Evidence of Combat in Triceratops

Abstract

BackgroundThe horns and frill of Triceratops and other ceratopsids (horned dinosaurs) are interpreted variously as display structures or as weapons against conspecifics and predators. Lesions (in the form of periosteal reactive bone, healing fractures, and alleged punctures) on Triceratops skulls have been used as anecdotal support of intraspecific combat similar to that in modern horned and antlered animals. If ceratopsids with different cranial morphologies used their horns in such combat, this should be reflected in the rates of lesion occurrence across the skull.Methodology/Principal FindingsWe used a G-test of independence to compare incidence rates of lesions in Triceratops (which possesses two large brow horns and a smaller nasal horn) and the related ceratopsid Centrosaurus (with a large nasal horn and small brow horns), for the nasal, jugal, squamosal, and parietal bones of the skull. The two taxa differ significantly in the occurrence of lesions on the squamosal bone of the frill (P = 0.002), but not in other cranial bones (P>0.20).Conclusions/SignificanceThis pattern is consistent with Triceratops using its horns in combat and the frill being adapted as a protective structure for this taxon. Lower pathology rates in Centrosaurus may indicate visual rather than physical use of cranial ornamentation in this genus, or a form of combat focused on the body rather than the head.

A New Horned Dinosaur Reveals Convergent Evolution in Cranial Ornamentation in Ceratopsidae

“…Convergent evolution of horns, or other display/signaling structures, between sister clades or more distantly related groups has been well documented in mammals [6,35,36] and recently found in hadrosaurid dinosaurs [37], but this marks the first occurrence within the diverse clade of horned dinosaurs. Based on disparate patterns of cranial ornamentation, the use of these horns and frills as display or sociosexual signaling structures has been suggested to be distinct between these two subfamilies of horn dinosaurs [29,38,39]. Convergent horn evolution in mammals often correlates with convergent social behaviors [6].…”

The socio-sexual behaviour of extant archosaurs: implications for understanding dinosaur behaviour

“…Similarly, Horner and Goodwin (2008) postulated that cranial epi-ossifications documented in Triceratops were ornaments that could have been used in conjunction with the forward-directed horns and wide frill to yield an enhanced visual display. Farke et al (2009) examined the incident rate of lesions on the nasal, jugal, squamosal and parietal bones for both Triceratops and Centrosaurus and found that the only significant difference was the frequency of damage to the squamosal bone of the frill. It was thus argued that the lower lesion rates for Centrosaurus suggested a bias towards either combat directed towards the flanks or the use of cranial ornaments for visual display.…”

Positive allometry for exaggerated structures in the ceratopsian dinosaur Protoceratops andrewsi supports socio-sexual signaling

“…In at least some ceratopsians the horns were used in intraspecific combat (Farke et al, 2009) and may have been involved in interspecific combat (Happ, 2008), though they may have served additional purposes (e.g., as aposematic signals). A particularly wide range of explanations has been proposed for the functions of the ceratopsian frill including: as a temperature regulating device, as an aposematic signal, as a defence against predators and for socio-sexual dominance signals.…”