Windows on the Evolution of Picrodus (Plesiadapiformes: Primates): Morphology and Relationships of a Species Complex From the Paleocene of Alberta

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

“…In NMMNH P-62239, there is a separate wear facet on the very low postcristid in line with the protoconid, which likely marks the position of the hypoconulid. This implies that the two lingually positioned cusps must be the entoconid and a neomorph, an interpretation consistent with Scott and Fox's (2005) observations. There is a low, blunt cristid obliqua that meets the postvallid buccally, beneath the apex of the protoconid, so that the hypoflexid is essentially absent.…”

“…However, Picrodus is the only genus known so far from the later Torrejonian (Tomida, 1982;Silcox and Gunnell, 2008), making an attribution for NMMNH P-62239 to that genus likely. Of the species of Picrodus for which m2 is known, NMMNH P-62239 is most similar to P. calgariensis, a species which Scott and Fox (2005) also report from the later Torrejonian. Like the m2 of P. calgariensis, NMMNH P-62239 differs from the m2 of Picrodus silberlingi and Picrodus lepidus in having a cristid obliqua that intersects the postvallid relatively buccally, beneath the apex of the protoconid.…”

“…Although this feature is shared by P. calgariensis and P. silberlingi, the talonid is more similar to the former in being quite narrow mesially. Among the other diagnostic characteristics of P. calgariensis are a retained m2 hypoconulid, and relatively smooth enamel (Scott and Fox, 2005). Wear to the talonid basin of NMMNH P-62239 makes these characteristics difficult to assess.…”

“…In addition to those listed below, the following original specimens were observed: UKMNH 9558, MCZ 292, MCZ 294, MCZ 594, MCZ 596, MCZ 2040, MCZ 2041, MCZ 2043. Published illustrations and descriptions were also consulted (Gidley, 1923;Simpson, 1955;Gazin, 1968Gazin, , 1969Gazin, , 1971Wilson and Szalay, 1972;Szalay, 1973;Kay and Cartmill, 1977;Wood et al, 1979;Rigby, 1980;Conroy, 1981;Rose and Bown, 1982;Gingerich et al, 1983;Gunnell, 1989;Rose et al, 1993;Van Valen, 1994;Beard and Wang, 1995;Williamson, 1996;Higgins, 2000Higgins, , 2003Bloch et al, 2002Bloch et al, , 2007Clemens, 2004;Scott and Fox, 2005;Secord, 2008;Clemens and Wilson, 2009;Fox et al, 2010;Fox, 2011). Dental measurements were taken with digital calipers or (in the case of P. woodi) a stereomicroscope fitted with a reticle.…”

“…There are two well developed cusps on the lingual margin of the talonid. As Scott and Fox (2005) discuss, the identification of these cusps has been a matter of debate. In NMMNH P-62239, there is a separate wear facet on the very low postcristid in line with the protoconid, which likely marks the position of the hypoconulid.…”