Famoso, Nicholas

Permanent URI for this collection

https://hdl.handle.net/1794/30136

Browse

Now showing 1 - 18 of 18

Open Access
Re-evaluating hypertragulid diversity in the John Day basin, Oregon, USA
(Acta Palaeontologica Polonica, 2024-09-25) Famoso, Nicholas; Jewell, Lana K.
Despite their relative abundance, members of the family Hypertragulidae (Artiodactyla, Mammalia) have proved a conundrum regarding species diversity in the Turtle Cove Member (Oligocene) of the John Day Formation, located in central and eastern Oregon. Three species and two separate genera are described in the area, but previous research lacks statistical support for this level of variation. We use coefficients of variation (V) on measurements of dentition and astragali of hypertragulid specimens designated Hypertragulus hesperius, Hypertragulus minutus, and Nanotragulus planiceps as a metric for determining whether there were multiple species present in the population. Asymptotic and modified signed-likelihood ratio V equality tests show that V values of anterior-posterior molar length and transverse molar width vary significantly when comparing single species of modern ecological analogs (Muntiacus muntjak, Muntiacus reevesi, and Tragulus javanicus) to groupings of a combined population. However, the V equality tests on dental and postcranial measurements yield almost no significant results when comparing variation in the extinct John Day hypertragulids to an extant population comprised of a single species. Similar comparisons between astragali measurements of hypertragulids and T. javanicus express no significant difference in the level of variation from the combined population to a modern single species. The low level of variation in the hypertragulids and the lack of differentiation between dental characters of individuals does not statistically support the hypothesis that there were multiple species present in the population, suggesting either that cryptic species may be present but impossible to identify without soft tissue remains, or there may have been taxonomic over-splitting of a single hypertragulid species in the John Day region.
Open Access
Discovery of Oligocene-aged mammals in Glacier National Park (Kishenehn Formation), Montana
(Geodiversitas, 2024-06-24) Famoso, Nicholas; Calede, Jonathan J., 1988-; Kehl, Winifred A.; Constenius, Kurt N.
The Kishnehn Formation crops out in Glacier National Park of northwest Montana where a rich fossil record of plant macrofossils, pollen and spores, insects, terrestrial and aquatic mollusks, and fish has been unearthed. Past research has also described an extensive mammal fauna from the Eocene (Uintan-Chadronian). Oligocene-aged fossil mammals have been reported before, but none has ever been published in the peer-reviewed literature. Here, we present the first Arikareean-aged fossil mammals from the Kishenehn Formation, the youngest fossil mammals ever discovered in the park. The fossils consist of a set of lower jaws of the leptomerycid Pronodens transmontanus (Douglas, 1903) and a partial lower jaw of the rodent Paciculus montanus Black, 1961, both endemics of the northern Rocky Mountains. These new fossils enable us to explore the morphological variation in Pronodens Koerner, 1940 and Paciculus Cope, 1879. Our analyses suggest the existence of a single widely distributed and sometimes locally abundant species of Pronodens, which may co-occur with a rare and very large second species. Our revised diagnoses for the genus and species show the need for additional work on this little-studied artiodactyl genus. Similar efforts on the systematics of cricetid rodents will benefit from building upon our analysis of tooth morphology in Paciculus to shed light on the rise of leidymines. The last fossil we describe, partial paired dentaries of Miohippus Marsh, 1874, is the northern-most occurrence of the genus in the Rocky Mountains and shows the potential for future work in the Kishenehn Formation to enable the study of faunal change across the Eocene-Oligocene boundary in the northern Rocky Mountains.
Open Access
First occurrences of Palaeogale von Meyer, 1846 in the Pacific Northwest, United States
(Geodiversitas, 2022-04-08) Famoso, Nicholas; Orcutt, John D.
The feliform carnivoran Palaeogale von Meyer, 1846 first appears in the Eocene of North America and had a Holarctic distribution in the Oligocene and early Miocene. Despite its large range, Palaeogale has not previously been reported from the Pacific Northwest of North America. We report three new specimens from the John Day Basin of Oregon that fill in this geographic gap. The oldest of these is a largely complete cranium from the Turtle Cove Member of the John Day Formation (Oligocene, 30.0-28.9 Ma). The other two specimens are a left and a right dentary from separate individuals, both recovered from the Kimberly Member (Oligocene, 25.3-23.5 Ma). Because Palaeogale species are almost entirely distinguished by their lower dentition, the cranium cannot be identified to species. However, the cranium is the oldest occurrence of the genus in the Pacific Northwest. The absence of a posterior accessory cusp on the p4 and of lateral expansion of the m1 protoconid allows the dentaries to be assigned to an endemic North American species, P. dorothiae MacDonald, 1963. This is not only the first instance of this species in the Pacific Northwest and outside of South Dakota and Nebraska, but also the last known occurrence of P. dorothiae. We expect that these specimens will inform future analyses of phylogenetics, systematics, morphology, and biogeography in Palaeogale.
Open Access
From public lands to museums: The foundation of U.S. paleontology, the early history of federal public lands and museums, and the developing role of the U.S. Department of the Interior
(The Geological Society of America Special Papers, 2018-11-27) Liggett, Gregory A.; Childs, S. Terry; Famoso, Nicholas; McDonald, Gregory H.; Titus, Alan L.; Varner, Elizabeth; Liggett, Cameron L.
Today, the United States Department of the Interior manages 500 million acres of surface land, about one-fifth of the land in the United States. Since enactment of the Antiquities Act in 1906, historic and scientific resources collected on public land have remained government property, held in trust for the people of the United States. As a result, the Department of the Interior manages nearly 204 million museum objects. Some of these objects are in federally managed repositories; others are in the repositories of partner institutions. The establishment of the United States as a nation corresponded with the development of paleontology as a science. For example, mastodon fossils discovered at or near present-day Big Bone Lick State Historic Site, Kentucky, found their way to notable scientists both in the United States and in Europe by the mid-eighteenth century and were instrumental in establishing the reality of extinction. Public land policies were often contentious, but generally they encouraged settlement and use, which resulted in the modern pattern of federal public lands. Continued investigation for fossils from public land filled the nation’s early museums, and those fossils became the centerpieces of many museum exhibitions. Case studies of the management of fossils found in Fossil Cycad National Monument, the John Day fossil beds, the Charles M. Russell National Wildlife Refuge and surrounding areas of public land, the American Falls Reservoir, and Grand Staircase– Escalante National Monument are outlined. These examples provide a sense of the scope of fossils on federal public land, highlight how their management can be a challenge, and show that public land is vital for continued scientific collection and research.
Open Access
How do diet and body mass drive reproductive strategies in mammals?
(Biological Journal of the Linnean Society, 2018-04-19) Famoso, Nicholas; Hopkins, Samantha S.B.; Davis, Edward Byrd
Larger body size tends to lead to lower reproductive rates in mammals, but we do not understand how diet impacts this relationship. Reproductive strategies vary from K-selected (producing few offspring with extensive parental care) to r-selected (producing many offspring with little parental care). Here, we investigate how diet and body size impact the reproductive strategies of mammals within a phylogenetic framework using an index for reproductive strategy. For all diet categories we find larger mammals to be more K-selected. This relationship is significant for herbivores and omnivores, but not for carnivores, although the relationship for carnivores is comparable to that of herbivores and omnivores. The relationship is non-linear in carnivores and may be a consequence of differences between insect and vertebrate predators. Ultimately, the trend of more K-selected strategies with larger body size holds true for herbivores and omnivores, but different trajectories exist for carnivores depending on diet.
Open Access
Correction to the holotype (AMNH FM 9394) of Merychippus proparvulus Osborn, 1918 (Perissodactyla, Equidae)
(Journal of Vertebrate Paleontology, 2014-09-09) Famoso, Nicholas; Hopkins, Samantha S.B.
"Correction to the holotype (AMNH FM 9394) of Merychippus proparvulus Osborn, 1918 (Perissodactyla, Equidae)." Journal of Vertebrate Paleontology, 34(5), pp. 1249–1250
Open Access
A Comparison of the Clarendonian Equid Assemblages from the Mission Pit, South Dakota and Ashfall Fossil Beds, Nebraska
(University of Nebraska - Lincoln, 2011-11) Famoso, Nicholas; Pagnac, Darrin
The Mission Pit locality (SDSM V5314), near Mission, South Dakota, has produced a large collection of equid teeth obtained from the Miocene Ash Hollow (=Thin Elk) Formation. Ashfall Fossil Beds (UNSM Ap-116), near Royal, Nebraska, has yielded an extensive collection of equid cranial elements and teeth derived from the Cap Rock Member, Ash Hollow Formation. The two sites are interpreted to be Clarendonian in age [12.5 to 9.0 Ma], but may contain faunal assemblages from differing Clarendonian subages. The two sites exhibit a notably similar composition of equid genera, including the tribes Equini (Pliohippus, Calippus, and Protohippus), and Hipparionini (Cormohipparion, Neohipparion, and Pseudhipparion). Both sites share the same proportion of the equid tribes Hipparionini and Equini. Approximately seventy-five percent of the equids at both sites are members of the Hipparionini tribe, whereas twenty-five percent are of the Equini tribe. The comparative composition within the Equini tribe between the two sites is nearly identical with differences in the absence of Calippus at Ashfall and a larger proportion of Protohippus at Mission. Only slight differences are observed in the composition of genera within the Hipparionini tribe between the two sites, with the Mission Pit containing a higher percentage of Neohipparion. The striking taxonomic similarity between the two sites is not only unique but also rare, suggesting a correlative relationship within the early to medial Clarendonian (Cl1 or Cl2). This similarity also suggests unique paleoecological relationships among equids and has a potential for insight into plant ecology and equid niche partitioning during this time interval.
Open Access
Occlusal Enamel Complexity in Middle Miocene to Holocene Equids (Equidae: Perissodactyla) of North America
(PLOSone, 2014-02-27) Famoso, Nicholas; Davis, Edward Byrd
Four groups of equids, “Anchitheriinae,” Merychippine-grade Equinae, Hipparionini, and Equini, coexisted in the middle Miocene, but only the Equini remains after 16 Myr of evolution and extinction. Each group is distinct in its occlusal enamel pattern. These patterns have been compared qualitatively but rarely quantitatively. The processes influencing the evolution of these occlusal patterns have not been thoroughly investigated with respect to phylogeny, tooth position, and climate through geologic time. We investigated Occlusal Enamel Index, a quantitative method for the analysis of the complexity of occlusal patterns. We used analyses of variance and an analysis of co-variance to test whether equid teeth increase resistive cutting area for food processing during mastication, as expressed in occlusal enamel complexity, in response to increased abrasion in their diet. Results suggest that occlusal enamel complexity was influenced by climate, phylogeny, and tooth position through time. Occlusal enamel complexity in middle Miocene to Modern horses increased as the animals experienced increased tooth abrasion and a cooling climate.
Open Access
Occlusal enamel complexity and its implications for lophodonty, hypsodony, body mass, and diet in extinct and extant ungulates
(Palaeogeography, Palaeoclimatology, Palaeoecology, 2013-07-14) Famoso, Nicholas; Feranec, Robert S.; Davis, Edward B.
Tooth morphology and rates of wear have strong controls on how well mammals survive in their habitats. Herbivorous mammals, specifically ungulates, combat the effects of wear through a combination of changing the occlusal (chewing surface) enamel length, and changing hypsodonty (relative height of tooth). Changes in these two attributes are most notably seen in the fossil record of ungulates as they adapted to living in cooler, drier, and more open habitats. We expect enamel length and hypsodonty to be greater in ungulate taxa that feed on grasses than in non-grass feeders. We tested this hypothesis by digitally photographing 213 maxillary tooth rows from 84 species of extinct and extant ungulates (n = 1083 teeth) and measuring their occlusal enamel length and true occlusal area. We then statistically compared the influences of taxonomy, feeding strategy, tooth position, and tooth area on both hypsodonty and occlusal enamel length using principal components analysis (PCA) and a nested multivariate analysis of variance (MANOVA). The results of our PCA indicated a strong correlation between enamel length and tooth area, but little correlation of either with hypsodonty. Our nested MANOVA showed that tooth position had no significant relationship with hypsodonty (p = 0.1539), while all other factors were significant for both hypsodonty and occlusal enamel length. Our results suggest that the occlusal enamel length in ungulate teeth is constrained by both the size of the tooth (and, by proxy, the mass of the individual) and diet. Absolute tooth crown height is similarly affected by a combination of body size and diet, leading to the use of a ratio, hypsodonty index, to characterize the diet component. We propose a similar ratio, the occlusal enamel index (OEI) which reduces the effect of body mass to clearly indicate the component of enamel length determined by abrasiveness of ingested material.
Open Access
Are Hypsodonty and Occlusal Enamel Complexity Evolutionarily Correlated in Ungulates?
(Journal of Mammalian Evolution, Springer Link, 2015-05-13) Famoso, Nicholas; Davis, Edward Byrd; Feranec, Robert S.; Hopkins, Samantha S. B.; Price, Samantha A.
The spread of grasslands and cooling climate in the Miocene contributed to an increasingly abrasive diet for ungulates. This increase in abrasiveness is proposed to select for both hypsodonty and increasing complexity of occlusal enamel bands. If these traits evolved in response to strong selection to resist tooth wear while feeding in grassland habitats, we might expect them to have evolved in a correlated fashion. If, on the other hand, there was a developmental or physiological constraint, or if selection was not strong on total enamel production, we would expect species to have evolved one or the other of these traits at a time, producing an uncorrelated, or even inversely correlated, pattern of trait evolution. To test these hypotheses, we examined the Occlusal Enamel Index (OEI) and Hypsodonty Index (HI) of 773 ungulate teeth. We tested the dependence of OEI on HI for the orders Artiodactyla and Perissodactyla using phylogenetic generalized least squares regression (PGLS). The two traits are not significantly correlated in the PGLS, for Artiodactyla and Perissodactyla. Despite their physical proximity, close functional utility, and conventional correlation, our results reject the hypothesis that HI and OEI are evolutionarily linked in these lineages, suggesting that selection to resist tooth wear was not so strong as to drive the overall evolutionary trajectory of both these traits at the same time.
Open Access
On the relationship between enamel band complexity and occlusal surface area in Equids (Mammalia, Perissodactyla)
(PeerJ, 2016-07) Famoso, Nicholas; Davis, Edward Byrd
Enamel patterns on the occlusal surfaces of equid teeth are asserted to have tribal-level differences. The most notable example compares the Equini and Hipparionini, where Equini have higher crowned teeth with less enamel-band complexity and less total occlusal enamel than Hipparionini. Whereas previous work has successfully quantified differences in enamel band shape by dividing the length of enamel band by the square root of the occlusal surface area (Occlusal Enamel Index, OEI), it was clear that OEI only partially removes the effect of body size. Because enamel band length scales allometrically, body size still has an influence on OEI, with larger individuals having relatively longer enamel bands than smaller individuals. Fractal dimensionality (D) can be scaled to any level, so we have used it to quantify occlusal enamel complexity in a way that allows us to get at an accurate representation of the relationship between complexity and body size. To test the hypothesis of tribal-level complexity differences between Equini and Hipparionini, we digitally traced a sample of 98 teeth, one tooth per individual; 31 Hipparionini and 67 Equini. We restricted our sampling to the P3-M2 to reduce the effect of tooth position. After calculating the D of these teeth with the fractal box method which uses the number of boxes of various sizes to calculate the D of a line, we performed a t -test on the individual values of D for each specimen, comparing the means between the two tribes, and a phylogenetically informed generalized least squares regression (PGLS) for each tribe with occlusal surface area as the independent variable andDas the dependent variable. The slopes of both PGLS analyses were compared using a t -test to determine if the same linear relationship existed between the two tribes. The t -test between tribes was significant (p<0:0001), suggesting differentDpopulations for each lineage. The PGLS for Hipparionini was a positive but not significant (pD0:4912) relationship between D and occlusal surface area, but the relationship for Equini was significantly negative (p D 0:0177). was 0 for both tests, indicating no important phylogenetic signal is present in the relationship between these two characters, thus the PGLS collapses down to a non-phylogenetic generalized least squares (GLS) model. The t -test comparing the slopes of the regressions was not significant, indicating that the two lineages could have the same relationship between D and occlusal surface area. Our results suggest that the two tribes have the same negative relationship between D and occlusal surface area but the Hipparionini are offset to higher values than the Equini. This offset reflects the divergence between the two lineages since their last common ancestor and may have constrained their ability to respond to environmental change over the Neogene, leading to the differential survival of the Equini.
Open Access
Statistical analysis of dental variation in the Oligocene equid Miohippus (Mammalia, Perissodactyla) of Oregon
(Journal of Paleontology, Cambridge University Press, 2017-07-20) Famoso, Nicholas
As many as eight species of the “anchitherine” equid Miohippus have been identified from the John Day Formation of Oregon, but no statistical analysis of variation in these horses has yet been conducted to determine if that level of diversity is warranted. Variation of the anterior-posterior length and transverse width of upper and lower teeth of Turtle Cove Member Miohippus was compared to that of M. equinanus, Mesohippus bairdii, Equus quagga, and Tapirus terrestris using t tests of their coefficients of variation (V). None of the t tests are significant, indicating that the variation seen in Turtle Cove Miohippus is not significantly different from any of the populations of other perissodactyls examined in this study. Data also indicate that Mesohippus is present in the Turtle Cove Member. Additionally, hypostyle condition, used to diagnose all species of Miohippus, was found to be related to stage of wear using an ordered logistic regression. Only two species of equid, one Miohippus and one Mesohippus, in the Turtle Cove Member can be identified, therefore only Miohippus annectens, the genotype and first species described from the region, can be recognized as the sole Miohippus species known from the Turtle Cove assemblage. There are insufficient data to determine which species of Mesohippus is present. The dependence of hypostyle condition on crown height in Miohippus implies that wear stage must also be considered in investigations of dental morphology in the “Anchitheriinae.”
Open Access
Mammalian community response to historic volcanic eruptions
(Mammalian Biology, 2020-03-09) Famoso, Nicholas
It is clear that ecosystems are devastated after a volcanic eruption coats the landscape with a layer of ash; however, the ecological recovery of mammalian communities after eruptions is poorly understood. Volcanic eruptions vary with magnitude and type and only a fraction of them have been analysed for effects on mammalian communities. To better understand mammalian community recovery, I investigated how species richness, evenness, and similarity change across volcanic boundaries in the 1980 Mount Saint Helens (MSH), Washington, and 1914–1917 Mount Lassen, California, eruptions. I compared these eruptions to Mount Rainier, Washington and Mount Shasta, California as controls for regional changes in the fauna. Richness and evenness remain relatively unchanged in Lassen. MSH saw an immediate drop in richness, followed by an increase over 5 years to pre-eruptive levels. Chord distance analysis suggests no long-term change in the Lassen fauna. The pre- and post-MSH fauna are different from one another. The post-eruptive fauna was more similar to neighbouring regions. It is clear from my results that larger eruptions tend to have a greater impact on mammalian community recovery than smaller eruptions, but ultimately, mammalian populations are robust and the presence of neighbouring communities is important for recolonizing devastated areas.
Open Access
Paleobiology of a large mammal community from the late Pleistocene of Sonora, Mexico
(Cambridge University Press, 2021) Short, Rachel A.; Emmert, Laura G.; Famoso, Nicholas; Martin, Jeff M.; Mead, Jim I.; Swift, Sandy L.; Baez, Arturo
A paleontological deposit near San Clemente de Térapa represents one of the very few Rancholabrean North American Land Mammal Age sites within Sonora, Mexico. During that time, grasslands were common, and the climate included cooler and drier summers and wetter winters than currently experienced in northern Mexico. Here, we demonstrate restructuring in the mammalian community associated with environmental change over the past 40,000 years at Térapa. The fossil community has a similar number of carnivores and herbivores whereas the modern community consists mostly of carnivores. There was also a 97% decrease in mean body size (from 289 kg to 9 kg) because of the loss of megafauna. We further provide an updated review of ungulates and carnivores, recognizing two distinct morphotypes of Equus, including E. scotti and a slighter species; as well as Platygonus compressus; Camelops hesternus; Canis dirus; and Lynx rufus; and the first regional records of Palaeolama mirifica, Procyon lotor, and Smilodon cf. S. fatalis. The Térapa mammals presented here provide a more comprehensive understanding of the faunal community restructuring that occurred in northern Mexico from the late Pleistocene to present day, indicating further potential biodiversity loss with continued warming and drying of the region.
Open Access
Microtomography of an enigmatic fossil egg clutch from the Oligocene John Day Formation, Oregon, USA, reveals an exquisitely preserved 29-million-year-old fossil grasshopper ootheca
(Parks Stewardship Forum, 2024) Lee, Jaemin; Famoso, Nicholas; Lin, Angela
Eggs are one of the least understood life stages of insects, and are poorly represented in the fossil record. Using microtomography, we studied an enigmatic fossil egg clutch of a presumed entomological affinity from the Oligocene Turtle Cove Member, John Day Formation, from the National Park Service-administered lands of John Day Fossil Beds National Monument, Oregon. A highly organized egg mass comprising a large clutch size of approximately 50 slightly curved ellipsoidal eggs arranged radially in several planes is preserved, enclosed in a disc-shaped layer of cemented and compacted soil particles. Based on the morphology of the overall structure and the eggs, we conclude that the specimen represents a fossilized underground ootheca of the grasshoppers and locusts (Orthoptera: Caelifera), also known as an egg pod. This likely represents the oldest and the first unambiguous fossil evidence of a grasshopper egg pod. We describe Subterroothecichnus radialis igen. et isp. nov. and Curvellipsoentomoolithus laddi oogen. et oosp. nov., representing the egg pod and the eggs, respectively. We advocate for adopting ootaxonomy in studying fossil eggs of entomological affinities, as widely practiced with fossil amniotic eggs. An additional 26 individual and clustered C. laddi collected throughout the A–H subunits of the Turtle Cove Member suggest the stable presence of grasshoppers in the Turtle Cove fauna, and we discuss the paleoecological implications. Oothecae have convergently evolved several times in several insect groups; this ovipositional strategy likely contributed to the fossilization of this lesser-known ontogenetic stage, enriching our understanding of past insect life.
Open Access
New occurrences of mammals from McKay Reservoir (Hemphillian, Oregon)
(Journal of Paleontology, 2024-05-07) Orcutt, John D.; Schmer, Christiana J.; Lubisich, Jeffrey P.; Abrams, Lacy T.; Famoso, Nicholas
Encompassing global cooling, the spread of grasslands, and biogeographic interchanges, the Hemphillian North American Land Mammal Age is an important interval for understanding the factors driving ecological and evolutionary change through time. McKay Reservoir near Pendleton, Oregon is a natural laboratory for analyses of these factors. It is remarkable for its small vertebrate fauna including rodents, bats, turtles, and lagomorphs, but also for its larger mammal fossils like camelids, rhinocerotids, canids, and felids. Despite the importance of the site, few revisions to its faunal list have been published since its original description. We expand on this description by identifying taxa not previously known from McKay Reservoir based on specimens collected during fieldwork and through reidentification of previously collected fossils. Newly identified taxa include the borophagine canid Borophagus secundus (Matthew and Cook, 1909), the camelids Megatylopus Matthew and Cook, 1909 and Pleiolama Webb and Meachen, 2004, a dromomerycid, and the equids Cormohipparion Skinner and MacFadden, 1977 and Pseudhipparion Ameghino, 1904. Specimens previously assigned to Neohipparion Gidley, 1903 and Hipparion de Christol, 1832 lack the features necessary to diagnose these genera, which are therefore removed from the site's faunal list. The presence of Borophagus secundus, Cormohipparion, and Pseudhipparion is especially important, because each occurrence represents a major geographic range extension. This refined understanding of the fauna lays the foundation for future studies of taphonomy, taxonomy, functional morphology, and paleoecology—potentially at the population, community, or ecosystem levels—at this paleobiologically significant Miocene locality.
Open Access
Mammalian Community Recovery from Volcanic Eruptions in the Cenozoic of North America
(University of Oregon, 2017-09-27) Famoso, Nicholas; Davis, Edward
It is clear that ecosystems are devastated after a volcanic eruption coats the landscape with a layer of ash; however, the ecological recovery of mammalian communities after eruptions is poorly understood. Volcanic eruptions vary with magnitude and type and only a fraction of them have been analyzed for effects on mammalian communities. To better understand mammalian community recovery, I investigated three different lines of evidence. First, I created a new numeric metric for statistically analyzing reproductive strategies in mammals and tested the impact of diet and body size on reproductive strategies within a phylogenetic framework as proof of concept. The trend of lower reproductive rates and larger body size hold true for herbivores and omnivores, but different trajectories exist for carnivores. Second, I investigated how species richness, evenness, and similarity change across volcanic boundaries in the 1980 Mount St. Helens (MSH), Washington, and 1914-1917 Mount Lassen, California, eruptions. Richness and evenness remain unchanged in Lassen. MSH saw an immediate drop in richness followed by an increase over five years to pre-eruptive levels. Chord distance analysis suggests no long-term change in the Lassen fauna. The pre- and post-MSH fauna are different from one another. The post-eruptive fauna was more similar to neighboring regions. Lastly, I tested whether the Oligocene horse Miohippus demonstrated morphological changes across the volcanic Picture Gorge ignimbrite (PGI; 29.069 Ma) in the John Day Formation of Oregon. Variation in upper and lower teeth was first tested to define a single species in the assemblage. Length, width, and wear of teeth were compared across the PGI and there were no significant differences between pre- and post-PGI assemblages. It is clear from my results that larger eruptions tend to have a greater impact on mammalian community recovery than smaller eruptions, but ultimately, mammalian populations are robust and the presence of neighboring communities is important for recolonizing devastated areas. There are two supplemental files associated with this dissertation, a CSV file of raw data downloaded for Chapter III and an excel file of raw data and coefficient of variation calculations for Chapter IV. This dissertation includes both unpublished and co-authored material.
Open Access
The Evolution of Occlusal Enamel Complexity in Middle Miocene to Recent Equids (Mammalia: Perissodactyla) of North America
(University of Oregon, 2013-10-03) Famoso, Nicholas; Davis, Edward
Four groups of equids, "Anchitheriinae," Merychippine-grade Equinae, Hipparionini, and Equini, coexisted in the middle Miocene, and only the Equini remains after 16 million years of evolution and extinction. Each group is distinct in its occlusal enamel pattern. These patterns have been compared qualitatively but rarely quantitatively. The processes controlling the evolution of these occlusal patterns have not been thoroughly investigated with respect to phylogeny, tooth position, and climate through geologic time. I investigated two methods of quantitative analysis, Occlusal Enamel Index for shape and fractal dimensionality for complexity. I used analyses of variance and an analysis of co-variance to test hypotheses of process. Results suggest that enamel shape was controlled by phylogeny, tooth position, and climate. The lower taxonomic levels are shown to have a strong effect on complexity, suggesting behavior is driving complexity rather than overarching phylogenetic constraint.

Browse

Browsing Famoso, Nicholas by Most Recent

Results Per Page

Sort Options