Tag: Samantha Hopkins

The Effects of Browsing and Grazing on Body Mass

Presenter: Mathew Beattie

Mentor: Samantha Hopkins

Poster: 3

Major: Biology/Geology 

Diet of mammals affects the metabolic rate, intelligence, and many other physical and behavioral characteristics. Understanding how the diets of mammals affect the development, evolutionary history, and overall biomass of species can be instrumental in understanding the needs of endothermic mammals and the large energy costs that it takes to maintain their bodies. Most large mammalian herbivores fall into two main dietary categories: browsers (animals that feed on the leaves, twigs, and the fruits of trees and shrubs) and grazers (animals that eat grasses
and forbs). It takes more mass of grass or forb to sustain a mammal than it does leaves or twigs; therefore, grazers must eat more food than browsers and will therefore have more body mass as a result of their dietary preference. A species body form is directly related to the actions it needs to do to survive. Therefore, by analyzing the phylogenetic relationship between the diet of Artiodactyla or “hooved mammals” in the families Bovidae (cows, sheep, goats, and antelope) and Cervidae (deer, moose, and elk), and the average body mass of species in each category, we have found that there is a strong correlation between increased body mass and grazing. However, this effect is mediated by habitat; those taxa that graze also tend to inhabit more open habitats, where the increased predation pressure may also select for greater size. Therefore, we will be analyzing the effect of diet, body size, habitat, and eventually tooth morphology to understand the evolutionary history of Artiodactyla.

Paleoecology of the Enigmatic Rhinoceros Chilotherium in Central Asia

Presenter: Selina Robson

Mentors: Samantha Hopkins and Edward Davis, Geology

Poster: 56

Majors: Geology and Psychology 

We report a new occurrence of the rhinocerotid Chilotherium in the Kochkor basin in Kyrgyzstan. While some geologic reports refer to Chilotherium in Kyrgyzstan, no described material exists from the country and all published material has gone missing. Therefore, our new material is important for not only recognizing the occurrence of the genus, but also understanding the evolution, ecology, and dispersion of various fossil taxa including Chilotherium. Few studies have examined the global distribution of Chilotherium. While the taxon is not uncommon, we found that 84% of Chilotherium specimens were found in China. Thus, the Kyrgyz specimens represent an important geographic extension of the taxon, and may clarify the relationship between ecology and species diversity. Our database of Chilotherium occurrences only reports localities above 2,000m elevation. While paleoaltitudes may be different than modern altitudes, recent studies support the construction of both the Himalayan and Tien Shan ranges prior to the late Mio/Pliocene. This indicates that Chilotherium occupied an ecological niche that is different from other rhinos. Of the collected fossils from Kyrgyzstan, Chilotherium is the most abundant taxon. A species level diagnosis of Chilotherium is difficult because the taxonomy is poorly constrained. There are three valid species but close to 20 published species. By mapping occurrences globally, we hope to clarify taxonomic relationships as well as to assign the new Kyrgyz material to a species level.

Fossil Eulipotyphla from Oregon’s Middle Miocene: New Occurrences and Biogeographic Patterns

Presenter: Danielle Oberg

Mentors: Samantha Hopkins and Edward Davis, Geology

Poster: 48

Major: Geology 

Insectivores (euliptophylans) are not well understood in the Miocene of Oregon. Recent discoveries from a new locality, Cave Basin, in the John Day Formation suggest a greater diversity of insectivores than was previously known. Early Miocene records are extremely poor and lack small mammals entirely. However, the Middle and Late Miocene explode with new families never seen before in southern Oregon. The Middle Miocene has the greatest insectivore diversity with occurrences of ancient shrews (heterosoricidae), red-toothed shrews (soricidae), true moles (talpidae), and hedgehogs (erinaceidae) clustering around the Oregon-California border in southeastern Oregon. Fourteen Middle Miocene localities have red-toothed shrews and true moles, while hedgehogs and ancient shrews are found in two localities. Diversity rapidly decreases for ancient shrews and hedgehogs throughout the Late Miocene and into the Clarendonian, but remains relatively constant for true moles and red-toothed shrews. Red-toothed shrew Late Miocene localities are further south and less clustered than Middle Miocene ones. True mole localities have a greater spread across eastern Oregon, ranging from the Oregon-Washington state line to the southern corner of Oregon. These new discoveries in the Oregon Miocene are a significant addition to the understanding of the Oregon fossil record. Furthermore, these insectivores reveal new insight into the paleoecology of the Miocene, changes in diversity over time, and evolution of insectivores that are still found in Oregon today.

The Ups and Downs of the Mammal World: How Mammal Diversity Has Changed in the United States throughout the 20th Century

Presenter: Kendra Walters

Faculty Mentor: Edward Davis, Samantha Hopkins

Presentation Type: Oral

Primary Research Area: Science

Major: Geology, Biology

Funding Source: Presidential Undergraduate Research Scholar, Undergraduate Research Opportunity Program, $5,000

Biodiversity loss is recognized as a global crisis. Current research strives to create models that predict regions that are at high risk for a significant drop in biodiversity levels. These models must be scaled by analyses of historic changes in biodiversity. However, no study has yet to analyze the changes in mammal richness in the United States at a high enough spatial and temporal resolution to produce a predictive model of mammal diversity. Our research is a high-resolution analysis of the changes in mammal richness in the contiguous United States from 1906 to 1995. We collected mammal occurrence data from the online database VertNet and BISON and individual museum collections, divided it into ten year increments, and used scripts in R to produce sampling-standardized patterns of mammal richness for each decade. We then analyzed the geographic distribution of change in richness over the 20th century. From our results, we were able to determine which regions experienced a significant rise in diversity levels and which experienced a significant drop. We also identified regions where sampling intensities remain too low to conclusively determine how mammal diversity has changed. Regions experiencing the most severe biodiversity changes, as well as those without adequate data, should be focal areas for continued research in conservation efforts.

Hyenas through Space and Time: Using Teeth to Study Changing Ecological Niches

Presenter: Selina Robson

Faculty Mentor: Samantha Hopkins, Win McLaughling

Presentation Type: Oral

Primary Research Area: Science

Major: Geology, Psychology

Funding Source: Presidential Undergraduate Research Scholarship, University of Oregon $5,000; UROP Mini- grant, University of Oregon $1,000; Walter Youngquist Scholarship, Department of Geology at the University of Oregon, $1,500

The four modern hyena species are some of the most specialized carnivores on the planet. Three hyena species are bone-crushers—the only living mammals that are specialized for this—and one species is an insect eater, feeding on social insects such as termites. Hyenas are uniquely adapted for both of these diets. However, little is known about how hyenas evolved these capabilities. Unlike their modern relatives, the earliest hyenas were small omnivores that consumed plant material as well as meat. Some of these ancestral hyenas developed more carnivorous traits and eventually became the bone crushers we are familiar with today. We can study the evolution of hyena diets, and by extension hyena ecological niches, by examining the shape and proportions of their teeth. I have applied this method to a hyena species recently discovered in Kyrgyzstan. The new hyena, currently designated as Hyaenictitherium sp. nov., has transitional dentition indicating an omnivorous but meat-dominated diet. The hyena was alive approximately 7 million years ago, making it a relatively young species. I am examining the ecological niche of this new hyena and determining how the specimen enhances our understanding of hyena evolution. Then, I am looking at other hyena species to determine if hyenas are following previously hypothesized patterns of dietary and ecological change.

New Geomyoidea from the Miocene Cave Basin Fauna of Oregon

Presenter(s): Megan Wyatt − Biology, Earth Sciences

Faculty Mentor(s): Samantha Hopkins

Poster 7

Research Area: Natural Science

Oregon contains a rich fossil record of Miocene flora and fauna, giving us a glimpse into complex ecological interactions in deep time. The Mascall Formation of central Oregon is one of the best-preserved middle Miocene mammal assemblages in the Northwest. Past work on the Mascall fauna has found a rich carnivore and large herbivore fauna, but studies have yet to reveal which small mammals lived there during the Miocene. Recent screen washing efforts by the vertebrate paleontology lab at the University of Oregon have discovered a large small mammal assemblage in the Cave Basin region of central Oregon, which, when identified, will reveal a previously unknown part of the intricate ecosystem that existed in Oregon 17.5 to 15 million years ago. In studying the geomyoids (gophers and pocket mice), I have identified three different genera of rodents including Perognathus, Harrymys, and Mojavemys, and there are likely other genera within the superfamily Geomyoidea in this collection. I can use measurements and variations of molar enamel cusp patterns to identify them to a species level. However, observation and two-dimensional measurements are often inadequate for distinguishing Perognathus interspecies variation. Researchers have quantified species variation in other rodent lineages including voles and pocket gophers, using geometric morphometrics. I propose to use this method to identify these geomyoid molars. Species identification for these teeth will provide a baseline for future research of Oregon Miocene faunal ecology and be one step closer to understanding these ecological interactions.

Description of Pleistocene-Holocene carnivoran, Meles leucurus, from Kyrgyzstan

Presenter(s): Julien Royer − Anthropology

Faculty Mentor(s): Win McLaughlin, Samantha Hopkins

Poster 8

Research Area: Paleontology

Kyrgyzstan has a scarce paleontological history with most of the previous and current studies focusing on the Miocene- Pliocene. However, Russian geologists in 2012 mapped regional faults and reconstructed uplift rates in the Tien Shan mountains, where the material present in this study was recovered from the Kochkor basin and classified as Meles leucurus from the Pleistocene-Holocene. The fossil record present in Kyrgyzstan reflects mostly large ungulates from the Miocene- Pliocene. This specimen is the first described carnivore from the Late Pleistocene-Holocene from Kyrgyzstan. The carnivoran fossil was recovered from the QIII abandoned river terrace (the regional convention for naming uplifted terraces) with an approximate age of 5,000-20,000 years old through carbon dating of other QIII river terraces. In addition, an associated snail shell and vertebra, rib, tibia from the specimen were used for radio carbon dating material. Moreover, a CT scan of the encapsulated m1 is used for positive morphological diagnosis. A domestic dog skeleton, being a carnivoran sharing similar anatomical shapes with the studied material, is used for morphological comparisons. The tribosphenic shape of the single deciduous tooth, its sharp cusps, and high protocone leaves us to believe this fossil to be a carnivoran burrowing mammal. The specimen diagnosis is Meles leucurus through the average size of the bones and robustness of the long bones and ankle bones needed to burrow. The fossil is a juvenile, resulting from an encased adult m1 in the lower right jaw, a single deciduous tooth, and unfused epiphyseal plates. Considering the location of the origin of genus Meles in the Pliocene, ‘’the out of Tibet hypothesis’’ supports a migration pattern from the Tibetan Plateau to Kyrkygzstan through antecedent species of badgers. Although we believe the fossil to be a part of species leucurus, it is cautious for us to suppose the specimen might belong to another species or sub-species because of a sympatric zone shared by Japanese, European, and Eurasian badgers occurring in the West of the Tien Shan during Pleistocene-Holocene.

Identifying Fossils: Horses of Kyrgyzstan in the Miocene

Presenter(s): Dylan Carlini − Geology

Faculty Mentor(s): Samantha Hopkins, Win Mclaughlin

Oral Session 4O

Research Area: Earth and Biological Science

In paleontology, correct identification of fossils is of paramount importance to the scientific process. In locations with sparse fossil records and little preexisting literature, such as Kyrgyzstan, fossil identification can be particularly difficult. For this study, I identified two previously unidentified specimens from the University of Oregon Kyrgyz fossil collection as a mandible and a cheek tooth from the genus Hipparion, a member of family Equidae. Following a review of relevant paleontological literature, I used digital calipers to gather precise measurements of the specimens and conducted a careful analysis of tooth cusp morphology in order to make the determination. While the two specimens cannot be definitively attributed to the same individual, I determined that both came from adult individuals of the genus Hipparion. Using tooth morphology from the mandible, I also estimated the age of the individual at the time of death. These identifications add to our knowledge of the biodiversity of Miocene central Asia. Additionally, this study serves to demonstrate the process of fossil identification.

Fossils of Oregon: Mammalian Body Mass Communities in the Miocene

Presenter(s): Dylan Carlini − Geology

Faculty Mentor(s): Samantha Hopkins, Dana Reuter

Poster 9

Research Area: Earth and Biological science

Funding: Presidential Undergraduate Research Scholarship
UROP Mini-Grant

The size of an organism relates to a host of other characteristics about a species such as diet, metabolism, and trophic level. Changes in body mass through deep time are often the result of changing environments and climates. Previous research has examined how the patterns of mammalian body size at a community scale are shaped by the environments the organisms inhabit. However, the fossil record of Eastern Oregon has never been investigated through that lens. The extensive fossil record and well-studied long-term environmental shifts in Eastern Oregon make it an ideal location to study the effects of environmental changes on mammalian body masses. This study intends to classify and quantify the effects of the spread of grasslands on body size structure of mammals in the Miocene. I estimated body mass for Miocene mammals using measurements from fossil teeth as a proxy. These estimates derive from measurements taken with digital calipers and from the computer program Image J. I then organized the body masses into size categories and compared the changes in size structures as Oregon developed from a closed woodland in the middle Miocene to a more open, grassland environment in the late Miocene. If a pattern is discovered, it could help inform biologists and ecologists which varieties of mammal are at the greatest risk of climate-change related extinction in the near future.

Variation in Tooth Size and Shape In Species of Pinniped

Presenter(s): Caitlyn Boatman – Biology

Faculty Mentor(s): Samantha Hopkins

Poster 54

Research Area: Biology

Animals that maintain constant internal body temperatures have high energy requirements. In a resource limited ecosystem, efficient food processing is vital to ensure that these animals extract enough energy from their food to heat their bodies. Tooth size and shape, along with the precise contact between top and bottom teeth (occlusion), are adaptations that allow for efficient food processing. Because of this relationship between energy extraction and tooth function, the size of those teeth with precise occlusion are often highly conserved in terrestrial species like bears and foxes. Some work has been done on studying dental variation in terrestrial animals with precisely occluding cheek teeth, such as the carnassial pair in some carnivores. However, few studies have investigated dental variation in aquatic carnivores with homodont (homogenous), non-occluding cheek teeth. To fill this gap, I investigated dental variation in pinnipeds, a clade of aquatic carnivores with homodont (identical) cheek teeth that are not used for processing food. Studying these species allowed me to determine if various measures of tooth size are conserved in species that swallow their food whole. Specifically, I examined how tooth number, individual tooth area and size, total tooth area, tooth row length, and shearing-blade length vary within species, across species, and across families in clade pinniped. I used the program ImageJ to make my measurements. I determined that variation is high in pinniped dentition compared to the dentition of terrestrial mammals. These results suggest that tooth shape and size are not evolutionary constrained in pinnipeds.