This fossil is a broken off section of an extinct ammonite shell from the genus, Mortoniceras. It was found in Arkansas in a dried up riverbed. The shell is characterized by deep keels and ribbing. It lived mainly during the Cretaceous Period beginning 145.0 million years ago and ending 66 million years ago when the dinosaurs died out. The chambers inside the animal’s shell held special gases which helped it descend deep down ocean depths or float up to shallower depths.
The ammonites were ocean predators crushing their victims with powerful extended tentacles. They could move with jet propulsion in spurts by siphoning the ocean water and thus pushing it out powerfully. They had large heads and were intelligent. Their tentacles contained special sensors which helped it navigate in the vastness of the ocean.
Phylum: Mollusk (large diverse group of invertebrates possessing a shell, i.e. clams, snails,oysters, etc.)
Order: Ammonitida (characterized by thick, ribbed patterned shells)
Class: Cephalopod (means prominent head and tentacles, i.e. octopuses, squids, nautilus)
Genus: Mortoniceras (characterized by deep keels and ribbing)