Abstract
The Clarkia lagerstätte (Latah Formation) of Idaho is well known for its beautifully preserved plant fossils as well as a fauna of insects and fish. Here we present the first known tetrapod fossil from these deposits. This specimen, recovered from the lower anoxic zone of the beds, is preserved as a carbonaceous film of a partial skeleton associated with a partial lower incisor and some tooth fragments. The morphology of the teeth indicates that the first tetrapod reported from Clarkia is a rodent. Its skeletal morphology as well as its bunodont and brachydont dentition suggests that it is a member of the squirrel family (Sciuridae). It is a large specimen that cannot be assigned to a known genus. Instead, it appears to represent the first occurrence of a new taxon with particularly gracile postcranial morphology likely indicative of an arboreal ecology. This new specimen is a rare glimpse into the poorly known arboreal mammal fossil record of the Neogene. It supports a greater taxonomic and ecological diversity of Miocene Sciuridae than previously recognized and offers new lines of inquiry in the paleoecological research enabled by the unique preservation conditions of the Clarkia biota.
Highlights
The mid-Miocene is a critical interval for studies of the relationship between climate and paleoecological change
This is in large part due to the mid-Miocene climatic optimum (MMCO), a 2 C warming event that peaked ca. 17 to 15 million years ago (Ma) and was the last sustained interval of climatic warming in the Cenozoic (Zachos et al, 2001; Zachos, Dickens & Zeebe, 2008)
Material—From the Latah Formation, Idaho: University of Washington Burke Museum (UWBM) C2830: UWBM 113209 (partial skeleton preserved as a carbonaceous film including skull, partial dentary, partial left and right scapulae, humeri, radii, and ulnae; left(?) manus, and partial vertebral column associated with ribs and sternum; fragments of the cheek teeth and a partial lower incisor are preserved as three-dimensional elements)
Summary
The mid-Miocene is a critical interval for studies of the relationship between climate and paleoecological change. Harris et al, 2017; Kohn & Fremd, 2007; Sheldon, 2006) records available in the region and to the wealth of terrestrial fossil floras and faunas preserved there These include the vertebrate faunas of the Mascall (Downs, 1956; Maguire, Samuels & Schmitz, 2018), Sucker Creek (Scharf, 1932), and Virgin Valley formations (Merriam, 1911), which, along with other localities in the region, have served as the basis for several analyses of vertebrate macroecology (Badgley & Finarelli, 2013; Calede, Hopkins & Davis, 2011; Harris, 2016; Maguire, 2015; Orcutt & Hopkins, 2013)
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