Palaeosaurus

Genus of reptiles (fossil)

Palaeosaurus (or Paleosaurus) is a genus of indeterminate archosaur known from two teeth found in the Bromsgrove Sandstone Formation and also either the Magnesian Conglomerate or the Avon Fissure Fill of Clifton, Bristol, England (originally Avon). and the curator of the Bristol Institution, Samuel Stutchbury (15 January 1798 – 12 February 1859), began to excavate "saurian remains" at the quarry of Durdham Down, at Clifton, presently a part of Bristol, which is part of the Magnesian Conglomerate. In 1834 and 1835, they briefly reported on the finds. They provided their initial description in 1836, naming two new genera: Palaeosaurus and Thecodontosaurus. Riley and Stutchbury did not mean to assign these species to Saint Hilaire's genus of teleosaurids; they simply did not know the name had been used. Thecodontosaurus was also named in this publication. Only in 1840 do Riley and Stutchbury fully describe their two species of Palaeosaurus, each based on a single sharp tooth from the Late Triassic Period. The spellings were then corrected to read Paleosaurus cylindrodon and Paleosaurus platyodon. In 1842, Sir Richard Owen created the name Dinosauria. In the same publication, he attempted to redescribe Riley and Stutchbury's Paleosaurus and Thecodontosaurus, which he did not consider to be dinosaurs. Not knowing of the change in spelling, he changed the name back to Palaeosaurus, and this spelling was followed by all subsequent authors until 1959. Owen assigns other bones to Palaeosaurus, which would later be re classified to the prosauropod dinosaur Thecodontosaurus. Contrary to Owen, in 1870, Thomas Henry Huxley described both Thecodontosaurus and Palaeosaurus as dinosaurs for the first time. He considered Palaeosaurus platyodon to be synonymous with Thecodontosaurus antiquus, most likely due to the Thecodontosaurus bones that Owen assigned to the former genus. However, Huxley regarded P. cylindrodon as an unrelated carnivorous theropod. American paleontologist Edward Drinker Cope named a third species, Palaeosaurus fraserianus, in 1878, for an isolated tooth found in Triassic rocks in Pennsylvania. Today these are regarded as belonging to an indeterminate sauropodomorph dinosaur unrelated to Palaeosaurus.

In 1932, Von Huene assigned new material to Palaeosaurus; numerous prosauropod bones found in Germany. Because of Owen's Thecodontosaurus bones misassigned to Palaeosaurus cylindrodon, the species was thought to be a prosauropod. Von Huene therefore referred his new species to Palaeosaurus, creating the name P. diagnostica. In 1973, Peter Galton, a British paleontologist, moved the species into its own genus, creating the new combination Efraasia diagnosticus. For several decades, most scientists considered Efraasia a junior synonym of Sellosaurus; however, in 2003 Adam Yates, another British palaeontologist, redescribed the bones assigned to Sellosaurus. He resurrected the genus Efraasia for some of these bones, to which he also assigned the bones that had been first described as Teratosaurus minor as well (although leaving out the teeth, which were recognized as non dinosaurian). Like Galton in 1973, Yates's Efraasia also included the remains previously known as Palaeosaurus diagnosticus, although unlike Galton, Yates calls the species Efraasia minor, synonymizing both species. E. minor was claimed to have priority because von Huene described Teratosaurus minor several pages before Palaeosaurus diagnosticus in his 1908 publication. The name minor therefore would take precedence over diagnostica for this species.