Description
Early Ordovician (Arenigian)
Upper Fezouata Formation
Zagora, Draa Valley, Morocco
7mm positive on 58mm slab.
Arthropod.
A synziphosurine is a member of a suborder of arthropods, Synziphosurina, ancestral to the Order Xiphosura, which includes extinct and modern horseshoe crabs.
You have to be pretty ancient to be the ancestor of horseshoe crabs.