Spiriferida

Spiriferida is an order of extinct articulate brachiopod fossils which are known for their long hinge-line, which is often the widest part of the shell. In some genera (e.g. Mucrospirifer) it is greatly elongated, giving them a wing-like appearance. They often have a deep fold down the center of the shell. The feature that gives the spiriferids their name ("spiral-bearers") is the internal support for the lophophore; this brachidium, which is often preserved in fossils, is a thin ribbon of calcite that is typically coiled tightly within the shell.

Spiriferids first appear in the Early Ordovician. They were rare during the Silurian but underwent a dramatic evolutionary radiation during the Devonian period, reaching peak development in variety and numbers. Spiriferida survived the great Permian extinction, finally becoming extinct during the Early Jurassic.

Fossils of this order are often preserved as pyrite.

Taxonomy

Order Spiriferida