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 exhibit 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 juvenile Stingray specimen known as Heliobatis radians (Order: Rajiformes; Family: Dasyatidae), at once a rare and highly sought species, and the only species of ray from this formation. 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. Heliobatis is highly sought not only for the rarity, but alos because a specimen such as this makes for an awesome display.

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.

It is accompanied by a 65 mm long Diplomystus dentatus in one corner, 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, as is thought to have been a predator of smaller surface-feeders such as Knightia. I was told by the preparator that the Diplomystus was found during preparation of the ray; it can be seen that it was preserved at a slightly different time as the two fish are not on the same plane of the matrix.

This is a wonderful association plate of two different fish, having two different water depth preferences locked together from 50 million years.