Cetiosaurus was in 1842 the first sauropod from which bones were described and is the most complete sauropod found in
marine creature, initially an extremely large crocodile, 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 original type species
, Cetiosaurus medius, and so C. 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.
. It had a shorter tail and neck than most sauropods. The forelimbs on the other hand, were relatively long. C. oxoniensis is estimated to have been about 16–18 metres (52–59 ft) long and to have weighed roughly 11 tonnes (12 short tons).
Discovery and species
Initial finds
Cetiosaurus is, with the exception of the tooth genus Cardiodon, the first sauropod to be discovered and named as well as being the best known sauropod from England.[2] Numerous species have been assigned to Cetiosaurus 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 to Cetiosaurus have mainly been found in England but also in France, Switzerland and Morocco.[3]
The first fossils, vertebrae and limb elements, were discovered near
Thomas Huxley had published a letter by Phillips in which the latter named a Cetiosaurus giganteus based on specimen OUMNH J13617, a left femur earlier found at Bletchingdon;[10] as the letter did not contain a description, this is a nomen nudum.[3]
A century later, a new C. oxoniensis specimen (LCM G468.1968) called the "Rutland Dinosaur" was discovered on 19 June 1968 by the driver of an
chevrons, the ilium, the right femur, and rib and limb fragments.[11]
The incomplete fossil is 15 metres (49 ft) long and has been displayed since 1985 in the Leicester 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, five sacrals and about fifty caudals.[3][11] The dinosaur display was taken to London to be featured on the children's television programme Blue Peter.[citation needed]
Later species
In 1874,
John Whitaker Hulke named Cetiosaurus humerocristatus, "with a crested humerus", based on specimen BMNH 44635, a humerus found that year at Sandsfoot near Weymouth in Dorset.[12] In 2010, this was made a separate genus Duriatitan.[13] In 1905, Arthur Smith Woodward renamed Ornithopsis leedsii Hulke 1887 into Cetiosaurus leedsi.[14] This today is often considered a nomen dubium.[3] In 1970 Rodney Steel renamed Cardiodon Owen 1841, based on a now lost tooth, into Cetiosaurus rugulosus, "the wrinkled one".[15] If the species were cogeneric to Cetiosaurus, the name of the genus would however be Cardiodon 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,
Eric Buffetaut e.a. referred a chevron found in the French Ardennes, specimen A775, to a Cetiosaurus sp.[20]
A Cetiosaurus species has been based on Swiss material. In 1932, Friedrich von Huene renamed Ornithopsis greppini Huene 1922 into Cetiosaurus greppini.[21] This is today considered a nomen dubium.[22] In 2020, it was proposed to assigned C. greppini to the new genus Amanzia.[23]
The question of the type species
In principle for every genus a type species must be indicated to serve as its type in an ostensive definition. Traditionally, C. medius had been considered the type species of Cetiosaurus. In 1888 Richard Lydekker had formally assigned C. oxoniensis as the type species but by the modern rules of the ICZN one of the species named by the original author, in this case Owen, must be selected. In 2003, Paul Upchurch and John Martin determined that C. "hypoolithicus" and C. "epioolithicus" could not be used because they were nomina nuda. Of the four species named in Owen's second 1842 article, C. brevis, C. brachyurus, C. longus and C. medius, only C. brevis would not be a nomen dubium. This they interpreted as implying that C. brevis was the type species. This conclusion, if correct, would cause considerable taxonomic instability, because the genus Pelorosaurus 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 into C. oxoniensis, the best known species from the Middle Jurassic, which the genus Cetiosaurus 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 a nomen 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 assigned C. medius as the
metacarpal
, OUMNH J13748), and a claw (OUMNH J13721), probably from different fossil sites and different individuals.
The ICZN accepted the proposal to change the type species in 2014 (Opinion 2331), officially making C. oxoniensis the type species in place of the original C. medius.[24] Making C. oxoniensis the type species of Cetiosaurus secured the name Cetiosaurus for the animal with which it has been traditionally associated.[4]
Valid Species
The complex naming history can be summarised in a list of Cetiosaurus species:
Cetiosaurus oxoniensis Phillips, 1871: type species of Cetiosaurus
Cetiosaurus, or specifically the neotype species C. 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 the
lectotype 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.[25] A single tooth crown, OUMNH J13597, has provisionally been referred to the species.[3]