Rudist Reefs

About 100 million years ago, during the heyday of the dinosaurs, reefs were built by mollusks called rudist clams. They looked very different from today's coral reefs. Discover more about the evolution of marine life in our Ocean Over Time interactive.

Color illustration of an ancient bivalve.
Notice the pink tentacles, which “recliners” used to filter feed.A rendering of an underwater marine scene depicting life ~145-65 million years ago, when rudist clams were the major reef builders.