Brachiopods are marine animals that, upon first glance, look like clams. They are actually quite different from clams in their anatomy, and they are not closely related to the molluscs. Although they seem rare in today's seas, they are fairly common; however, they often make their homes in very cold water, either in polar regions or at great depths in the ocean. There are about 300 living species of brachiopods.

Depsite their relative obscurity today, brachiopods have a long and rich paleontological history. During the Paleozoic era, they were extremely abundant. They diversified into a number of different morphologies and even participated in the build-up of ancient reefs. At the end of the Paleozoic, some 250 million years ago, they were decimated in the worst mass extinction of all time, the Permo-Triassic event. Their numbers have never been as great since that time.
 

This critter "on the half-shell" shows some of the internal anatomy of a brachiopod quite well. First note the two valves or shells. All brachiopods have two shells. This makes brachiopods look superficially like bivalved molluscs (clams, oysters, etc.) However, a closer inspection shows some striking differences. Note that each shell valve is symmetrical about the midline, but the two shell valves are often unequal in size. This is unlike most clams, which have two equal valves, each of which is slightly torted and thus asymmetrical across the midline.

Notice the typical brachiopod feeding structure, the lophophore curled up on the right side. The rest of the anatomy is easier seen in this schematic cross-section of a brachiopod.

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 The Above information on Brachiopods was borrowed from the University of California Paleontology Museum.  This is one of the premire palentology sites on the net, with a very large amount of information on a lot of diverse subjects.  I highly recomend a vist.  The buttons below are links to the museum under the subject of brachiopods, and gives you access to more information than I have space to display.

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Page Last Updated: August 1, 2000