1.3" Xiphosurida Arthropod With Pos/Neg - Horseshoe Crab Ancestor

This is a rare, Lower Ordovician arthropod which would be a member of order Xiphosurida. Xiphosurida is believed to be a very ancient ancestor or at least closely related to the modern day horseshoe crab. It comes from the Upper Fezouata Formation near Zagora, Morocco.

This specimen is 1.3" long including its "tail spine" and both the positive and negative split of the fossil is included. There is a second example with it's tail spine running off of the rock associated with it.