Mucrospirifer is a genus of extinct brachiopod

Brachiopod

Brachiopods are a phylum of marine animals that have hard "valves" on the upper and lower surfaces, unlike the left and right arrangement in bivalve molluscs. Brachiopod valves are hinged at the rear end, while the front can be opened for feeding or closed for protection...

 in the class Rhynchonellata

Rhynchonellata

The Rhynchonellata is a class of articulate brachiopods that combines certain orders from within the Rhynchonelliformea . The class ranges from the Lower Cambrian to Recent....

 (Articulata) and the order Spiriferida

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 it is greatly elongated, giving them a wing-like appearance. They often have a deep fold down the center of the shell...

. They are sometimes known as "butterfly shells". Like other brachiopods, they were filter feeders. These fossils

Fossil

Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...

 occur mainly in Middle Devonian

Devonian

The Devonian is a geologic period and system of the Paleozoic Era spanning from the end of the Silurian Period, about 416.0 ± 2.8 Mya , to the beginning of the Carboniferous Period, about 359.2 ± 2.5 Mya...

 strata

Stratum

In geology and related fields, a stratum is a layer of sedimentary rock or soil with internally consistent characteristics that distinguish it from other layers...

.

The biconvex shell was typically 2.5 cm, but they could grow to 4 cm long. It has a fold, sulcus and costae. It was greatly elongated along the hinge line, which extends outward to form sharp points. This gave them a fin- or wing-like appearance. The apex area (umbo) of the pedicle valve contains a small fold for the pedicle

Pedicle (zoology)

In zoology, the pedicle refers to a fleshy line brachiopods and some bivalve mollusks use to attach and anchor to a substrate. In brachiopods, the pedicle emerges from a pedicle opening. Some brachiopods do not have a functional pedicle, and thus do not have this pedicle opening....

. They lived in muddy marine sediment

Sediment

Sediment is naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of fluids such as wind, water, or ice, and/or by the force of gravity acting on the particle itself....

s, and were attached to the sea floor via the pedicle.They sometimes look like two seashells stuck together.

Select species

• Mucrospirifer albanensis
• Mucrospirifer arkonensis
• Mucrospirifer bouchardi
• Mucrospirifer diluvianoides
• Mucrospirifer grabaui
• Mucrospirifer medfordsis
• Mucrospirifer mucronatus
• Mucrospirifer paradoxiformis
• Mucrospirifer profundus
• Mucrospirifer prolificus
• Mucrospirifer refugiensis
• Mucrospirifer thedfordensis
• Mucrospirifer williamsi