Microwear in burrowing rodents

research7microwear

The study of microwear features on the enamel surface of mammalian teeth is widely used to reconstruct paleodiets of extinct mammals. Few of these prior studies have focused on rodents and those that did often focused on a single taxon or a few related taxa. We focused on mylagaulids and geomyids, two groups of extinct subterranean rodents present in the Great Basin during the Miocene. Knowledge of their diet will allow further investigation of the paleoecology of this peculiar family of fossil rodents.

The results of this research were presented at the annual meeting of the Society of Vertebrate Paleontology in Pittsburgh (2010) and are part of my M.S. thesis at the University of Oregon.

Collaborator: Samantha Hopkins

Leptarctus oregonensis and Oregon leptarctines

research4leptarctine

Leptarctines are enigmatic, yet common, mustelids in the North American and Asian fossil record. No consensus has yet been reached about their paleoecology. Differing interpretations of dental and cranial features and a lack of available postcranial elements have left the diet and locomotor habits of this subfamily uncertain. Initial interpretations of their ecology include coati-like omnivory, badger-like carnivory, kinkajou-like frugivory, and koala-like herbivory. The comparison to a koala-like diet implied a strongly arboreal lifestyle for leptarctines. Most recently, the cranial and dental morphology have been interpreted as evidence for a crushing omnivorous diet.
We have been studying a partial skeleton of a late early Hemphillian (7.5 – 6.7 Ma) leptarctine from the Rome fauna of Malheur County, Oregon as well as a nearly complete skull of Leptarctus oregonensis, a small Leptarctus from the Mascall Formation of central Oregon (early Barstovian, 15.9 – 14.8 Ma) with the goal of improving our understanding of the Leptarctine paleoecology.

Preliminary results have been presented by Winifred Kehl at the Geological Society of America annual meeting in Portland (2009) and the Oregon Academy of Sciences annual meeting in Portland (2010).

Collaborators: Winifred Kehl, Edward Davis, Samantha Hopkins

Habitat preferences in the fossil record

research6habitat

We tested hypotheses of drivers of mammalian evolution through an examination of apparent competitive replacements of burrowing rodents at a regional scale in the middle to late Miocene fossil record of the northern Great Basin. At that time, mylagaulids became very abundant within the burrowing herbivore niche, including all burrowing rodents. This peculiar group of subterranean small mammals is most abundant in the Hemingfordian through Clarendonian NALMAs (17.5 to 9 Ma) and declines in the Hemphilian (9 to 5 Ma), giving way to the now very abundant family Geomyidae. We tested the hypothesis that this turnover of the most abundant group within the guild was associated with changes in habitat.

The results of this research were presented at the annual meeting of the Society of Vertebrate Paleontology in Pittsburgh (2010) by Dr. Samantha Hopkins and are part of my M.S. thesis at the University of Oregon. The article has been published in Palaeogeography, Palaeoclimatology, Palaeoecology.

Calede, J.J., S.S.B., Hopkins, E.B., Davis. 2011. Turnover in burrowing rodents: the role of competition and habitat change. Palaeogeography, Palaeoclimatology, Palaeoecology 311:242-255.
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Collaborators: Samantha Hopkins, Edward Davis