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Validity of the pachycephalosaurid dinosaur species Stygimoloch Spinifer and Dracorex Hogwartsia
Topic Started: Nov 20 2015, 07:24 AM (830 Views)
Thalassophoneus
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Pelagic Killer
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The species Stygimoloch Spinifer and Dracorex Hogwartsia were recognised as independent species and genera of pachycephalsoaurids, very closely related to Pachycephalosaurus. What distinguishes those three animals is the different structure of the head.

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However, a recent theory suggests that the specimens from which Stygimoloch and Dracorex are known might actually have been juvenile or young adult specimens of Pachycephalosaurus.

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With the existing material paleontologists, and therefore we, can support this theory or be opposed to it only by judging from the morphology of the skulls. This thread is for this purpose.
"The confusion is traced to their bizarre head ornaments, ranging from shields and domes to horns and spikes, which changed dramatically with age and sexual maturity, making the heads of youngsters look very different from those of adults."

The main reason why I doubt this theory is that those changes seem abnormal. The theory suggests that as a Pachycephalsoaurus approaches adulthood it enters the "Dracorex stage", then the "Stygimoloch stage" and then becomes a normal adult Pachycephalosaurus. However I think it would be really strange for an animal to start growing such huge spikes almost until adulthood but then suddenly have its spikes shrinking again while a dome appears.
Edited by Thalassophoneus, Nov 21 2015, 06:08 AM.
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