Gigantspinosaurus – the ‘lost’ Chinese stegosaur

As promised a second guest post, this time by Susie Maidment and on the incredibly elusive Giganspinosaurus. So few people know about this stegosaur that despite being described in 1992 it didn’t even make it into that dinosaur encyclopedia that is ‘The Dinosauria‘ in 2003:

Studying dinosaurs inevitably involves a great deal of travel. During my four years studying stegosaurs, I visited 32 institutions on three continents, adding up to a total of about five months in dark basements looking at bones. I visited China for a month in 2004 in search of a number of illusive stegosaurian specimens with names that proved almost impossible to pronounce correctly, along with a fellow PhD student. Half way through our month-long trip, we arrived in Zigong, a small (by Chinese standards) city in Sichuan Province. Zigong achieved worldwide fame, at least in palaeontology circles, in the 1970s and 80s due to the discovery of a vast collection of dinosaurian fossils from the Shaximiao Formations, dating from the lowermost Middle Jurassic to the Late Jurassic. The area was at the time a lush flood plain, but periodic floods, droughts and other natural disasters led to the accumulation of large numbers of extremely well-preserved dinosaurian fossils. The discovery of a bone bed just outside Zigong led the authorities to build the imaginatively named Zigong Dinosaur Museum over the site, and today tourists can view a large collection of dinosaurian remains still in the ground, with additional specimens on display.


I was in Zigong to study one of the most interesting ornithischian dinosaurs ever discovered: the basal stegosaur Huayangosaurus. Although clearly a stegosaur because of the parallel rows of dermal plates extending vertically from the back, it bears a number of features that link it with much more primitive armoured dinosaurs, and it has helped to elucidate the order of acquisition of certain features in the evolutionary history of these ornithischians. At Zigong, they found at least one almost entirely complete specimen of Huayangosaurus, including a complete, articulated skull. Only one other complete stegosaurian skull is known from anywhere in the world: they are incredibly rare.

The road out to the Zigong Dinosaur Museum (ZDM) is a narrow strip of tarmac with a lane of dirt either side. Enormous trucks with wheels the size of your average Toyota thunder down the road and taxis weave in and out, onto the dirt and back onto the tarmac again, gambling with your life at every corner. Car travel throughout Asia is the same: there is one simple rule – don’t look out the front. Having mystifyingly defied certain death on multiple occasions, we arrived at the ZDM and were introduced to the curator, who claimed to have no knowledge of our visit and of many of the specimens we were interested in seeing. However, a few calls back to Beijing and all was sorted out: we were assigned an English-speaking guide and taken to the collections.

Unfortunately it turned out that Huayangosaurus, the specimen that I had travelled half way around the world to study, was currently part of a touring exhibition, and was at that moment on display in the Queensland Museum, Australia. However, the beautiful complete skull, too delicate and precious to be sent out of the museum, let alone out of the country, was available for me to study, and I set to work on that. Two days later and I had looked at, photographed, drawn and described the skull from every possible angle and I was wondering what I was going to do for the next week. I decided to take a look at the exhibition hall, which turned out to be a dimly lit room (why are dinosaur halls always dimly lit? Is it supposed to make it atmospheric or something? It’s not like there wasn’t any sun in the Jurassic) featuring dioramas of various dinosaurs, one of which, in the corner, was a stegosaur. I wandered over and read the name label: Gigantspinosaurus sichuanensis. I’d heard the name before, but only on an internet mailing list. I’d been unable to uncover anything at all about the specimen, and yet here it was, mounted, and apparently reasonably complete.

skull-photo2I decided to take a look and make some notes for comparative purposes, and I decided to include the specimen in my cladistic analysis. Studying a specimen on display is always difficult. Not only are you unable to rotate the elements, look at and photograph them from multiple orientations, there’s never enough light, so you need to do everything by torch light (that dimly lit atmospheric thing again). Also, you get members of the public (invariably seven year old boys) asking you difficult questions about dinosaurs you’ve never heard of. Fortunately my three-week intensive Chinese language course didn’t extend much beyond the basics, so I was unable to converse with most of the visitors, who watched perplexed as I lay underneath the specimen trying to draw the pelvis.

Gigantspinosaurus proved to be a fascinating specimen. It was found sometime prior to 1986, when an article in the Asian journal Vertebrata Palasiatica announced the discovery of some stegosaurian shoulder spines. The one page article is in Chinese but there is a photograph of the specimen, with a caption in English. The specimen is not named in the article, but it is undoubtedly Gigantspinosaurus: the exhibition about the specimen in the ZDM has a plaster replica of how the specimen was found and it is identical to the photograph.

Large spines, extending at a low angle from a flat, plate-like base, are known in Kentrosaurus, and there has always been some discussion about where on the body these spines would have been located. It was originally thought that they were located over the hips – and they were described as parasacral spines. However, the discovery of Gigantspinosaurus proved this to be incorrect: the specimen was recovered with both spines lying adjacent to the scapulae, and the spines have been renamed parascapular spines. Gigantspinosaurus certainly lives up to its name: the parascapular spines, which are comma-shaped, are nearly twice the length of the scapulae and extend either side of the body: they are absolutely massive. I cannot imagine how this animal turned around: if it swung its shoulders one way or the other it would have stabbed itself in the hips! If they were covered in a keratin sheath, as has been proposed for stegosaurian dermal armour, they would have been even bigger – maybe two or three inches longer that currently preserved.

gigintspin-mountThe specimen was named and briefly described by Ouyang in 1992 in an obscure conference proceedings volume, completely in Chinese, and it has been on display since 1996 at the ZDM. Some aspects of the anatomy of Gigantspinosaurus are reminiscent of Huayangosaurus; for example the morphology of the lower jaw and the vertebrae are similar. Most stegosaurs, like Stegosaurus and Kentrosaurus, have dorsal vertebrae that are greatly elongated above the neural canal: they look like they have been stretched from above and below. However, those of Gigantspinosaurus, like those of Huayangosaurus, are not ‘stretched’ but are similar to the dorsal vertebrae of basal thyreophorans (the early armoured dinosaurs) like Scelidosaurus. Another fascinating feature of the vertebrae of Gigantspinosaurus is the presence of ossified tendons extending down the dorsal vertebral column. Until I noticed these features in Gigantspinosaurus and also in Huayangosaurus, they were thought to be absent from all stegosaurs. They are not seen in any of the well-known specimens of Stegosaurus, and have not been identified in Dacentrurus or Kentrosaurus either. Despite similarities to Huayangosaurus, there are also a number of differences. The pelvic area of Gigantspinosaurus is more similar in morphology to that of other stegosaurs such as Stegosaurus and Kentrosaurus, whose anterior processes project both forwards and laterally, and differs markedly from the pelvis of Huayangosaurus, in which these processes project more anteriorly.

The specimen of Gigantspinosaurus on display at the ZDM also has an interesting pathology: its left upper leg bone, the femur, was broken about midway down the shaft during life. The bone was badly broken: not just cracked but the two halves were offset from each other, but had healed – new bone had grown around the fracture. This shows that the broken leg didn’t kill the animal, but I suspect it probably contributed to its death: the ZDM Gigantspinosaurus probably limped badly.

My cladistic analysis suggests that Gigantspinosaurus was the most primitive stegosaur, more primitive even than Huayangosaurus. To be honest I am not confident about that assignment: I think we need further fossils and a more detailed study of the currently known material to decide where it fits into the stegosaurian family tree. I hope that the staff at the ZDM will get a full description of this fascinating animal out soon: it is key to our understanding of stegosaurian phylogenetic relationships.

17 Responses to “Gigantspinosaurus – the ‘lost’ Chinese stegosaur”

  1. 1 Christopher Collinson 13/11/2008 at 1:55 pm

    Do we know for certain the correct orientation of Parascapular spines? Tracy Ford has illustrated them on the opposite shoulders so that they are directed up and over the back.

  2. 2 David Hone 13/11/2008 at 8:01 pm

    I can’t answer that unfotunately as although I have seen the specimen, I couldn’t get past the barriers to have a good root around (and probably would not know what I was looking for in any case). Susie it turns out is away this weekend so may not be able to tell you (or answer any other queries) for a few dyas but she will get back on here later.

  3. 3 Thomas R. Holtz, Jr. 13/11/2008 at 9:54 pm

    Easily the weirdest stegosaur mount I’ve ever seen…

  4. 4 David Hone 14/11/2008 at 8:40 am

    That’s true Tom. When I saw it, it was in the same position but had been moved away from that background, and then they had put a nest of eggs underneath as if it as rearing up whilst laying. Made it looks slightly less wiers, but not by much.

  5. 5 Zach Miller 14/11/2008 at 9:38 am

    I’m with Christopher. Upon seeing the photograph, my mind instantly went to, “they’re oriented the wrong way!” Very strange, but awesome, stegosaur.

  6. 6 Susie Maidment 14/11/2008 at 11:39 am

    The spines were found lying along side the specimen, apparently in place. They have previously been illustrated so that they projected from the top of the basal plate, like an upside down comma rather than the right way up comma, as they are mounted here. But it seems that this was their orientation, from how the specimen was found. What we don’t have any information about is whether they projected posteriorly, as shown here, or whether they projected posterodorsally, since the specimen was of course flattened by the burial process. It’s an interesting question and one we need more information to answer.

    As for the mount – very weird. It had a nest of eggs under it when I saw it too – although that may not be clear from the photo. Still, quite a strange way of mounting it… it’s sort of squatting to lay eggs. Weird idea. There’s not much information about whether stegosaurs could have reared up bipedally. Modelling has shown that their centre of gravity was just anterior to the hips, but their forelimbs are so much shorter than their hindlimbs my gut feeling is that it would have been quite difficult for them. My next research project, if I ever get any funding to do it, is to look at the change from bipedalism to quadrupedalism in ornithischians, and the associated muscle changes that accompany it. I want to do some modelling to narrow down the selective pressures that contributed to the move to quadrupedality in several ornithischian groups. Hopefully that research would lead to a better understanding as to whether animals like Gigantspinosaurus could have reared up like this.

  7. 7 Darren Naish 14/11/2008 at 5:36 pm

    Great post Susie. The mount was originally in a more conventional quadrupedal pose, judging from older photos. I like the way its hands are about three times broader than its arm. Sigh.

  8. 8 Susie Maidment 15/11/2008 at 1:08 am

    hmmm… maybe the hands are a perspective thing… otherwise that is quite weird…

  9. 9 Brad McFeeters 15/11/2008 at 4:22 am

    I think it’s neat how the museum itself looks a little like a dinosaur. 🙂

  10. 10 Dark Hero 16/11/2008 at 4:27 pm

    Can a stegosaurian standing on 2 feet like that?
    Nah I dont think so!
    But you know what!
    This is one of my favorite dinosaur!

  11. 11 David Hone 16/11/2008 at 6:36 pm

    Well there is certainly some research that suggests stegosaurs could rear up in this manner. As I have discussed before on here, there are plenty of animals capable of things that one might never expect from their anatomy alone. Elephants for example can rear up onto their hindlegs quite happily and these would be far more front heavy than stegosaurs.

  12. 12 Jim Kirkland 05/03/2009 at 8:50 am

    I got to spend some quality time with thith beast in Zigong last spring. It is certainly impressive and the fact, that the spines were found in near life position is a pretty critical piece of information about parascapula spines. I mean picture this beast having to walk through a thicket of vegetation if those spines were directed anteriorly.

  13. 13 Tim Williams 09/03/2009 at 3:00 pm

    Is the _Gigantspinosaurus_ type specimen the same stegosaur skeleton that was mentioned by Gao et al. (1986) and assigned by them to _Tuojiangosaurus_? Galton and Upchurch (p.355 in the Dinosauria II volume) use this specimen to justify the presence of parascapular spines in _Tuojiangosaurus_ – but might these just be _Gigantspinosaurus_?

    BTW, what a weird stegosaur!

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