Phenacodus

Phenacodus Temporal range: Late Paleocene–Middle Eocene PreꞒ Ꞓ O S D C P T J K Pg N
P. primaevus skeleton at American Museum of Natural History
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Mammalia
Family:	†Phenacodontidae
Subfamily:	†Phenacodontinae
Genus:	†Phenacodus Cope, 1873
Species[1]
†P. bisonensis †P. condali †P. grangeri †P. intermedius †P. lemoinei †P. magnus †P. matthewi †P. primaevus (type species) †P. teilhardi †P. trilobatus †P. vortmani
Synonyms
Trispondylus Cope, 1884

Phenacodus (Greek: "deception" (phenax), "tooth' (odus)

Phenacodus intermedius reached 10 to 39 kg (22 to 86 lb), while P. trilobatus is estimated at 22 to 87 kg (49 to 192 lb).[3] The typical Phenacodus primaevus was a relatively small ungulate about 1.5 m (4 ft 11 in) long and weighed up to 56 kg (123 lb), of slight build, with straight limbs each terminating in five complete toes, and walking in the

In habits, the animal was cursorial and herbivorous, or possibly carnivorous. In the early Paleocene of North America, the place of the above species was taken by Tetraclaenodon puercensis, an animal only half the size of P. primaevus, with the terminal joints of the limbs intermediate between hoofs and claws, and the first and fifth toes taking their full share in the support of the weight of the body. These two genera may be regarded as forming the earliest stages in the evolution of the horse, coming below Hyracotherium (see Equidae). As ancestors of the artiodactyl section of the Ungulata, we may look to forms more or less closely related to the North American Lower Eocene genus Mioclaenus, typifying the family Mioclaenidae. The species of Mioclaenus were five-toed, bunodont Condylarthra, with a decided approximation to the perissodactyl type in the structure of the feet. A second type of Condylarthra from the North American Lower Eocene is represented by the family Meniscotheriidae, including the genus Meniscotherium.

A 2014 cladistic analysis places both Phenacodus and Meniscotherium within stem perissodactyls.^[6]

Teeth and jaws probably referable to the Condylarthra have been obtained in European early Tertiary formations. All Ungulata probably originated from Condylarthra.

Phylogeny

Cladogram after Gelfo and Sigé, 2011:^[7]

Gallery

• 
  Restoration by Charles R. Knight
• 
  Skeleton of Phenacodus primaevus
• 
  Restoration by Heinrich Harder
• 
  Comparison of P. primaevus with a human

References