Crustaceans

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Ocypode quadrata
© 2003 Roger Portell, Florida Museum of Natural History

Balanus gregarius
© 2009 Ana Luisa Carreno

Squilla empusa
© 2005 Yale Peabody Museum

What are Crustaceans? Crustaceans include a diversity of marine, freshwater, and terrestrial animals. All crustaceans have a head with five pairs of appendages, two of which are antennae. But the number of body segments, appendages on the thorax and abdomen, and presence of a tail vary between groups. Many microscopic crustaceans, like krill and brine shrimp, are members of the marine plankton, an important food source for other animals in the sea. Shrimp, lobsters, crabs, crayfish, and barnacles are crustaceans, as are the pill bugs found on the forest floor or city sidewalk.

First known fossil occurrence: Cambrian.

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

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