At the 2007 Society of Vertebrate Paleontology meeting Jack Horner presented a talk on Pachycephalosaurus, Stygimoloch and Dracorex, basically saying that Stygimoloch and Dracorex are growth stages of Pachycephalosaurus. This talk has been being debated pretty much every day since it was given by someone (see an example of past blog post discussion here). Now people can finally read the findings of Horner and Goodwin in PLoS ONE (here). As I have not even had a chance to read it yet I will leave the analyzing and debating to the numerous other blog post that I am sure will start to trickle in today and throughout the rest of the week. Enjoy!
Dracorex (top left) and Stygimoloch (top right), as growth stages of Pachycephalosaurus (bottom). Art by Holly Woodward from the November 23rd, 2007 issue of Science.
Citation: Horner JR, Goodwin MB (2009) Extreme Cranial Ontogeny in the Upper Cretaceous Dinosaur Pachycephalosaurus. PLoS ONE 4(10): e7626. doi:10.1371/journal.pone.0007626 (link)
Horner JR, Goodwin MB, Woodward H (2007) Synonymy consequences of dinosaur cranial ontogeny. J Vert Paleont 27: 92A