Suchosaurus Girardi

''Suchosaurus'' (meaning "crocodile lizard") is a spinosaurid dinosaur from Cretaceous England and Portugal, originally believed to be a genus of crocodile. The type material, consisting of teeth, was used by British palaeontologist Richard Owen to name the species ''S. cultridens'' in 1841. Later in 1897, French palaeontologist Henri-Émile Sauvage named a second species, ''S. girardi'', based on two fragments from the mandible and one tooth discovered in Portugal. ''Suchosaurus'' is possibly a senior synonym of the contemporary spinosaurid '' Baryonyx'', but is usually considered a dubious name due to the paucity of its remains, and is considered an indeterminate baryonychine. In the Wadhurst Clay Formation of what is now southern England, ''Suchosaurus'' lived alongside other dinosaurs, as well as plesiosaurs, mammals, and crocodyliforms.

History of discovery

In about 1820, British palaeontologist Gideon Mantell acquired teeth discovered near Cuckfield in the Wadhurst Clay of East Sussex, part of a lot with the present inventory number BMNH R36536. In 1822, he reported these, after an identification by William Clift, as belonging to crocodiles. In 1824, the teeth were mentioned and illustrated by Georges Cuvier, representing the first fossil illustration of a spinosaurid dinosaur (though this group wouldn't be recognized for nearly another century). In 1827 Mantell described additional teeth, pointing out the similarities to the crocodilians ''Teleosaurus'' and ''Gavialis''. One of these teeth is the present specimen BMNH R4415, others are part of BMNH R36536.

In 1841, British palaeontologist Richard Owen named, based on BMNH R36536 as a syntype series, a subgenus ''Crocodylus (Suchosaurus)'' with as type species ''Crocodylus (Suchosaurus) cultridens''.Owen, R. (1840–1845). ''Odontography''. London: Hippolyte Baillière, 655 pp, 1–32 The subgeneric name was derived from Greek σοῦχος, ''souchos'', the name of the Egyptian crocodile god Sobek. This reflected the presumed taxonomic affinities; at the time the crocodile-like snouts of spinosaurids were not known. The specific name is derived from Latin ''culter'', "dagger", and ''dens'', "tooth", in reference to the elongated form of the teeth. In 1842, Owen again mentioned the taxon as a subgenus, subsequently he and other workers would use it as a full genus ''Suchosaurus''. In 1842 and 1878 Owen referred some vertebrae (backbones) to ''Suchosaurus'', but these were later identified by Richard Lydekker as likely belonging to ornithischian dinosaurs instead. In 1884, Owen indicated a tooth as "''Suchosaurus leavidens''" in a caption, this is usually seen as a '' lapsus calami'' (or "slip of the pen") because this species is not further mentioned.

In 1897, French palaeontologist Henri-Émile Sauvage named a second species: ''Suchosaurus girardi'', based on two jaw fragments (specimen MG324) and a tooth, found in the Papo Seco Formation of Portugal by Swiss-Portuguese geologist Paul Choffat. The specific name honours French geologist Albert Girard.Sauvage, H. E. (1897–1898). ''Vertébrés fossiles du Portugal. Contribution à l’étude des poissons et des reptiles du Jurassique et du Crétacique.'' Lisbonne: Direction des Travaux géologiques du Portugal, 46p The tooth was considered lost but was rediscovered and in 2013 reported as specimen MNHN/UL.I.F2.176.1, part of remains recovered after a fire in 1978.

During the nineteenth and most of the twentieth century, ''Suchosaurus'' was usually considered to have been some obscure crocodilian, perhaps belonging to the Pholidosauridae. Single comparable teeth discovered in England were referred to the genus.Lydekker, R., 1888, ''Catalogue of the Fossil Reptilia and Amphibia in the British Museum (Natural History), Cromwell Road, S.W., Part 1. Containing the Orders Ornithosauria, Crocodilia, Dinosauria, Squamata, Rhynchocephalia, and Proterosauria''. British Museum of Natural History, London. 309 pp However, when publishing a redescription of '' Baryonyx'' in 1998, British palaeontologist Angela Milner realised that the teeth of that spinosaurid dinosaur were extremely similar to those of ''Suchosaurus''. In 2003, she suggested both genera represented one and the same animal. An identity would imply the name ''Suchosaurus'' has priority. However, the ''Suchosaurus'' teeth are also indistinguishable from those of ''Cristatusaurus'' and ''Suchomimus'', making it an indeterminate baryonychine.

In 2007, French palaeontologist Eric Buffetaut considered the teeth of ''S. girardi'' very similar to those of ''Baryonyx'' (and ''S. cultridens'') except for the stronger development of the ribs (lengthwise ridges) on the tooth crown, suggesting that the remains belonged to the same genus. Buffetaut agreed with Milner that the teeth of ''S. cultridens'' were almost identical to those of ''B. walkeri'', but with a ribbier surface. The former taxon might be a senior synonym of the latter (since it was published first), depending on whether the differences were within a taxon or between different ones. According to Buffetaut, since the holotype specimen of ''S. cultridens'' is one worn tooth and that of ''B. walkeri'' is a skeleton it would be more practical to retain the newer name.Buffetaut, E. (2007). "The spinosaurid dinosaur ''Baryonyx'' (Saurischia, Theropoda) in the Early Cretaceous of Portugal." ''Geological Magazine'', 144(6): 1021-1025. In 2011, Portuguese palaeontologist Octávio Mateus and colleagues agreed that ''Suchosaurus'' was closely related to ''Baryonyx'', but considered both species in the former genus (''Suchosaurus'') ''nomina dubia'' (dubious names) since their holotype specimens were not considered diagnostic (lacking distinguishing features) and could not be definitely equated with other taxa.

Description

In 2012, American vertebrate palaeontologist Thomas R. Holtz Jr. tentatively estimated ''Suchosaurus'' at around in length and weighing between .Holtz, Thomas R. Jr. (2011) ''Dinosaurs: The Most Complete, Up-to-Date Encyclopedia for Dinosaur Lovers of All Ages,'
Winter 2010 Appendix.
/ref> And in 2016, Spanish palaeontologists Molina-Pérez and Larramendi estimated ''S. cultridens'' at approximately long, tall at the hips and weighing . The teeth of ''Suchosaurus girardi'' were curved, oval in cross section, and had tall roots that were one and a half times taller than the crown. Its teeth, like some other spinosaurids, bore flutes (lengthwise grooves), in ''S. girardi'', there were eight flutes on the lingual side (which faced the inside of the mouth), and four less distinct flutes on the labial side (which faced the outside of the mouth). The tooth enamel, or outermost layer, had a microscopic wrinkled texture.

Palaeoecology

The Wadhurst Clay Formation, part of the Wealden Group, is dated to the Valanginian stage of the Early Cretaceous Period, about 139.8 to 132.9 million years ago.Hopson, P.M., Wilkinson, I.P. and Woods, M.A. (2010) ''A stratigraphical framework for the Lower Cretaceous of England''. Research Report RR/08/03. British Geological Survey, Keyworth. It consists mainly of shales and mudstones.Lake, R.D. & Shepard-Thorn, E.R. (1987) ''Geology of the country around Hastings and Dungeness: Memoir for 1:50,000 geological sheets 320 and 321''. British Geological Survey, London. Other dinosaurs that shared this environment with ''Suchosaurus'' included the iguanodontians '' Barilium'' and '' Hypselospinus'', as well as the dubious species ''Megalosaurus dunkeri'' and an unnamed maniraptoran.Naish, D. and Sweetman, S.C. (2011). "A tiny maniraptoran dinosaur in the Lower Cretaceous Hastings Group: evidence from a new vertebrate-bearing locality in south-east England." ''Cretaceous Research'', 32: 464-471. They coexisted with the plesiosaur '' Hastanectes'', the crocodyliform ''Goniopholis'' and the mammals ''Loxaulax'', ''Aegialodon'', ''Laolestes'',Foster, J. (2007). "Appendix." ''Jurassic West: The Dinosaurs of the Morrison Formation and Their World''. Indiana University Press. pp. 327-329. and ''Spalacotherium''.

References

External links

First post of a long discussion of ''Suchosaurus'' as a dinosaur and its implications
in the Dinosaur Mailing List Archives

{{Taxonbar, from=Q3472673

Spinosaurids
Barremian life
Valanginian life
Early Cretaceous dinosaurs of Europe
Cretaceous England
Fossils of England
Cretaceous Portugal
Fossils of Portugal
Fossil taxa described in 1841
Taxa named by Richard Owen
Nomina dubia