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Pachycephalosaur cranial pathologies from head-butting

From: Ben Creisler

New in PLoS ONE:

Joseph E. Peterson, Collin Dischler & Nicholas R. Longrich (2013)
Distributions of Cranial Pathologies Provide Evidence for Head-Butting
in Dome-Headed Dinosaurs (Pachycephalosauridae).
PLoS ONE 8(7): e68620.

Pachycephalosaurids are small, herbivorous dinosaurs with domed skulls
formed by massive thickening of the cranial roof. The function of the
dome has been a focus of debate: the dome has variously been
interpreted as the product of sexual selection, as an adaptation for
species recognition, or as a weapon employed in intraspecific combat,
where it was used in butting matches as in extant ungulates. This last
hypothesis is supported by the recent identification of cranial
pathologies in pachycephalosaurids, which appear to represent
infections resulting from trauma. However, the frequency and
distribution of pathologies have not been studied in a systematic
fashion. Here, we show that pachycephalosaurids are characterized by a
remarkably high incidence of cranial injury, where 22% of specimens
have lesions on the dome. Frequency of injury shows no significant
difference between different genera, but flat-headed morphs (here
interpreted as juveniles or females) lack lesions. Mapping of injuries
onto a digitial pachycephalosaurid skull shows that although lesions
are distributed across the dome, they cluster near the apex, which is
consistent with the hypothesis that the dome functioned for
intraspecific butting matches.