Palaeictops, Matthew, 1899

Velazco, Paúl M. & Novacek, Michael J., 2016, Systematics of the genus Palaeictops Matthew, 1899 (Mammalia: Leptictidae), with the description of two new species from the Middle Eocene of Utah and Wyoming, American Museum Novitates 2016 (3867), pp. 1-42 : 32-33

Palaeictops spp.

REMARKS: Two designated species from Middle Eocene beds are clearly leptictids, but their validity as separate taxa is dubious. The species are Hypictops syntaphus described by Gazin (1949) from a maxilla with a right P1–M3 (USNM 13445) found north of Lone Tree in the Bridger Basin of Wyoming, and Viverravus ? nitidus Marsh (1872) , known only from a left dp5 (YPM VP 11888) from Henry’s Fork, also in the Bridger Basin.

The teeth of Hypictops syntaphus are badly worn ( Gazin, 1949: fig. 1), but they are comparable in size to upper teeth that would occlude with the lower dentition of the holotype of Palaeictops bridgeri (contra Simpson, 1959). The M2 of “ Hypictops ” is also similar to the M2 from Tabernacle Butte referred here to P. bridgeri .

Matthew (1909: 342) remarked that YPM VP 11888, the type of Viverravus ? nitidus Marsh, 1872 , was probably a deciduous last lower premolar of a leptictid. McKenna et al. (1962) suggested that this tooth could be a permanent p4 (equals p5 of this paper) of Hypictops syntaphus . Either assessment might be correct. The posterior position of the metaconid in YPM VP 11888 is very similar to the condition of the p 5 in Palaeictops bridgeri . Some differences are apparent, however, and perhaps this is related to differences found between deciduous and permanent teeth of the same taxon.

Thus, there is a strong possibility that Viverravus ? nitidus , Hypictops syntaphus , and Palaeictops bridgeri are one and the same taxon. Synonymy would unfortunately establish YPM VP 11888, a single enigmatic tooth, as the type for Palaeictops nitidus , and the only specimen referable to Hypictops is too badly worn to allow positive identification. It seems best to resist the action of synonymy in these cases.