Xuanhanosaurus: The Four-legged Theropod?

Illustration of Xuanhanosaurus as a quadruped by Ghedo, from Wikipedia

Last week I visited an exhibit on Chinese dinosaurs. I enjoyed the exhibit greatly, but all the thoughts about dinosaurs from China got me thinking of a particular dinosaur from that country. The dinosaur in question is Xuanhanosaurus (although you might have figured that out from the title). Not much that has or can be said about this Jurassic theropod. For the most part it seems to be treated as just another taxon to use in completing a relevant cladistic analysis. However, there is at least one interesting point of discussion about this apparently unremarkable dinosaur, and it has to do with a rather unorthodox interpretation of the animal's anatomy and behavior.

In 1984, famed Chinese paleontologist Dong Zhiming published the paper naming and describing Xuanhanosaurus. In the paper, Dong made note of the long, robust forelimbs of the skeleton. With this in mind, he made the unusual proposition that Xuanhanosaurus was actually a quadruped. This is certainly an intriguing idea, but unfortunately it has not held up well with current paleontological knowledge. The biggest problem with this idea is that it is now known that theropods were not capable of pronating their hands. For this dinosaur to have walked on all fours, it would have to walk on its knuckles like a giant anteater, a position most would find quite unlikely for a theropod. As a result, it is highly unlikely that Xuanhanosaurus, or indeed any theropod, was a quadruped. It's a bit of a shame to me, as I think a theropod walking on four legs would be kind of cool.

It should also be noted that Dong's proposition actually appears to have had an oft overlooked effect on dinosaur pop culture. In Safari Ltd.'s Dinosaurs of China line, the Yangchuanosaurus is depicted in an odd quadrupedal pose. Could Ely Kish (who originally sculpted the models) have heard of the idea of Xuanhanosaurus being a quadruped and thought it might apply to another Chinese theropod? It seems like a very real possibility to me.