Lobster - Palaeonephrops browni

Palaeonephrops browni lobsters have long been found within the Bearpaw Shale of Montana and the Bearpaw Formation in Alberta, Canada. Despite the numerous found lobster remains from the Bearpaw Formation, it is not common to find fossils of crustaceans in most parts of the world because the delicacy of their carapaces and exoskeletons allows them to be crushed easily during the layering of sedimentation during fossilization. But this lobster specimen has been remarkably preserved with a complete carapace and multiple appendages in fine detail.

The Bearpaw Shale in eastern Montana is a Late Cretaceous-age seabed deposit. The Bearpaw Formation spans from Alberta and Saskatchewan in Canada and outcrops into Montana. It is known for fossil ammonites and ammolites, fish, lobsters, turtles, birds, mosasaurs, plesiosaurs, and even a few dinosaur fossils that lived in or near the Bearpaw Sea of the Western Interior Seaway. 

The famed American paleontologist, Barnum Brown--who discovered the first Tyrannosaurus rex fossils in 1902--collected concretions containing remains of what would later be classified under the new genus of lobster, Palaeonephrops, in the Bearpaw Shale of Montana. The surprisingly well-preserved remains of the Bearpaw Shale lobsters are mostly found within limestone concretions with little compression. 

A large reason for these articulated fossils is that seafloor sediment surrounding the deceased lobster made its way under the exoskeleton and calcite slowly filtered into the leftover spaces, creating a supportive and protective concretion. Many of the lobsters died in their burrows, which provided an extra layer of protection.

This particular Palaeonephrops lobster specimen is 7.75 x 4.13 x 2.88 inches. It is in remarkable condition within an elliptical limestone concretion. The cephalothorax and flexible abdomen are beautifully articulated in a dark brown-black color, and both of its front claws are prevalent and detailed. A few of the walking appendages are displayed near the underside of the body and the tail is curled and clearly visible. Despite dying nearly 66 million years ago in an ancient sea, this lobster looks as if it could have been plucked from the ocean today. 




Lobster - Palaeonephrops browni
Arthropoda: Malacostraca
Cretaceous
Bearpaw Shale, Camp Creek, Montana