A new, early Puercan (earliest Paleocene) species ofPurgatorius(Plesiadapiformes, Primates) from Saskatchewan, Canada

Abstract

The early PaleocenePurgatoriusVan Valen and Sloan is the most primitive plesiadapiform primate yet discovered, mostly known from middle to late Puercan strata in Montana, deposited during the interval C29N of the geomagnetic polarity time scale. Here we describePurgatorius coracisn. sp. from the Ravenscrag Formation, at the Rav W-1 horizon, Medicine Hat Brick and Tile Quarry, southwestern Saskatchewan. This horizon occurs within C29R, makingP. coracisthe earliest known primate, while strengthening the evidence that plesiadapiforms, and hence primates, originated and underwent their initial evolutionary diversification in North America. Most North American mammalian local faunas correlating with C29R have been assigned to the Pul (earliest Puercan) interval zone, but the taxonomic composition of the mammals accompanyingP. coracisat Rav W-1 more resembles local faunas of Pu2 age. The occurrence at Rav W-1 of Pu2 aspect mammals within C29R agrees with similar occurrences at the Hiatt and PITA Flats localities in Montana and North Dakota, also possibly correlated with C29R. The evidence from these three sites, all in the Williston Basin, suggests that in some areas of the Western Interior Pu2 aspect local faunas were coeval with those of latest Pu1 age, having evolved earlier than has commonly been assumed.

New discoveries of early Paleocene (Torrejonian) primates from the Nacimiento Formation, San Juan Basin, New Mexico

“…One of the groups to benefit was the Primates, who appear shortly after the boundary (Wilson, 2004;Fox and Scott, 2011). However, the diversity of the Order remains very low during the first North American Land Mammal Age (NALMA) of the Paleocene, the Puercan (66ew64.8 Ma [millions of years ago]), with only four to six 1 species in two genera (Purgatorius, Pandemonium) being recognized from that time period (Van Valen and Sloan, 1965;Van Valen, 1994;Buckley, 1997;Fox and Scott, 2011).…”

Oldest known euarchontan tarsals and affinities of Paleocene Purgatorius to Primates

“…Among the oldest known placental mammals, the putative primate Purgatorius has been documented in the western interior of North America during the first million years after the K-Pg boundary (2)(3)(4)(5) to within the first few hundred thousand years of the Paleocene (6). Although the fossil record of Purgatorius has been restricted to dentitions long recognized as uniquely similar to those of primates (3,4), these anatomical data are limited.…”

Morphological Evidence for Primate Origins and Supraordinal Relationships

“…As noted above, the earliest known primate, Purgatorius, is from the earliest Paleocene (Fox and Scott 2011). In light of the primitive nature of this taxon, the fossil record is not consistent with a date much earlier than this, putting the origin of the group in the earliest Paleocene or latest Cretaceous.…”

“…Plesiadapiforms do not possess all of these traits. If plesiadapiforms constitute the primate stem lineage, discussing "primate origins" then involves dealing with at least two sets of evolutionary transitions -first, the branching off of the primate stem and evolution of the earliest primate (Purgatorius; Van Valen and Sloan 1965;Johnston and Fox 1984;Fox and Scott 2011) and, second, the origin of Euprimates. Earlier discussions of "primate origins" that explicitly endeavored to explain only the latter transition (e.g., Cartmill 1972;Rasmussen 1990;Sussman 1991) are inherently flawed in trying to account for the concerted evolution of character complexes that did not arise at the same time, mixing the effect of multiple evolutionary transitions.…”

“…Although one possible specimen of this genus is described as coming from the latest Cretaceous (Van Valen and Sloan 1965;Van Valen 1994), it is not a particularly diagnostic tooth (Clemens 2004;Silcox 2008) and comes from a deposit that is time averaged (Lofgren 1995). The earliest, well-dated, diagnostic primate material that has been published in detail pertains to Purgatorius coracis from the earliest Paleocene (Pu2) of Saskatchewan (Johnston and Fox 1984;Fox and Scott 2011;see Clemens and Wilson 2012 for a possible even earlier occurrence). Most of the rest of the early primate fossil record is North American, including all definitive micromomyids and palaechthonids, most microsyopids, and all the most primitive paromomyids, carpolestids, plesiadapids, and possibly saxonellid (Fox 1991).…”