My son Gordon and his family recently visited us at the Lake House. With the water level down for winter maintenance he found
this rock on the shore with trilobite fossils on the under side.
Trilobites are fossils of extinct marine arthropods.Trilobites first appeared in the Early Cambrian Period 521 million years ago. Trilobites were among the most successful of all early animals roaming the oceans for over 270 million years.
Arthropods are invertebrate that have an exoskeleton, a segmented body, and paired jointed appendages. The trilobite body is divided into three major sections: cephalon, thorax, and pygidium. The exoskeleton cuticle is made of chitin mineralized with calcium carbonate. The rigid cuticle inhibits growths it is replaced periodically by molting.
Most of what is commonly seen is the fossilized thorax.
I first learned of fossils through a school science project in the late 1940's. My friend Dan Wegner
and I found trilobites in the Braidwood quarry south of my hometown in northern Illinois.