Past and Present Research
2016-Present: Miocene walrus diversification
Today, walruses are represented by a single species, Odobenus rosmarus, which is confined to the Arctic. However, millions of years ago walruses were numerous and widespread throughout the Pacific. Ongoing phylogenetic studies identify two major radiations of walruses, one in the early Miocene and one in the late Miocene, but have a gap in data from the middle Miocene. I am describing new fossil walrus skulls from the Los Angeles Basin in order to provide more information on the timing of walrus diversification events (filling in the “middle Miocene gap”) as well as tying these events to climatic changes occurring in the Miocene.
2014-2016: The fauna and paleoenvironment of Turlock Lake, CA
The upper Mehrten Formation is an early Pliocene (~5 m.a.) unit exposed at Turlock Lake in the Central Valley of California. The lake is exceedingly rich in fossils, yielding remains of mammals, reptiles, amphibians, fish, and plants. I was primarily interested in some of the lake's more unusual fauna as well as how the paleoenvironment of the area 5 million years ago had changed over time. I described and identified new material of a giant tortoise and investigated developmental changes occurring in a migratory giant spike-toothed salmon. In addition, I used the stratigraphy, lithology, and fossils of the lake to interpret changes in depositional environment, relief, and drainage patterns.
Sankey, J.; Biewer, J.; Basuga, J.; Palacios, F.; Wagner, H.; Garber, D. (2016). The giant, spike-toothed salmon, Oncorhynchus rastrosus (early Pliocene) and the “Proto-Tuolumne River” of Central California. Paleobios. University of California Museum of Paleontology, Berkeley, California, 30 pp, 15 figures, 2 tables.
Biewer, J.; Sankey, J.; Hutchison, H.; Garber, D. (2016). A fossil giant tortoise from Northern California. PaleoBios. University of California Museum of Paleontology, Berkeley, California, 24 pp, 12 figures, 3 tables.