Phenacodontidae is an extinct family of large herbivorous mammals traditionally placed in the “wastebasket taxon” Condylarthra, which may instead represent early-stage perissodactyls.

[4] These animals had a variety of body sizes, and could be as small as domestic cats (Tetraclaenodon and Ectocion) and as large as sheep (Phenacodus).

Some species had tapir-like adaptations suggestive of the presence of a short proboscis or a strong prehensile lip.

[5] The teeth of phenacodontids, particularly in the latter forms, were quite specialized: The molars and premolars were equipped with low cusps that sometimes joined in ridges, similar to the condition found in some perissodactyls.

[7] According to more recent views, instead of a monophyletic clade, the condylarths are better understood as an evolutionary grade that lead to the true ungulates.