Phyllocarid

Crustacean
Late Mississippian
Bear Gulch Limestone
Fergus county, Montana, USA

72mm phyllocarid on 120mm slab. Nice detail.

Phyllocarids belong to a subclass of crustaceans (Phyllocarida) known primarily from their bivalved carapaces – the hardest parts of their anatomy.  Their fossils have been collected from various parts of the world from the Yukon Territory, Canada to Bolivia and California to Scotland, dating back to the Early Cambrian with one order still living today. In rare cases, some of the soft anatomy is preserved as well.