| Gigantspinosaurus | |
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| Skeletal mount ofGigantspinosaurus in theZigong Dinosaur Museum | |
Scientific classification | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Clade: | Dinosauria |
| Clade: | †Ornithischia |
| Clade: | †Thyreophora |
| Clade: | †Stegosauria |
| Genus: | †Gigantspinosaurus Ouyang, 1992 |
| Species: | †G. sichuanensis |
| Binomial name | |
| †Gigantspinosaurus sichuanensis Ouyang, 1992 | |
Gigantspinosaurus (lit. 'giant-spined lizard') is agenus of herbivorousornithischiandinosaur from theLate Jurassic. It was astegosaur found inChina.
The first fossil was found in 1985 byOuyang Hui atPengtang nearJinquan and was reported upon in 1986 byGao Ruiqi and colleagues, mistaking it for a specimen ofTuojiangosaurus.[1] Thetype species,Gigantspinosaurus sichuanensis, was described and named by Ouyang in 1992 in an abstract of a lecture.[2] The generic name is derived fromLatingigas orgiganteus, "enormous", andspina, "spine", in reference to the gigantic shoulder spines. Thespecific name refers to Sichuan.
The name was generally considered anomen nudum in the West,[3] until in 2006 it was disclosed that the abstract contained a sufficient description.[4] Despite its uncertain nomenclatural status, images ofGigantspinosaurus had appeared in several sources. Public awareness of this animal was increased in early 2006 whenTracy Ford,[5] considering it a validly established taxon, published a short article on reconstructing it. Ford suggested that earlier reconstructions ofGigantspinosaurus attached the shoulder spines upside-down, and his new reconstruction shows the spine extending somewhat upwards, ending higher than the top of the animal's back.Susannah Maidment andWei Guangbiao in 2006 concluded thatG. sichuanensis was a valid taxon in their review of Late Jurassic Chinese stegosaurs, but did not redescribe it because at that time it was under study byZigong Dinosaur Museum staff.[4] In fact, a Chinese redescription byPeng Guangzhao and colleagues in 2005 would predate Maidment's publication.[6]
Theholotype,ZDM 0019, was found in layers of theUpper Shaximiao Formation ofZigong (Sichuan province), which date to theOxfordian. It consists of a partial skeleton of a probably subadult individual missing the skull (though the lower jaws are present), hind feet, and the tail end. Apart from skeletal elements also plates, spines and scutes have been found. At the left shoulder an impression of the skin had been preserved. The specimen is part of the collection of the Zigong Dinosaur Museum and has as a mounted restored skeleton been on display since 1996. In 2005 Peng e.a. reported a second specimen, ZDM 0156, a pelvis found atChenjia near Fuquan.
Gigantspinosaurus was described by Peng and colleagues as a "medium-sized stegosaur". It was estimated byGregory S. Paul in 2010 to have been about 4.2 metres (14 ft) long and 700 kilograms (1,500 lb) in weight.[7]Gigantspinosaurus has a distinctive appearance with relatively small dorsal plates and greatly enlarged shoulder spines,spinae parascapulares, twice the length of theshoulder blades on which they rested via large flat bases. The plates on the neck are small and triangular. The head must have been relatively large with thirty teeth in each lower jaw. The hips are very broad and the low neural spines of the four sacral vertebrae and the first tail vertebra have been fused into a single plate. It also had robust forelimbs.
The skin impressions were described byXing Lida and colleagues in 2008. They cover a surface of 414 square centimetres (64.2 sq in) and show rosettes with a central pentagonal or hexagonal scale surrounded by thirteen to fourteen ridged smaller square, pentagonal or hexagonal scales with a diameter of 5.7 to 9.2 millimetres (0.22 to 0.36 in).[8]
A study by Maidment indicated thatGigantspinosaurus is the most basal known member of theStegosauria.[9] A 2018 redescription by Haoet al clarified aspects of the anatomy and found that it was an intermediate basal stegosaur, sharing basal traits with huayangosaurids as well as somewhat more advanced traits with other stegosaurs. Nevertheless, this analysis found that it was not the most basal stegosaur, as the huayangosauridsChungkingosaurus andHuayangosaurus were considered more basal.[10]
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