Tag: Paleontology

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.

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.

Lobodon carcinophaga: Evolutionary constraints on the spatial variability of crabeater seal postcanine teeth for successful filter-feeding foraging strategies

Presenter(s): Megan Pollak—Earth Sciences—Paleontology

Faculty Mentor(s): Kellum Tate-Jones

Session 6: The Earth, Sky & Everything In Between

Pinnipeds, the group that includes true seals, eared seals, and walruses, generally display highly variable tooth spacing . Previous studies have credited this variability to the typical pinniped feeding mechanism, a combination of suction feeding and pierce feeding known as the “grab-and-gulp” method, which does not require precise dental occlusion . However, the crabeater seal (i .e ., Lobodon carcinophaga) is unique among pinnipeds as a filter-feeder . The distinct sieve-like postcanine tooth processes such as high-cuspation and intricate trellis-like morphology allow the crabeater seal to effectively strain small krill from the water . I hypothesize that individuals in this group with unevenly spaced teeth are unlikely to survive ecological pressures and are thus removed from the population by natural selection, leading to lesser variation in crabeater seal tooth spacing than in grab-and-gulp feeders . I test this hypothesis by assessing whether the distinctive feeding method of the crabeater seal constrains tooth spacing by comparing the variability in tooth gaps of crabeater seals to that of bearded seals (i .e ., Erignathus barbatus) . I measured the tooth gaps between the postcanine teeth of 21 specimens of L . carcinophaga and 11 specimens of E . barbatus . I then performed an F test of equal variance on these two datasets . I found that crabeater seal tooth gaps are significantly less variable in spacing than those of bearded seals . This result supports my hypothesis that natural selective processes have generated evolutionary constraints for lower variability in tooth spacing in the filter- feeder, L . carcinophaga, than in grab-and-gulp feeders such as E . barbatus .