Journal of Mammalian Evolution

, Volume 17, Issue 4, pp 227–243

A New Small-Bodied Species of Palaeonictis (Creodonta, Oxyaenidae) from the Paleocene-Eocene Thermal Maximum


    • Department of AnthropologyYale University
  • Jonathan I. Bloch
    • Florida Museum of Natural HistoryUniversity of Florida
  • Ross Secord
    • Florida Museum of Natural HistoryUniversity of Florida
    • Department of GeosciencesUniversity of Nebraska
  • Doug M. Boyer
    • Department of Anthropology and Archaeology, Brooklyn CollegeCity University of New York
Original Article

DOI: 10.1007/s10914-010-9141-y

Cite this article as:
Chester, S.G.B., Bloch, J.I., Secord, R. et al. J Mammal Evol (2010) 17: 227. doi:10.1007/s10914-010-9141-y


Oxyaenid creodonts are extinct carnivorous mammals known from the Paleogene of North America, Europe, and Asia. The genus Palaeonictis is represented by three species that together span the late Paleocene to early Eocene of North America, and at least one species from the early Eocene of Europe. Previously, only a single trigonid of Palaeonictis was known from the interval encompassing the Paleocene-Eocene Thermal Maximum (PETM) in North America. We describe Palaeonictis wingi sp. nov. from the PETM in the Cabin Fork drainage, southeastern Bighorn Basin, Wyoming, based on associated right and left dentaries with P2-M2. Palaeonictis wingi sp. nov. is substantially smaller than the other North American congeners, making it similar in size to P. gigantea from the earliest Eocene of Europe and the previously described PETM specimen. We suggest that a form similar to the large-bodied late Paleocene P. peloria from North America gave rise to two smaller species in the earliest Eocene of North America (P. wingi) and Europe (P. gigantea). Palaeonictis wingi may have given rise to P. occidentalis following the PETM in North America. Dispersal of Palaeonictis to Europe coincided with rapid global warming of 5–10°C and related geographic range shifts in plants and other animals during the PETM. It has been suggested that certain mammalian lineages decreased in body size during the PETM, possibly in response to elevated temperature and/or higher CO2 levels. Results from a dietary analysis of Palaeonictis indicate that it was an omnivore that primarily consumed meat. This suggests that the decreased nutritious quality of vegetation caused by increased CO2 levels was not the direct contributing factor that caused body size reduction of this lineage during the PETM. Other selective pressures such as temperature, aridity, and prey size may have also contributed to the smaller body size of carnivorous mammals during this interval, although the presence of smaller species could also be explained by latitudinal range shifts of mammals during the PETM.


PalaeonictisOxyaenidaeClimate changePETMDwarfingOrientation patch count

Copyright information

© Springer Science+Business Media, LLC 2010