Fossils of Imagotaria are known from the early late Miocene of California (c. 10-12 million years ago).

The 1.8 metres (6 ft) long pinniped more closely resembled in its overall shape a sea lion rather than a walrus.

Unlike the extant walrus (Odobenus rosmarus), Imagotaria did not possess elongate, ever-growing tusks, but instead bore enlarged canines (with respect to other pinnipeds).

Conical, unworn teeth and the lack of a vaulted palate indicate that Imagotaria did not feed on molluscs like modern walrus.

Additionally, fossils of Imagotaria (and the earlier Neotherium, c. 15 million years ago) demonstrate that early walruses had, by the middle and late Miocene, already developed extreme sexual dimorphism (males and females having different body sizes).