| Macrurosaurus | |
|---|---|
 | |
| Vertebra ofM. semnus | |
Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Clade: | Dinosauria |
| Clade: | Saurischia |
| Clade: | †Sauropodomorpha |
| Clade: | †Sauropoda |
| Clade: | †Macronaria |
| Clade: | †Titanosauriformes |
| Genus: | †Macrurosaurus Seeley, 1869 |
| Type species | |
| †Macrurosaurus semnus Seeley, 1869 | |
| Other species | |
| Synonyms | |
| |
Macrurosaurus (meaning "large-tailed lizard") is the name given to agenus ofdinosaur from theEarly Cretaceous. It was atitanosauriform which lived in what is nowEngland. The type species,M. semnus, was named in 1876.[1] A second species,M. platypus, may also exist.[2][3]
The genusMacrurosaurus was named byHarry Govier Seeley in 1869 in his index of fossils from theCambridge Greensand.[4] In 1876 Seeley more thoroughly described thetype species,Macrurosaurus semnus, making the name valid.[1] The generic name is derived from Greekmakros, "large", andoura, "tail". Thespecific name is derived from Greeksemnos, "stately" or "impressive". A second species,M. platypus, from theChalk Group ofEngland, may also exist.[2] Seeley in 1869 named it as a species of theankylosauridAcanthopholis butFriedrich von Huene named it as a second species ofMacrurosaurus in 1956.[3] It is known from the specimenCAMSM B55454-55461.[5] In 1999Xabier Pereda-Superbiola andPaul M. Barrett reviewed allAcanthopholis material. They concluded that all species werenomina dubia whose syntype specimens were composites of non-diagnostic ankylosaur and ornithopod remains. For example, the metatarsals included in the syntype series ofAcanthopholis platypus are from a sauropod, but the remaining syntypes are not.[6]
Theholotype ofMacrurosaurus,SM B55630, consists of two series of caudal vertebrae found around 1864 nearCambridge, England in the Cambridge Greensand, strata themselves deposited during theCenomanian but containingreworked fossil material dating perhaps from around the lateAlbian.[7] The first was acquired by theWoodwardian Museum from William Farren who had it dug up atColdhams Common nearBarnwell. This series is made up of 25 proximal vertebrae. The second was found by Reverend W. Stokes-Shaw at a slightly more western location nearBarton. It contained fifteen smaller distal vertebrae, from the tail end. Seeley, acting on the presumption that both finds belonged to the same species if not individual, combined the two series into one tail of about 4.5 metres length.
Other fragmentary fossils fromEngland (Acanthopholis platypus),[2]France andArgentina have later been referred toMacrurosaurus[8] but the identity is today doubted.[2]
A 2022 review consideredMacrurosaurus to be an indeterminate macronarian, while "Acanthopholis"platypus was treated as indeterminate within Eusauropoda or Neosauropoda.[9]
Macrurosaurus was by Seeley himself estimated to be about ten metres long. Often a length of around twelve metres (39 ft) is indicated in the popular literature. Thevertebrae in front areprocoelous, meaning that the vertebral centra are hollow at the front end and convex at the back. Those behind areamphicoelous: hollow at both ends. Seeley assumed that the full count of tail vertebrae would have been about fifty.
Macrurosaurus was by Seeley assigned to theDinosauria.Richard Lydekker in 1888 understood it belonged to theSauropoda.[10] In 1929Friedrich von Huene referred it to theTitanosauridae.[11] In recent years however, it has been commonly concluded that the species cannot be further determined than a more generalTitanosauriformes. Also it is today often seen as anomen dubium.
