Diversity starts early: notharctid primates from the Sandcouleean (Early Eocene) of the Powder River Basin, Wyoming, USA

Abstract

Abundant specimens, mostly isolated teeth, of the Primate family Notharctidae occur in the Early Eocene rocks of the Powder River Basin of northeastern Wyoming, USA. Very early in the North American history of the family, the notharctid species diversified and this diversity may have been widespread, and not restricted to more southerly areas in the Rocky Mountains. The diversity is shown by detailed analysis of the molar dentition. Two new genera are established: Megaceralemur with Megaceralemur trigonodus as its type and Megaceralemur matthewi sp. nov. as a Sandcouleean species and Pinolophus, with Pinolophus meikei sp. nov. as its type, for a form with an entoconid notch on lower molar 1. Megaceralemur has a prominent nannopithex-fold which dominates the posterior cingulum of upper molars 1–2 and a cristid obliqua on lower molar 1 which attaches to the metaconid, not the metalophid as it does in Cantius and other genera. A small species, Cantius lohseorum sp. nov., is named for a derived lineage the size of Cantius torresi.

urn:lsid:zoobank.org:pub:066DC515-A2DD-40AF-AD8A-3834E2AFD0FB

Keywords:

• Primates
• Notharctidae
• Early Eocene
• Sandcouleean
• Powder River Basin

Acknowledgements

I am indebted to the late Malcolm McKenna for access to the American Museum of Natural History specimens and to Philip Gingerich and Gregg Gunnell for access to the UMMP Collection. Ranie Hinds of the Wyoming State Geological Survey provided information on the well core sampling in the PRB. Many of the specimens cited here were collected from exposures on public land managed by the USDI Bureau of Land Management, under several permits, the most recent of which is PA-96-WY-022 (extended). Significant collections came from private land owned by the Garrett, Lohse, Meike, Reculusa, Streeter and Urruty families. Many colleagues, friends and former students helped with the field collection. Among these were Richard Kay, Blythe Williams, Herbert Covert, Patricia Monaco, the late Donna Engard and Donald Kron, Neil Huber, Logan Ivy, Kentaro Doi, Ann Creighton, Diana Ayers-Darling, Paul Murphey, Judith Harris, Kenneth Carpenter and Emmett Evanoff. Paola Villa helped with the construction of the figures. Herbert Covert kindly read and provided comments on an earlier draft of the manuscript. I am indebted to a reviewer for providing helpful comments. Field funds were provided by the University of Colorado Museum.