STL Science Center

STL Science Center

06 April 2013

Flying Stegosaurs

Prior to the readjustment of Gigantspinosaurus (I meant to admit yesterday that I find it very hard to not write "Gigant-o-spinosaurus" like its written in the figure caption) it appeared as though this rather large dinosaur was poised to take flight at any moment. In my head I can even see a cartoon in which the animal can move those shoulder spikes between those two positions, though that would be uncalled for, energetically taxing, and require a very odd set of muscles along the shoulder and back. Regardless, I am pleased to note that the spikes have been allowed to assume a more relaxed position officially. Either way, the weight of the spike at the shoulder like that would create a considerable stress on the animal whether it was a solid core of bone or mostly a hallow keratinous sheath, so there are definite implications to be considered in regards to those spikes and the impact they would have on feeding, mating, locomotion, display, defense... and we could go on.

Updated 20:33: Just to update the above without tearing it apart and rewriting the whole thing, I wrote the description of that backwards. It should state that the updated version from this diagram has the spikes facing dorsally rather than swinging ventrally. That alone may cause some confusion, and I apologize for that. I think my brain was in backwards this morning!

©Phil Wilson
Unfortunately, prior to the shift in hypotheses, some paleontologists and illustrators did get around to releasing images of the giant spikes of Gigantspinosaurus as protruding downwards from the shoulder. As we have seen, of course, the times change and the illustrations sometimes either follow very closely behind, get left behind, or become classics. The scene portrayed here, though not very old, is a classic representation of the newly hypothesized posture of Gigantspinosaurus' shoulder spikes and is done with very good scientific accuracy. Because that thinking has changed does not necessarily make any illustration outdated and certainly does not make it terrible; everyone has their viewpoints in paleontology and sometimes we simply just do not agree with one another (take a class in paleo with a diverse background of students if you do not believe me!).

©Chuang Zhao
Defensively speaking the spikes were probably much more a deterrent than a weapon; their rear facing angle, either pointed up off the shoulder or down off the shoulder, was not well adapted for thrusting or stabbing at encroaching rivals or predators. Being a stegosaur, even a basal stegosaur or huayangosaur as the case may prove, Gigantspinosaurus possessed a formidable weapon in the form of the tail spikes that were discovered with the skeleton. These were more than likely used in the same manner that is thought that other stegosaurs used their tail spikes to ward off predators. As with other stegosaurs, the dorsal plates were more than likely for display or some other purpose rather than defensive in nature.

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