Sinohydrosaur reptile is 15.75 inches long as measured from
the nose to the tip of the tail along the backbone. The slab itself is 6 inches
x 15.5 inches x 0.625 inch thick. Like all fossils from this brittle rock
formation, the specimen has been reassembled from smaller pieces due to
shattering during excavation. This 125 million year old reptile fossil is a Sinohydrosaurus lingyuanensis and was found in the Yixian Formation in Lingyuan,
Liaoning Province in northeast China. This same formation is famous for several
recently discovered species of bird fossils as well as dinosaurs with primitive
feathers.
This reptile is a new discovery as well, having been first formally described
and named in 1999 by Li Jianjun and colleagues of the Beijing Natural History
Museum. The name translates into "China" (sino) "Water" (hydro) "Lizard" (saurus),
with the suffix "lingyuanensis" added to honor the place of its discovery. Also
in 1999, working independently, Gao Keqin and others at the Institute of
Vertebrate Paleontology and Paleoanthropology in Beijing named the same species
"Hyphalosaurus lingyuanensis" -- being completely unaware that they were working
with the counter-slab of the same specimen that the other team was studying! The
two names are used interchangeably today, although Sinohydrosaurus is easier to
remember while Hyphalosaurus is now the official name. Sinohydrosaurus was
neither a fish nor an amphibian. Rather, it was a reptile that phylogenetically
descended from a land-dwelling ancestor (similar to how the ancestors of whales
were once land dwellers) to become a fresh-water dweller. It looks very similar
to the Keichousaurus, but is smaller and differs in the osteological structure
by having no clavicles; instead having a T-shaped interclavicle. In addition, it
lived in the Cretaceous Period 125 million years ago, about 100 million years
later than the Keichousaurus.