gigantspinosaurus

The giant-spined Lizard, Gigantspinosaurus (1992)

Phylum : Chordata
Class : Reptilia
Order : Ornithishia
Suborder : Tyreophora
Infraorder : Stegosauria
Genus : Gigantspinosaurus
Species : G. sichuanensis

  • Late Jurassic (163,5 - 157,3 Ma)
  • 4,2 m long and 700 kg (size)
  • China, Sichuan (map)

Gigantspinosaurus was described by Peng and colleagues as a “medium-sized stegosaur”. It was estimated by Gregory S. Paul in 2010 to have been about 4.2 metres long and 700 kilograms in weight. Gigantspinosaurus has a distinctive appearance with relatively small dorsal plates and greatly enlarged shoulder spines, spinae parascapulares, twice the length of the shoulder 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. The forelimbs are robust.

The name was generally considered a nomen nudum in the West, until in 2006 it was disclosed that the abstract contained a sufficient description. Despite its uncertain nomenclatural status, images of Gigantspinosaurus had appeared in several sources. Public awareness of this animal was increased in early 2006 when Tracy Ford, considering it a validly established taxon, published a short article on reconstructing it. Ford suggested that earlier reconstructions of Gigantspinosaurus 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 and Wei Guangbiao in 2006 concluded that G. 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 by Zigong Dinosaur Museum staff. In fact, a Chinese redescription by Peng Guangzhao and colleagues in 2005 would predate Maidment’s publication.

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Gigantspinosaurus sichuanensis: Extreme Body Armor.

Size: 14 feet (4.2 meters) long.
Time Period: The Oxfordian Stage of the Late Jurassic.

Locale: The Shaximao Formation of China, a part of the Dashanpu Formation.

Name: “Giant-spined lizard from Sichuan, China.”

Stegosaurs, as I’ve mentioned before, get more press than their more successful relatives despite the fact that they couldn’t keep up with said relatives (see my post on Dravidosaurus). The most distinctive member of the Stegosauria is Stegosaurus itself, who actually didn’t possess some of the defining features of its relatives, such as spines on the back and shoulders. This leads some to believe that all stegosaurs possessed plates like those of Stegosaurus, but guess what? They’re wrong.

Sporting some particularly fine spines was Gigantspinosaurus from the Late Jurassic of China. They, along with the animal’s intriguing taxonomical history, are the reason that this post even came to be.

First comes the history of the fossils themselves. The fossils of Gigantspinosaurus were discovered in 1985 and described soon after in 1986. The describers actually mistook the animal for the contemporaneous species Tuojiangosaurus. Until 2006, Gigantspinosaurus was considered to be a nomen nudum or ‘naked name’ in the Western world. Then, it was disclosed that there was a sufficient description of the animal’s remains in the abstract written by the describers of the animal. Images of the animal had already appeared in sources prior to ’06, when Tracy Ford published an article on reconstructing the animal, considering Gigantspinosaurus to be a perfectly valid taxon. The animal was concluded to be a valid taxon that same year but wasn’t redescribed fully.

Phylogenetic analyses place Gigantspinosaurus as the basalmost known member of the Stegosauria. Given the scanty fossil record of early representatives of this group, we don’t know how the hell the animal’s distinctive spines evolved and may never know. Some subsequent analyses placed it in Huayangasauridae, a primitive branch of the group. I’m not too sure myself as to the affinities of the animal, but I think it may be likely that it was a sort of stepping stone between basal and more derived stegosaurs.

Now, I could talk about nomenclature and phylogeny some more, but I’m sure everybody wants to hear about Gigantspinosaurus’s huge macho spines, which gave it a really distinctive appearance. Anyway, Gigantspinosaurus  had small dorsal plates for its size, but greatly enlarged shoulder spines that were two times the length of the shoulder blades that they rested on by way of large flat bases. The first reconstructions of the animal show downward-pointing spines, which was later proven to be an error by the aforementioned Tracy Ford, who suggested that these reconstructions had incorrectly attached the animals shoulder spines upside-down. Subsequent reconstructions (Including Xing Lida’s, shown above this post) showed it with spines that extended upwards and ended higher than the top of the animal’s back, but not higher than its distinctive plates. In addition, the animal was found with skin impressions, described by the aforementioned Xing Lida in 2008.

So why were these spines needed? Were they for attracting mates, warding off predators, or for something else entirely? They certainly drew public attention to Gigantspinosaurus, but the questions remain unanswered. It seems ironic that the spines of the animal, its most iconic feature, have not been found to have any discernible use so far! Macho spines or not, this animal is very cool.