Pachycephalosaurus: Are Stygimoloch and Dracorex Valid?

In 2009, Pachycephalosaurus, Stygimoloch, and Dracorex, three unique dome-headed dinosaurs, were determined to be the same species.
Dinosaurs ontogeny has caused confusion in the description of multiple dinosaur taxa, but none comes close to the case of Pachycephalosaurus. It arguably underwent the most remarkable growth curve amongst all other dinosaurs. Their crowns seemingly morph into different shapes throughout their lifetime and have fooled paleontologists who've split them into 3 distinct genera and in total of 5 different species.

References:
[1] https://www.tandfonline.com/doi/abs/1...
[2] https://www.ncbi.nlm.nih.gov/pmc/arti...
[3] https://www.ncbi.nlm.nih.gov/pmc/arti...
[4] https://www.ncbi.nlm.nih.gov/pmc/arti...
[5] https://www.researchgate.net/publicat...
[6] http://www.jstor.org/stable/4523906
[7] http://repository.si.edu/bitstream/ha...
[8] https://www.ncbi.nlm.nih.gov/pmc/arti...
[9] https://www.jstor.org/stable/4523163
[10] https://www.researchgate.net/publicat...
[11] http://www.robertmsullivanphd.com/upl...
[12] https://www.jstor.org/stable/4624250

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1. Images:
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• Architecture bones building city from Pexels
• Close up photo of fossils Photo by Alejandro Quintanar from Pexels
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#pachycephalosaurus #stygimoloch #dracorex #dinosaur