Browsing by Author "Cote, Susanne"
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Item Open Access Additional hominoid fossils from the early Miocene of the Lothidok Formation, Kenya(Wiley, 2022-07-24) Rossie, B. James; Cote, SusanneObjectives: Hominoid fossils are abundant at early Miocene fossil sites in the Lothidok Range, located directly west of Lake Turkana in northern Kenya. The West Turkana Miocene Project (WTMP) has worked in the Lothidok Range since 2008 with the goal of further elucidating the paleobiology of the hominoids through the recovery of new specimens and detailed documentation of their paleoecological context. To date our research has focused largely on the Kalodirr and Moruorot Site Complexes, both radiometrically dated to ~ 17.5 – 16.8 Ma. Materials and Methods: Our ongoing fieldwork at the Kalodirr Site Complex resulted in the discovery of new dentognathic specimens of the three previously identified species of fossil hominoids – Turkanapithecus kalakolensis, Simiolus enjiessi, and Afropithecus turkanensis. Results: A new mandible and an isolated M3 of T. kalakolensis from Kalodirr further clarify the lower molar morphology of the species and permit identification of KNM-MO 1 as a mandible of T. kalakolensis. A new mandible of S. enjiessi provides evidence of the relative proportions of the first and second lower molars. A new male specimen of A. turkanensis shows unusual P4 morphology that may be a developmental anomaly or a previously unknown morphological variant. Discussion: An improved understanding of the lower molar morphology of T. kalakolensis further strengthens its identification as a nyanzapithecine. Our new specimens and subsequent re-identification of existing collections makes it clear that all three Lothidok hominoids are known from both the Moruorot and Kalodirr Site Complexes. The Lothidok Range holds great promise for further documenting hominoid evolution.Item Open Access An Analysis of North American Taeniolabidoid Multituberculate (Mammalia, Allotheria) Dentitions Using Mammalian Dietary Proxies(2018-12-20) Robson, Selina Viktoria; Theodor, Jessica M.; Scott, Craig S.; Cote, Susanne; Syme, Douglas A.; Zelenitsky, Darla K.In this thesis, a set of dietary proxies – dental microwear analysis, cusp row ratios (CRR) (similar to shearing ratios), relief index (RFI), orientation patch count rotated (OPCR), and Dirichlet normal energy (DNE) – was used to infer diets of North American taeniolabidoid multituberculates. Based on the signals recovered by these proxies, taeniolabidoid diets did not vary consistently with body size: small-bodied and large-bodied taeniolabidoids had similar dietary signals for almost all proxies, the only difference being in microwear feature dimensions. Dental microwear signals suggest that taeniolabidoids and non-taeniolabidoid cimolodontans may have had different diets, but all other proxies have recovered equivalent signals between the two groups. Dietary classifications are inconsistent among CRR, RFI, OPCR, and DNE. This suggests that these proxies are not equally good predictors and that their generalizability to non-therian mammals may need to be re-evaluated.Item Open Access Assessing Genetic Adaptations for Ethanol Metabolism using Comparative Genetics(2022-04) Pinto, Swellan; Melin, Amanda; Cote, Susanne; de Koning, Jason; Barclay, RobertEthanol naturally occurs in fermenting fruits and nectars consumed by mammals. To avoid harmful side effects of ethanol consumption, natural selection might have favoured the persistence and spread of genetic variants that improve ethanol metabolism in frugivorous and nectarivorous mammals. Variation in humans and other primates has fueled debate over adaptive hypotheses, which will be informed by a better understanding of comparative variation across mammals. Ethanol is primarily metabolized via enzymes encoded by ADH and ALDH genes. I studied these genes along with the CAT gene across a range of mammals with diverse diets. I used bioinformatics tools to look for evidence of positive selection in species with high dietary ethanol exposure due to reliance on fruits and/or nectars, relaxed selection in species with low dietary ethanol exposure, and convergent evolution among diverse frugivorous and/or nectarivorous species. Among genes of interest, the ADH7 gene is critical for ethanol metabolism in humans. I additionally investigated amino acid variation at a site (294) within the ADH class IV enzyme (encoded by ADH7) that is important for enzymatic function. I found no evidence of positive selection or of excess non-random convergent substitutions across ADH, ALDH, and CAT genes. However, I did find evidence that several ALDH genes and the CAT gene are under intensified or relaxed selection in lineages with low dietary ethanol exposure. Finally, I found that several leaf-nosed bats, a flying fox, and several opossums vary with the amino acid they possess at site 294. I also identified premature stop codons along ADH7 in two leaf-nosed bats, a rodent, a shrew, two sloths, and two opossums. Intensified selection on the ALDH genes and CAT gene suggest these genes are involved in important bodily processes that have led to their maintenance. Variation at the critical site of ADH7 in bats may indicate increased efficiency for ethanol metabolism in these species. My findings suggest variation in the strength of selection pressures acting on genes underlying ethanol metabolism and potentially adaptive variation in the ADH7 gene. Together these findings extend our understanding of molecular variation in the context of dietary ecology.Item Open Access An Earliest Carboniferous Actinopterygian Fauna from the Horton Bluff Formation of Nova Scotia(2020-01) Wilson, Conrad Daniel Mackenzie; Anderson, Jason S.; Theodor, Jessica M.; Cote, Susanne; Jamniczky, Heather A.; Anderson, Jason S.This thesis examines four earliest Carboniferous (Tournaisian) actinopterygian specimens from the Horton Bluff Formation of Nova Scotia. I used traditional and μCT descriptive techniques in order to better understand actinopterygian evolution and the transition between Devonian and Carboniferous vertebrate faunas. NSM 017.GF.017.001 was investigated using microscopy and latex peel techniques and represents the oldest occurrence of a deep-bodied actinopterygian. NSM 017.GF.017.007 and NSM 017.GF.017.004 were investigated using microscopy and μCT. Neither specimen can be assigned to genus or species, however, each can be compared to a broader group. NSM 017.GF.017.007 is most similar to Devonian taxa, whereas NSM 017.GF.017.004 is most similar to actinopterygians deeply nested in a broad post-Devonian radiation. NSM 017.GF.017.005 was examined using μCT and was incorporated into a phylogenetic analysis. In this specimen, the plesiomorphic anatomy of the dermal shoulder girdle, pectoral fin, and opercular-gular series are contrasted with the derived anatomy of the hyoid arch. In the phylogenetic analysis, it is recovered as a late-diverging member of a grade of otherwise Devonian actinopterygians. The presence of NSM 017.GF.017.001 and NSM 017.GF.017.004 suggests that derived actinopterygians faunas were established by the Tournaisian; whereas the presence of NSM 017.GF.017.007 and NSM 017.GF.017.005 suggests that Hangenberg extinction survivorship was inclusive of early-diverging actinopterygians. NSM 017.GF.017.001 and NSM 017.GF.017.005 also evince actinopterygian body plan exploration, perhaps related to resource acquisition, in the Tournaisian and revise previous models of post-Hangenberg actinopterygian differentiation. More broadly, the disparity of this fauna weakens interpretations of a homogeneous earliest Tournaisian caused by mass extinction and suggest that faunal turnover was more gradual than expected, at least in Actinopterygii.Item Open Access Evidence for rapid faunal change in the early Miocene of East Africa based on revised biostratigraphic and radiometric dating of Bukwa, Uganda(Elsevier, 2017-11-29) Cote, Susanne; Kingston, John; Deino, Alan; Winkler, Alisa; Kityo, Robert; MacLatchy, LauraField expeditions to Bukwa in the late 1960s and early 1970s established that the site had a small but diverse early Miocene fauna, including the catarrhine primate Limnopithecus legetet. Initial potassium-argon radiometric dating indicated that Bukwa was 22 Ma, making it the oldest of the East African early Miocene fossil localities known at the time. In contrast, the fauna collected from Bukwa was similar to other fossil localities in the region that were several million years younger. This discrepancy was never resolved, and due to the paucity of primate remains at the site, little subsequent research took place. We collected new fossils at Bukwa, reanalyzed the existing fossil collections, and provided new radiometric dating. 40Ar/39Ar incremental heating ages on lavas bracketing the site indicate that the Bukwa fossils were deposited ~19 Ma, roughly 3 Ma younger than the original radiometric age. Our radiometric dating results are corroborated by a thorough reanalysis of the faunal assemblage. Bukwa shares taxa with both stratigraphically older localities (Tinderet, Napak) and with stratigraphically younger localities (Kisingiri, Turkana Basin) perfectly corresponding to our revised radiometric age. This revised age for Bukwa is important because it indicates that significant faunal turnover may have occurred in East Africa between 20 and 19 Ma. Bukwa samples immigrant taxa such as large suids, large ruminants, and ochotonids that are absent from stratigraphically older but well-sampled localities in the region, such as Tinderet (~20 Ma) and Napak (20 Ma). Further age refinements for Bukwa and the entire East African early Miocene sequence will help to constrain the timing of this faunal turnover event, of particular importance in paleoanthropology since this temporal sequence also provides us with what is currently our best window into the early evolution of cercopithecoid and hominoid primates. We collected new fossils at Bukwa, reanalyzed the existing fossil collections, and provided new radiometric dating. 40Ar/39Ar incremental heating ages on lavas bracketing the site indicate that the Bukwa fossils were deposited ~19 Ma, roughly 3 Ma younger than the original radiometric age. Our radiometric dating results are corroborated by a thorough reanalysis of the faunal assemblage. Bukwa shares taxa with both stratigraphically older localities (Tinderet, Napak) and with stratigraphically younger localities (Kisingiri, Turkana Basin) perfectly corresponding to our revised radiometric age. This revised age for Bukwa is important because it indicates that significant faunal turnover may have occurred in East Africa between 20 and 19 Ma. Bukwa samples immigrant taxa such as large suids, large ruminants, and ochotonids that are absent from stratigraphically older but well-sampled localities in the region, such as Tinderet (~20 Ma) and Napak (20 Ma). Further age refinements for Bukwa and the entire East African early Miocene sequence will help to constrain the timing of this faunal turnover event, of particular importance in paleoanthropology since this temporal sequence also provides us with what is currently our best window into the early evolution of cercopithecoid and hominoid primates.Item Open Access The Genetics Underlying Male-Female Facial Sexual Dimorphism(2021-12-21) Da Silva, Cassidy; Hallgrimsson, Benedikt; Wilson, Warren; Cote, SusanneThe genetic mechanisms underlying facial sexual dimorphism are currently unknown. My thesis addresses this gap by shedding light on the genetic and biological mechanisms underlying sexual dimorphism in human facial shape, as well as normal facial variation more broadly. I evaluated the shape differences between males and females, scored their shapes for sexual dimorphism, and looked for genetic loci and genes that had significant associations with sexually dimorphic facial shape. While none of the SNPs reached genome-wide significance, testing revealed seven independent signals with suggestive associations (p < 1 × 10-5) to facial sexual dimorphism, spanning coding regions in four different genes. Three of these genes, RBFOX1, CACNA2D3 and ATP6V1E1, have previously been implicated in processes of craniofacial development. I also examined the shapes and genetic aetiologies associated with sex chromosome aneuploidies, Turner syndrome (X0) and Klinefelter syndrome (XXY), which yielded no clear indication of the role of the X chromosome in sexual dimorphism of the face. These findings support the most recent evidence that the same genes influence facial sexual dimorphism in both males and females. Furthermore, by identifying genes previously linked to normal facial variation, I provide preliminary evidence for developmental mechanisms underlying shared variation in facial sexual dimorphism between the sexes. Only by properly understanding the mechanisms underlying facial sexual dimorphism will we be able to form a complete picture of its role in human evolution.Item Open Access Paleoenvironmental Reconstruction of Kalodirr and Moruorot, Kenya using Stable Carbon Isotopes(2019-01-24) Butts, Catherine Frances Rita; Cote, Susanne; Theodor, Jessica M.; Katzenberg, Mary AnneEarly Miocene environments in East Africa are proposed to have consisted of entirely dense forest systems composed strictly of C3 vegetation, which has affected our understanding of Miocene ape habitats. However, new environmental data from the early Miocene sites of Moroto (21 Ma), Napak (20 Ma), Tinderet (20 Ma), Rusinga Island (20-18 Ma), and Bukwa (19 Ma) indicate a more open environment consisting of open canopied forests, woodlands and wooded grasslands with evidence of some C4 vegetation. This study builds on this new data by analyzing stable carbon isotopes in mammalian tooth enamel collected from Kalodirr and Moruorot, Kenya (17.5-16.8 Ma). These δ13Cenamel signatures suggest a mosaic of C3 vegetation too enriched to indicate a closed canopy forest. Rather, they are more similar to values found in woodlands, with some indications of C4 vegetation. This supports the hypothesis that the forest canopies of East Africa were opening before the middle Miocene, demonstrating that the environmental history of East Africa was more dynamic than previously described.Item Embargo Reconstructing locomotion in fossil rodents using semicircular canal morphology(2024-07-03) Hou, Lily; Cote, Susanne; Rolian, Campbell; Bertrand, Ornella C.; Theodor, Jessica; Cote, Susanne; Rolian, CampbellAnatomical structures vary among mammals with different locomotor behaviours, including sensory structures such as the semicircular canals (SCCs) in the inner ear. Recent research suggests that SCC morphology correlates with different locomotor behaviours in various extant and extinct mammalian taxa, but there is a lack of research on rodents, the most speciose and diverse mammalian group. In this thesis, an extant sample of rodent SCCs from 98 individuals across seven different locomotor behaviours (arboreal, fossorial, gliding, ricochetal, semiaquatic, semifossorial, terrestrial) was used to understand the correlations between SCC morphology and locomotion. The extant dataset was then used to create a Canonical Variates Analysis Model to predict probable locomotor modes in fossil rodents with unknown locomotor behaviours. Fossil rodent material consists mostly of craniodental remains; hence reconstructing fossil locomotion has been challenging. The fossil sample contains 7 specimens from four different rodent species from Napak, Uganda (site age: 20 Ma). This thesis provides the first micro-computed tomography scans of the SCCs from Diamantomys luederitzi, Paranomalurus bishopi, Paraphiomys pigotti, and one unidentified small thryonomyoid. The extant model predicted that Diamantomys luederitzi was semifossorial, Paranomalurus bishopi was semiaquatic, Paraphiomys pigotti was terrestrial, and the small thryonomyoid was terrestrial. While the model performed well with predicting specialized locomotor behaviours, the model should be complemented with postcranial and skull morphology for generalist forms of locomotion as it is difficult to distinguish the morphology between generalist locomotor categories.Item Open Access Revisiting the Paleoenvironment and Mammal Fauna of the late Uintan Swift Current Creek Locality, Saskatchewan(2023-06) Ehrman, Benjamin A.; Theodor, Jessica; Theodor, Jessica; Anderson, Jason; Dutchak, Alex; Cote, SusanneThe Swift Current Creek (SCC) locality was previously described as being similar to the “Rocky Mountains” fauna, an informal grouping of near-coeval assemblages in Utah and Wyoming, but otherwise having high faunal endemism (Storer 1984). Its paleoenvironment was described as a semi-arid, “tropical,” enclosed forest (Storer 1984). This interpretation of its environment contradicts the “Rocky Mountains” fauna comparison, as its Utah component (Myton Pocket- MP) is now interpreted to have been a savannah. This thesis sought to review SCC’s paleoenvironment and faunal endemism using a revised faunal list with palaeoecological methods not applied during previous studies of SCC. First, a rarefaction analysis was used to quantify the locality’s level of sampling, the likelihood of finding new mammal genera, and the diversity of specific taxonomic groups. A cenogram analysis was used to interpret SCC’s paleoenvironment based on body mass distribution (BMD) data. Similarity index calculations served to quantify SCC’s generic faunal similarity with near-coeval localities, including the Rocky Mountain’s MP and Badwater 6 (BW6; in Wyoming) localities. Faunal endemism was interpreted using a distance decay regression analysis, with Holocene localities serving as a baseline for comparative interpretation of differing patterns in faunal similarity. The rarefaction analysis results indicated that SCC is moderately sampled, and that continued sampling may result in the discovery of new mammal genera (especially rodents). The cenogram’s BMD is reflective of a humid, warm, enclosed forest. Some diversity signals from the rarefaction analysis support the interpretations of SCC’s environment, while others leave room for doubt. Descriptions of SCC being similar to the “Rocky Mountains” fauna were found to be inaccurate. The Swift Current Creek locality has high similarity value with BW6, but not with MP. The distance decay regression for SCC and its coeval localities did not express a significant decline in faunal similarity, and the rate of declining faunal similarity was much less drastic than in Holocene localities; demonstrating that SCC’s faunal endemism is not as high as past literature has indicated.Item Open Access Ruminant mesowear reveals consistently browse-dominated diets throughout the early and middle Miocene of eastern Africa(Elsevier, 2021-04-01) Hall, Abigail S.; Cote, SusanneThe ecological preferences of ruminant artiodactyls are commonly used to reconstruct the paleoenvironment of Neogene fossil localities throughout Africa. However, comparatively little research has focused on the ecology of ruminant artiodactyls from the Miocene of Africa. Here, we contribute new molar mesowear and hypsodonty data for the ruminant artiodactyls from the early and middle Miocene of Kenya and Uganda. Macroscopic dental characteristics of 608 tragulids, stem pecorans, giraffoids, and bovids dated to between 20 and 13.7 Ma were analyzed. Our hypsodonty results reveal that, whereas tragulids remain brachydont throughout the early and middle Miocene, pecoran ruminants experience an increase in hypsodonty due to the appearance of high-crowned bovids and climacoceratids that migrate into eastern Africa in the middle Miocene. Results from dental mesowear analysis suggest that all tragulids and pecorans were likely browsers, with only one taxon showing mesowear values that overlap with both browsers and mixed feeders in both the upper and lower molars (Canthumeryx sirtensis). None of the taxa analyzed had mesowear scores indicative of a grazing diet. Surprisingly, middle Miocene bovids and climacoceratids, despite possessing gross tooth morphologies adapted to abrasive diets, were largely utilizing a browsing diet. Although the early and middle Miocene habitats of eastern Africa were likely very heterogenous, none of the ruminant artiodactyls present in these habitats is interpreted as having incorporated grasses into their diet in significant quantities.Item Open Access Social and Hormonal Correlates of Life History Characteristics and Mating Patterns in Female Colobus vellerosus(2017) Vayro, Josie; Sicotte, Pascale; Fedigan, Linda; Pavelka, Mary; Katzenberg, Mary Anne; Tecot, Stacey; Cote, SusanneThis dissertation uses behavioural and hormonal data to describe female life history characteristics in Colobus vellerosus. It explores female behaviour patterns that may influence female reproductive success, and focuses on the effect of male group membership on female mating behaviour and investment in offspring. My team and I collected behavioural and faecal data between May 2012 and May 2013 at Boabeng-Fiema Monkey Sanctuary, in central Ghana. From June 2013 to September 2013 I extracted female reproductive hormones (progesterone and oestradiol) from the faecal samples at the Wisconsin National Primate Research Center and mapped the hormone values onto female hormone profiles. I documented ovarian cycle length (24 days), gestation length (mean=168.5 days, range=159-178 days, n = 2), age at first birth (5.87 years, range=4.66-7.08, n=8), and inter-birth interval for females whose infants survived to nutritional independence (mean=16.5 months, range=8.3-24.0 months, n=11) and for females whose infants did not survive to nutritional independence (mean=11.4 months, range=8.0-17.1 months, n=9). I investigated whether or not post-conceptive mating in female C. vellerosus is a by-product of fluctuating and/or elevated oestradiol and progesterone levels during pregnancy, or if it is a result of females' access to multiple males. I found that female progesterone and oestradiol levels increased throughout pregnancy and female mating patterns were associated with elevated progesterone levels. Females directed solicitations significantly differently among group types, and females directed solicitations significantly more in unstable multi-male groups than in stable multi-male groups. Females in stable and unstable multi-male groups copulated more with dominant than non-dominant males. I also investigated if female C. vellerosus stack investment in their offspring by conceiving a new offspring while a previous infant is still in nipple contact. I found that eight out of 16 females stacked investment. Females in stable multi-male groups stacked investment significantly more than those in unstable multi-male groups. Females that stacked investment spent a higher proportion of time with an infant in nipple contact than did those that did not stack investment. The combination of behavioural and endocrine data used in this study contributes to a growing body of work describing primate life history variables and mating systems.Item Open Access A test of the effect of hindlimb elongation on jumping performance using Longshanks mice(2019-04-26) Bradley, Madison Meta; Cote, Susanne; Rolian, Campbell; Bertram, John Edward Arthur; Syme, Douglas A.This study is the first to study mammalian jumping performance at the population level by using a forward-engineered body plan. Jumping mammals, including jumping primates, have long hindlimbs relative to their forelimbs and relative to generalized quadrupedal species. The influence of hindlimb elongation on the dynamics of jumping has rarely been studied within a species, especially within mammals. The Longshanks mice, which were selectively bred for longer tibiae, allowed for a direct test of which aspects of jumping dynamics change when an animal has relatively longer hindlimbs. Longshanks mice voluntarily jumped higher than random-bred Control mice. Near behavioral maximum, Longshanks exerted lower maximal ground reaction forces than Control mice jumping to the same height. Using Longshanks, I was able to link hindlimb elongation with differences in hindlimb force generation that occur independent of muscular changes. These biomechanical data can help to understand the selective advantages that shaped the extreme elongation of hindlimbs in jumping primate species.Item Open Access The fishes of Bukwa, Uganda, a lower Miocene (Burdigalian) locality of East Africa(Taylor & Francis, 2017-06-22) Murray, Alison M.; Argyriou, Thodoris; Cote, Susanne; MacLatchy, LauraABSTRACT—Renewed research at the early Miocene fossil site of Bukwa in northeastern Uganda has resulted in new fossil finds, including fish, with representatives of two families, Cichlidae and Alestidae. Although the two families were previously briefly reported from Bukwa, we here give a more detailed account of the fishes based on newly collected material. The cichlid material, mainly composed of vertebrae, can be tentatively assigned to one or more species of Pseudocrenilabrinae. The alestid material, comprising a diversity of teeth, likely represents several different species of Alestes, Brycinus and/or Bryconaethiops. Although the ichthyofaunal diversity of Bukwa is low, the fishes are important to indicate the paleoenvironment and hydrographic connections of Bukwa. The early Miocene was a critical time for African faunas, as it was during this time that the Afro-Arabian and Eurasian plates came into contact with one another, ending the long isolation of Africa, which, along with rifting in East Africa, created new terrestrial and hydrological connections allowing faunal interchanges. Bukwa is one of only a few African early Miocene localities known that sample fish, and, based on these fish, probably represents an area of interconnected lakes and large rivers including floodplains.Item Open Access You Should Look a Gifted Mammal in the Mouth: Using Dental Morphology to Understand the Evolution of Mammalian Dentition(2022-08-12) Ashbaugh, Austin J.; Theodor, Jessica; Dutchak, Alex; Cote, Susanne; Jamniczky, HeatherDentition is vital to our understanding of mammalian evolution. In this thesis, I use dental morphology as a basis for investigating various phenomena in mammalian dentition. First, I investigate the utility of shape, form, and linear measurement when differentiating species of the genus Mesodma – part of an early group of mammals known as the multituberculates. I found that shape and size metrics reveal different classifications of species. I conclude this chapter by suggesting these methods of differentiation should be investigated further along with the genus. Second, I investigate if cusp shape covariation across the premolar-molar boundary can highlight dental morphology covariance patterns that may contribute to the evolution of molarization in mammals. I found a significant difference in the cusp shape modularity among the two extant orders of hoofed mammals. I infer there are differences in the mechanism of molarization contributing to this differentiation. Further studies are required to infer a mechanism. The studies I present in these chapters showcase how dentition continues to provide important discoveries in the history of mammalian evolution.