3.7" Rooted Fossil Sea Lion (Allodesmus) Tooth - Bakersfield, CA

About Allodesmus

Allodesmus was a large, extinct marine mammal that lived during the Middle Miocene, about 15–13 million years ago. A distant relative of modern sea lions and seals, it belonged to an early group of pinnipeds that thrived in the warm, shallow seas that once covered much of central California.

Fossils of Allodesmus are well known from the famous Shark Tooth Hill Bonebed (Round Mountain Silt) near Bakersfield, California. This site preserves one of the richest marine fossil assemblages in the world, and Allodesmus is among its most impressive marine mammals. Specimens from Shark Tooth Hill often include vertebrae, ribs, limb bones, and occasionally partial skull material.

Allodesmus was a substantial animal, typically measuring around 8–10 feet (2.5–3 meters) in length and likely weighing several hundred pounds. Its streamlined body and powerful forelimbs made it an efficient swimmer, well adapted for pursuing fish and other marine prey. Like modern sea lions, it probably hauled out on shorelines or sandbars to rest and breed.

Shark Tooth Hill fossils provide an important glimpse into California’s Miocene marine ecosystem, where Allodesmus lived alongside megalodon, dolphins, baleen whales, seabirds, and countless sharks. Its remains are a classic and highly collectible component of the Round Mountain Silt fauna, representing one of the dominant marine mammals of its time.