Perishinctes SP.

These are Upper Jurassic (160 million year old) ammonite fossils of the genus Perisphinctes collected in Tulear, Madagascar.

They have been lightly polished to a glossy finish.

Ammonites were shelled cephalopods that died out about 66 million years ago.

Ammonites were born with tiny shells and, as they grew, they built new chambers onto it.

They would move their entire body into a new chamber and seal off their old and now too-small living quarters with walls known as septa.