Pentamerids are a type of brachiopod that grew to sizes of over 10 cm, and they represent one of the largest types of dwellers within Silurian reefs. A thickened beak area served as a weight to stabilize the shell in the sediment, and there was no fixed attachment. Pentamerid brachiopods often lived as clumps of individuals, as shown in this reconstruction.
Pentamerid brachiopods occur abundantly in discrete beds on the reef flanks at Thornton. The shell material has been dissolved, and the brachiopods are preserved as internal and external molds.