SPIRIFER BRACHIOPOD Spinocyrtia granulosa (Conrad)
Spirifer brachiopods have a characteristic shape with wide or extended hinge lines, a prominent beak, and a well-developed sulcus and radial fold. Superficially, they resemble modern-day mussels in design and habit, but brachiopods have two unlike and unequal shells, whereas clams and mussels have two shells (valves) that are alike.

This mid-Devonian spirifer Spinocyrtia is the most common brachiopod on the IVFP reef, but this speciman is unique in that it exhibits a complete internal mold of both the dorsal and ventral shells.

Landlocked seas of the Paleozoic provided vast areas in which the water was rarely deeper than 600 feet and commonly less than 150. There brachiopods found light, placid water and almost incredible supplies of microscopic food. Thus favored, brachiopods like Spinocyrtia became very abundant and crowded onto banks and reefs as closely as blue mussels do on modern shores.

IVFP 0622003 D. Tuttle collection.