Perimecturus rapax
Crustacean
Late Mississippian
Bear Gulch Limestone
Fergus County, Montana, USA

Carboniferous.  Mantis shrimp

35mm on 78mm slab.

Perimecturus is a genus of extinct crustacean that has been informally called a “proto mantis shrimp though they didn’t have the “ballistic claws” and other adaptations of true mantis shrimp. In fact, Perimecturus was more like a flattened lobster in form – not directly related to lobsters either. It is known from the Early Carboniferous (Mississippian) of Montana.

Well-preserved example of this ancient crustacean.

For reference see: F. R. Schram and J. Horner. 1978.  Crustacea of the Mississippian Bear Gulch Limestone of Central Montana.  Journal of Paleontology 52(2): 394-406.