Upper Cretaceous Lobster
Paleonephrops browni
Bearpaw Formation
Upper Cretaceous (Campanian)
McCone County, Montana
This specimen is a good example of the fossil lobster Paleonephrops. It was preserved in a calcareous concretion and has good detail. The legs in this specimen are not visible but a portion of one of the antennae is present. Both chelipeds are present and display the variable size characteristic of the species. The left cheliped is long and slender of “nephropine” form and the right is a very stout “homarine” form and has broad dome-shaped crushing teeth. The overall length of the lobster is 10”. Preparation of these specimens is very time intensive. Restoration is minor filling of fractures

Fossil lobsters from the region of Northeastern Montana have been known for over 100 years. Originally collected by the famous American Museum of Natural History paleontologist and collector, Barnum Brown, the fossils were first named Hoploparia browni by Whitfield in 1907. The species has subsequently been referred to Paleonephrops by Mertin in 1941. The lobster bearing limestone concretions are found across a broad area of the Bearpaw Shale outcrops in northeastern Montana. The Bearpaw Shale outcrop extend in a north-south band from central Alberta, Canada through Montana and is the physical equivalent of the upper part of the Pierre Shale in the upper midcontinent. The fauna of the Beapaw Shale contains a broad array of mollusks, including ammonites which date the formation as Campanian.