Euprops danae-Illinois

Euprops was a primitive horseshoe crab that lived during the Pennsylvanian period in Illinois. One specimen (not this one)even has the brain preserved, which was nearly identical to modern horseshoe crabs. This specimen has a gorgeous carapace preserved and includes the positive and negative of the concretion.

Euprops danae, Pennsylvanian, Mason Creek fm., Illinois