Trilobites are ancient arthropods. They are distantly related to such modern arthropods as insects, spiders, shrimp, and lobsters. Trilobites arose in the early Cambrian Period about 550 mya (million years ago), and are among the first skeletonized animals of advanced anatomic grade to appear in the fossil record. They were common during much of Paleozoic time, but became extinct 245 million years ago (245 mya) at the end of the Paleozoic era.

The species you have is Phacops rana, which lived in great numbers in the warm, shallow sea covering what is now New York State during the middle Devonian Period (380 mya).


A1.1 Compare your specimen to the sketch of a trilobite below. What body parts are preserved in your specimen?


A1.2 Modern isopods (pillbugs) are among the closest living relatives of trilobites (but they are only very remotely related). Compare Phacops with the isopods. Identify one obvious similarity and one difference between trilobite and isopod.




A1.3 Poke the pillbug with your finger or the end of a pencil. How does the pillbug react to prodding?




A1.4 Is there any evidence in your trilobite to suggest that it behaved similarly?

A1.5 What does this imply about the antiquity of some aspects of modern animal behavior?


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Department of Geology
Brooklyn College
Brooklyn, NY 11210