Enrolled Kainops Trilobite With Hyolithid Fossil - Black Cat Mountain
This is a unusual association from the Black Cat Mountain quarry near Clarita, Oklahoma. There is a 1.5" long Hyolithid next to a .65" wide, enrolled Kainops trilobite. Hyoliths are animals with small conical shells, known as fossils from the Palaeozoic Era. They are lophophorates, a group which includes the brachiopods. Their fossils are fairly uncommon at this location.
Trilobites were a very diverse group of extinct marine arthropods. They first appeared in the fossil record in the Early Cambrian (521 million years ago) and went extinct during the Permian mass extinction (250 million years ago). They were one of the most successful of the early animals on our planet with over 25k described species, filling nearly every evolutionary niche. Due in large part to a hard exoskeleton (shell), they left a excellent fossil record.