Systematics of the late Eocene ‘oreonetine’ oreodonts (Merycoidodontidae: Artiodactyla)

ABSTRACT

The small, primitive ‘oreonetine’ oreodonts from the late Eocene (Chadronian) of North America have long been a systematic mess with gross oversplitting, failure to recognise post-mortem distortion of specimens and many errors in their descriptions. We describe some new fossils and review the group for the first time since 1956. Of the six genera and nine species recognised by Schultz & Falkenbach (1956), only three genera (Oreonetes, Limnenetes, and Bathygenys) and six species are now considered valid. The ‘Oreonetinae’ is a paraphyletic wastebasket group because some members are closer to more derived oreodonts than others, and Limnenetes is a primitive leptauchenine, not a merycoidodontine. These small, rare late Eocene oreodonts found only in Wyoming, Montana, and Texas are the precursors to the enormous radiation of oreodonts in the early Oligocene.

KEYWORDS:

• Artiodactyla
• oreodont
• Eocene
• Chadronian
• mammalia
• Merycoidodontidae

Acknowledgments

We thank Richard Tedford, Malcolm McKenna, Earl Manning, John Flynn, Meng Jin, Ruth O’Leary, and Judy Galkin for access to the AMNH and F:AM collections over the years. We thank A. Henrici and M. Lamanna for access to the CM collections. We thank S. Skwarcan, C. Bell, and C. Sagebiel for images and measurements of the TxVP specimens. We thank the late M.F. Skinner and the Frick Lab crews for all their discoveries that made this work possible. We thank E. Prothero for Photoshopping the illustrations. We thank M.O. Woodburne and an anonymous reviewer for helpful comments of the paper.

Disclosure statement

No potential conflict of interest was reported by the authors.

Correction Statement

This article has been corrected with minor changes. These changes do not impact the academic content of the article.