. 
NINTH CAUDAL: The most peculiar feature of the en-
tire vertebral column is the strange modification of 
the ninth and tenth caudals. Some of the abnormal-
ities of these two vertebra are evidently the result of 
a bone disease, and cannot be considered diagnostic. 
A full evaluation of the peculiarities of these two 
caudals may await the discovery of another skeleton. 
Similar abnormalities on vertebrae of the cetothere 
Pelocetus calvertensis were attributed to bone dis-
ease. The ninth caudal is considerably broader trans-
versely and vertically than the eighth, but is much 
shorter antero-posteriorly. The anterior end of the 
centrum is slightly concave. The neural spine is re-
duced to a thickened ridge. The metapophyses are 
represented by small rounded humps near the an-
terior end of the centrum. On each side of the cen-
trum, extremely heavy ridges and grooves are pres-
ent. They are most pronounced about half way to 
the top of the centrum and may be remnants of the 
transverse processes. These ridges run antero-pos-
teriorly. These features are obviously developed for 
the attachment of very heavy muscles. The sides of 
the centrum are covered with small pits and knobs. 
A small round depression is present on the median 
ventral surface of the centrum. This depression 
measures 24 mm antero-posteriorly. A low, rounded 
projection is present at the anterior and posterior 
ventral edges of the centrum. No chevron facets are 
apparent. The posterior end of the centrum is convex 
and smooth on the right border, but the rest is rough-
ened and depressed, and small fragments of bone 
protrude outward from it. It appears as if the ninth 
and tenth caudals were fused and that bone from 
both vertebrae had inter-mingled. 
TENTH CAUDAL: The anterior face of the centrum is 
much broader transversely than the posterior face. 
The entire upper surface of the anterior face of the 
centrum is roughened and depressed in the same 
manner as is the posterior face of the ninth caudal. 
At a point about half way up each side of the cen-
trum, a broad projection is present which extends 
backward well beyond the anterior edge of the cen-
trum. These projections are broad dorso-ventrally. 
The left one measures 40 mm dorso-ventrally and 
projects 26 mm anterior to the anterior edge of the 
centrum. The left metapophysis was broken away 
before fossilization. The right metapophysis projects 
to a point 33 mm anterior to the anterior edge of the 
centrum. When the ninth caudal is placed against 
this vertebra, the metapophysis and transverse proc-
esses of the tenth caudal fit tightly against the sides 
of the ninth. The neural spine of the tenth caudal is 
represented by a very feeble ridge. The sides of the 
centrum are much roughened and slope toward the 
posterior end of the centrum. A small oval depres-
sion is present on the median ventral surface of the 
centrum. The posterior end of the centrum is convex, 
rounded and considerably smaller than the anterior 
end. 
ELEVENTH CAUDAL (?) : This caudal is very thin an-
tero-posteriorly. The anterior end of the centrum is 
nearly the same size as the posterior end. It is nearly 
round, with a minor protuberance at the top which 
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1966 EMLONG: A NEW ARCHAIC CETACEAN 35 
is a remnant of the neural spine. No abnormalities 
are present. A very small oval depression is present 
on the ventral surface of the centrum. The sides of 
the centrum are roughened and pitted. The identifi-
cation of this vertebra as the eleventh caudal is tenta-
tive, since it was washed slightly away from the rest 
of the series before burial. It is considerably shorter 
antero-posteriorly than the tenth caudal. However, 
the rounded, convex posterior face of the centrum 
of the tenth caudal is much smaller in transverse 
diameter than is the anterior face of that centrum, 
and agrees fairly well with the dimensions of the 
eleventh caudal if a relative progressive diminish-
ment is taken into consideration. 
Several more caudals were probably present orig-
inally with the skeleton. 
Rrns 
Articulating rib facets are present on all 
twelve of the dorsal vertebrae. At least three 
ribs were free in the flesh, as this cetacean ap-
parently possessed no less than 15 ribs on each 
side of the rib cage. The ribs were scattered in 
the matrix. The left fifteenth rib was lodged be-
side the posterior lumbars. Twenty three com-
plete, or partial ribs were preserved. The mid-
dle ribs of this cetacean are long, and quite 
heavily constructed. The second through the 
tenth rib possess well defined necks which sep-
arate the tuberculum from the capitulum. The 
most prominent part of the tubercular swell-
ings on the ribs is located slightly external to 
the actual tubercular facet. Measurements other 
than those of the tubercular facet are based 
from the area of maximum swelling. The allo-
cation of these ribs must be regarded as tenta-
tive, in that they were scattered in the matrix, 
and some are not complete. The dissimilarity 
of this cetacean to other forms, and the lack of 
comparative material further hampers deduc-
tions. The posterior ribs strongly differ from 
one another. 
FIRST RIB: The first rib from the left side is incom-
plete. It lacks the head and the entire lower part of 
the shaft. This rib is very wide external-internally 
at the angle and tuberculum. It is thickened antero-
posteriorly at the tuberculum, but very thin antero-
posteriorly below the tuberculum and the protuber· 
ant angle. The tuberculum measures 17 mm antero-
posteriorly at the thickest point. The tuberculum is 
located 75 mm above the most protuberant part of 
the angle. The tuberculum is convex except for a 
small concavity near its posterior edge. A small lip-
like ridge projects anteriorly for a short distance just 
below the tuberculum on the external edge of the rib. 
The shaft narrows rapidly below the angle, becomes 
oval in cross section, measures 20 mm external-in-
ternally at the angle. 
SECOND RIB: The second rib from the left side is pre-
served and is complete. The neck is fairly wide dorso-
ventrally and thin antero-posteriorly. The tubercu-
lum is thinner, measures 14 mm antero-posteriorly 
at maximum. It is protuberant on the outer end. No 
definite inner border to the tubercular facet is dis-
cernible although the slightly convex surface narrows 
toward the capitulum. The neck is relatively short, 
but is distinct. The capitulum is thickened, heart-
shaped and protuberant on the inner edge. The me-
dian surface of the shaft inside the angle is concave 
on both the anterior and posterior side. The angle 
is less protuberant than on the first rib. The shaft 
is strongly curved, but tapers very gradually in 
external-internal thickness and remains thin antero-
posteriorly below the angle. The thinnest point ex-
ternal-internally is 25 mm at a point 190 mm below 
the angle in a straight line. The distal end of the 
shaft is widened, measures 11 mm antero-posteriorly 
near the rugose distal end. The shaft is slightly 
twisted antero-posteriorly toward the distal end. 
THIRD RIB: Both right and left ribs are preserved and 
are complete. The tuberculum is very proturberant 
and a distinct facet is developed which measures 18 
mm antero-posteriorly and 16 mm external-intern-
ally. The area between the tuberculum and capitulum 
is thin antero-posteriorly. The neck is relatively 
longer, and less thick dorso-ventrally than on the 
second rib. The capitulum is expanded, heart-shaped 
and pointed on the inner extremity. The median 
surface of the rib is somewhat concave inside the 
angle. The shaft narrows somewhat, below the angle, 
but remains fairly wide external-internally and thin 
antero-posteriorly. The shaft is narrowest external-
internally at a point 250 mm below the angle, where 
it measures 23 mm external-internally. It broadens 
out, measuring 31 mm external-internally and 14 mm 
antero-posteriorly near the faceted termination. The 
shaft near the distal end is strongly curved and some-
what twisted toward the distal end. 
FOURTH RIB: The right rib is nearly complete, but 
lacks a portion of the shaft at the angle and the two 
sections do not fit together, making total measure· 
36 BULLETIN, MUSEUM OF NATURAL HISTORY, UNIVERSITY OF OREGON 
ments approximate. A distinct facet is present on 
the tuberculum. This facet measures 1 7 mm antero-
posteriorly and 25 mm external-internally. The neck 
is relatively thin and the expanded capitulum is 
heart-shaped, and pointed inward. The angle 1s 
broken away. The shaft below the angle narrows and 
is oval in cross-section. A ridge is persent on the 
median anterior side and runs for about 75 mm. 
The shaft widens toward the distal end and a minor 
eminence is present on the external edge of the rib 
at a point 175 mm above the distal end, below which 
the shaft curves more sharply and twists slightly in 
a posterior direction. The slightly expanded distal 
end measures 25 mm external-internally and 13 mm 
antero-posteriorly at the roughened facet. 
FIFTH RIB: The right fifth rib is complete. The tuber-
culum is protuberant. The tubercular facet measures 
19 mm antero-posteriorly and 29 mm external-inter-
nally. The shaft is rather heavy, measures 17 mm 
antero-posteriorly at a point 185 mm below the 
angle and measures 28 mm external-internally at this 
point. Toward the distal end, the shaft rakes slightly 
backward. The distal end is not expanded. It meas-
ures 12 mm antero-posteriorly and 22 mm external-
internaly at the rugose facet. A portion of the left rib 
is present but lacks both extremities. 
SIXTH RIB: Only the distal third of the right rib is 
preserved. The shaft is slightly broader than the 
distal portion of the shaft of the fifth rib. It measures 
27 mm external-internally at a point 84 mm above 
the distal extremity. The distal extremity measures 
28 mm external-internally and 14 mm antero-posteri-
orly at the roughened distal facet. The shaft curves 
slightly backward toward the distal end. 
SEVENTH RIB: This rib is the longest and heaviest in 
the series and lacks only the head. The tuberculum is 
prominent at the outer edge. The tubercular facet 
measures 19 mm antero-posteriorly and 25 mm ex-
ternal-internally. The shaft is less thick external-
internally between the angle and tuberculum than in 
the preceding ribs, but is heavy antero-posteriorly 
and oval in cross-section. The shaft is expanded ex-
ternal-internally at a point 122 mm below the angle. 
It measures 29 mm external-internally at this point. 
It is also very heavy, measuring 20 mm antero-pos-
teriorly. The shaft tapers in antero-posterior thick-
ness toward the distal end, but remains broad ex-
ternal-internally with another slight expansion 130 
mm above the distal end. The measurements at the 
roughened distal facet are 11 mm antero-posteriorly 
and 25 mm external-internally. The shaft curves 
backward slightly toward the distal end. 
o~ 
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00 
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tj< 
No.3 
1966 EMLONG: A NEW ARCHAIC CETACEAN 37 
EIGHTH RIB: The head and tuberculum is missing, 
otherwise, the right rib is complete. The shaft is very 
heavy. It measures 19 mm antero-posteriorly, US 
mm below the angle. The lower part of the shaft is 
very broad, measures 30 mm external-internally at 
a point 250 mm below the angle, but is relatively thin 
antero-posteriorly at this point. The distal end tapers 
and rather than terminating in a squared facet, the 
internal edge of the end is pointed and slants upward 
to the external edge of this thinner, more rounded 
termination which measures 21 mm external-intern-
ally and 5 mm antero-posteriorly. The distal end of 
the shaft rakes backward. The left rib is represented 
by the distal third of the shaft. This shaft is slightly 
smaller than the right one, but the distal termination 
has the same basic shape. 
NINTH RIB: Both right and left ribs are preserved 
and each is complete. The external edge of the tuber-
culum is still fairly prominent, but less so than on 
the anterior ribs. The large tubercular facet mea-
sures 21 mm antero-posteriorly and 24 mm external-
internally. The neck of this rib is thick antero-post-
eriorly, measures 22 mm at the narrowest point and 
13 mm external-internally. The capitulum is semi-
triangular, but elongate toward the posterior edge. 
The shaft at the angle is narrower than on preceding 
ribs and is almost rectangular in profile. The shaft 
immediately below the angle is narrow and almost 
round in profile. The shaft then broadens and meas-
ures 27 mm external-internally at a point 226 mm 
below the angle. The shaft is relatively thin antero-
posteriorly at this point. Below this point, the shaft 
again narrows, and terminates in a slightly rounded 
end which measures 17 mni external-internally and 9 
mm antero-posteriorly. The right rib is very similar 
except that the distal termination is slightly thinner 
antero-posteriorly. 
TENTH RIB: Both right and left ribs are preserved, and 
are complete except for a tiny portion of the distal 
end of the right rib. The tuberculum is less protub-
erant. The tubercular facet measures 21 mm antero-
posteriorly and 29 mm external-internally. The cap-
itulum is elongate antero-posteriorly. It measures 
32 mm in this direction. The neck is similarly shaped 
to that of the ninth rib. The shaft between the angle 
and tuberculum is heavy. The rib widens external-
internally toward the distal end and is widest at a 
point 250 mm below the angle. Here it measures 28 
mm external-internally. The distal end tapers and 
measures 15 mm external-internally and only 2 mm 
antero-posteriorly at the squared end. The distal por-
tion rakes in a posterior direction. The right rib is 
similar to the left. 
ELEVENTH RIB: Only the distal two-thirds of the shaft 
of the left rib is preserved. The shaft is broad extern-
al-internally. The broadest point is located 155 mm 
above the distal end and measures 28 mm external-
internally. The distal end tapers. It measures 17 mm 
external-internally and 7 mm antero-posteriorly at 
the squared distal end. The distal end rakes back-
ward. The right rib is represented by its distal por-
tion. It is similar to the left rib, except the distal ter-
mination is thinner antero-posteriorly. 
TWELFTH RIB: The upper portions of the right and 
left ribs are preserved. On the left rib, the tuberculum 
is differentiated from the capitulum by a groove 
which measures 2 mm at its minimum width. The tu-
berculum has no distinct facet, the swelling measures 
20 mm external-internally and 15 mm antero-posteri-
orly and is convex. A slight concavity is present on 
the rounded capitulum. The distance between the tu-
berculum and angle is 99 mm. The shaft is strongly 
curved at the angle and is oval in cross-section at the 
broken point 60 mm below the angle. 
THIRTEENTH RIB: A small fragment of what is appar· 
ently the left rib is preserved. This fragment lacks 
both extremities. A weakly developed angle is pres-
ent. 
FOURTEENTH RIB: A nearly complete left rib is pre-
served which may represent the fourteenth rib. A 
fracture during excavation occurred and a small sec-
tion of the shaft below the angle was lost. The tuber-
culum is separated from the capitulum by 3 mm at 
a minimum. The convex tubercular swelling measures 
30 mm external-internally and 15 mm antero-post-
eriorly. No facet is developed. The surface of both 
the capitulum and tuberculum is convex and rugose. 
The shaft tapers markedly below the tuberculum 
and no swollen angle is present. The shaft measures 
only 20 mm external-internally at a point 197 mm 
above the distal end. The shaft is oval in cross-section 
at this point. Below this point, the shaft broadens ex-
ternal-internally and becomes thinner antero-poster-
iorly, measuring 29 mm external-internally at a point 
60 mm above the distal end. The distal extremity is 
tapered. It measures 15 mm external-internally and 
4 mm antero-posteriorly at the slightly rounded end 
which rakes slightly backward. 
FIFTEENTH RIB: This rib was lodged beside the post-
erior lumbar vertebrae on the left side. It somewhat 
resembles the innominate bones of some cetaceans, 
but is most likely a rib because of the thickened head, 
and the lack of a clearly defined pubic process. It is 
from the left side. The capitulum and tuberculum are 
completely fused. A slight angle is developed at a 
·. 
. 
·. 
• ;, 
: 
.. 
.. 
' 
. 
38 BULLETIN, MUSEUM OF NATURAL HISTORY, UNIVERSITY OF OREGON No. 3 
point 61 mm below the tuberculum, and the shaft is 
thin external-internally. Below the angle, this pecu-
liar rib curves in an anterior direction for 70 mm, 
and a second angle is developed which is broad, mea-
suring 22 mm external-internally. From here, the 
shaft curves slightly in the opposite direction for 61 
mm. At this point, a third external-internal swelling 
is developed, measuring 23 mm. Below this point, the 
direction of the curvature is again reversed. A groove 
runs obliquely downward from the external (dorsal) 
surface of the shaft, begining at a point 232 mm 
below the tuberculum. The shaft is broad external-
internally, and thin antero-posteriorly just above the 
distal end. The distal end is narrower external-inter-
nally, slightly indented medially, measures 16 mm 
external-internally, and 3 mm antero-posteriorly. 
HAEMAPOPHYSES 
Two chevron bones are preserved with the 
skeleton. Their exact placement beneath the 
caudal vertebrae is uncertain. The first chevron 
to be discussed is nearly complete, but slightly 
eroded along part of the ventral edge and the 
posterior end of the haemal spine. The upper 
articular facets of the arms of the haemal spines 
are very far apart. They are somewhat broad-
ened and flattened on their anterior edges. This 
chevron is quite elongate vertically. The length 
of the haemal canal is 60 mm. It is filled with 
spine extends beyond the end of the haemal 
canal. The external surfaces of the arms of this 
chevron are concave between the upper region 
and the ventral edge of the haemal spine. The 
other preserved chevron is incomplete, lacking 
most of the left arm and small portions of the 
right arm and ventral spine. The upper ends of 
the arms of the haemal spine were much closer 
together than those of the first mentioned chev-
ron. The bone is shorter vertically. The ventral 
edge of the haemal spine is very thin. The 
upper edge of the left haemal spine rises 50 
mm above the ventral edge at its maximum 
height. 
STERNAL BONES 
MANUBRIUM: This bone is heavily constructed. 
The two surfaces comprising the anterior end 
are pointed obliquely outward and downward. 
The right extension is broken away above the 
base. Dorsally, the medial portion between the 
two outward projections is concave and curves 
downward. This bone is very pitted and rugose, 
particularly on the edges. Posteriorly, the me-
dian dorsal surface curves upward and be-
comes convex antero-posteriorly, but still con-
cave transversely. The bone is narrowest trans-
versely about half way to the posterior end. 
The posterior end has two concave depressions 
to either side and a third median one. Laterally, 
two antero-posteriorly elongate depressions are 
present on the posterior half of the bone. The 
median ventral surface of this bone is slightly 
convex transversely and antero-posteriorly. 
TERMINAL SEGMENT (?) : An elongate bone 
which may be the terminal segment of the ster-
num was preserved. This bone is antero-pos-
teriorly long, constricted slightly, medially, 
with the dorsal side convex, and the ventral 
side concave. The anterior end possesses three 
facets, the median one is largest. The outer 
ones face obliquely outward. The posterior end 
is trianguar and tapers to a rounded point. 
TABLE 6 
MEASUREMENTS OF THE HAEMAPOPHYSES 
Dorso-ventral diameter 
Antero-posterior diameter right 
articular facet 
Tr across arms 
Antcro-post right arm 
a- incomplete 
TABLE 7 
1 2 
90a 
35 
61 
50 
58a 
17 
34a 
50 
MEASUREMENTS OF THE STERNAL BONES 
Manubrium Terminal 
Greatest antero-posterior 127 
Transverse at anterior end 90a 
Transverse at midpoint 46 
Transverse near posterior end 66 
Dorso-ventral near posterior end 25 
Dorso-ventral near anterior end 
a- incomplete 
69 
37 
35 
17 
' 
1, 
j. 
,-
; 
. 
1966 EMLONG: A NEW ARCHAIC CETACEAN 39 
COMPARISONS 
This archaic cetacean appears to be a defi-
nite antecedent to the mysticetes. The cranial 
architecture shows no tendency toward the re-
modeling necessary for the development to-
ward any modernized odontocete skull. It is 
very unlikely that this animal would possess so 
many mysticete features if it were not directly 
in mysticete lineage. 
Skulls of the archaic cetaceans Archaeodel-
phis, Agorophius, Patriocetus, and Agriocetus 
all have broad rostra, and resemble Aetiocetus 
in general form. However, it is possible that 
some of these resemblances are due to converg-
ence. Presumably, all cetaceans had to pass 
through a similar stage of cranial remodeling 
to adapt to marine environment. Both the broad 
snouted Agorophius and the archaic cetaceans 
Xenorophus and Microzeuglodon, which have 
narrow rostra, are thought to belong to the gen-
eralized odontocete stock. Therefore, the broad-
ness of the rostra of some archaic cetaceans is 
not necessarily indicative of mysticete relation-
ship. The critical features would appear to be 
the inter-locking maxillary which would pre-
vent the pronounced backward thrust of the 
rostral elements over the frontal, the elimina-
tion of the teeth, and the elongate posterior 
process of the periotic, a feature of all mysti-
cetes. The skull of Agorophius pygmaeus from 
the upper Eocene of South Carolina (True 
1907) much resembles mysticete skulls in gen-
eral form, but features such as the pronounced 
spread of the maxillaries over the frontals ex-
clude it from any close mysticete relationship. 
The archaic cetacean Patriocetus ehrlichi 
has been suggested as a possible mysticete ante-
cedent, but aside from other peculiarities, the 
maxillary has no ascending process, and in-
stead, slides under the frontal. The premaxil-
laries over-ride the frontal to a point well be-
hind the orbit. 
A contemporaneous near-relative of Patri-
ocetus, the genus Agriocetus is represented by 
a very incomplete skull. If the restoration is 
correct, the maxillaries over-ride the dorsal 
surface of the frontals to about the center of 
the orbit. They are shown to taper toward their 
posterior ends, rather than remaining broad as 
on the Agorophius skull. If correctly restored, 
the Agriocetus skull resembles Aetiocetus in 
this very important feature. However, the max-
illaries, premaxillaries, and nasals are not pre-
served on the type skull of Agriocetus, and the 
sutures are heavily coated with sand grains, 
making interpretations uncertain. The supra-
orbital processes of Agriocetus and Patriocetus 
do not have flaring postorbital projections, and 
meet the parietals in a manner that exclude 
these cetaceans from any close relationship to 
the cetacean described in this report. On the 
Patriocetus skull, and the Agriocetus skull a 
thin ledge-like projection of the parietal ex-
tends backward from the supraorbital process 
to the supraoccipital, and overhangs the tem-
poral fossa, whereas on the Aetiocetus skull, 
there is no ledge-like projection of the parietal. 
The frontals meet the parie~als on a constricted 
intertemporal area, and the suprambital proc-
esses extend outward abruptly, at right angles, 
anterior to the frontal-parietal contact. On the 
skulls of Agriocetus and Patriocetus, the supra-
orbital processes of the frontals extend gradu-
ally outward from their direct contact with the 
parietals. This relationship bears little resem• 
blance to that of Aetiocetus. Neither Patrio-
cetus or Agriocetus has a greatly elevated su-
praoccipital shield as is possessed by Aetio-
cetus. 
Both Patriocetus and the new cetacean had 
eleven teeth on each side of the rostrum. The 
molars and premolars of Patriocetus are dou-
ble rooted, whereas, the roots are single on all 
the teeth of this cetacean. The nature and form 
of the alveoli of Aetiocetus are among the 
strongest indications of its mysticete tenden-
cies, as the very shallow posterior alveoli 
would have little known functional value that 
would not be equally, or more adequately sup-
plied by deeper alveoli, and a thicker maxil-
lary. The form, and position of the palatines, 
and pterygoids, and most of the rest of the 
posterior ventral cranial region of Patriocetus 
40 BULLETIN, MUSEUM OF NATURAL HISTORY, UNIVERSITY OF OREGON No. 3 
are dissimilar to this region on the Aetiocetus 
skull. No full ventral view of the rostrum of 
Patriocetus is available for comparison, but it 
appears from the lateral, and partial ventral 
view that the alveoli do not have most of the 
peculiarities possessed by those of this ce-
tacean. 
Of all known cetaceans, the incomplete skull 
of Archaeodelphis patrius seems to bear the 
most resemblance to the cetacean described in 
this report. Archaeodelphis is considered by 
Kellogg ( 1928) to be the most primitive known 
cetacean excepting the zeuglodonts. The skulls 
of Archaeodelphis and Aetiocetus both possess 
an interlocking maxillary, with infraorbital 
and ascending proces~es ; both have an elongate 
posterior process of the periotic. The rounded 
supraoccipital shields are similar, however, the 
supraoccipital shield of Archaeodelphis is ap-
parently not greatly elevated above the inter-
temporal region. Both cetaceans possess a large 
orbit, and strongly outward flaring postorbital 
projections of the frontals. The form of the 
intertemporal regions are rather similar, and 
the parietal-frontal contact is somewhat simi-
lar. Both cetaceans have large pterygoid fossa. 
However, even though the maxillaries of 
Archaeodelphis have only telescoped backward 
to near the center of the orbit, their posterior 
ends remain relatively wide. They show no 
evidence in either the dorsal restoration (Kel-
logg 1928, p. 28) or in the published photo-
graphs and restoration (Allen 1921) of the 
marked narrowing toward their posterior ter-
minations, as is seen on the Aetiocetus skull, 
and all mysticete skulls. Rather, they run close 
to, and nearly parallel to the edge of the orbit. 
This is an odontocete feature. The narrow 
ascending portions of the premaxillaries and 
the long, narrow nasal bones are somewhat 
similar to the same bones on the Aetiocetus 
skull, and on known mysticete skulls. In odon-
tocetes there is a tendency toward shortening of 
the nasal bones. The entire rostrum of A rchaeo-
delphis is missing, and the teeth are unknown. 
The A rchaeodelphis skull is thought to be 
from the upper Eocene. If this age determina-
tion is correct (based solely on examination of 
the matrix), Archaeodelphis is considerably 
older than this cetacean. An important feature 
which differentiates these two skulls is the zy-
gomatic arch. On the new species, the zygoma 
is relatively elongate, and under-rides the 
supraorbital process of the frontal for a dis-
tance of 25 mm, and tapers to an extremely thin 
point. On the Archaeodelphis skull, the zy-
goma is very short, and does not taper to a thin, 
sharp point. Rather, the end is bluntly rounded, 
and points upward. It does not approach the 
posterior end of the postorbital projection of 
the frontal. The missing jugal of Archaeodel-
phis was probably shaped quite different from 
that of this cetacean, because on the Aetiocetus 
skull, the very narrow anterior end of the zy-
goma is directed obliquely downward, and the 
posterior portion of the jugal is firmly wedged 
between the median external surface of the 
zygoma, and the ventral surface of the frontal. 
It does not contact the tip of the zygoma, but 
rather, projects backward and upward along 
the median external surface of the zygoma to 
a point well behind the anterior tip. The jugal 
of Archaeodelphis could not have this relation-
ship, and probably under-rode the postorbital 
projection of the frontal, without contacting it 
as the zygoma does not closely approximate the 
postorbital projection. The zygoma of Archae-
edelphis has the same type of bluntly rounded 
point as is present on typical odontocete skulls. 
Therefore, there is no reason to think that the 
zygoma-jugal contact was any different than on 
other odontocete skulls in which the posterior 
end of the jugal contacts the rounded anterior 
tip of the zygoma squarely, and does not ex-
tend behind it. 
On the Patriocetus skull, the anterior tip of 
the zygoma is bluntly rounded, and terminates 
much behind, and below the level of the post-
orbital projection of the supraorbital process of 
the frontal. The posterior termination of the 
jugal, as is shown in the restoration ( Abel 
1913) rests squarely against the blunt anterior 
end of the zygoma. Its anterior end is shown to 
rest against the posterior external border of 
' 
1966 EMLONG: A NEW ARCHAIC CETACEAN 41 
the maxilary, which terminates at the level of 
the preorbital angle of the supraorbital process 
of the frontal. No lateral outward extension of 
the maxillary runs posterior to the level of the 
preorbital angle of the frontal, and only the 
very tip of the anterior extremity of the jugal 
touches the maxillary. The jugal remains far 
below the level of the postorbital projection of 
the frontal, and no contact was present between 
these surfaces. 
The upper Oligocene odontocete Microzeu-
glodon aff. caucasicum (Riabinin 1938) re-
sembles Aetiocetus in some respects. The zygo-
matics on the Microzeuglodon skull extend for-
ward to the level of the postorbital projections 
of the frontals. The parietal-frontal contact is 
similar on both cetaceans. Both have an infra-
orbital extension of the maxillary. In each the 
occipital condyles are widely separated at the 
top. The left exoccipital of both cetaeans is 
similarly proportioned. The two cetaceans are 
approximately the same size. The Microzeuglo-
don skull is badly deformed, and many of the 
sutures are unclear. Most of my comparisons 
are derived from the illustrations, as the pub-
lished photographs do not reveal sufficient 
detail. Confirmation of some of the bone rela-
tionships shown in the illustrations of the Rus-
sian cetacean ·may await the discovery of a 
better preserved skull. 
The general form of the crowns of the upper 
first molar and upper fourth premolar are sim-
ilar. However, the crowns of the anterior pre-
molars of Aetiocetus are narrower anterio-pos-
teriorly, and are more sharply pointed, and ex-
hibit more inward curvature. The roots of the 
teeth of both cetaceans have strong inward 
curvature. The posterior premolars and the 
molars of Microzeuglodon have two roots, con-
trasting with Aetiocetus. Microzeuglodon has 
one less molar in each maxillary than does the 
new cetacean. The molar teeth of early archae-
ocetes, so far as known including Protocetus, 
Prozeuglodon, Basilosaurus, Dorudon, and Zy-
gorhiza are located on the posterior end of the 
maxillary beneath the supraorbital process of 
the frontal and not anterior to this process as 
in Patriocetus, Microzeuglodon and Aetioce-
tus, and probably Agorophius and Archaeodel-
phis. 
On the M icrozeuglodon skull, the posterior 
dorsal portion of the maxillary is shown to 
terminate anterior to the level of the preorbital 
angle of the frontal. Furthermore, this portion 
of the maxillary does not narrow abruptly. 
Both these features contrast with Aetiocetus, 
but are characteristic of Patriocetus ( as re-
stored Abel 1913). The premaxillaries do not 
overspread the frontal on the Microzeuglodon 
skull, but do on Aetiocetus. According to Ria-
binin ( 1938) , the nasal bones on the Micro-
zeug lodon skull were probably very short. 
They are long on Aetiocetus. The supraoccipi-
tal of Aetiocetus is rounded. That bone is tri-
angular on the M icrozeuglodon skull. 
Although the zygomatics on the Microzeu-
glodon skull do extend beneath the postorbital 
projections of the frontals, these zygomatics 
are bluntly rounded on the anterior extremity, 
and are under-ridden by a portion of the post-
orbital projection of the frontal. The postorhi-
tal projection of the frontal does not extend 
below the level of the anterior ventral surface 
of the zygoma on the new cetacean skull. The 
right zygomatic of Microzeuglodon appears to 
be slightly more attenuated distally than is the 
left one, but does not approach the extreme at-
tenuation that is characteristic of the left zygo-
matic of Aetiocetus. The Aetiocetus zygomatic 
is much thinner transversely and dorso-ven-
trally, when compared with Microzeuglodon. 
On the restoration of Microzeuglodon (Ria-
binin 1938, p. 169), the jugal is shown to be in 
direct contact with the anterior tip of the zy-
goma, and does not extend behind that contact. 
The jugal is shown to lie well below the level 
of the postorbital projection of the frontal, hav-
ing no contact with the latter. If the restoration 
is correct, that hone has the same relationships 
and form as is present on odotocete skulls, con-
trasting with the new cetacean in this very 
important complex of features. When com-
pared with the Aetiocetus skull, the postorhital 
projection of the frontal on the Microzeuglo-
42 BULLETIN, MUSEUM OF NATURAL HISTORY, UNIVERSITY OF OREGON No. 3 
don skull projects more sharply downward, 
and less strongly outward relative to the anter-
ior outer edge of the frontal. No lateral out-
ward extension is present on the infraorbital 
process of the maxillary of Microzeuglodon. 
The jugal could not have the lateral contact 
with the maxillary that is present on the new 
cetacean skull. The posterior maxillary alveoli 
of Microzeuglodon are double. They are single 
on the new cetacean, as well as being much 
shallower and larger. On the Microzeuglodon 
skull, the outer edges of the maxillaries are 
much thicker dorso-ventrally and the rostrum 
is narrower. 
The basioccipital of Microzeuglodon is sim-
ilarly shaped to that of Archaeodelphis, lack-
ing the differentiated lateral protuberance seen 
on Aetiocetus. The posterior ventral portion of 
the vomer terminates much farther forward on 
Microzeuglodon, and it does not appear that a 
strong downward projecting keel or carina was 
developed. The palatines of Microzeuglodon 
are located much farther forward, and their 
anterior portion extend far forward in a nar-
rowed strip, bearing no resemblance to Aetio-
cetus. The ventral plates of the pterygoids are 
widely separated in Microzeuglodon, exposing 
the posterior narial channel to ventral view. On 
the skull of the new cetacean, that channel is 
roofed over and obscured to ventral view by 
the carina of the vomer, and the pterygoid and 
palatine bones. These three bones are carried 
far posterior to the level they occupy on Micro-
zeuglodon. The lachrymal is not shown to be 
dorsally exposed on the restorations of the Mi-
crozuglodon skull, and no dorsal extension of 
the maxillarly is shown in the region of the 
lachrymal, differing from Aetiocetus on both 
these points. 
The transverse process of the first lumbar 
vertebrae of Microzeuglodon extends outward 
to a sharp point posteriorly, and slants oblique-
ly inward anteriorly, whereas the distal ex-
tremity of the transverse process of the same 
vertebra of the new cetacean is more rounded 
antero-posteriorly. No strongly develop anter-
ior projection is present on the distal extrem-
ities of the transverse processes of the posterior 
lumbars and anterior caudals of M icrozeuglo-
don. The lumbers of Microzeuglodon possess 
relatively longer centra, and higher neural 
spines. Their metapophyses project strongly 
upward, and are not relatively flattened trans-
versely as in Aetiocetus. Microzeuglodon is 
shown to possess two more lumbars than Aetio-
cetus. The posterior caudals in the Microzeu-
glodon restoration are shown to be elongate 
antero-posteriorly, differing markedly from 
the antero-posterior thinness of the posterior 
caudals of the new cetacean. The transverse 
processes of the third and fourth caudal of 
Microzeuglodon are much more reduced than 
those of the same caudals of Aetiocetus, and 
possess dorso-ventrally thickened crests, con-
trasting with Aetiocetus. The neural spines of 
the anterior caudals of Aetiocetus are much 
more elongate antero-posteriorly than those of 
Microzeuglodon. The neural spines of the lum-
bars of M icrozeuglodon were apparently not 
greatly thickened transversely at their distal 
extremity. 
The features of the maxillary and premaxil-
lary, the zygoma-jugal form and relationships, 
and the form and position of the palatines ap-
pear to be major criteria, which when consid-
ered in conjunction with the other features of 
the skull and skeleton would appear to exclude 
Microzeuglodon from close relationship with 
Aetiocetus. Microzeuglodon appears to be a rel-
ative of the Agorophiidae and Patriocetidae 
and differs from Aetiocetus in most of the same 
general features as do the Agorophiidae and 
Patriocetidae. Thus, it may be assumed that 
Microzeuglodon is probably a member of the 
odontocete stock. 
The zygoma-jugal relationship of Aetiocetus 
is apparently unique among known Cetacea. 
The extremely narrow point present on the an-
terior termination of the zygoma is unlike that 
of any known odontocete, or mysticete. Nor 
does any known odontocete, or mysticete have 
a jugal in which the posterior end projects well 
behind the level of the anterior termination of 
the zygoma; yet on this skull, the posterior end 
.i 
" 
' 
.. 
. 
1966 EMLONG: A NEW ARCHAIC CETACEAN 43 
of the jugal extends 44 mm behind the anterior 
termination of the zygoma. The zygomatics of 
all known zeuglodont skulls have an attenuated 
anterior termination, but on these skulls, the 
tip of the zygoma is located well behind the 
level of the postorbital projection of the frontal. 
Another feature that differentiates Aetioce-
tus from Archaeodelphis, and Patriocetus, and 
other true cetaceans is the presence of a lateral 
extension of the infraorbital process of the 
maxillary. This dorso-ventrally thin plate ex-
tends outward, slightly beyond the edge of the 
orbit. The lateral portion of this plate is well 
separated from the ventral surface of the fron-
tal, and extends posteriorly 48 mm behind the 
anterior end of the jugal. The ventral surface 
of the jugal rests firmly, and evenly against this 
maxillary plate, and this relationship is main-
tained evenly from the anterior end of the 
jugal to the posterior edge of the maxilliary 
plate. This is a most important relationship. 
It is not duplicated on any typical cetacean 
skull, but is somewhat similar to the maxillary-
jugal relationship on Eocene zeuglodont skulls, 
on which the infraorbital process has a lateral 
extension that resembles the one present on 
the new species. However, on Eocene zeuglo-
dont skulls, this process bears teeth, whereas, 
the posterior alveolus on each maxillary on 
this cetacean skull is located anterior to the 
preorbital angles of the frontals, and no teeth 
were present on the infraorbital extensions of 
the maxillaries. On other zeuglodont skulls, the 
anterior termination of the jugal projects 
under the lachrymal. This is not the case on 
the skull of Aetiocetus, as the squared termina-
tion of the jugal rests against the posterior edge 
of the lachrymal. However, the ventral surface 
of the jugal is in contact with the outer poster-
ior extension of the maxillary, while on other 
zeuglodont skulls the inner portion of the jugal 
maintains direct contact with the posterior 
outer extension of the maxillary. The infra-
orbital plate on some cetothere skulls, such as 
Pelocetus calvertensis extends outward to the 
outer edge of the frontal, but is firmly attached 
to the ventral surface of the frontal, and does 
not contact the jugal in the manner present on 
the Aetiocetus skull. 
The position of the infraorbital plate on the 
skull of the new species could foreshadow the 
condition seen on cetothere skulls because the 
outward extension is retained. It could progres-
sively lose its connection with the jugal, and 
become firmly attached to the ventral surface 
of the frontal. As was previously mentioned, 
an outward extension is not present on the in-
fraorbital process of the maxillary on other 
suggested mysticete antecedents, such as Ar-
chaeodelphis and Patriocetus. 
On the Aetiocetus skull, the lateral protuber-
ance of the basioccipital projects outward, 
downward, and backward, and the posterior 
extremity is differentiated from the surround-
ing bone surface externally, interiorly, and 
posteriorly. The posterior portion is relatively 
flattened, and broadened, transversely, and 
only slightly convex medially. On the skull of 
Archaeodelphis, as is shown in the published 
photograph ( Allen 1921), the outer edges of 
the thin descending plate of the basioccipital 
forms a transversely thin ridge to either side of 
the median posterior trough of the basioccipi-
tal, and the ventral side of the basioccipital 
slopes evenly upward, and inward, to form the 
median trough, with no irregularity, or trans-
versely expanded projecting posterior protu-
berance to break the even continuity of the 
smooth surface. This plate has no observable 
differentiation from the median trough, except 
for the even slope. In this important feature, the 
basioccipital of Archaeodelphis resembles that 
of the squalodonts ,and modernized porpoises. 
The basioccipital of Aetiocetus resembles the 
same region on cetothere skulls more than the 
basioccipital of Archaeodelphis. On cetothere 
skulls, the lateral protuberances of the basi-
occipital are well developed, transversely ex-
panded, and well differentiated from the sur-
rounding bone surface. 
In Archaeodelphis, the pterygoids are wide-
ly separted and at their level the posterior 
narial channel is wide open. This channel also 
separates the posterior inner margins of the 
;. 
1 
44 BULLETIN, MUSEUM OF NATURAL HISTORY, UNIVERSITY OF OREGON No. 3 
palatines. Both the pterygoids and the pala-
tines are located considerably anterior to the 
level they occupy on the Aetiocetus skull. This 
region differs strongly on the Aetiocetus skull, 
on which a very well developed downward 
projecting carina of the vomer separates the 
posterior inner margins of the palatines, and 
also separates the inner margins of the ptery-
goids, and extends backward behind them, 
forming a transversely thin blade-like keel that 
descends 38 mm below the level of the basiocci-
pital. A similar feature is present on cetothere 
skulls. In contrast, the carina of the vomer on 
the Archaeodelphis skull terminates far for-
ward, at the level of the median posterior exten-
sions of the maxillaries, and does not project 
strongly downward. As previously mentioned, 
the open narial channel separates all but the 
anterior third of the palatines. 
In Patriocetus, the edge of the descending 
plate of the basioccipital does not appear in 
restoration (Abel 1913) to be relatively flat-
tened transversely. It appears to slope abrupt-
ly, and evenly inward from the outer edges. 
However, the posterior portion of the outer 
edge of the descending plate does turn outward 
more abruptly than on the Archaeodelphis 
skull. A ventral longitudinal carina of the 
vomer is present on Patriocetus, but terminates 
at a point much anterior to the one on the ven-
tral surface of the skull of Aetiocetus. The 
posterior extensions of the palatines terminate 
much father anterior on the ventral surface in 
Patriocetus than they do in Aetiocetus. The 
pterygoids of Patriocetus are very widely sepa-
rated. The posterior external portions of the 
pterygoids are located far behind the posterior 
termination of the palatines. This differs 
strongly from the new cetacean. The dorsal 
surface of the rostrum in Patriocetus somewhat 
resembles that of Aetiocetus, but the outer 
edges of the maxillaries do not appear to be as 
thin in Patriocetus. Patriocetus has an elongate 
posterior process of the periotic. Kellogg 
( 1928) suggested the possibility that the Patri-
ocetus skull may have had an ascending proc-
ess of the maxillary, which was destroyed on 
the type skull without leaving a trace. How-
ever, Abel's restorations do not show any evi-
dence of this. As pointed out by Kellogg 
( 1928), the relationships shown on Abel's res-
torations would be structurally unsound, as the 
maxillary would only be supported by the 
ascending process of the premaxillaries, and 
the vomer. Regardless of whether the Patrio-
cetus skull had an ascending process of the 
maxillary, or not, it is distinguished from 
Aetiocetus by the major differences in the zy-
goma-jugal relationship, the parietal-frontal 
relationship, the lack of an outward extension 
on the infraorbital process of the maxillary, 
the double-rooted teeth, the maxillary-jugal 
relationship, and the palatines, pterygoids, and 
vomer. 
The zygoma-jugal relationship, the ventral 
form of the vomer, the lack of an outward ex-
tension of the infraorbital process, and the 
probable lack of contact between the maxillary 
and jugal demonstrate the dissimilarity of Ar-
chaeodelphis to Aetiocetus. Archaeodelphis is 
considered to be a near relative of Agorophius. 
The type of telescoping seen on the Archaeo-
delphis skull would lead to the development of 
a skull similar to that of Agorophius more 
simply than to one similar to Aetiocetus as no 
great reversals of trends already established 
would be necessary. Elimination of the infra-
orbital process would be a progressive change 
when related to the many odotocete-like fea-
tures present on the Archaeodelphis skull. The 
tendency toward broadening of the ascending 
portions of the maxillaries in Archaeodelphis 
has already begun. Once started, it is likely that 
this trend would continue on its descendants. 
An inconsistency in the argument that the 
infraorbital process, when considered sepa-
rately, would impede development toward 
modernized odotocete-type crainial telescoping 
from archaic cetaceans, appears when it is 
recognized that the infraorbital process is pres-
ent on all known zeuglodont skulls, and is a 
normal mammalian relationship. Therefore, 
regardless of whether or not the zeuglodonts 
are antecedent to modernized odontocetes, the 
. 
•·"'!••,, ...... 
1966 EMLONG: A NEW ARCHAIC CETACEAN 45 
infraorbital process was in all probability 
present on the ancestral stock of odontocetes 
and would have to have been eliminated at 
some point in their development in any case. 
Therefore, when considered alone, the infra-
orbital process or for that matter the presence 
of an elongate posterior process of the periotic, 
which is developed on some zeuglodont skulls, 
may not be a good indication of close mysticete 
affiliation of Patriocetus, and Archaeodelphis. 
These features may simply be primitive. All 
that these two features really indicate is that 
mysticete remodeling would be possible, 
whereas, it would not be likely after these fea-
tures were eliminated. A definite tendency 
toward the mysticete line would only be indi-
cated when prerequisites, such as an infraorbi-
tal process of the maxillary and an elongate 
posterior process of the periotic, are coupled 
with a very large number of other mysticete 
features, including indications that the teeth 
were to be reduced. Aetiocetus exhibits more 
mysticete features than any other known 
toothed cetacean, and the peculiarities of the 
alveoli give added evidence as to its differenti-
ation from odontocetes. 
The lachrymal frontal-maxillary relation-
ship on this cetacean differs from that on the 
A rchaeodelphis skull for the lachrymal of 
Archaeodelphis contacts the maxillary only on 
its internal edge. No raised postero-external 
extension of the maxillary partially encircles 
the anterior exposed edge of the lachrymal, 
and on the A rchaeodelphis skull, the maxillary 
is shown to be about as transversely broad im-
mediately posterior to the lachrymal as it is 
immediately anterior to it. This is in direct 
contrast to the A etiocetus skull. According to 
Kellogg ( 1928) the lachrymal of Archaeodel-
phis is actually over-ridden dorso-internally by 
the maxillary. This is not the case on either the 
Aetiocetus skull, or the skull of the archaeocete 
Zygorhiza kochii ( Kellogg 1936). The exter-
nal edge of the lachrymal on the A etiocetus 
skull is well differentiated from the frontal, 
and projects outward well beyond the preorbi-
tal angle of the frontal. This is not the case in 
Archaeodelphis. The position, and form of the 
lachrymal of Aetiocetus more resembles the 
relationship on the skull of the mysticete Bal-
aenoptera borealis ( Kellogg 1928) than that of 
Archaeodelphis. However, the form, and posi-
tion of the lachrymal on the new cetacean is es-
sentially primitive, and is very similar to the 
lachrymal of Zygorhiza kochii ( Kellogg 1936), 
bearing much more resemblance to the lachry-
mal of this archaeocete than to the lachrymal 
of any typical cetacean. 
The alisphenoid is not exposed in the wall 
of the pterygoid fossa on the skull of Aetioce-
tus. The alisphenoid has no ventral exposure 
at all. On the skull of Archaeodelphis, the alis-
phenoid-pterygoid relation is entirely differ-
ent, and the alisphenoid helps to form the outer 
wall of the pterygoid fossa on the ventral side 
of the skull. 
The upper Oligocene Yaquina Formation 
may be about contemporaneous with the Aqui-
tanian stage of Europe in which Patriocetus 
and Agriocetus were discovered. A cetothere, 
Cetotheriopsis lintianus ( see Kellogg 1928), 
also occurs in sediments of this European 
stage. This fact does not exclude Aetiocetus 
from direct mysticete lineage because this 
genus could have survived from an earlier 
epoch, and could have given rise to mysticetes 
in the early or middle Oligocene. Long sur-
vivals are not uncommon among cetothere 
genera. 
Most early cetotheres had antero-posteriorly 
elongate, narrow supraoccipital shields, as 
does the genus Cetotheriopsis. The cetothere 
A ulocetus sammarinensis as illustrated, ( see 
Kellogg 1928) has a skull with a rounded su-
praoccipital similar to that of Aetiocetus. Fur-
thermore, the basic shape of the ascending 
processes of the maxillaries, premaxillaries 
and the nasal bones are similar, except that 
they are telescoped further backward on the 
A ulocetus skull. The preorbital angles of the 
frontals on the skull of Aulocetus flare outward 
strongly and are under-ridden by the zygomat-
ics, which, however, are more robust than those 
of Aetiocetus. The braincase, so far as can be 
46 BULLETIN, MUSEUM OF NATURAL HISTORY, UNIVERSITY OF OREGON No. 3 
seen in the illustration is also similar in 
Aulocetus. 
The mysticete-like features of the new spe-
cies are not confined to the skull alone. The 
vertebral formula, closely coincides with that 
of Cetotherium furlongi Kellogg ( l 925A). 
This early Miocene cetothere had seven cervi-
cals, twelve dorsals, ten lumbars, and twelve 
caudals. The strong projection of the anterior 
edges of the antero-posteriorly broad trans-
verse processes of the lumbar, and anterior 
caudal vertebrae is also a prominent feature 
on the lumbar, and anterior caudal vertebrae 
of Cetotherium furlongi. The antero-posterior 
elongation of the low neural spines is another 
cetothere-like feature present on the vertebrae 
of the new cetacean. The low neural canals, and 
their transverse broadness on the cervical, and 
anterior dorsal vertebrae are other major fea-
tures suggestive of the mysticetes. The well-
marked depressions present on the distal por-
tions of the transverse processes of the ninth 
and tenth lumbar, and first and second caudal 
vertebrae are unusual among the typical ceta-
cea, and may indicate that the pelvis was better 
developed than on some modernized cetaceans. 
The transverse processes on the sacral verte-
brae of the archaeocete Basilosaurus cetoides 
bear slight modifications to accommodate the 
pelvis ( Kellogg 1936). Most cetotheres appar-
ently possessed only twelve pairs of ribs. The 
modernized mysticete, N eobalena marginata 
possessed seventeen pairs ( Kellogg 1928) . 
This cetacean possessed at least fifteen pairs, 
and the archaeocetes Basilosaurus cetoides, and 
Zygorhiza kochii both possessed fifteen pairs 
of ribs ( Kellogg 1936). Odontocetes, such as 
the porpoise Ker.triodon pernix (Kellogg 
1927) possessed only eight pairs. The porpoise 
Eurhinodelphis bossi Kellogg ( l 925B) prob-
ably had eleven pairs, according to Kellogg. 
The manubrium of Aetiocetus bears a strong 
resemblance to the manubrium of Basilosaurus 
cetoides. 
When comparisons are made between this 
cetacean, and other cetaceans referred to the 
Archaeoceti, it must be remembered that to 
date, our knowledge of this suborder has been 
almost exclusively limited to Eocene forms. 
No Oligocene archaeocete skull has previously 
been described, and only a few, generally frag-
mentary bones and teeth are known from de-
posits later than Eocene. Few major conclu-
sions can be drawn from this scanty material. 
The form of the entire squamosal bone of 
Aetiocetus is essentially primitive and more 
resembles the same bone on Eocene archaeocete 
skulls, such as Zygorhiza kochii, and Basilo-
saurus cetoides than the squamosal of modern-
ized cetaceans. On cetothere skulls, the inner 
ventral portion of the squamosal ( anterior to 
the root of the zygoma) is expanded laterally. 
This region is less developed on the new ceta-
cean skull, and is quite similar to that region on 
Eocene archaeocete skulls. The foramen ovale 
is not exposed on ventral views of early archae-
ocete skulls, and the same is the case on the 
Aetiocetus skull. The foramen ovale on early 
archaeocete skulls is obscured to ventral view 
by the downward projecting falciform process 
of the squamosal, also a feature of the Aetio-
cetus skull. On cetothere skulls, the foramen 
ovale is prominently exposed to ventral view, 
and the squamosal does not project strongly 
downward on the inner edge of this foramen. 
The postglenoid process of cetothere skulls is 
more robust than on the new cetacean skull. 
The glenoid fossa of this cetacean is more 
similar to that on Eocene archaeocetes, than 
to modernized Cetacea, but is more strongly 
developed than on early archaeocetes. It is 
deeper and wider transversely, and antero-
posteriorly. The postglenoid process has the 
general shape typical of the Archaeoceti, being 
relatively thin antero-posteriorly, with a 
strongly downward curved projection (see 
Zygorhiza kochii Kellogg 1936). The contact 
of the zygoma with the jugal differs on Eocene 
archaeocetes, but as was already mentioned, 
the narrow anterior termination of the zygoma 
is a feature of older archaeocetes, as well as a 
feature of the new species. The close under-
riding of the zygoma beneath the postorbital 
projection of the frontal, and the peculiarities 
1966 EMLONG: A NEW ARCHAIC CETACEAN 47 
of the jugal on the Aetiocetus skull are prob-
ably mainly the result of the constriction of the 
intertemporal region, and the downward com-
pression of the frontal. The lambdoid crest of 
the Aetiocetus skull does not flare backward 
as strongly as on skulls of Eocene archaeocetes, 
but the rounded supraoccipital is characteristic 
of early archaeocetes. 
The posterior dorsal terminations of the 
maxillaries, premaxillaries, and nasal bones 
are similar in general form, and position to 
the same bones on Eocene archaeocete skulls, 
except that they have telescoped backward on 
the Aetiocetus skull. The same V-shaped hump 
comprises the posterior extensions of these 
bones, on the new cetacean skull, as is present 
on earlier archaeocete skulls. The posterior 
dorsal portions of the maxillaries of Zygorhiza 
kochii narrow posteriorly and are almost iden-
tical in shape to those on the Aetiocetus skull. 
It should be particularly emphasized that both 
the dorsal and the ventral terminations of the 
maxillaries, plus the general basic shape and 
position of the premaxillaries, and the elon-
gated nasal bones on the Aetiocetus skull have 
the same basic configuration as is present on 
Eocene archaeocete skulls, and that these same 
general features are present on mysticete 
skulls, with the exception that they are tele-
scoped backward on mysticete skulls, and the 
infraorbital process is completely fused to the 
under-surface of the frontal. On some Eocene 
archaeocete skulls, the posterior portions of 
the nasal, and premaxillary bones terminate 
slightly anterior to the posterior ends of the 
maxillaries, differing from Aetiocetus, and 
most mysticetes. However, these minor dissimi-
larities are not comparable to the radical de-
partures in the form of these bones on modern-
ized odontocete skulls, such as the much short-
ened nasal bones, and the dorsal posterior 
broadening of the maxillaries. 
The palatines, pterygoids and vomer on the 
Aetiocetus skull have undergone much modi-
fication, and are located much further back on 
the skull than are these bones on Eocene archae-
ocete skulls. A large pterygoid fo::da is devel-
oped on the skull of the archaeocete Dorudon 
( Kellogg 1936), and is suggestive of mysticete 
affiliation according to Kellogg ( 1936). As was 
before mentioned, the pterygoid fossa is devel-
oped on the new cetacean skull, but it is more 
similar in shape to the pterygoid fossa on 
cetothere skulls than to that feature on the 
Dorudon skull, the fossa being very long, and 
narrow antero-posteriorly on the Dorudon 
skull. The anteriorly broadened, and antero-
posteriorly elongated palatines on the Aetio-
cetus skull are similar to those bones on ceto-
there skulls except that the posterior termi-
nations of the palatines on the new cetacean 
skull retain the transversely narrowed V-shape 
characteristic of earlier archaeocetes. The form 
of the exoccipital, and its relation to the squa-
mosal, on the A etiocetus skull is similar to the 
corresponding features on the skull of Basilo-
saurus cetoides. Basilosaurus has a well devel-
oped paraoccipital process, as does the new 
cetacean. The external· auditory channel is 
very similarly proportioned on both these 
skulls, and the posterior process of the periotic 
on the Basilosaurus and Aetiocetus skulls has 
a similar shape, and also very similar relation-
ship with the auditory channel. The posterior 
process of the periotic is slightly longer, and 
broader, however, on the new cetacean skull. 
The postero-external wall of the external audi-
tory channel on the Aetiocetus skull is formed 
by a protuberant, dorso-ventrally directed, 
ridge of the squamosal. This ridge is differen-
tiated both anteriorly, and posteriorly, being 
distinct from the postglenoid process anteri-
orly, and is very distinct from the exoccipital, 
posteriorly. This feature is similarly developed 
on Basilosaurus, but is not on the Agorophii-
dae, or most modernized Cetacea. 
The upper portions of the occipital condyles 
of Eocene archaeocetes are widely separated. 
This is also the case on the new cetacean skull. 
The jugal on all known archaeocete skulls 
extends behind the level of the postorbital pro-
jection of the frontal, and the same is the case 
on the A etiocetus skull. Other known archaeo-
cetes have ten teeth in each upper jaw, whereas 
48 BULLETIN, MUSEUM OF NATURAL HISTORY, UNIVERSITY OF OREGON No. 3 
the new cetacean has eleven. The postorbital 
projections of the frontals are strongly devel-
oped on most Eocene archaeocete skulls, as is 
the case on the A etiocetus skull. On Eocene 
archaeocetes, a narrow process of the pre-
maxillary extends posteriorly on the median 
ventral surface of the skull, to a point well 
behind the outer posterior ventral terminations 
of the premaxillaries. This feature is strongly 
developed on the Aetiocetus skull. Due to the 
fewer dorsal, lumbar, and caudal vertebrae, 
Aetiocetus was quite obviously much shorter 
in relative body proportion than the long 
bodied archaeocetes, such as Basilosaurus 
( Kellogg 1936). The lumbars and caudals of 
Basilosaurus are much more elongate than are 
those vertebrae of the new cetacean. The lum-
bars and anterior caudals of Zygorhiza kochii, 
a short bodied zeuglodont ( Kellogg 1936), are 
shorter antero-posteriorly than are those verte-
brae of Aetiocetus. However, Zygorhiza pos-
sessed seven cervicals, fifteen dorsals, fifteen 
lumbars, and twenty one caudals, and was ap-
parently slightly longer in relative body pro-
portion than Aetiocetus. The new cetacean was 
probably much fatter dorso-ventrally than the 
early archaeocetes, and perhaps more re-
sembled the mysticetes in post-crainial body 
form, due to the heavy construction of the low, 
antero-posteriorly elongate neural spines, the 
relatively large size of the centra of the lumbar 
and caudal vertebrae, and also the dense bone 
structure of the relatively long middle ribs. 
The skull of Aetiocetus is small in proportion 
to body length when compared to the mysti-
cetes, which have large crainia relative to the 
rest of the body, hut the new cetacean skull is 
relatively larger in proportion to the rest of the 
body when compared to other archaeocetes. 
TAXONOMIC POSITION 
Five widely divergent genera of the families 
Agorophiidae, Patriocetidae and Microzeuglo-
dontidae have the typical zygoma-jugal rela-
tionship of the odontocetes. This, in conjunc-
tion with the other differentiating features must 
he full considered when comparisons are made 
between Aetiocetus and archaic odontocetes. 
The zeuglodont-like lateral extension of the 
infraorhital process of the maxillary, and its 
direct parallel contact with the jugal, is re-
tained on the upper Oligocene Aetiocetus skull. 
This primitive relationship is not known on 
archaic odontocete skulls by upper Eocene 
times, nor is it present on later members of the 
line, such as the upper Oligocene Patriocetus. 
When these factors are considered together, 
they indicate that Aetiocetus was at least sepa-
rated from the typical odontocete line for a 
long time, and suggest the possibility that this 
cetacean may have descended from a some-
what different ancestoral stock. This differen-
tiation of the progenitors of the two stocks from 
one another may have occurred in the Archaeo-
ceti. The rate of evolution in the two stocks may 
have also differed. Kellogg (1936) referred 
to a statement by Stromer which suggested that 
the mysticete line may have been detached 
from the common stem before the appearance 
of the primitive archaeocete Protocetus. On the 
ventral side of the new cetacean skull, the 
ventral roofing of the posterior narial passage 
by the palatines and the hamular process of 
the pterygoids has been carried far posteriorly. 
This is also a feature of the Archaeoceti and 
Mysticeti. This feature is not well developed 
on any odontocete group except the Ziphidae, 
a modernized family of cetaceans far removed 
from Aetiocetus in other characteristics. The 
fact that this feature is not well developed on 
the more primitive odontocetes gives added 
evidence as to the long separation of the new 
cetacean from the odontocete line. 
I have two other well preserved skulls, and 
partial skeletons of Oligocene cetaceans. One 
of these (Emlong collection No. 240) is from 
the upper Oligocene Yaquina Formation, and 
the other is from the middle Oligocene Toledo 
Formation. (Emlong collection No. 80) Both 
these skulls have zygomatics which are almost 
identical to the zygomatic on the Aetiocetus 
skull. Both the other skulls have the same 
extremely narrow anterior termination of the 
zygomatic, which projects under, and closely 
1966 EMLONC: A NEW ARCHAIC CETACEAN 49 
approximates the postorbital projection of the 
frontal. The backward overthrust of rostral 
elements on these two skulls is less advanced 
than on the A etiocetus skull, and much less 
advanced than on any agorophiid skull. Other 
importance features are similar to those of this 
cetacean, but some features of these other two 
skulls such as the very narrow, and elongated 
intertemporal region on both skulls are very 
suggestive of the Archaeoceti. These skulls 
bear little resemblance to any known archaic 
cetacean other than Aetiocetus. The intertem-
poral regions, and zygomatics of Eocene agoro-
phiids are shortened, in contrast with these two 
Oligocene skulls. The teeth of these Oligocene 
skulls closely resemble the teeth of Aetiocetus. 
The undescribed Y aquina skull has a rostrum 
that is nearly as broad as the one possessed by 
Aetiocetus. The older skull has a much nar-
rower rostrum that is more similarly shaped 
to the rostra of Eocene archaeocetes. I plan to 
make detailed studies of both these specimens 
in the near future, and they will give added 
clarification to the relationships of the cetacean 
described in this report. 
The manner of implanation of the teeth in 
the very shallow alveoli at the outer edge of 
the extremely thin, fragile maxillaries indi-
cate that Aetiocetus may not have been adapted 
to the rigors necessary in procuring large prey. 
Some early sperm whales, such as ldiophyseter 
merriami Kellogg ( 1925 A) had teeth present 
in the upper jaws, and these teeth were appar-
ently implanted rather loosely in alveoli that 
slightly resemble those of the new cetacean. 
However, the alveoli of these early predaceous 
sperm whales do not extend to the outer edges 
of the maxillaries. The teeth probably did not 
slant outward to a great degree, and the edges 
of the maxillaries on these sperm whales are 
much thicker dorso-ventrally, and much better 
suited for stress. The large conical teeth of 
sperm whales are well suited for grasping large 
prey. The slight similarity of the alveoli 0£ 
Idiophyseter to those of this cetacean is con-
vergence because the crainial and skeletal fea-
tures of the new cetacean show no significant 
resemblance to those of sperm whales. The 
teeth in the upper jaws of Miocene sperm 
whales, such as Idiophyseter were reduced, and 
the living Physeter catodon has no distinct 
alveoli in the upper jaws. However, the loss of 
teeth in both jaws would not aid sperm whales 
because these whales are presently very well 
adapted to environment in their present feeding 
habits. 
Aetiocetus may have fed upon small fish, or 
other easily caught prey. The wear on some 
of the crowns suggests that they were subjected 
to considerable abrasion. Though possibly 
coincidental, numerous crab carapaces are 
present in the fine grained sandstone at the type 
locality. The food habits of this early cetacean 
could have been important to the direction of 
its evolutionary tendencies. For example, the 
consumption of easily caught prey, such as 
crustaceans, etc., rather than the pursuit of 
large, fast moving prey could help to establish 
tendencies toward adaptation of mysticete 
characteristics. 
Aulocetus sammarinensis is not necessarily 
a direct descendant of Aetiocetus. However, a 
continuation of the type of telescoping present 
on the Aetiocetus skull would lead to a cranium 
similar to that of Aulocetus. Aulocetus sam-
marinensis is from the early, or middle Mio-
cene of Italy. However, constriction of the 
supraoccipital shield would not be a difficult 
step. An upper Miocene cetothere Aulocetus 
latus was tentatively referred to the genus Aulo-
cetus by Kellogg ( 1940). The features of this 
skull, aside from the supraoccipital shield, are 
similar to those of the Aulocetus sammarinen-
sis skull, but the supraoccipital shield has the 
triangular shape characteristic of the majority 
of cetotheres. The shape of the supraoccipital 
shield is not among the most diagnostic of fea-
tures, and is extremely variable in some species 
of mammals because of factors such as age, 
sex, and individual variation. 
The zygoma-jugal form and relationship, 
and the form and relationship of the infra-
orbital plate of the maxillary differentiate 
Aetiocetus from all known agorophiids. These 
50 BULLETIN, MUSEUM OF NATURAL HISTORY, UNIVERSITY OF OREGON No. 3 
two major relationships also differentiate this 
cetacean from all odontocete groups other than 
the Agorophiidae. In view of the inconsisten· 
cies which would be present in the allocation 
of this form to the Agorophiidae, it seems ap-
propriate to erect a new family, the Aetioceti-
dae, for the reception of this cetacean. The 
placement of this new family within the sub-
order Odontoceti would not be consistent with 
either the advanced, or primitive features of 
the cranium, or skeleton of the species de-
scribed in this report. The presence of a func-
tional dentition on this mature specimen pre-
cludes allocation within the Mysticeti. The two 
previously mentioned major differentiating 
features of the zygoma-jugal form, and rela-
tionship, and the form, and relationship of the 
infraorbital plate of the maxillary are more 
primitive than those same bones on any known 
odontocete, or mysticete skull, and are strongly 
suggestive in many respects to those bone rela-
tionships on archaeocete skulls. In view of the 
presence of these features on a skull which is 
also strongly differentiated from odontocete 
skulls in many other respects, I am placing this 
family in the suborder Archaeoceti. This form 
is obviously far advanced when compared with 
other described archaeocete families, and the 
degree, and trend of telescoping of cranial 
bones, and any of the features of the skeleton 
are more suggestive of the Mysticeti than of the 
Archaeoceti. However, when all considerations 
are carefully evaluated, the most logical deduc-
tion is to regard this form as an aberrant late 
survivor of an archaeocete line, and a close 
antecedent to the Mysticeti. Future studies of 
the two undescribed Oligocene cetaceans men-
tioned in this report will add a great deal to our 
knowledge of this group. 
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Allen, G. M., 1921, A new fossil cetacean: Bull. Mus. 
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Harrison, G. H. and A. Eaton, 1920, Report on in-
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51 

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