Pujilia darwini (Rybczynski, Dawson and Tedford 2009; Late Oligocene 23 mya;1m in length) was originally considered an extinct species of seal based chiefly on skull and tooth traits. Here it nests at the base of the clade that produced phocid seals, not otarid seals. It was derived from a sister to Mustela the river otter and lived in and near high Arctic lakes.

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 with the seal, Phoca. 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, Palaeosinopa has a long, robust tail. Like seals, the medial manual and pedal digits, especially digit 2 are longer than the others. The femur is short and robust. The scapulae are similar in shape.

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."