Strophomenida

Strophomenida is an extinct group of small sea creatures called brachiopods that lived a very long time ago, from the Ordovician period to the middle of the Carboniferous period. They were part of a larger group known as Strophomenata and were the biggest group of brachiopods ever known, with over 400 different types. Some of the largest and heaviest brachiopods ever found were from this group.

During the Ordovician period, strophomenids were very common and diverse, but many of them disappeared during a big event called the Late Ordovician mass extinction. The ones that survived changed their shapes and grew in new ways during the Silurian period, but faced another difficult time during the Late Devonian mass extinction. Even so, they managed to live until the end of the Permian period.

Adult strophomenids did not have an opening for a special stalk called a pedicle, so they either rested freely on the ocean floor or stuck their lower shell to a hard surface. Young strophomenids had a tiny hole for the pedicle, but it closed up as they grew. Their shells had special shapes, with the top shell usually flat or curved inward, while the bottom shell was always curved outward. The back part of their shell, called the hinge line, was wide and almost straight. Many of their shells were wider than they were long. Inside their shells, there were tiny bumps made of a mineral called calcite, which helped support their structure.

Subtaxa (superfamilies)

The Strophomenida group includes two main superfamilies. These are:

• †Plectambonitoidea (paraphyletic?)
• †Strophomenoidea