Rudist Bivalve Fossil | Saudi Arabia | Late Cretaceous

Rudist bivalves are an extinct marine mollusk that operated as major reef builders in the Late Cretaceous. Their shell structure was heteromorphic, they often possessed a thick, calcitic attached valve and a smaller free upper valve. While rudists themselves are known for their strange and varied shapes, some groups within this subclass exhibit homeomorphic evolution, where unrelated species evolved similar, often parallel forms.

This item is 8” x 4” and weighs 4 lbs 7.1 oz