A new plesiadapiform (mammalia: plesiadapiformes) from the early Eocene of the bighorn basin, Wyoming

Kenneth D. Rose, Thomas M. Bown

Research output: Contribution to journalArticle


Dentaries of a very small, specialized plesiadapiform from the lower Eocene Willwood Formation are the basis for a new genus and species, Picromomys petersonorum. It was the smallest known plesiadapiform, weighing only about 10 g. Like some other plesiadapiforms, the new taxon has a strongly procumbent, hypertrophied medial incisor, followed by very reduced dentition between the incisor and P4. Unlike all other plesiadapiforms, it has a unique semimolariform P4 reminiscent of M1 in picrodontids, as well as lower molars bearing an accessory trigonid cusp anterobuccal to the protoconid. The closest known relative of Picromomys appears to be Bridgerian Alveojunctus, and we group these two genera here in the new family Picromomyidae. Picromomyids share derived similarities with several plesiadapiform families but are probably most closely related to either Micromomyidae or uintasoricine Microsyopidae.

Original languageEnglish (US)
Pages (from-to)305-319
Number of pages15
JournalAnnals of Carnegie Museum
Issue number3
StatePublished - Aug 30 1996


ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics
  • Geology

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