Middle Silurian
Gower Formation
Clinton County, IA, USA
65mm with soft parts on 112mm slab.

Phyllocarid. Arthropod. Crustacean. Soft-bodied.

Phyllocarids are a subclass of crustaceans (Phyllocarida) known primarily from isolated carapaces in the fossil record.  In rare cases some of the soft anatomy is preserved.  They date back to the Early Cambrian with one order still living today.