leucrotta:

North American river o.tter skull! This was an adult individual, not sure of the sex (female, maybe?), and it’s my first mustelid. A couple neat features of o.tter skulls that I didn’t know about before (unless this one is just an oddity) are that they have these super tiny, probably-useless premolars(?) behind their canines, possibly something they’re evolving not to have, and also, their jaws are sort of locked into place. In the fourth picture you can see how those bone flanges hold it from falling off. I’m not sure what purpose that served in life, but it’s very fun to play with.