Invertebrates

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Diacalymene clavicula
© 1998 Dr. Richard Paselk, Humboldt State University Natural History Museum

Cedaria minor
© 2002 The Virtual Fossil Museum

Trimurus delphinocephalus on Eospirifer eudora
© 2005 Falls of the Ohio State Park

What are Invertebrates? Invertebrates are multicellular animals without backbones. This very large group makes up 95% of living animal species, including such familiar organisms as insects, crabs, clams, and earthworms, as well as less familiar trilobites, brachiopods, and crinoids. Invertebrates dominate habitats as diverse as the deep sea, tide pools, coral reefs, rocks on stream bottoms, and soils. Although some invertebrates fossilize better than others, this group has a long fossil record, extending back to the Precambrian.

First known fossil occurrence: Precambrian.

Last known fossil occurrence: Quaternary. This group has living relatives.

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