Middle Miocene
Round Mountain Silt, Sharktooth Hill Bonebed
Ernst Ranch, Bakersfield, Kern County, CA, USA
7.75 inch bone.
Mammal, Pinniped.

Allodesmus is a genus of marine mammal that would have looked like a large seal but it was neither a seal nor sea lion nor walrus.  It belongs to the extinct family of pinnipeds, the Desmatophocidae, that appeared in the Middle Miocene and died out by the end of the epoch.

The baculum is not often found as a fossil.  Not all mammal genera have this bone in their skeleton.