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What is Pachycephalosauria?

Pronunciation: pak-ee-SEF-a-lo-SOR-ee-uh
Meaning: Thick-headed lizards (See etymology)
Authors: Maryanska and Osmólska
Year: 1974
Locomotion: Bipedal (two legs)
Synonyms: Homalocephalidae (Dong, 1978)
[Sereno, 2005]Definition
The most inclusive clade containing Pachycephalosaurus wyomingensis but not Triceratops horridus, Hypsilophodon foxii, Heterodontosaurus tucki, Ankylosaurus magniventris.
About
Pachycephalosaurs, also known colloquially as "bone heads", were small to medium sized herbivores who lived during the Mid to Late Cretaceous, and have been the cause of much head-banging between palaeontologists for decades because of one seemingly unanswerable question; "were they head-bangers or not?"

Some researchers insist that the domed skulls of pachycephalosaurs, which in some cases are eight inches thick, were made from brittle bone, and those with particularly high and curved domes would require the precision of a surgeon to pull off anything more than a glancing blow. Also, despite being quite stocky and well made, their head, neck and spine could not be aligned in such a way to transmit stress, unlike modern day Musk Ox. So perhaps, instead, they participated in bouts of flank-butting which would inflict pain-a-plenty on whatever was on the receiving end, especially when you consider the lumps and horns that adorn some domes.

The opposition researchers, well, they are all for head banging. As well as a unique "wall" of bone on the inside of the eye socket to perhaps secure the eyeball and protect it from contact-shock during ramming contests, around 22% of 100 pachycephalosaur skulls that were scrutinized as part of a 2013 study sported damage that had previously been brushed off as artifacts of preservation, but which were consistent with osteomyelitis; an infection of the bone resulting from penetrating trauma, or trauma to the tissue overlying the skull leading to an infection of the bone tissue. Unless consistent external factors were at work, it seems likely that these surface wounds, which had healed as well as could be, were incurred during bouts of head-to-head combat. Flat-headed specimens, which are probably all juveniles, were damage free.

Of course, whether pachycephalosaurs were head bangers or not we'll never know for sure, but we're willing to bet that males with the biggest domes were more popular with females than those with smaller ones.

Click here to search Dinochecker for pachycephalosaurs.
Relationships
References
• Brett-Surman, Holtz and Farlow (2012) "The Complete Dinosaur: Second Edition". /uk.
• Peterson J.E., Dischler C., Longrich N.R. (2013) "Distributions of Cranial Pathologies Provide Evidence for Head-Butting in Dome-Headed Dinosaurs (Pachycephalosauridae)". PLoS ONE 8(7): e68620. doi:10.1371/journal.pone.0068620
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To cite this page:
Atkinson, L. "DinoChecker FAQ entry :: What is Pachycephalosauria?"
http://www.dinochecker.com/dinosaurfaqs/what-is-pachycephalosauria›. Web access: 25th Sep 2017.
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