It is a vertebra body
In view number 2 portions of transverse process are visible.
The animal or fish it belonged to is difficult perhaps impossible to determine. I would suggest taking it to the local college biology instructor for positive ID or guessImation of its origin.
Many years ago my tribe traveled often to the wilds of Baja California - one tip was to Scammon's Lagoon where the whales met, greet, breed, have baby whales and yes pass on to the great whale migration in the sky.
One trip we came upon an old disjointed whale skeleton. So we, of course took so a few parts including whale vertebrae . We drug them home fibre glassed them and proceeded to convert them into stools for our "pads."
Marriage determined they were not a item for the living room so off to the garage. Time, home changes and suddenly they became a part of our dive adventures of the past
SDM