Sphenosaurus is a poorly known genus

Genus

In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

 of procolophonid

Procolophonid

The Procolophonids - family Procolophonidae - are a group of small reptiles. Skulls have been discovered, roughly 5 cm in diameter....

, a type of prehistoric reptile

Reptile

Reptiles are members of a class of air-breathing, ectothermic vertebrates which are characterized by laying shelled eggs , and having skin covered in scales and/or scutes. They are tetrapods, either having four limbs or being descended from four-limbed ancestors...

 from the Permian

Permian

The PermianThe term "Permian" was introduced into geology in 1841 by Sir Sir R. I. Murchison, president of the Geological Society of London, who identified typical strata in extensive Russian explorations undertaken with Edouard de Verneuil; Murchison asserted in 1841 that he named his "Permian...

. Originally assigned the name Palaeosaurus sternbergii, by
German paleontologist Leopold Joseph Fitzinger in 1840, the generic name was already preoccupied by not one but two other reptiles assigned the name Palaeosaurus

Palaeosaurus

Several very different genera of prehistoric animals have been named Palaeosaurus or Paleosaurus since the 1830s. Further confusing the matter, all of the species are poorly known or poorly preserved and both spellings have been used interchangeably, even by the same authors.The repeated recurrence...

. In 1847, Hermann von Meyer recognized the original 1833 usage of Palaeosaurus and moved P. sternbergii to a new genus, Sphenosaurus.