Department of Earth Sciences

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https://hdl.handle.net/1794/9581

Beginning September 1, 2016 the department changed its name from the Department of Geological Sciences to the Department of Earth Sciences.

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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
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
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
Inequalities of ice loss: a framework for addressing sociocryospheric change
(Cambridge University Press, 2023-05-12) Carey, Mark; Moulton, Holly
Cryospheric change occurs in unequal spaces. Societies living near ice are divided by race, class, gender, geography, politics and other factors. Consequently, impacts of ice loss are not shared equally, and everyone experiences cryospheric changes differently. Responsibility for recent ice loss is also driven by a relatively small portion of humanity: those who emit the most greenhouse gases. Additionally, people who study the cryosphere come from institutions and societies where inequality is often systemic, making research on ice and snow a symptom of and contributor to social inequality. To better understand unequal effects of cryospheric change within and across diverse communities, including research communities, this paper focuses on three areas, drawing primarily from glacier-related work: (1) the social context of cryospheric changes; (2) attribution and responsibility for cryospheric changes and (3) imbalances in knowledge about the cryosphere. Addressing these dimensions of ice loss requires transdisciplinary approaches that connect research to societies and link glaciology and other cryospheric sciences with social sciences and humanities. These concepts, cases and suggestions to help address inequalities also reveal that no singular conceptualization of sustainability exists. Different societies, residents and researchers possess distinct understandings of and goals for ‘ice in a sustainable society’.
Open Access
Accumulation of radiocarbon in ancient landscapes: A small but significant input of unknown origin
(Nature Communications, 2023-05-08) Broz, Adrian; Aguilar, Jerod; Xu, Xiaomei; Silva, Lucas C. R.
The persistence of organic carbon (C) in soil is most often considered at timescales ranging from tens to thousands of years, but the study of organic C in paleosols (i.e., ancient, buried soils) suggests that paleosols may have the capacity to preserve organic compounds for tens of millions of years. However, a quantitative assessment of C sources and sinks from these ancient terrestrial landscapes is complicated by additions of geologically modern (~ 10 Ka) C, primarily due to the infiltration of dissolved organic carbon. In this study, we quantified total organic C and radiocarbon activity in samples collected from 28- to 33-million-year-old paleosols that are naturally exposed as unvegetated badlands near eastern Oregon’s “Painted Hills”. We also used thermal and evolved gas analysis to examine the thermodynamic stability of different pools of C in bulk samples. The study site is part of a ~ 400-m-thick sequence of Eocene–Oligocene (45–28 Ma) paleosols, and thus we expected to find radiocarbon-free samples preserved in deep layers of the lithified, brick-like exposed outcrops. Total organic C, measured in three individual profiles spanning depth transects from the outcrop surface to a 1-m depth, ranged from 0.01 to 0.2 wt% with no clear C-concentration or age-depth profile. Ten radiocarbon dates from the same profiles reveal radiocarbon ages of ~ 11,000–30,000 years BP that unexpectedly indicate additions of potentially modern organic C. A two-endmember mixing model for radiocarbon activity suggests that modern C may compose ~ 0.5–2.4% of the total organic C pool. Thermal and evolved gas analysis showed the presence of two distinct pools of organic C, but there was no direct evidence that C compounds were associated with clay minerals. These results challenge the assumption that ancient badland landscapes are inert and “frozen in time” and instead suggest they readily interact with the modern C cycle.
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
Direct measurement of optical properties of glacier ice using a photon-counting diffuse LiDAR
(Cambridge University Press, 2022-04) Allgaier, Markus; Cooper, Matthew G.; Carlson, Anders E.; Cooley, Sarah W.; Ryan, Jonathan C.; Smith, Brian J.
The production of meltwater from glacier ice, which is exposed at the margins of land ice during the summer, is responsible for a large proportion of glacier mass loss. The rate of meltwater production from glacier ice is especially sensitive to its physical structure and chemical composition which combine to determine the albedo of glacier ice. However, the optical properties of near-surface glacier ice are not well known since most prior work has focused on laboratory-grown ice or deep cores. Here, we demonstrate a measurement technique based on diffuse propagation of nanosecond-duration laser pulses in near-surface glacier ice that enables the independent measurement of the scattering and absorption coefficients, allowing for a complete description of the processes governing radiative transfer. We employ a photon-counting detector to overcome the high losses associated with diffuse optics. The instrument is highly portable and rugged, making it optimally suited for deployment in remote regions. A set of measurements taken on Crook and Collier Glaciers, Oregon, serves as a demonstration of the technique. These measurements provide insight into both physical structure and composition of near-surface glacier ice and open new avenues for the analysis of light-absorbing impurities and remote sensing of the cryosphere.
Open Access
Seeing the forest for the trees through metabolic scaling
(Oxford Academic, 2022-03-10) Volkov, Igor; Tovo, Anna; Anfodillo, Tommaso; Rinaldo, Andrea; Maritan, Amos; Banavar, Jayanth R.
We demonstrate that when power scaling occurs for an individual tree and in a forest, there is great resulting simplicity notwithstanding the underlying complexity characterizing the system over many size scales. Our scaling framework unifies seemingly distinct trends in a forest and provides a simple yet promising approach to quantitatively understand a bewilderingly complex many-body system with imperfectly known interactions. We show that the effective dimension, Dtree, of a tree is close to 3, whereas a mature forest has Dforest approaching 1. We discuss the energy equivalence rule and show that the metabolic rate–mass relationship is a power law with an exponent D/(D + 1) in both cases leading to a Kleiber’s exponent of 3/4 for a tree and 1/2 for a forest. Our work has implications for understanding carbon sequestration and for climate science.
Open Access
The largest hoplophonine and a complex new hypothesis of nimravid evolution
(Nature Research, 2021-10) Barrett, Paul Zachary
Nimravids were the first carnivorans to evolve saberteeth, but previously portrayed as having a narrow evolutionary trajectory of increasing degrees of sabertooth specialization. Here I present a novel hypothesis about the evolution of this group, including a description of Eusmilus adelos, the largest known hoplophonine, which forces a re-evaluation of not only their relationships, but perceived paleoecology. Using a tip-dated Bayesian analysis with sophisticated evolutionary models, nimravids can now be viewed as following two paths of evolution: one led to numerous early dirk-tooth forms, including E. adelos, while the other converged on living feline morphology, tens of millions of years before its appearance in felids.
Open Access
A record of vapour pressure deficit preserved in wood and soil across biomes
(Nature Research, 2021-01-12) Broz, Adrian; Retallack, Gregory J.; Maxwell, Toby M.; Silva, Lucas C. R.
The drying power of air, or vapour pressure deficit (VPD), is an important measurement of potential plant stress and productivity. Estimates of VPD values of the past are integral for understanding the link between rising modern atmospheric carbon dioxide (pCO2) and global water balance. A geological record of VPD is needed for paleoclimate studies of past greenhouse spikes which attempt to constrain future climate, but at present there are few quantitative atmospheric moisture proxies that can be applied to fossil material. Here we show that VPD leaves a permanent record in the slope (S) of least-squares regressions between stable isotope ratios of carbon and oxygen (13C and 18O) found in cellulose and pedogenic carbonate. Using previously published data collected across four continents we show that S can be used to reconstruct VPD within and across biomes. As one application, we used S to estimate VPD of 0.46 kPa ± 0.26 kPa for cellulose preserved tens of millions of years ago—in the Eocene (45 Ma) Metasequoia from Axel Heiberg Island, Canada—and 0.82 kPa ± 0.52 kPa—in the Oligocene (26 Ma) for pedogenic carbonate from Oregon, USA—both of which are consistent with existing records at those locations. Finally, we discuss mechanisms that contribute to the positive correlation observed between VPD and S, which could help reconstruct past climatic conditions and constrain future alterations of global carbon and water cycles resulting from modern climate change.
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
Novel analysis of locality data can inform better inventory and monitoring practices for paleontological resources at John Day Fossil Beds National Monument Oregon, USA
(Palaeontologia Electronica, 2020-04) Famoso, Nicholas; Kort, Anne E.
We evaluated the current inventory and monitoring practices at John Day Fossil Beds National Monument (JODA) with an analysis of fossil yield based on locality data. While JODA covers a range of fossiliferous Cenozoic rock, most paleontological fieldwork conducted by the park staff occurs in the highly fossiliferous Oligocene Turtle Cove Member of the John Day Formation. To optimize the number of fossils collected, JODA established a schedule that cycled fieldwork every four years between the five most fossiliferous areas of the park. We digitized over 1000 field collections from 1999- 2019 to evaluate whether the four-year return interval allowed enough time for new fossils to be exposed through erosion in an area between visits as intended by the schedule. We found no significant difference in fossil yield between areas that had not been visited for 1, 2, 3, 4, or 5+ years. Based on these results, we infer that the claystones of the Turtle Cove Member are erodible and fossiliferous enough that one winter of erosion will expose enough fossils to fully “recharge” an area that had been thoroughly inventoried the previous year. Because of limited staff and high fossil yield, not every fossil will be collected. Therefore, we use this analysis to shift JODA’s paleontological inventory and monitoring practices away from a rigid schedule and propose a flexible new system. The paleontology staff will use a tracker geodatabase of locality data from past years to set priorities each year based on past collection and current available staff and space.
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
First mesonychid from the Clarno Formation (Eocene) of Oregon, USA
(Palaeontologia Electronica, 2019-06) Robson, Selina V.; Famoso, Nicholas; Davis, Edward Byrd; Hopkins, Samantha S.B.
A recently identified left dentary of Harpagolestes cf. uintensis represents the first mesonychid material known from the Pacific Northwest. The specimen is from the Hancock Quarry (Clarno Unit, John Day Fossil Beds National Monument), which is in the uppermost subunit of the Clarno Formation (middle Eocene, ~40 Ma). The sediments of the Hancock Quarry were deposited by a meandering river system during the middle Eocene when north-central Oregon had a subtropical climate. As with many other mammals from the Hancock Quarry, Harpagolestes participated in an Asian-North American faunal interchange; species of Harpagolestes are known from the Eocene of both continents. Harpagolestes was carnivorous, and members of the genus were likely bone-crushers. Characteristic bone-crushing wear is visible on the occlusal surfaces of the Hancock Quarry specimen’s premolars and molars. With the aid of CT scans, it has been determined that the Hancock Quarry Harpagolestes contains the alveoli for c1, p1-2, and m3, and preserves the crowns of p3-4 and m1-2. The molariform teeth have a large, conical trigonid with a bulbous talonid. The protoconid of p3 and p4 is tilted posteriorly. This specimen of Harpagolestes cf. uintensis represents a new large carnivore in the Hancock Quarry ecosystem, adds to the known diversity of the Oregon middle Eocene, and is the only known occurrence of a mesonychid in the Pacific Northwest.
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
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
Paleosol data from Kenya.
(2016-11-21) Retallack, Greg J.
Data collected in several areas of Kenya with Cenozoic deposits well known for fossil mammals, including islands and shores of Lake Victoria, the central and southern Gregory Rift, and the basin of Lake Turkana. Data are largely measurements of key characteristics of fossil soils (paleosols) in the field: depth to the carbonate (Bk) horizon, thickness of the carbonate (Bk) horizon and size of the carbonate nodules.
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.

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