Suchosaurus (meaning "crocodile lizard") is a dubious genus of large theropod dinosaur that lived during the Early Cretaceous in what is now Europe. The type species, S. cultridens, was originally described in 1841 by Richard Owen based on a chimeric assemblage of fossil teeth and vertebrae discovered in the Tilgate Forest, of Sussex, England, in sediments of the Wealden Supergroup. The second species, S. girardi, was established in 1897 by Henri Émile Sauvage from a tooth and fragmentary jaw material recovered from the Papo Seco Formation in Portugal. Initially and generally interpreted as a crocodilian for nearly two centuries (as reflected by its generic name), Suchosaurus was not formally reidentified as a spinosaurid until a 2003 publication by Angela Milner, who also considered it as a possible senior synonym of Baryonyx. This proposal was followed by several authors until 2011, when Octávio Mateus and colleagues regarded the genus as dubious due to the non-diagnostic nature of the assigned fossil material. Named only one year before Owen introduced the term Dinosauria in 1842, Suchosaurus is therefore among the first dinosaurs ever described in the history of paleontology and also represents the very first named spinosaurid, although it was not recognized as such at the time of its original descriptions.
Although known from very limited fossil material, Suchosaurus is estimated to have reached a length of between , with a minimum body mass of around one tonne. Like other spinosaurids, Suchosaurus was probably a large bipedal carnivore with well-built forelimbs and elongated, crocodile-like skulls. The teeth of Suchosaurus, which constitute the main fossils documenting this taxon, were slightly recurved and displayed a conical to subconical cross-section. The crown also beared numerous longitudinal flutes, and most of the teeth appeared to have fine serrations. Although now considered as a dubious spinosaurid, Suchosaurus is generally assigned to the subfamily Baryonychinae due to its dental characteristics, which it shares with other genera such as Baryonyx and Suchomimus. Like other members of this group, its teeth were most likely adapted for a piscivorous diet. Based on the fossil record associated with the taxon, the animal lived and hunted in fluvial environments alongside numerous other dinosaurs, as well as pterosaurs, crocodylomorphs, turtles, plesiosaurs, fishes, various invertebrates, and even early mammals.
Research history
The taxonomic history of Suchosaurus begins in 1822, when British palaeontologist Gideon Mantell and his partner Mary Ann mentioned, in their book The Fossils of the South Downs, teeth that had been discovered by Mantell in a quarry in Tilgate Forest, near Cuckfield in West Sussex, England. Based on their morphology, characterized by well-defined lateral ridges, Mantell's mentor William Clift, then curator of the Hunterian Museum, London, suggested that these fossils might belong either to a crocodile or to a monitor lizard, the couple favoring the former interpretation. In June 1823, Scottish geologist Charles Lyell brought the fossils described by the Mantell couple to Paris, France, so that they could be examined by French naturalist Georges Cuvier. In his work published the following year, Cuvier endorsed the initial 1822 interpretation, although he described most of the teeth only very briefly. Nevertheless, he illustrated four of the Tilgate fossil teeth discovered by Mantell. In 1827, Mantell redescribed these fossils in greater detail, distinguishing them as belonging to two types of crocodilians, separating the blunt- teeth from the more slender and recurved ones, which he considered comparable to those of gharials. Although he did not erect any scientific name to formalize this observation, he attributed the teeth of the second category to a crocodilian that he referred to by the common name "gavial of Tilgate Forest".
In 1841, British palaeontologist Richard Owen established, within the genus Crocodilus, a subgenus and species he named Crocodilus (Suchosaurus) cultridens, based on the fossils discovered by Mantell. The name Suchosaurus comes from the Ancient Greek σοῦχος (souchos, "crocodile"), and σαῦρος (saûros, "lizard"), reflecting its then-accepted affinities with crocodilians. The specific name comes from the Latin culter, "little knife", and dens, "tooth", in reference to the taxon's dental morphology. In his work published the following year (the same work in which he first coined the term Dinosauria), Owen retained Suchosaurus at the rank of subgenus and also referred to it two fossil vertebrae collected by Mantell, without, however, providing any justification for this association. He further considered the expression "gavial of Tilgate Forest" to be the vernacular name of this taxon. The holotype, cited in the scientific literature since the Cuvier's work, consists of a single tooth broken at the upper third of the crown. Like many fossils discovered at Tilgate, this tooth is now housed in the palaeontological collections of the Natural History Museum, London. The original specimen number was BMNH R36536, but it was later re-catalogued as NHMUK PV R36536.
In the years following the publication of Owen's two works, Suchosaurus was elevated to the rank of a distinct genus by Owen himself as well as by other authors. In a work published posthumously in 1867, the French naturalist Charles Léopold Laurillard nevertheless made a taxonomic error regarding this animal: although he acknowledged that Suchosaurus had been named by Owen, he nonetheless attributed the origin of the species name cultridens to Mantell. In an 1878 article, Owen illustrated for the first time the previously mentioned vertebrae, noting that they were not found in direct association with Mantell's teeth, including the holotype. In the second volume of his 1884 work, when he figured again this latter, Owen named it as S. laevidens. This designation was probably a lapsus calami, as he did not use this specific epithet elsewhere in the same publication. In 1888, British naturalist Richard Lydekker determined that the two vertebrae previously attributed to the genus actually belonged to ornithischian dinosaurs. He assigned the first to the family Iguanodontidae and suggested that the second might be referred to the ankylosaur Hylaeosaurus. Lydekker also regarded S. laevidens as a junior synonym of S. cultridens, a position likewise adopted in 1890 by British palaeontologists Arthur Smith Woodward and Charles Davies Sherborn.
In 1896, the French palaeontologist Henri-Émile Sauvage reported the presence of Suchosaurus in Portugal based on fossils discovered by the Swiss geologist Paul Choffat in the locality of Boca do Chapim. Consisting of two jaw fragments and an isolated tooth, this material enabled Sauvage to erect the second species Suchosaurus girardi, the specific name honouring the Portuguese naturalist Albert Girard. The two jaw fragments are currently numbered as MG 324 at the in Lisbon. In 2007, French palaeontologist Éric Buffetaut noted that the associated single tooth had not been relocated in the institution and therefore regarded it as lost. However, he identified a third mandibular fragment, probably complementary to one of the first two and previously undescribed. In a conference abstract published in 2013, Portuguese palaeontologist Elisabete Malafaia and her colleagues reported the rediscovery of the isolated tooth in the palaeontological collections of the National Museum of Natural History and Science, Lisbon. Now catalogued as MNHN/UL.I.F2.176, the tooth is among the fossils that were saved from a fire that destroyed a significant part of the museum in 1978.
After some fossil teeth collected in Sussex and on the Isle of Wight were routinely labelled to the genus, Suchosaurus was only rarely mentioned in the scientific literature after the late 19th century, probably due to the very limited nature of the fossil material. One of the few notable mentions during the following century comes from Spain, where the palaeontologist in 1927 attributed to this genus fossils discovered in the deposits of Morella, in Castellón. However, these specimens were never described in detail afterwards and appear to have been lost during the Spanish Civil War. They were nevertheless briefly mentioned in 1960 by the Spanish palaeontologist .
In 1986, British palaeontologists Alan Charig and Angela Milner described the theropod dinosaur Baryonyx walkeri on the basis of a relatively well-preserved partial skeleton discovered near the Ockley, in Surrey. Its initial descriptions highlighted distinctive dental characters, which led some authors to assign several isolated teeth uncovered in the Wealden Supergroup of England to this genus. On the basis of these same morphological criteria, Milner suggested in 2003 that some teeth previously referred to Megalosaurus and Suchosaurus might instead belong to Baryonyx. In his 2007 study, Buffetaut considered the teeth of S. girardi very similar to those of Baryonyx (and S. cultridens) except for the stronger development of the tooth crown flutes (or "ribs"; lengthwise ridges), 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 a single tooth and that of B. walkeri is a skeleton, it would be more practical to retain the newer name.
In a 2010 review of the taxonomic history of spinosaurids before the original description of the type genus Spinosaurus in 1915, Buffetaut recognized Cuvier's 1824 illustration of the holotype tooth of S. cultridens as the earliest known published depiction of a spinosaurid fossil and one of the oldest published figures of a dinosaur fossil, although neither of these groups had been defined or named when it appeared in print. Buffetaut also stated that it is very likely that the fossils attributed to Suchosaurus by Royo y Gómez in 1927 belonged to the baryonychines, in light of the discovery of fossil teeth from this subgroup at Morella. The discovery of these same teeth was first reported in a conference abstract by the Spanish paleontologist José Ignacio Canudo and his colleagues in 2004. In 2011, Portuguese paleontologist Octávio Mateus and colleagues agreed that Suchosaurus was closely related to Baryonyx, but considered both species in the former genus nomina dubia (dubious names) since their holotype specimens were not considered diagnostic (lacking distinguishing features) and could not be definitely equated with other taxa. However, following its formal reidentification in the early 21st century, Suchosaurus is recognized as the first spinosaurid to have been named, as well as one of the first dinosaurs described in the history of paleontology, although it was not initially identified as such.
Description