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Great Basin Naturalist

Abstract

The distinctive but inadequately known Paleocene faunas of central Utah are significant in that they sample a time interval not well represented by sequences in other areas. New materials from the Wagon Road (late Puercan) and Dragon (early Torrejonian) local faunas, North Horn Formation, provide additional information on the composition of the assemblages and systematics of included mammal taxa. The proteutherian ?Propalaeosinopa is recorded for the first time, from the Wagon Road fauna, indicating a significant extension for the enigmatic family Pantolestidae, otherwise first known from the Torrejonian. Associated premolars of Aphronorus simpsoni, a pentacodontid proteutherian from the Dragon fauna, indicated that the species is more distinct from its Torrejonian congener, A. fraudator, than previously suspected. New materials of Desmatoclaenus hermaeus uphold the synonymy of this species with D. paracreodus and permit more adequate definition of the genus with respect to the arctocyonid Loxolophus and the phenacodontid Tetraclaenodon; because Desmatoclaenus appears to share derived morphology with Loxolophus, we refer it to the basal condylarth family Arctocyonidae. The periptychid condylarth Haploconus, represented in the Wagon Road fauna by the geologically oldest described species of the genus, H. elachistsus, is shown to be distinctive in the configuration of lower molars and premolars; H. elachistus appears to be more primitive than species known from the Torrejonian of New Mexico. Some features of Haploconus are suggestive of the Conacodontinae, a distinctive clade of diminutive periptychids.

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