Two unusual specimens of Helaletes in the Yale Peabody Museum collections, and some comments on the ancestry of the Tapiridae (Perissodactyla, Mammalia)

A calvarium, mandible and partial skeleton of Helaletes nanus and a partial upper dentition of Helaletes intermedius, both from the middle Eocene (Bridgerian) of Wyoming, are described and illustrated. Previously unrecognized cursorial specializations in the hindlimb of H. nanus suggest that it was not the direct ancestor of the Tapiridae, as hypothesized by some earlier workers. Alternatively, if H. nanus was the true ancestor of the Tapiridae, an initial tendency toward cursoriality in the hindlimb was later reversed. Only four described specimens are presently referred to H. intermedius. Due to morphological differences observed between these specimens, it is unclear if they all pertain to the same species-level taxon. As presently constituted, the species H. intermedius, might be better referred to a separate genus from Helaletes nanus