Palaeosinopa veterrima (Matthew 1901, Rose and von Koenigswald 2005; Late Paleocene, 56-48 mya; YPM VP 027216) was originally considered a pantolestid insectivore, but here nests between Puijila, the weasel and Phoca, the seal. It has been known as an amphibious piscivore and perhaps mollusc eater as the molars of older specimens tend to be worn flat. Unlike seals, but like weasels, Palaeosinopa has a long, robust tail with chevrons. Manual digit 2 is longer than the others. Pedal digit 3 is longer. The femur is short and robust.

Phoca vitulina (the harbor or common seal, Linneaus 1758, up to 1.8 m in length, Pliocene, 10 mya to present) has transformed its limbs into flippers. It is a swimming piscivore derived from Procyon and a sister to Canis. The parallel interphalangeal lines on the extremities are not compled largely because they are not supposted to flex and extend during use.

Seals are diphyletic. Marine forms had separate terrestrial ancestry. Phoca is an earless seal (family: Phocidae) derived from a sister to Paleaosinopa. Zalophus is an eared seal (family: Otariidae) derived from a sister to Hyopsodus and Miacis. Thus the clade Pinnipedia is no longer monophyletic.

According to Wikipedia: "Otariids use their front limbs primarily to propel themselves through the water, while phocids and walruses use their hind limbs. Otariids and walruses have hind limbs that can be pulled under the body and used as legs on land. By comparison, terrestrial locomotion by phocids is more cumbersome. Otariids have visible external ears, while phocids and walruses lack these."

Odobenus rasmanus (Linneaus 1758) is the extant walrus, a sister to Phoca, the seal. The canines are much enlarged here. The other teeth are flat and barely erupt. The naris is elevated. The scapula is robust.