In the Subungulata the pes is sometimes plantigrade and pentedactylate, the cuboid sometimes does not articulate with the astragalus, and the tarsal bones sometimes do not interlock.
In Typotherium (Toxodontia) the hallux is absent and the other four digits are well developed; in Toxodon and Nesodon the pes is tridactylate. The tarsal bones have the regular Subungulate arrangement, the cuboid not articulating with the astragalus. The calcaneum articulates with the fibula as in Artiodactyles. The astragalus in most forms, but not in Astrapotherium, resembles that of the Ungulata vera in having a grooved proximal surface.
In Phenacodus (Condylarthra) the tarsus is very little modified, five digits are present, the first and fifth being small and not reaching the ground.
In Procavia only the three middle digits are present with a vestige of the fifth metacarpal.
In the Amblypoda the pes (fig. 108) is very short and broad, all five digits are functional, and at any rate in Coryphodon plantigrade, the hallux being the smallest. The astragalus is very flat, and the tarsals interlock to a slight extent, the cuboid articulating with both calcaneum and astragalus.
The pes in the Proboscidea much resembles that in the Amblypoda, but differs in that the astragalus does not articulate with the cuboid, the tarsals not interlocking at all.
In the Rodentia the structure of the foot is very variable. In Beavers the foot is very large, all five digits being well developed; the fifth metatarsal articulates with the outer side of the fourth metatarsal, and not with the cuboid, and there is a large sesamoid bone on the tibial side of the tarsus. In the Rats, Porcupines and Squirrels, there are five digits, in the Hares only four, and in the Capybara and some of its allies only three. In the Jerboa (Dipus) a curious condition of the pes is met with, as it consists of three very long metatarsals fused together and bearing three short toes, each formed of three phalanges. Lophiomys differs from all other Rodents in having the hallux opposable.
Carnivora. In the Carnivora vera the pes is regular and shows little deviation from the normal condition. All the usual tarsal bones are present, but sometimes as in the Dogs, Cats, and Hyaenas, the hallux is vestigial. Sometimes as in the Bears the pes is plantigrade, sometimes as in the Cats and Dogs it is digitigrade. In this respect and in the character of the ungual phalanges, the pes closely corresponds with the manus. In the Sea Otter (Latax) the foot is large and flattened and approaches in character that of the Pinnipedia.
In the Pinnipedia the pes differs much from that in the Carnivora vera. In the Seals in which the foot cannot be used for walking, and is habitually directed backwards, the first and fifth digits are much longer and stouter than any of the others. In the Sea Lions which can use the pes for walking, the digits are all of nearly the same length, and in the Walrus the fifth is somewhat the longest.
In the Insectivora the pes is almost always normal, and provided with five digits.