Systematics of the genus Palaeictops Matthew, 1899 (Mammalia: Leptictidae), with the description of two new species from the Middle Eocene of Utah and Wyoming Author Velazco, Paúl M. Author Novacek, Michael J. text American Museum Novitates 2016 2016-11-18 2016 3867 1 42 http://www.bioone.org/doi/10.1206/3867.1 journal article 5852 10.1206/3867.1 1d6299e9-5c62-4abd-be37-59efcb217cbf 0003-0082 4598386 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. FIG. 18. Right ramus of Palaeictops robustus CM 11954 (holotype) in lateral (top) and medial (bottom) views. Scale bar = 2 cm. 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.