New earliest Tiffanian [Late Paleocene] mammals from Cochrane 2, Southwestern Alberta, Canada

Abstract

New mammalian fossils at Cochrane 2, Paskapoo Formation, Alberta, Canada, document five new species and two new combinations: Ptilodus gnomus sp. nov. and Baiotomeus russelli sp. nov. (Multituberculata), Thryptacodon orthogonius comb. nov. and Litomylus grandaletes sp. nov. (“Condylarthra”), Pararyctes rutherfordi sp. nov., Bessoecetor septentrionalis comb. nov., and Paleotomus junior sp. nov. (Eutheria incertae sedis). These new taxa supplement a taxo− nomically diverse Cochrane 2 local fauna, representing one of the most species rich Paleocene mammalian localities in the world. An earliest Tiffanian age is estimated for the locality based on the presence of the index taxa Plesiadapis praecursor, Nannodectes intermedius, and Ectocion collinus. The Cochrane 2 local fauna fails to demonstrate a decrease in species number relative to those of late Torrejonian localities from the United States, as would be predicted by current paleoclimate scenarios; the rarity of earliest Tiffanian localities in North America suggests sampling error as a partial ex− planation for the apparent incongruity.