Pinnipeds are seals, sea lions, and walruses. Some scientists classify the pinnipeds as
a suborder of the order Carnivora.
B. Family -- Odobenidae.
While the odobenids share some characteristics with the other two pinniped families,
behaviorally they more closely resemble the Otariidae (the eared seals). Some researchers
divide the Odobenidae into two subfamilies: the Odobeninae (living walruses) and the
Dusignathinae (fossil walruses).
C. Genus, species -- Odobenus rosmarus.
1. Most scientists recognize two subspecies of walruses: Odobenus
rosmarus rosmarus (Atlantic) and Odobenus rosmarus divergens (Pacific). Odobenus
comes from the Greek "tooth walker," and refers to the walruses' method of
pulling themselves up onto the ice with their long tusks.
a. These two subspecies are physically and reproductively isolated: O. r. divergens
lives in the Pacific Ocean and O. r. rosmarus lives in the Atlantic Ocean.
b. The Pacific walrus is larger, with longer tusks and a wider skull.
c. A third subspecies, Odobenus rosmarus laptevi, has been suggested based on
specimens from the Laptev Sea in the Pacific Ocean. O. r. laptevi has skull
characteristics similar to the Pacific walrus. Its size is intermediate to the Atlantic
and Pacific subspecies.
2. The common name, walrus, originated with the Danish word hvalros,
meaning "sea horse" or "sea cow." The Russian word for walrus is morzh.
Eskimos call the walruses aivik (Inuit) or aivuk (Yu'pik).
D. Fossil record.
1. The earliest of the odobenid fossils date back to the middle Miocene, about 14
million years ago.
2. The Dusignathinae, or fossil walruses, were abundant in the North Pacific 11 to 14
million years ago. Unlike the modern walrus with its elongated upper canines (tusks), the
upper and lower canine teeth of these fossil walruses were about the same size.
3. Ancestors of the Odobeninae, or modern walrus, probably made their way from the
northern Pacific Ocean to the Atlantic during the late Miocene, 6.5 million years ago, by
way of a Central American seaway.
4. Within the last one million years, walruses re-entered the Pacific via the Arctic.
The modern Pacific walrus originated from this Atlantic stock.