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KGS Home > Fossils > Invertebrate Fossils

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Perhaps the most sought-after fossils in Kentucky are the attractive, but extinct trilobites. Trilobites lived in ancient seas during the Paleozoic Era, but became extinct during the Permian Period.

Trilobite fossils have been found in Ordovician, Silurian, Devonian, Mississippian, and Pennsylvanian rocks in Kentucky, but are perhaps most commonly found in the Ordovician and Silurian rocks. One of the most abundant trilobite fossils is Flexicalymene meeki, which is typically found in the rolled-up form. Fossils of the large Isotelus gigas (up to 1 foot long) have also been found in the Ordovician rocks in the Blue Grass Region. The Silurian Calymene trilobites found near Bardstown are beautifully preserved by crystalline dolomite.

The upper half of a large Isotelus gigas trilobite from the Ordovician of Kentucky. Some trilobites were as much as 18 inches long, although most were 2 inches or less in length.

Two enrolled Flexicalymene and associated burrow fossil from the Ordovician of Kentucky. Some trilobites could roll up for protection.

Because trilobites are arthropods, they shed their exoskeletons, a process called molting, as they grew. This is why broken fragments of trilobites are common in Ordovician rocks. The fossils below are fossil molts of Ordovician trilobites. See if you can find the fossil molt fragments.

Can you find the trilobite fossils? Click here to see if you are right.

Dolomitized cast of calymenid trilobite from the Silurian of Kentucky.

Silurian Gravicalymene trilobite
Devonian Phacops from the Silver Creek Member of the North Vernon
Devonian Phacops from the Speed Member of the North Vernon
Mississippian trilobite from Somerset Shale

Trilobite Fact Sheet (in pdf format)

Links to other sites about Trilobites:

 

 

Red areas in the photo are cephalon fragments, green are either thorax or pygidium fragments.