fossils

Tiny bonehead skull uncovers the early life of Pachycephalosaurus

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Franz
Anthony

Editor and Artist
Just like every other organism on earth, Pachycephalosaurus started out tiny. And just like most other dinosaurs known to the general public, it is associated with the adult specimens of the animal. It doesn’t help that remains of Pachycephalosaurus and its relatives are often fragmentary, complicating efforts to identify and classify the dinosaurs.

Just like every other organism on earth, Pachycephalosaurus started out tiny. And just like most other dinosaurs known to the general public, it is associated with the adult specimens of the animal. It doesn’t help that remains of Pachycephalosaurus and its relatives are often fragmentary, complicating efforts to identify and classify the dinosaurs.


In 2009, paleontologists Jack Horner and Mark Goodwin suggested that specimens labeled Stygimoloch and Dracorex were actually the juvenile forms of Pachycephalosaurus. All three thick-headed dinosaurs originated from the Hell Creek Formation of North America and lived near the end of Cretaceous age.


Interestingly, only adult specimens of Pachycephalosaurus have been found, while Dracorex and Stygimoloch are only known from juveniles. These observations, in addition to the comparison of multiple specimens, lead the paleontologists to conclude that the animal had different shaped head ornaments in different stages of their lives. The subadult form Stygimoloch likely lost its prominent spikes and developed domes as they matured to be the specimens referred to as Pachycephalosaurus.


The three newly discovered fragments from the baby skull add a new layer to this story. According to author David Evans, parts from the back of its skull clustered similarly to the specimens of Dracorex and Stygimoloch, and some Pachycephalosaurus. The flat bone from the skull roof shows similarity to the youngest form Dracorex, suggesting that although the ornamentation changed over time, the overall structure was already set since they were young. Such finding further supports the argument proposed by Horner and Goodwin that the differently shaped skulls potentially represented various life stages of the same animal.


While the juveniles’ bumps were deemed fairly useless against Hell Creek’s predators, Evans argued that these age-specific features could have helped the animals to visually recognize each other by age.


Original findings published in Journal of Vertebrate Paleontology.

Image Credit: Julio Lacerda

8e6ac47821297aeee8c843e680637dca

Franz
Anthony

Editor and Artist


http://sulc.us/bqe9r
http://www.eartharchives.org/articles/paleontologists-uncover-the-tiniest-bonehead-dinosaur/