Green River Female Heliobatis radians Stingray Fossil Fish

Description: This 50 million year old, Eocene-Era fossil fish comes from one of the world's famous Laggerstatten, the Green River Formation in Wyoming. A small portion of the fish fossils from Green River exhibits such fine preservation. The significant extent of soft-tissue preservation that makes the site famous is evident in this specimen.

This is an exquisite, museum quality female Stingray specimen known as Heliobatis radians (Order: Rajiformes; Family: Dasyatidae), and the only species of ray from the Green River Formation that was known up until 2004  when Carvalho et al. (2004) described Asterotrygon maloneyi. Like modern stingrays, this extinct genus had spikes on its tail. The preservation is superb and the preparation is the best there is. Note in the pictures the details in the barbs and the thorn-like spines of the tail. This one is known to be a female due to the absence of claspers used by the male in mating.

Rays belong to the Chondrichtyes, as do the sharks. All have an inner skeleton made of cartilage. Since cartilage comprises more organic material (collagen and elastic tissues) than bone, it decays more rapidly. As a result, fossils of cartilaginous fishes generally are rare. The cartilaginous fishes appeared in Silurian time, and their ancestors remain one of the most successful groups of marine animals.

It is accompanied by traces of a bony fish, most likely a Diplomystus dentatus near the edge of the plaque, making for a wonderful contrast between one of the most rare and most common fish found in Green River deposits. Diplomystus has the body form and mouth placement of a surface feeder, and is thought to have been a predator of smaller surface-feeders such as Knightia.

Reference: Carvalho, M.R.; Maisey, J.G.; Grande, L. (2004). "Freshwater stingrays of the Green River Formation of Wyoming (early Eocene), with the description of a new genus and species and an analysis of its phylogenetic relationships (Chondrichthyes, Myliobatiformes).". Bulletin of the American Museum of Natural History 284: 1–136.

Attribution: Stone Relic CC BY-NC 4.0

Also see: Class Chondrichthyes Fossils Museum and Rare Fish Fossils