UWEC -- Geomorpholgy Fall 2007 -- Team A

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Cephalopods (squid-like animals) were 15-20 feet long and are the ancestors to present-day squid, octopus, and nautilus. They had hard heads (present-day they have softer, more flesh-like heads) and tentacles.
Gastropods are also known as univalves (having one valve) and are related to the cephalopods, but did not suffer severe casualties to the species during the Cambrian mass extinction as the cephalopods did. Modern gastropods include snails, slugs, limpets, and conchs.
Eurypterid is known as the ancestors to our modern day arachnids. The species found here is Pterygotus, which is the largest known arthropod to have lived and have been found at 2.8m long (most were less than 20 cm). Eurypterids were among the first animals to go from a water environment to walking on land, and went extinct during the Permian-Triassic extinction event 251.4 million years ago.
Trilobites (the Wisconsin state fossil) were generally 3 feet from head to tail, and were similar to present-day crabs. They existed most successfully in the Cambrian period, although they were prevalent throughout the Paleozoic Era and all but one order (Proetida) died out during the Mass extinction during the Late Devonian (approximately 360 million years ago), although the last of the trilobites disappeared during the extinction event at the end of the Permian (250 million years ago). Because of their hard exoskeleton, they were easily fossilized and so are one of the most commonly known fossils (second to dinosaurs).

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