| Cetiosaurus | |
|---|---|
 | |
| Mounted skeleton,Leicester Museum & Art Gallery | |
Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Clade: | Dinosauria |
| Clade: | Saurischia |
| Clade: | †Sauropodomorpha |
| Clade: | †Sauropoda |
| Family: | †Cetiosauridae |
| Subfamily: | †Cetiosaurinae Lydekker, 1888 |
| Genus: | †Cetiosaurus Owen, 1841 |
| Species: | †C. oxoniensis |
| Binomial name | |
| †Cetiosaurus oxoniensis Phillips, 1871 | |
Cetiosaurus (/ˌsiːtioʊˈsɔːrəs,ˌsiːʃi-/[1] meaning 'whale lizard', from theGreekketeios/κήτειος meaning 'sea monster' (later, 'whale') andsauros/σαυρος meaning 'lizard'), is agenus of herbivoroussauropoddinosaur from the MiddleJurassicPeriod, living about 171 to 165million years ago during theBajocian andBathonian ages in what is now Britain and probably France.
Cetiosaurus was named in 1842, making it the first sauropod from which bones were described and is the most complete sauropod found inEngland. It was so named because its describer, SirRichard Owen, supposed it was amarine creature, initially an extremely largecrocodile, and did not recognise it for a land-dwelling dinosaur. Because of the early description many species would be named in the genus, eventually eighteen of them. Most of these have now been placed in other genera or are understood to be dubious names, based on poor fossil material. The last is true also of the originaltype species,Cetiosaurus medius, and soC. oxoniensis was officially made the new type species in 2014.C. oxoniensis is based on three more-or-less-complete specimens, discovered from 1868 onwards. Together they contain most of the bones, with the exception of the skull.Cetiosaurus was aquadrupedal, long-necked, small-headedherbivore. It had a shorter tail and neck than most sauropods. The forelimbs on the other hand, were relatively long. It is estimated to have been about 16 metres (52 ft) long and to have weighed roughly 11 tonnes (12 short tons).
Cetiosaurus is, with the exception of the tooth genusCardiodon, the first sauropod to be discovered and named as well as being the best known sauropod from England.[2] Numerous species have been assigned toCetiosaurus over the years belonging to several different groups of sauropod dinosaurs. The genus thus functioned as a typical "wastebasket taxon".[3][4] Fossilized remains once assigned toCetiosaurus have mainly been found inEngland but also inFrance,Switzerland andMorocco.[3]
The first fossils, vertebrae and limb elements, were discovered nearChipping Norton,Oxfordshire in the early nineteenth century and were reported upon by collector John Kingdon in a letter read on 3 June 1825 to the Geological Society; they were seen as possibly belonging to a whale or crocodile. In 1841biologist,comparative anatomist andpalaeontologist SirRichard Owen, named these as the genusCetiosaurus, the year before he coined the termDinosauria. Owen initially did not recogniseCetiosaurus for a dinosaur but considered it a gigantic sea-dwelling reptile. This was reflected by the name, derived from Greek κήτειος,kèteios, "sea-monster".[5] In 1842 Owen named two species in the genus:Cetiosaurus hypoolithicus andCetiosaurus epioolithicus. Thespecific names reflected whether the finds had been made below (hypo) or above (epi) the so-calledoolithic layers. The first species was based on the material of Kingdon; the latter on vertebrae and metacarpals found atWhite Nab inYorkshire.[6] The publication did not contain a sufficient description and the species are often considerednomina nuda.[3] The same year in a subsequent publication Owen named four additionalCetiosaurus species:Cetiosaurus brevis, "the short one";Cetiosaurus brachyurus, "the short-tailed";Cetiosaurus medius, "the medium-sized", andCetiosaurus longus, "the long one". Owen had abandoned the two earlier names, as shown by the fact that their fossils were referred to several of the new species. These again were each mostly based on disparate material, from often geographically widely separated sites.[7]
As became apparent in 1849, some of these bones were not sauropod in nature at all but ofIguanodontidae. That yearAlexander Melville, in a misguided attempt to clear matters up, named the authentic sauropod material ofC. brevis asCetiosaurus conybeari but thereby merely created ajunior objective synonym of the former name.[8] In 1842, Owen noted a partial skeleton of a sauropod dinosaur consisting of "five vertebrae, a scapula, coracoid, sternal plate, and portions of limb bone", found in rock exposed by railway construction nearBlisworth,Northamptonshire, which he attributed to the speciesCetiosaurus medius.[3][7]101 However this specimen was lost by 1871, as in a book by ProfessorJohn Phillips published that year he was unable to locate the specimen. It has been suggested that two tail vertebrae mentioned byRichard Lydekker in 1888 as being the collection of the Natural History Museum in London, which were catalogued as BMNH R16090 and R160901, and recorded as having been purchased from Blisworth by the museum in 1843, originate from the Blisworth skeleton. However in a 2003 paper on the taxonomy ofCetiosaurus, neither of the two vertebrae were able to be located in the museum's collections by the paper's authors.[3]
In March 1868, workers nearBletchingdon discovered a sauropod right femur. Between March 1869 and June 1870 ProfessorJohn Phillips, further investigating the site, in a layer dating from theBathonian uncovered three skeletons and additional bone material. In 1871 based on these he named two species:Cetiosaurus oxoniensis (originally spelledCeteosaurus Oxoniensis) andCetiosaurus glymptonensis. "Oxoniensis" refers toOxford, "glymptonensis" toGlympton.[9] Already in 1870Thomas Huxley had published a letter by Phillips in which the latter named aCetiosaurus giganteus based on specimen OUMNH J13617, a left femur earlier found at Bletchingdon;[10] as the letter did not contain a description, this is anomen nudum.[3]
A century later, a newC. oxoniensis specimen (LCM G468.1968) called the "Rutland Dinosaur" was discovered on 19 June 1968 by the driver of anexcavating vehicle. It was found at the base of theRutland Formation dating to theBajocian. Staff from Leicester City Museums arrived on 20 June 1968. It was not confirmed that all the preserved material was collected. It is the most complete sauropod fossil, and one of the most complete specimens of a dinosaur, ever found in the United Kingdom. It was only in around 1980 that there was interest in the fossil. It took around four years to find the dinosaur bones. Of the about two hundred bones in a cetiosaurus, it has preserved a nearly completecervical series (2–14), most of thedorsal vertebrae, a small part of thesacrum andanterior caudals, thechevrons, theilium, the rightfemur, and rib and limb fragments.[11]
The incomplete fossil is 15 metres (49 ft) long and has been displayed since 1985 in theLeicester Museum & Art Gallery. Only the more structurally sound parts of the dinosaur are on display, with the more-fragile parts stored elsewhere. Much of what can be seen in the display is a representation (replica), and not the actual dinosaur. The model's vertebral column seen on display has fourteen cervicals, ten dorsals, fivesacrals and about fifty caudals.[3][11] The dinosaur display was taken to London to be featured on the children's television programmeBlue Peter.[citation needed]
In 1874,John Whitaker Hulke namedCetiosaurus humerocristatus, "with a crested humerus", based on specimen BMNH 44635, a humerus found that year atSandsfoot nearWeymouth inDorset.[12] In 2010, this was made a separate genusDuriatitan.[13] This today is often considered anomen dubium.[3]
Ornithopsis leedsii was named in1887 byJohn Hulke for apelvis, vertebrae andribs collected byAlfred Nicholson Leeds, an English farmer and amateurfossil collector who throughout his life compiled numerous collections of fossils from the Oxford Clay.[14][15] It was described in more detail by Seeley in1889, where he consideredOrnithopsis hulkei (which had been described byHarry Seeley in 1870 based on vertebrae from the Early CretaceousWessex Formation of theIsle of Wight in southern England[16]),C. oxoniensis andO. leedsii to all be in the same genus, bearing the nameCetiosaurus. ButnaturalistRichard Lydekker discussed with Seeley, before the publication of Seeley's 1889 paper, thatCetiosaurus andOrnithopsis were not the same taxon. Lydekker suggested that Wealden fossils (includingO. hulkei) belonged toOrnithopsis and the Jurassic remains (includingO. leedsii andC. oxoniensis) toCetiosaurus.[17] Lydekker in1895 changed his mind and referred the speciesO. leedsii toPelorosaurus (known already from the speciesP. brevis, once namedCetiosaurus brevis)—asP. leedsi—and referred the genus toAtlantosauridae.[18] Arthur Smith Woodward supported Seeley's classification scheme in 1905, placingC. leedsi inCetiosaurus, including withinC. leedsi a partial sauropod skeleton collected from the Oxford Clay of Peterborough, England.[19] In 1927,Friedrich von Huene assignedC. leedsi to the separate genusCetiosauriscus.[20] The holotype material of"C." leedsi, NHMUK R1988, consisting of a left and rightischium, is today considered indeterminate eusauropod remains, rendering the species anomen dubium,[21][22] while the sauropod skeleton described by Woodward from Peterborough in 1905 is now assigned to the valid separate speciesCetiosauriscus stewarti.[22]
In 1970Rodney Steel renamedCardiodon Owen 1841, based on a now lost tooth, intoCetiosaurus rugulosus, "the wrinkled one".[23] If the species were cogeneric toCetiosaurus, the name of the genus would, however, beCardiodon as this name has priority. In 2003, Upchurch & Martin rejected the identity.[3]
In addition to the thirteen species based on British material, three were named by French researchers. In 1874,Henri Émile Sauvage namedCetiosaurus rigauxi based on a vertebra found byEdouard Edmond Joseph Rigaux atLe Portel, west ofBoulogne-sur-Mer,[24] in layers dating from theTithonian. In 1903, however, he was forced to conclude it represented apliosaurid.[25] In 1880, Sauvage named another species:Cetiosaurus philippsi.[26]
In 1955,Albert-Félix de Lapparent namedCetiosaurus mogrebiensis based on three skeletons found inMorocco from theEl Mers Formation dating to the Bathonian. The specific name refers to theMaghreb.[27] This is today sometimes seen as a valid taxon, but one not belonging toCetiosaurus.[3]
In principle for every genus atype species must be indicated to serve as its type in anostensive definition. Traditionally,C. medius had been considered the type species ofCetiosaurus. In 1888Richard Lydekker had formally assignedC. oxoniensis as the type species but by the modern rules of theICZN one of the species named by the original author, in this case Owen, must be selected. In 2003,Paul Upchurch andJohn Martin determined thatC. "hypoolithicus" andC. "epioolithicus" could not be used because they werenomina nuda. Of the four species named in Owen's second 1842 article,C. brevis,C. brachyurus,C. longus andC. medius, onlyC. brevis would not be anomen dubium. This they interpreted as implying thatC. brevis was the type species. This conclusion, if correct, would cause considerable taxonomic instability, because the genusPelorosaurus had since been based on its fossils, and recognized as a totally different kind of sauropod. Therefore, Upchurch & Martin suggested to request the ICZN to change the type species intoC. oxoniensis, the best known species from the Middle Jurassic, which the genusCetiosaurus had generally come to be identified with.[3][4]
However, in 2009, when their request was officially filed, Upchurch and Martin had changed their position. They acknowledged that being designated anomen dubium does not prevent a species from having been made the type of a genus. Furthermore, they had identified a passage in the 1842 article in which Owen himself had already assignedC. medius as thetype species: "it is principally on these bones [i.e. those ofC. medius], with others subsequently discovered and in the collection of Mr. Kingdon, that the characters of theCetiosaurus were first determined". Nevertheless, they still advocated a change in type becauseC. medius is known only from undiagnostic material. Itssyntype series consists of eleven separate tail vertebrae, (specimina OUMNH J13693–13703), some sacral ribs with a foot bone (metatarsal, OUMNH J13704–13712), a hand bone (metacarpal, OUMNH J13748), and a claw (OUMNH J13721), probably from different fossil sites and different individuals.
TheICZN accepted the proposal to change the type species in 2014 (Opinion 2331), officially makingC. oxoniensis the type species in place of the originalC. medius.[28] MakingC. oxoniensis the type species ofCetiosaurus secured the nameCetiosaurus for the animal with which it has been traditionally associated.[4]
In 2011, achevron suggested to belong to the genusCetiosaurus proper was reported fromArdennes in northeast France. This region was likely part of the same landmass asCetiosaurus specimens known from Britain.[29] Severalfossil tracks discovered in 1997 and 2024 at twoOxfordshire, UK sites have been suggested to beCetiosaurus footprints, though identification with adiplodocoid is also possible.[30][31]
The complex naming history can be summarised in a list ofCetiosaurus species:
Cetiosaurus, or specifically the neotype speciesC. oxoniensis, is known from relatively complete fossils. These include the three skeletons found by Phillips. One of these is a larger animal (catalogued as OUMNH J13605–13613, J13615–16, J13619–J13688 and J13899), which was chosen by Upchurch & Martin as thelectotype of the species; the second consists of limb bones of a smaller individual (OUMNH J13614) and the third skeleton represents the shoulder blade and hindlimb of a juvenile animal (OUMNNH J13617–8, J13780–1). The Rutland specimen, about 40% complete, increases considerably the number of known skeletal elements, especially in the neck. The skull is largely unknown, perhaps with the exception of the brain case represented by specimen OUMNH J13596.[32] A single tooth crown, OUMNH J13597, has provisionally been referred to the species.[3]
Cetiosaurus was, as any sauropod, a long-neckedquadrupedal animal. In 2010,Gregory S. Paul estimated the body length at 16 metres (52 ft) and body mass at 11 tonnes (12 short tons).[33] Its neck was moderately long; no longer than its body. The tail was considerably longer, consisting of at least forty caudal vertebrae. Its dorsal vertebrae, the bones along the back, had the original heavy build with limited air chambers, unlike the extremely hollowed-out bones of later sauropods likeBrachiosaurus. Its forearm was as long as theupper arm, unlike most other sauropods, resulting in a forelimb equalling the hindlimb in length. Itsthigh bone was approximately six feet long.
In his original descriptions, Owen was unable to indicate any differences betweenCetiosaurus and other sauropods for the simple reason these latter were not yet discovered. Now that such relatives have been found, the uniqueness ofCetiosaurus oxoniensis and its status as a validtaxon must be proven by indicating its new derived traits orautapomorphies. In their 2003 revision of the genus, Upchurch & Martin identified five autapomorphies ofC. oxoniensis. The rear neck vertebrae and the front back vertebrae have spines on their tops that are low, symmetrical and in the shape of a pyramid. With the spines of all back vertebrae a ridge is absent between the spine and thediapophysis, the top rib joint; it has been lost or perhaps fused with the ridge running between the spine and thepostzygapophysis, the rear joint process. The vertebrae of the middle tail have a tongue-shaped process at the top of the front face of the vertebral body; this is an extension of the floor of theneural canal. The chevrons of the front tail vertebrae have shafts of which the lower ends are flattened from the front to the rear instead of transversely. The lower process of theilium, to which thepubic bone was attached, features on the outer surface of its base a triangular depression.[3]
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Owen initially was unsure about the precise relationships ofCetiosaurus. He understood it was areptile and most researchers at the time accordingly assigned it to theSauria.[34] However, he at first did not recognise its dinosaurian nature; when in 1842 he named the Dinosauria,Cetiosaurus was not included. This was influenced by the preconception that such a large animal must have been sea-dwelling. Owen assumed crocodylian affinities. In the early 1850s,Gideon Mantell began to suspect thatCetiosaurus was a land animal as a result of his studies ofPelorosaurus. This idea, however, was only slowly accepted by other scientists. In 1859 Owen still classifiedCetiosaurus in theCrocodylia.[35] In 1861, Owen concentrated all such forms in a group of their own: theOpisthocoelia.[36] In 1869Thomas Huxley stated explicitly thatCetiosaurus was a dinosaur.[37]
In 1888 Lydekker assignedCetiosaurus to its own family: theCetiosauridae.[38] For a long time this functioned as a large ill-defined family of typically "primitive" sauropods. Today, however, many considerably more basal sauropods thanCetiosaurus are known. Modern exactcladistic research has not resulted in a single clear outcome about the position ofCetiosaurus oxoniensis in the sauropod tree. Sometimes a Cetiosauridae was recovered, aclade unitingCetiosaurus oxoniensis with species as the IndianBarapasaurus, the South AmericanPatagosaurus or the AfricanChebsaurus. Other studies indicate that the traditional Cetiosauridae wereparaphyletic and recoverCetiosaurus oxoniensis in a basal position in theEusauropoda, basal in theNeosauropoda[39] or just outside of this clade.[40]
Cladogram of Sauropoda after Holwerda et al. 2021, showing the position ofCetiosaurus:[41]
| Sauropoda |
| ||||||||||||||||||||||||||||||||||||
Cladogram after Gomez et al. (2024):[42]
During the Middle Jurassic whenCetiosaurus lived, Europe was an archipelago surrounded by shallow seas.Cetiosaurus inhabited theLondon–Brabant Massif, atectonic high that during this period formed an island landmass including parts of southern Britain and adjacent areas of northern France, the Netherlands, Belgium and western Germany, suggested to be comparable in size to Cuba with an area of around 100,000 square kilometres (39,000 sq mi). It has been questioned why the dinosaurs of the island did not experienceinsular dwarfism, as would be expected for an island of this size. A possible explanation for this is that the island remained ecologically connected to the much larger landmass comprising northern Britain (the Scottish Massif), theFennoscandian Shield and the now submerged region in theNorth Sea between them.[29]
Other dinosaurs roughly contemporaneous toCetiosaurus in the Bajocian-Bathonian of Britain include the large theropod dinosaursMegalosaurus,Magnosaurus andDuriavenator (all belonging toMegalosauridae), the small tyrannosauroidProceratosaurus andparavians (suggested to includedromaeosaurs andtroodontids), and possibletherizinosaurs,[43] as well as indeterminateheterodontosaurids,stegosaurs andankylosaurs.[44]
The environment in whichCetiosaurus lived wasfloodplain and open woodland. Paul consideredCetiosaurus a feeding generalist, eating at both a low and a medium-high level, in view of its moderately long neck and limb proportions.[33] During the Bathonian the London-Brabant Massif is thought to have had a seasonally dry climate, with the flora found in theTaynton Limestone Formation of Oxfordshire, likely representing the nearshore vegetation, dominated byaraucarian andcheirolepidiacean conifers, the probable coniferPelourdea, andbennettitaleans, with other plants includingcycads (Ctenis), ferns (Phlebopteris,Coniopteris),Caytoniales, the living genusGinkgo, and theseed fernsPachypteris andKomlopteris.[45]
Huxley, Thomas H. (1870). "Further Evidence of the Affinity between the Dinosaurian Reptiles and Birds".Quarterly Journal of the Geological Society of London. Vol. 26. pp. 12–31.doi:10.1144/GSL.JGS.1870.026.01-02.08 – viaWikisource.{{cite book}}:|journal= ignored (help)
