Sea lions, seals, and the walrus belong to the group of marine mammals called pinnipeds. The sea lions such as the California and Stellar sea lions as well as the fur seals, belong to the family otariidae while the true seals such as elephant seals and harbor seals belong to the phocid family. Walrus are in their own family called odobenids.
The California sea Iion (Zalophus californianus) is the most commonly stranded pinniped in California. California sea lions are light to chocolate brown in color and exhibit marked sexual dimorphism. Males can weigh up to 390kg (850lbs) and have a distinctive raised bony bump on their head known as a sagittal crest. Females are smaller and weigh up to 110kg (220lbs) and have no sagittal crest. California sea lions can sometimes be confused with the Stellar sea lion which are found rarely in central and northern California. These two species are distinguished most easily by the presence of a thumb-sized gap between the most rear tooth and the next tooth in the skull which is present in Stellar sea lions but not in California sea lions. This gap is called a diastema. You can further explore the anatomy of the California sea lion below.
The harbor seal (Phoca vitulina) is the most widely occurring phocid seal in the world. In the United States, it is found on both the east and west coasts. Their size varies fairly widely across their distribution with the smallest animals weighing around 80-90kg (N. Gulf of Alaska) and the largest animals weighing up to about 170kg (Aleutian Islands). Coloration patterns can also vary between individuals within a population such that they can appear light with dark spots or dark with lighter spots, though often times it is difficult to tell the difference within a population. There is also sexual dimorphism present in this species with males being generally larger than females. You can further explore the normal anatomy of the harbor seal below. Note that many images in the normal anatomy section also feature the Northern Elephant Seal, another phocid species.
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