A late Triassic or early Jurassic Ichthyosaur jaw section from near the rear of the mandible just prior to the tooth groove.

 From the Penarth coast south Wales, well known for it's exposed Triassic bone bed & fossils from the late Triassic & early Jurassic

If you have time check out my other vintage, antique rare & unusual listings. I often have coprolites & the occasional fossil too. 

Good luck & happy hunting