Palaechthon nacimienti (Wilson and Szalay 1972) ~4cm skull length, middle Palaeocene, was originally and subsequently considered a basal plesiadapiform. Here Palaechthon is a member of Glires close to Microsyops. This taxon is known from several partial specimens combined to make the incomplete skull drawing shown here:

Purgatorius onio (Van Valen and Sloan 19 65; Late Cretaceous, Palaeocene) is known from a jaw fragment that is similar to Palaechthon. It was once thought to be basal to Plesiadapis when plesiadapiformes were wrongly considered basal to primates.

Protungulatum donnae (Sloan and Van Valen 1965; LateCretaceous) is known from a jaw fragment.

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Kay RF and Cartmill M 1977. Cranial Morphology and Adaptation of Palaechthon nacimienti and Other Paromomyidae (Plesiadapoidea, Primates), with a Description of a New Genus and Species. Journal of Human Evolution, Vol. 6, 19-53.

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Silcox MT, Gunnelll GF and Bloch JI 2020. Cranial anatomy of Microsyops annectens (Microsyopidae, Euarchonta, Mammalia) from the middle Eocene of Northwestern Wyoming. Journal of Paleontology, 28pp. 0022-3360/20/1937-2337
doi: 10.1017/jpa.2020.24

Sloan RE and Van Valen L 1965. Cretaceous mammals from Montana. Science 148:220–227

Van Valen L and Sloan R 1965. The earliest primates. Science. 150(3697): 743–745.

Wible JR, Rougier GW, Novacek MJ and Asher RJ 2007. Cretaceous eutherians and Laurasian origin for placental mammals near the K/T boundary.” Nature volume 447: 1003-1006

Wilson RW and Szalay FS 1972. American Museum Novitates 2499:1.

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