Museum Paleonephrops Cretaceous Lobster Fossil from Bear Paw

Paleonephrops browni

(Whitfield 1907)

Geological Time: Cretaceous

Size: Lobster fossil would be 20.9 cm (8.25”) in length if outstretched

Fossil Site: Bear Paw Shale, North Eastern Montana

Fossil Code: PFD212

Price: $2900.00


Paleonephrops browni Lobster FossilDescription: Offered is a superbly preserved dorsal-side 3D lobster from the Cretaceous of Montana. It is a male specimen as evident by the large right side crusher claw. Both arms and claws are fully extended, inflated and almost completely intact. The eyestalks are potntially in place. Note the pustulate carapace and arms. This one even has its walking legs preserved! The telson is tucked under, but was masterfully prepped out. The abdomen and telson show little compression. However, there is some crushing to the top left hand side of the abdomen. The thorax and head have incurred some substantial crushing.

This Paleonephrops browni is from an old collection. The site is now closed to all collecting. It is quite doubtful you will ever find another available in the future. My talented master preparator Rod Bartlett just recently completed the air abrasion work. Rod specializes in crustacean preparation. He painstakingly invested over thirty hours of work into curating this specimen. This magnificent specimen truly earns our highest accolade of museum fossil.

Background: Only a few of these specimens have been preserved in this state of preservation. This species is found in the same areas as the more famous and numerous iridescent ammolite ammonites Placenticeras. Those rare lobsters discovered normally shatter when the concretion is broken, or are in a poor state of preservation. According to the previous owner, this one was obtained from a small research collection, of which, the rest went to a university for study. For comparison sake, consider this the crustacean discovery equivalent of a fully complete T-rex skeleton

The lobsters are preserved in argillaceous limestone concretions that have the shape of slightly flattened prolate ellipsoids. The concretions that contain lobsters generally contain only a single animal. However, a few contain two lobsters, and one contained a lobster and a crab. The lobsters are preserved as sediment filled exoskeletons which usually have the claws, cephalothorax and abdomen articulated, preserved in an upright position and stretched out along the axis of the animal. The abdomen may be enrolled to varying degrees. Most specimens show some evidence of minor dorsal-ventral compression and a few are laterally compressed. Diagenetic changes have altered the chitinous exoskeletons although preservation is delicate enough to have preserved internal (endophragmal) skeletons in some individuals. The lobster corpses and molts decayed on the sea bottom and as the articulating membranes decomposed the surrounding sediment found its way into the interior of the exoskeleton. Calcite precipitated and filled the interstitial spaces in the mud in and around the lobsters forming the argillaceous limestone concretions. (From the Journal of Paleontology, November 1977, Robert F. Feldman).

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