| Streptospondylus | |
|---|---|
 | |
| Tibia, astragalus and calcaneum ofStreptospondylus altdorfensis at theGallery of Paleontology and Comparative Anatomy, Paris. | |
Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Clade: | Dinosauria |
| Clade: | Saurischia |
| Clade: | Theropoda |
| Clade: | †Megalosauria |
| Genus: | †Streptospondylus von Meyer,1832 |
| Species: | †S. altdorfensis |
| Binomial name | |
| †Streptospondylus altdorfensis von Meyer, 1832 | |
| Synonyms[1] | |
Streptospondylus, fromAncient Greek στρεπτός (streptós), meaning "twisted", and σπόνδυλος (spóndulos), meaning "vertebra", is agenus oftetanurantheropoddinosaur known from the LateJurassic period ofFrance, 161 million years ago. It was a medium-sized predator with an estimated length of 6 meters (19.5 ft) and a weight of 500 kg (1,100 lbs).[2]
Streptospondylus was one of the first dinosaurs collected and was the first described, though not the first dinosaur named.[1]
In 1778, abbey Charles Bacheley, a Norman naturalist, reported the presence of fossil bones in the Callovo-Oxfordian formations, either theMarnes de Dives or the overlyingMarnes de Villers, probably the former, exposed at the foot of theVaches Noires cliffs betweenVillers-sur-Mer andHoulgate.[3][4] These fossil materials contained theropod vertebrae and marine crocodilian remains. After the death of Bacheley, his fossil cabinet was acquired by the "Ecole centrale de Rouen".[3] Louis-Benoît Guersent (1777–1848), professor of natural history in this school, drew the attention ofGeorges Cuvier to these remarkable fossil bones. With the agreement of theprefect ofSeine-Inférieure, countJacques Claude Beugnot, Guersent sent the collection to theMuséum National d'Histoire Naturelle inParis. In 1800, these fossils were briefly mentioned byGeorges Cuvier who misspelled the name of their former owner as Bachelet.[5]
In 1808, Cuvier scientifically described the theropod vertebrae as the first dinosaur remains ever. However, he considered them to be crocodilian and associated them with fossils of theTeleosauridae and theMetriorhynchidae.[6] In 1822, Cuvier by the work ofHenry De La Bèche became aware that these finds were very disparate, stemming from different periods. He abstained from naming them but in 1824 concluded that there were two main types. In 1825Étienne Geoffroy Saint-Hilaire accordingly named two crocodilian skulls as the genusSteneosaurus, the one, specimen MNHN 8900, becomingSteneosaurus rostromajor, the other, MNHN 8902,S. rostrominor.[7]
In 1832 however, the GermanpaleontologistChristian Erich Hermann von Meyer split the material.Steneosaurus rostrominor was renamedMetriorhynchus geoffroyii whileSteneosaurus rostromajor becameStreptospondylus altdorfensis. To the last species the theropod remains were referred.[8] Thegenus name comes from Ancient Greek στρεπτός (streptós), meaning "twisted", and σπόνδυλος (spóndulos), meaning "vertebra", alluding to the fact that the vertebrae differed from typical crocodile elements in beingopisthocoel: convex in front and concave behind. Thespecific name refers toAltdorf where some teleosaurid remains had also been found. Von Meyer's name was the firstbinomial name (also) referring to a theropod.
In 1842Richard Owen pointed out that von Meyer had been incorrect in changing the original specific name and created the correct combinationStreptospondylus rostromajor forStreptospondylus altdorfensis. At the same time he created a second species:Streptospondylus cuvieri based on a single damaged vertebra from theBajocian, found nearChipping Norton.[9] In 1861, Owen would refer the entire Cuvier material toS. cuvieri, despite the fact that if it were cospecific the nameS. rostromajor would have priority. From that timeS. cuvieri was generally accepted in the literature as the valid name, though some workers split off the theropod remains from the crocodilian bones,Edward Drinker Cope in 1867 naming aLaelaps gallicus andFriedrich von Huene in 1909 aMegalosaurus cuvieri.
In 1964,Alick Donald Walker discovered Owen's mistake, referring the entire theropod material to the new speciesEustreptospondylus divesensis which, however, had a skull not belonging to the Cuvier material as thetype specimen, MNHN 1920–7.[10] In 1977Philippe Taquet created the genusPiveteausaurus for this species.
In 2001,Ronan Allain concluded that no connection could be proven betweenPiveteausaurus and the referred other theropod material fromNormandy. He also pointed out that the skull von Meyer had basedStreptospondylus altdorfensis on was in fact a composite of bones from two species, since namedSteneosaurus edwardsi Deslongchamps 1866 andMetriorynchus superciliosum Blainville 1853 (Steel 1973). Alectotype had never been chosen from one of the composite parts to give the nameStreptospondylus priority over either one of these species. Allain used this situation to remove all the crocodilian material from theStreptospondylus type by designating the complete (postcranial) theropod material as the lectotype. AsSteneosaurus rostromajor had been based on the composite skull, the epithetrostromajor now no longer had priority overaltdorfensis. This way in 2001Streptospondylus altdorfensis became the valid name andtype species of a theropod.Laelaps gallicus andMegalosaurus cuvieri are its objectivejunior synonyms.[1]
The lectotype specimens, MNHN 8605-09, 8787-89, 8793-94, 8907, were probably found at the coast in layers of the Falaises des Vaches Noires nearCalvados, dating from the lateCallovian or earlyOxfordian, about 161 million years old. They consist of several vertebrae series, single vertebrae, a partial leftpubis and limb elements. The longest vertebra has a length of 97 millimetres, indicating a total body length of about seven metres. Also a partial leftfemur, MNHN 9645, has been referred.Streptospondylus has been diagnosed by the unique bifurcation (split) of the hypapophyses (processes which extend from the lower surface of a vertebra) in the anterior dorsal vertebrae.[11]
Owen also named two other species,S. major[9] (S. recentior is a museum label for syntype specimens[12]) andS. meyeri,[13] of which the former is based oniguanodont material. HisS. cuvieri, of which the type specimen is lost, is today considered anomen dubium.
In 2010Gregory S. Paul renamed (as an informal name)Magnosaurus intoStreptospondylus nethercombensis.[2]
In 2022, theropod specimens from the same locality as the type ofStreptospondylus, long held in private collections, were described. It was found that some dorsal vertebrae (MNHN.F.RJN472;B5) bore autapomorphies ofStreptospondylus, while a cervical vertebra (MPV 2020.1.11), a tibia (MPV 2020.1.2) and a femur were referred to the species, based on shared characters with the related genusEustreptospondylus.[14]
Earlier assigned to crocodilian groups,Streptospondylus was in the 20th century typically classified in theMegalosauridae.
Recent analyses indicate thatStreptospondylus is atetanurantheropod. Allain in 2001 suggested that it was closely related toEustreptospondylus in theSpinosauroidea.Roger Benson in 2008 and 2010 concluded that whether it is amegalosauroid,allosauroid, or a more primitive form cannot be determined because of its extremely fragmentary remains.[15] Latercladistic analysis by Benson and colleagues from 2010 indicated thatStreptospondylus was the sister species ofMagnosaurus within theMegalosauridae.[16] Carranoet al. (2012) placedStreptospondylus atMegalosauriaincertae sedis due to its fragmentary nature.[17]
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