Brachiopod Fossils

Lingulella chenjiangensis (soft pedicle)

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Anomaloglossa porca (lingulid part and counterpart)

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Platystrophia ponderosa (original shell orthid)

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Kirkidium knighti (original shell pentamerid)

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Desquamatia zonata (original shell atrypid)

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Stringocephalus burtini (original thick shelled pentamerid)

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Australospirifer ceres (internal mold of spiriferid)

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Paraspirifer brownockeri (pyritized spiriferid)

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Mucrospirifer mucronatus (internal mold of spiriferid)

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Cyrtospirifer thalattodoxa (original shell spiriferid)

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Dictyoclostus portlockianus (original shell productid)

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Neospirifer dunbari (original shell spiriferid)

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Cyclantharia kingorum (prorichthofenid or brachiopod)

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Collemataria elongata (leptodid or brachiopod)

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Paucispinifera auriculata (productid silicified)

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Johndearia isbelli (original shell of thick shelled spiriferid)

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Lingula sp. (original shell of lingulid)

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Magellania grandis (original shell terbratulid)

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Magasella sanguinaria, Waltonia inconspicua

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Terebratella sanguinea (living terbratulid)

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The most common seashells at the beach today are bivalves: clams, oysters, scallops, and mussels. From the Cambrian to the Permian (542-252 million years ago), however, fossil seashells are dominated by another group of organisms with two hinged valves, Phylum Brachiopoda. Over 12,000 fossil species of brachiopods have been described, but only 330 species remain alive today. Bivalves and brachiopods are both sessile filter feeders, sitting on the seafloor and filtering water for food and oxygen. Their abundance reversed at the end of the Permian, when the greatest of all known mass extinctions eliminated more than 95% of Earth’s ocean species. The Permian extinction involved a crisis of low oxygen in the atmosphere that favored the more muscular and actively respiring mollusks over the passively respiring brachiopods. Clams and their relatives are much more efficient at extracting oxygen from seawater, so they were more successful after the extinction. Unlike bivalves, brachiopods are symmetrical along the midline of the shell, which inspired the Chinese name "stone butterflies." Their beauty and variety is illustrated by this selection from the recently acquired Retallack collection. Photography by Win McLaughlin, text by Greg Retallack, and web development by Keith Hamm. Images © Museum of Natural and Cultural History.