I dug this bone up and it has obvious bone growth beyond the ordinary.
It does look as if there is a chunk missing which may have been a bite mark, perhaps during a mating fight or the like since it does not appear to be from a shark bite.
Mid. Miocene, Temblor Formation, Bakersfield, California
What do you suppose is the cause?
This shows a bite out of the bone, but isn't consistent with a shark bite pattern.