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.
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.
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.
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.
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.
Relic CC BY-NC 4.0
Also see: Class
Chondrichthyes Fossils Museum and Rare Fish Fossils