Tag: Geology

Climate Change and Preservation Bias in the Pliocene Ringold Formation

Presenter: Christina Wilson, Geology

Poster: D-5

Mentor: Samantha Hopkins, Geology

Before oscillations of glacial and interglacial cycles began, the climate within the Pliocene epoch, (5.3 – 2.6 Ma) was relatively temperate –similar to more conservative projections for the next 100 years of our current climate. Therefore, this time period provides an excellent basis for predicting how present fauna may respond to climate change. This study compares sites with different geologic ages but similar locations to examine faunal changes over time. This will show how different factors, including climate, impact the ecosystem. I researched the Ringold Formation, located in South-Central Washington, which is early Blancan in age (4.75-1.80 Ma) and within the Pliocene epoch. I picked fossils from screened sediment, identified different types of fossil, and classified those most amenable to identification. One of the main components of the collection is Mimomys teeth. Classification of 419 teeth shows that the morals are not in the same proportions as in living Mimomys, suggesting preservation bias and highlighting the importance of sampling all members of an ecosystem. Rabbit and squirrel teeth were also classified. These were fewer in number, so conclusions could not be drawn as clearly. Further identification and cataloguing of species will enable a fuller picture of the environment preserved and continue to shed light on the changing fauna through time.

Biostratigraphy of Miocene Camelids in the Juntura Formation

Presenter: Brianna McHorse, Biology

Poster: C-1

Mentor: Samantha Hopkins, Geology

Paleoecological research relies largely on the accuracy with which fossil specimens can be identified. Species-level identifications provide the most precise data for measuring diversity and communities through changing environments, space, and time. While cranial (skull) fossils allow a researcher to quickly identify specimens to the species level because of the density of characters (teeth, foramina, sutures, etc.), postcranial elements tend to be less diagnostic. However, postcranial material is favorably preserved in the fossil record. Previous studies have shown that the dimensions of camelid metapodials (cannon bones) tend to cluster in a species- specific way, as well as provide some indication of the presence or absence of a pacing gait. This study carries out measurements on Miocene camel metapodials from the Black Butte site in the Juntura Formation to identify each specimen more precisely, suggest the presence or absence of pacing, and examine whether sexual dimorphism was likely. A more precise understanding of the Juntura camel paleoecology will help to place them in ecological context relative to the other animals with which they lived. Preliminary results suggest that the two different camels present in this fauna had similar but distinct patterns of locomotion.

Deposition Bias in the Late Miocene McKay Reservoir

Presenter: Kelsey Stilson, Geology

Poster: C-7

Mentor: Samantha Hopkins, Geology

Fossils found in association have the potential to tell us about the ecology of a specific time and place in geologic history, suggest 9something about the changing prehistoric world, and give clues about the effects of present-day anthropogenic climate and habitat change. However, this is no simple process of counting up the number of bones found. A community is rarely, if ever, fossilized in the same proportions as it lived. This study suggests ways to measure the preservation bias in a system and extrapolate the composition of original fauna. My site is McKay Reservoir in north-central Oregon, where fossils were deposited by fluvial transport in the late Miocene (5.5 million years ago). Current approaches to depositional bias in such systems use the shape and evidence of postmortem damage to the bones in an assemblage to estimate the degree of sorting due to river flow. Voorhies diagrams, which use bone type (e.g. radius or metapodial) to determine the degree of sorting, indicate the McKay bones were transported at high velocity and were deposited relatively close to where they entered the water. Another method suggests that the bones were not exposed to air for long (little to no weathering) and rolled a medium distance along the stream bed (moderate abrasion). These results show that the bones came from nearby, perhaps as little as a mile from the site of desiccation to the site of final burial, and would therefore be relatively accurate indicators of ancient local species distribution.

Humans and the North American Pleistocene Megafaunal Extinction

Presenter: Kelsey Stilson

Paleontology (Geology)

Oral Presentation

The Pliestocene Megafaunal Extinction (PME) culled two-thirds of the world’s megafauna (mammal species with an average mass of >44 kg) over the relatively short period of 50,000 to 3,000 years ago. Megafauna are usually the first animals to become extinct in a weakened ecosystem. Human impact and climate change are considered the two main catalysts of the PME. This study looks at this global event from a North American lens, where extant species have been shown to have been genetically altered by the N. American PME and a Bison trans-continental migration has been shown to have a higher correlation with the PME in N. America than human impact or climate change. The ‘overkill’ or ‘blitzkrieg’ model concerning human impact is overturned in favor of a more moderate approach considering the available data. The PME must be thought of on both a local and global scale, where global events greatly increase the likelihood of extinction, but local variation is the ultimate determinate in megafaunal survival, much like the endangered megafauna today.

Tooth Eruption Sequence of Eporeodon occidentalis

Presenter: Kendra Walters

Co-Presenters: Meaghan Emery

Mentor: Edward Davis

Poster: 33

Major: Geology/Biology

Oreodonts lived in North America during the Cenozoic Era and were especially abundant from the Eocene to Miocene Epochs. Despite their abundance, they have no modern descendants. The dentition of fossil oreodonts is often well preserved, including deciduous or “baby” teeth. In order to understand more about oreodont behavior and development, our research examines the tooth eruption sequence for juvenile Eporeodon occidentalis. Tooth eruption sequences differ among groups of animals and reflect their specific life history patterns, including time of weaning and overall lifespan. We created 3D models of the crania of juvenile Eporeodon occidentalis individuals using Agisoft PhotoScan, and examined these models to stitch together the eruption sequence. Interestingly, the eruption sequence showed only the permanent first premolar which means the deciduous first premolar either did not exist or fell out extremely early, possibly before birth. This is a unique feature shared with pigs which may be evidence of a close relationship, similar behaviors, or similar life histories. By comparing the tooth eruption sequences of Eporeodon occidentalis and modern species such as pigs, camels, and sheep, I was able to infer possible life history patterns of Eporeodon occidentalis from known life history patterns of the modern species. In the future, this tooth eruption sequence will be compared to that of other oreodonts to evaluate differences and similarities in behavior, phylogeny, and life histories.

Mandible Morphology and Habitat in the Extant Tribes Marmotini and Sciurini (Rodentia:Sciuridae)

Presenter: Eva Biedron

Mentor: Samantha Hopkins

Poster: 4

Major: Geology/Biology

Morphological convergence among rodents living in similar habitats is common and well recorded. While upper incisor angle has been studied in connection with diet, lower incisor angle has been relatively neglected, despite textbook assertions that it correlates to habitat. Due to the difference in diets and jaw use between the terrestrial tribe Marmotini and the arboreal tribe Sciurini, it is expected that the tribes will display different mandible morphology, specifically lower incisor angle and diastema depth. The inclination of the lower incisor was quantified by measuring its angle relative to the occlusal surface of the lower molars with the mandible in lateral view. Diastema depth was measured as a vertical line along the anterior edge of the mental foramina, again viewing the mandible laterally. Preliminary data supports a relationship between smaller lower incisor angles and arboreality (t22 = 2.652, p = 0.015), but does not support diastema depth (t12 = 0.375, p = 0.714) as a predictor of arboreality. Changing habitats during the early Oligocene could have prompted the radial evolution of sciurids; by understanding how modern squirrels’ morphology is related to the habitat they live in, paleontologists will be able to better reconstruct a fossil squirrel’s paleoenvironment by using measurements of commonly preserved cranial elements as a proxy for actual habitat data.

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.

Influences on U.S. Mammal Diversity over the 20th Century: Implications for Future Response to Climate Change

Presenter: Kendra Walters

Mentor: Edward Davis, Geology

Poster: 63

Majors: Geology and Biology

Biodiversity loss is recognized as a global crisis. Current research strives to quantify and predict the change in biodiversity throughout the world, focusing on a wide range of taxa. However, current predictive models of mammal diversity in the United States suffer from low precision. They are not scaled with adequate spatial or temporal resolution because richness has not been evaluated at a broad spatiotemporal scale. Our research is a high- resolution analysis of the changes in mammal diversity in the continental United States through the last 110 years.

We collected mammal occurrence data from the online database VertNet and individual museum collections, divided it into ten year increments, and used scripts in ArcGIS 10.2 to produce sampling-standardized patterns of mammal diversity in each decade. We then analyzed the geographic distribution of diversity change over the 20th century. Mammal diversity in the last century increased in two regions: one northern horizontal strip between 43° and 47° latitude and one southeast strip from Texas to North Carolina. Diversity decreased throughout the rest of the United States. Our study describes regions in the United States that are experiencing the most severe biodiversity changes which suggests that those regions should be focal areas for conservation efforts. Further directions include testing hypotheses about the role of climate and human population change to influence these patterns of mammal diversity shifts.

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.