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| Palaeosaurus | |
|---|---|
 | |
| Teeth BRSMG *Ca7449/4 (left) and BRSMG *Ca7448/3 (right) - of which both comprise the holotype | |
Scientific classification | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Clade: | Archosauromorpha |
| Clade: | Archosauriformes |
| Clade: | Archosauria |
| Genus: | †Palaeosaurus Riley and Stutchbury, 1836 |
| Type species | |
| †Palaeosaurus cylindrodon Riley and Stutchbury, 1840 | |
| Synonyms | |
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Palaeosaurus (orPaleosaurus) is a genus of indeterminate archosaur known from two teeth found in theBromsgrove Sandstone Formation and also either theMagnesian Conglomerate or theAvon Fissure Fill ofClifton, Bristol,England (originallyAvon).[1] It has had a convoluted taxonomic history.[2]
Richard Owen's mistake of associating prosauropod skeletal remains with the carnivorous teeth which Riley and Stutchbury calledPalaeosaurus, combined withFriedrich von Huene'sTeratosaurus minor, which was also a combination of carnivore and prosauropod remains, led paleontologists to viewprosauropods as carnivorous animals for quite a long time. This error made it into several textbooks and other dinosaur reference works.[2]
In the autumn of 1834,surgeonHenry Riley (1797–1848)[3] and thecurator of theBristol Institution,Samuel Stutchbury (15 January 1798 – 12 February 1859), began to excavate "saurian remains" at the quarry ofDurdham Down, atClifton, presently a part ofBristol, which is part of theMagnesian Conglomerate. In 1834 and 1835, they briefly reported on the finds.[4] They provided their initial description in 1836, naming two new genera:Palaeosaurus andThecodontosaurus.[1] In 1836 Riley and Stutchbury briefly and informally published on two new fossil teeth (the holotype tooth ofP. platyodon is listed under BRSMG *Ca7448/3 and the holotype tooth ofP. cylindrodon is listed under BRSMG *Ca7449/4. Both are now listed under the latter species) found in or near the city ofBristol,England, which they calledPalaeosaurus cylindrodon andPalaeosaurus platyodon.[1][5] Riley and Stutchbury did not mean to assign these species toSaint-Hilaire's genus ofteleosaurids; 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 ofPalaeosaurus, each based on a single sharp tooth from the LateTriassic Period. The spellings were then corrected to readPaleosaurus cylindrodon andPaleosaurus platyodon.
In 1842,Sir Richard Owen created the nameDinosauria. In the same publication, he attempted to redescribe Riley and Stutchbury'sPaleosaurus andThecodontosaurus, which he did not consider to be dinosaurs. Not knowing of the change in spelling, he changed the name back toPalaeosaurus, and this spelling was followed by all subsequent authors until 1959. Owen assigns other bones toPalaeosaurus, which would later be re-classified to the prosauropod dinosaurThecodontosaurus. Contrary to Owen, in 1870,Thomas Henry Huxley described bothThecodontosaurus andPalaeosaurus as dinosaurs for the first time. He consideredPalaeosaurus platyodon to be synonymous withThecodontosaurus antiquus, most likely due to theThecodontosaurus bones that Owen assigned to the former genus. However, Huxley regardedP. cylindrodon as an unrelatedcarnivoroustheropod.
American paleontologistEdward Drinker Cope named a third species,Palaeosaurus fraserianus, in 1878, for an isolated tooth found in Triassic rocks inPennsylvania. Today these are regarded as belonging to an indeterminatesauropodomorphdinosaur unrelated toPalaeosaurus.[6] In 1881, a fourth species is created,Palaeosaurus stricklandi; these are now recognized to be those of aphytosaur.[7]
Von Huene, in 1908, recognized the tooth ofPalaeosaurus platyodon belonged to a phytosaur and placed it into the new genusRileya, forming the new combinationRileya platyodon.
One of theholotype teeth ofP. cylindrodon, presumably BRSMG *Ca7448/3, was destroyed duringWorld War II, in 1940. The other tooth survives to this day.
In 1959 German paleontologistOskar Kuhn, for the first time since 1840, recognized that the genusPalaeosaurus created by Riley and Stutchbury in 1836 waspreoccupied and created the new generic namePalaeosauriscus to containPalaeosaurus cylindrodon and all other species that had previously been described underPalaeosaurus.
In 1964, Owen's mis-classified specimens caused AmericanEdwin Harris Colbert to classify prosauropods into two groups – Palaeosauria, which includedPalaeosaurus andTeratosaurus, thought to be carnivorous because of the chimaeric nature ofPalaeosaurus; andPlateosauria, which includedThecodontosaurus andPlateosaurus, which had been described with the correct skulls, and therefore were correctly described as aherbivorous group.
Thecodontosaurus was redescribed by a team of paleontologists led byMichael Benton in 2000, which placed Owen's mis-classified material under the genusThecodontosaurus rather thanPalaeosaurus, and this is still followed today. Most of the skeletal bones ever assigned toPalaeosaurus cylindrodon andP. platyodon were also reassigned toThecodontosaurus. The generaRileya andPalaeosauriscus, as well as the speciesPalaeosaurus cylindrodon andPalaeosaurus platyodon, were all declarednomina dubia.
In 2007, Peter Galton, reviewing thearchosaurian fossils of the 1834Bristol finds, reaffirmed the identification of the two teeth and humeri ofPalaeosaurus platyodon (Rileya) as belonging to a phytosaur, and regardedP. cylindrodon (Palaeosauriscus) as an indeterminate archosaur. He agreed with Benton thatRileya is dubious, but suggested thatPalaeosauriscus may be valid, based on its now-destroyed tooth with a "subcircular cross-section and fine, obliquely inclined denticles".[2]
In 1932, Von Huene assigned new material toPalaeosaurus; numerous prosauropod bones found in Germany. Because of Owen'sThecodontosaurus bones misassigned toPalaeosaurus cylindrodon, the species was thought to be a prosauropod. Von Huene therefore referred his new species toPalaeosaurus, creating the nameP. diagnostica.
In 1973,Peter Galton, a British paleontologist, moved the species into its own genus, creating the new combinationEfraasia diagnosticus. For several decades, most scientists consideredEfraasia a junior synonym ofSellosaurus; however, in 2003Adam Yates, another British palaeontologist, redescribed the bones assigned toSellosaurus. He resurrected the genusEfraasia for some of these bones, to which he also assigned the bones that had been first described asTeratosaurus minor as well (although leaving out the teeth, which were recognized as non-dinosaurian). Like Galton in 1973, Yates'sEfraasia also included the remains previously known asPalaeosaurus diagnosticus, although unlike Galton, Yates calls the speciesEfraasia minor, synonymizing both species.E. minor was claimed to have priority because von Huene describedTeratosaurus minor several pages beforePalaeosaurus diagnosticus in his 1908 publication. The nameminor therefore would take precedence overdiagnostica for this species.
Type species: "Palaeosaurus"cylindrodon (nomen dubium) Riley and Stutchbury 1836 (an indeterminatearchosauromorph later renamed the type species ofPalaeosauriscus cylindrodon, asPalaeosaurus was pre-occupied)[8]
Other species:
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