Excerpted from Colbert, M. W. 2005. The facial skeleton of the early Oligocene Colodon (Perissodactyla, Tapiroidea). Paleontologia Electronica 8:12A:27p

ABSTRACT

Two skulls of the early Oligocene Colodon from the White River Group in South Dakota are much more derived than previously reported. In particular, morphologies of the facial skeleton and narial region are surprisingly modern, including a deeply retracted nasoincisive incisure, and other indicators of prehensile proboscis development. High resolution X-ray computed tomography (HRXCT) is used to explore the internal anatomy of these tapiroids, and reveals frontal sinuses, and an internal facial skeletal anatomy approaching that of modern tapirs. This not only records an earlier origin for these anatomical conditions than than previously indicated, but in a phylogenetic context indicates that Colodon is more closely related to Tapirus than is Protapirus.

This specimen was collected from the Orellan of South Dakota in the 'Metamynodon sandstone,' a channel sand in the lowest Brule Formation located just below the lower nodular layer. The locale is mid-way between Cottonwood Pass and Stronghold Table. The specimen was made available to The University of Texas High-Resolution X-ray CT Facility for scanning by Matthew Colbert of the Department of Geological Sciences, The University of Texas at Austin courtesy of the South Dakota School of Mines, Museum of Geology.

Dorsal view	Left-lateral view	Ventral view

This specimen was scanned by Matthew Colbert on 15 march 2003 along the coronal axis for a total of 576 slices. Each slice is 0.45 mm thick, with an interslice spacing of 0.45 mm and a field of reconstruction of 112 mm.

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Colbert, M. W. 2005. The facial skeleton of the early Oligocene Colodon (Perissodactyla, Tapiroidea). Paleontologia Electronica 8:12A:27p

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