Pelorosaurus
| Pelorosaurus Temporal range: Lower Cretaceous
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| Genus: | Pelorosaurus Mantell, 1850
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Pelorosaurus (Template:Pron-en pel-LORR-o-SAWR-əs, meaning "monstrous lizard") was a huge plant-eating dinosaur. Pelorosaurus was one of the first sauropod dinosaurs ever discovered. Pelorosaurus lived during the Early Cretaceous period, about 138-112 million years ago. Fossils have been found in England and Portugal. It was about 16 metres (50 feet) long. It is known from a humerus, vertebrae, a sacrum, pelvis and limb fragments, as well as from skin impressions; it was covered in hexagonal scales.
History
Pelorosaurus was the first sauropod to be identified as a dinosaur, although it was not the first to be discovered. Richard Owen had discovered Cetiosaurus in 1841 but had incorrectly identified it as a gigantic sea-going crocodile-like reptile.[1] In identifying Pelorosaurus as a dinosaur Mantell was able to do the same for Cetiosaurus.[2]
The taxonomic history of Pelorosaurus and Cetiosaurus, as noted by reviewers including Taylor and Naish, is fairly confusing. The type species of Cetiosaurus, C. brevis, was named by Richard Owen for several specimens from the early Cretaceous Period, some of which turned out to actually belong to Iguanodon. Noticing Owen's mistake in assigning iguanodont bones to Cetiosaurus, in 1849 Melville re-named the sauropod bones Cetiosaurus conybeari. However, this itself was a mistake, as technically the sauropod bones, not the iguanodont bones, should have retained the name C. brevis since they were the type specimens. Therefore, C. conybeari was a junior objective synonym of C. brevis (that is, C. brevis is not only an older name, but one based on the exact same fossils as the younger, invalid name).[3]
Not realizing Melville's naming error, Gideon Mantell in 1850 decided that C. conybeari was different enough from C. brevis that it needed a new genus, so he reclassified is under the new name Pelorosaurus conybeari (Mantell apparently had originally intended to use the name "Colossosaurus", but upon discovering that colossus was Greek for "statue" and not "giant", he changed his mind). In subsequent years, more specimens continued to be assigned to both Pelorosaurus and Cetiosaurus, and both were studied and reported on extensively in the scientific literature.[3]
Due to this chain of events, however, Pelorosaurus is actually an objective synonym of Cetiosaurus. To complicate matters further, no new specimens were ever assigned to C. brevis. Instead, the most well-known species of Cetiosaurus became C. oxoniensis, named by Phillips in 1871. C. oxoniensis, however, is from a different British geological formation and a much earlier time period (the mid-late Jurassic). By the 1970s paleontologists had recognized that C. oxoniensis is in fact a completely different, more primitive type of sauropod, different enough from C. brevis that is clearly belongs to a different genus and would require a new name. This would result in a situation where the correct name for the well-known dinosaur Pelorosaurus is actually Cetiosaurus, itself a well-known name, where the name Pelorosaurus would be discarded as invalid, and where Cetiosaurus itself would require a new name. To avoid such a situation, paleontologists Upchurch and Martin announced plans in 2003 to petition the ICZN asking for the type species of Cetiosaurus to be changed from C. brevis to C. oxoniensis, for the name Pelorosaurus conybeari to be preserved, and for C. brevis itself to be suppressed.[3]
Classification and species
A number of species have been assigned to the genus Pelorosaurus, most of which are dubious. Pelorosaurus has come to be a wastebasket taxon for any European sauropod. However, in recent years much work has been done to rectify the confusion. The genus probably belongs to the family Brachiosauridae.
- P. conybearei (Melville 1849) (type) = P. armatus (Gervais, 1852/Lydekker, 1889), P. brevis (Owen 1842/von Huene 1927), Pleurocoelus valdensis, Ornithopsis conybearei, Cetiosaurus brevis, C. conybearei, Morosaurus brevis, Oplosaurus armatus and Astrodon valdensis. Some hold that the type is a nomen dubium.
- P. becklesii (Mantell 1852) = Morosaurus becklesii
- P. hulkei (Seeley 1870)= Ornithopsis hulkei.
- P. humerocristatus (Hulke 1874/Sauvage 1887) - nomen dubium = Cetiosaurus humerocristatus and Ornithopsis humerocristatus.
- P. leedsii (Hulke 1887) - nomen dubium = Ornithopsis leedsii, Cetiosauriscus leedsii and Cetiosaurus leedsii.
- P. mackesoni (Owen 1884/Steel 1970) - nomen dubium or junior synonym of Dinodocus mackesoni.
- P. manseli (Hulke 1874) - nomen dubium = (possibly) Ischyrosaurus manseli, Ornithopsis manseli and Morinosaurus typus.
- P. megalonyx (Seeley 1869)- nomen dubium = Gigantosaurus megalonyx.
- P. praecursor (Sauvage 1876/1895) = Neosodon praecursor.
References
- ^ Owen, R. (1842). "Report on British fossil reptiles, Part II." Reports of the British Association for the Advancement of Science, 11: 60-204.
- ^ Mantell, G.A. (1850). "On the Pelorosaurus: an undescribed gigantic terrestrial reptile, whose remains are associated with those of the Iguanodon and other saurians in the strata of Tilgate Forest, in Sussex." Philosophical Transactions of the Royal Society of London, 140: 379-390.
- ^ a b c Taylor, M.P. and Naish, D. (2007). "An unusual new neosauropod dinosaur from the Lower Cretaceous Hastings Beds Group of East Sussex, England." Palaeontology, 50(6): 1547-1564. doi: 10.1111/j.1475-4983.2007.00728.x
- Cadbury, D. (2001). The Dinosaur Hunters, Fourth Estate, Great Britain.
