The holotype specimen includes a partial hindlimb and a pair of caudal vertebrae, and two eggshell fragments were found alongside these bones.

Hypselosaurus has been found in the same formation as the dromaeosaurids Variraptor and Pyroraptor, the ornithopod Rhabdodon, and the ankylosaurian Rhodanosaurus, as well as indeterminate bones from other groups.

In 1846, Pierre Philippe Émile Matheron, a French geologist and paleontologist, described several large bones from Provence, France.

[2] In the spring of 1869, Matheron formally described these remains, including a partial femur, fibula and possible tibia and a pair of associated caudal vertebrae, as the holotype specimen of a new taxon, Hypselosaurus priscus.

[1] When originally named, Matheron proposed that Hypselosaurus was an aquatic crocodile, as was suggested for similar taxa like Pelorosaurus, Cetiosaurus, Streptospondylus and Steneosaurus by their describers.

[1] As preserved, the left tibia is largely incomplete, with only a small section of the shaft, just proximal to the distal condyles, known.

Age determination studies performed on the fossilized remains have been inconclusive, with results ranging from a few decades to several hundred years.

Another potential explanation for variation in eggshell thickness is that the thinner eggs were laid by younger individuals than the thicker shell eggs laid by older individuals or that it was a consequence of natural variations of eggshell thickness within a single species.

This formation, dating to the early Maastrichtian approximately 70 mya, has provided fossils of several different groups of dinosaurs.

The theropods Variraptor and Pyroraptor, both considered to be within the family Dromaeosauridae, have been found in the Grés á Reptiles Formation, in addition to the nodosaurid ankylosaurian Rhodanosaurus (a dubious genus[15]); a bone fragment potentially belonging to Abelisauridae; and the rhabdodontid ornithopod Rhabdodon.

[3] Although the material between Variraptor and Pyroraptor cannot be compared, and they may in fact belong to the same taxon, there are at least two separate dromarosaurids present in the formation.