Brachiopod Fossil

This grooved shell is a fossil from the order Rhynchonellida. These brachiopods have been around since the Ordovician period, about 485 million years ago. Their population declined significantly during the Permian and Triassic extinctions about 252 million years ago, but the Rhynchonellida group became the most common brachiopod group of the Mesozoic Era.

This group can be recognized by their deep furrows and short hinges, which often end in a tip. These bivalves were the first to develop tooth sockets, which help align the two shell halves when they close and make it more difficult for predators to open the shell by twisting the valves.

It has been hypothesized that the radial groove pattern helps regulate the flow of water in and out of the shell.