Mucrospirifer thedfordensis - fossil brachiopod A.JPG

Fossil Brachiopod - Mucrospirifer thedfordensis (Front and back views)

Widder Formation, Ontario, Canada
Middle Devonian 383-393 Million Years ago
Mucrospirifer is a genus of extinct brachiopods in the class Rhynchonellata (Articulata) and the order Spiriferida. They are sometimes known as "butterfly shells". Like other brachiopods, they were filter feeders. These fossils occur mainly in Middle Devonian strata. The biconvex shell was typically 2.5 cm long, but sometimes grew to 4 cm. The shell of Mucrospirifer has a fold, sulcus and costae. It is greatly elongated along the hinge line, which extends outward to form sharp points. This gives them a fin- or wing-like appearance. The apex area (umbo) of the pedicle valve contains a small fold for the pedicle. Mucrospirifer lived in muddy marine sediments, and were attached to the sea floor via the pedicle. The shell sometimes looks like two seashells stuck together. Brachiopods, sometimes called lamp shells, are filter feeders and are attached to the sea floor by a fibrous pedicle that extends from a hole in the pedicle valve. The “wings” of the spirifers possibly stabilized the shell in the sea floor sediments. In order to feed, brachiopod shells had to be open. The lophophore, a combination of a feeding and respiratory organ, had a number of tiny tentacles that created a current to allow filter feeding. It was supported by two arms attached to the interior of the brachial valve. This was an evolutionary disadvantage when compared to bivalve molluscs, which could feed through siphons with the shells tightly closed. The first brachiopods appeared in the early Cambrian. Some brachiopods have survived competition from molluscs, today generally living in very deep or cold water.
Kingdom: Animalia
Phylum: Brachiopoda
Class: Rhynchonellata
Order: †Spiriferida
Family: †Mucrospiriferidae
Genus: †Mucrospirifer
Species: †thedfordensis