Evidence of Combat in Triceratops

Palaeontologia Electronica, 2004

Triceratops, a common chasmosaurine ceratopsid dinosaur from the Late Cretaceous of North America, is known for its cranial ornamentation, including a single nasal horn and large, paired supraorbital horns. It is commonly surmised that Triceratops used its horns in intraspecific combat, but this hypothesis has not been rigorously tested. Scale models of Triceratops skulls were used to determine if it could physically lock horns as has been suggested. Three hypothetical horn locking positions were found, involving varying orientations of the combatants' skulls. Based on these positions, it was hypothesized that injuries caused by horns were especially likely in certain portions of the frill, jugals, and postorbital horncore tips. This corresponds to some previously reported pathologies in chasmosaurine specimens. Uncertainties in this modeling exercise center around variations in horn orientation, size, shape, and the possible existence of a keratinous supraorbital horncore sheath. Triceratops differs from modern horned mammals in its horn orientation, which suggests that if it engaged in intraspecific combat, its fighting style was quite different from these modern animals. During hypothetical horn locking in Triceratops, most of the force was directed against the medial and lateral surfaces of the horn cores. This has implications for future studies of ceratopsid cranial functional morphology, especially as related to horn architecture and the development of the frontal sinus complex.

PLoS ONE, 2013

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.

Scientific Reports

In the collective imagination derived from scientific and popular literature, Triceratops often faced each other in combat. Thus, from the second half of the twentieth century, these ceratopsids were described as pugnacious animals. This arises primarily from the interpretation of extracranial fenestrae in ceratopsids being the result of combat trauma. However, the diagnosis of the traumatic nature of these anatomical variants of their neck frill requires evidence of bone healing and remodelling by microscopy analysis. Here, we present the case of the Triceratops horridus known as Big John, which is one of the largest specimens discovered in the Hell Creek Formation (Upper Cretaceous; MT, USA). Its right squamosal bone shows an extrafenestra with irregular margins and signs of inflammation. Microscopy analysis revealed newly formed and healing bone, with histological signs typical of the bone remodelling phase. Chemical analysis revealed sulphur that was derived from glycosaminoglyc...

2021

In the collective imagination derived from scientific and popular literature, Triceratops often faced each other in combat. Thus, from the second half of the twentieth century, these ceratopsids were described as pugnacious animals. This arises primarily from the interpretation of extracranial fenestrae in ceratopsids being the result of combat trauma. However, the diagnosis of the traumatic nature of these anatomical variants of their neck frill requires evidence of bone healing and remodelling by microscopy analysis. Here, we present the case of the Triceratops horridus known as Big John, which is one of the largest specimens discovered in the Hell Creek Formation (Upper Cretaceous; MT, USA). Its right squamosal bone shows an extrafenestra with irregular margins and signs of inflammation. Microscopy analysis revealed newly formed and healing bone, with histological signs typical of the bone remodelling phase. Chemical analysis revealed sulphur that was derived from glucosaminoglyc...

Gaia, 15 1998

Examples of healing parallel gouging or grooves on skulls of several theropod taxa are described and illustrated. The healing nature of the lesions indicates they are not evidence of predation or scavenging, but were acquired earlier in life and were undergoing active healing at time of death. In some cases, the parallel nature of the lesions are indicative of tooth strikes received from the spaced teeth in the jaw of another theropod, possibly a conspecific. As such, these lesions can provide insight into possible behaviors of large carnivorous dinosaurs. The authors consider various behaviors that may have lead to intraspecific face-biting behavior. *** Please note that due to a printing error beyond our control, several errors appear on page 171, paragraph 2 of this paper. This paragraph should read as follows: "The right maxilla bears four toothstrike lesions. The first is situated 52 mm above the second and third teeth, measures 20 mm in length, and is up to 9 mm wide. It is shallow and shows a mildly rugose bone texture suggestive of localized bone infection. The second lesion is found above the seventh tooth, measures 16 X 6.5 mm, and is 3.5 mm deep. It appears to represent a healed Type 1 tooth puncture wound. Normal, smooth bone was found on the floor of the other maxillary lesions. A 19 X 13 mm depression is present on the external side of the jugal near the ventral border. This 3.5 mm deep lesion also appears to represent the healed remnant of a Type 1 puncture. A small patch of slightly raised, rugose textured bone posterior to this lesion might represent another healed puncture wound."

Historical Biology, 2013

Journal of Vertebrate Paleontology, 2006

The discovery of the smallest Triceratops skull (UCMP 154452) provides a new ontogenetic end member for the earliest stage of ceratopsid (Centrosaurinae plus Chasmosaurinae) cranial development. The lack of co-ossification among the parietal, squamosals, postorbitals, quadratojugal arch, and the braincase preserves sutural contacts and bone surfaces that later become obscured in adults. The ability to document the early development and morphology of the horns and frill in Triceratops allows a reevaluation of their functional roles. UCMP 154452 shows that the cranial ornamentation of the frill and the postorbital horns were not restricted to adults, but began at an early age in this species. This evidence supports the hypothesis that the function of ceratopsid horns and frills was potentially important for visual communication and species recognition because in this young form it could not have functioned in sexual display. Although some features of UCMP 154452 anticipate or mimic the adult character states, some braincase characters recapitulate the juvenile and adult stages of more basal neoceratopsians.

Proceedings. Biological sciences / The Royal Society, 2006

This is the first cranial ontogenetic assessment of Triceratops, the well-known Late Cretaceous dinosaur distinguished by three horns and a massive parietal-squamosal frill. Our analysis is based on a growth series of 10 skulls, ranging from a 38 cm long baby skull to about 2 m long adult skulls. Four growth stages correspond to a suite of ontogenetic characters expressed in the postorbital horns, frill, nasal, epinasal horn and epoccipitals. Postorbital horns are straight stubs in early ontogeny, curve posteriorly in juveniles, straighten in subadults and recurve anteriorly in adults. The posterior margin of the baby frill is deeply scalloped. In early juveniles, the frill margin becomes ornamented by 17-19 delta-shaped epoccipitals. Epoccipitals are dorsoventrally compressed in subadults, strongly compressed and elongated in adults and ultimately merge onto the posterior frill margin in older adults. Ontogenetic trends within and between growth stages include: posterior frill marg...

The placement of over 50 skulls of the well-known horned dinosaur Triceratops within a stratigraphic framework for the Upper Cretaceous Hell Creek Formation (HCF) of Montana reveals the evolutionary transformation of this genus. Specimens referable to the two recognized morphospecies of Triceratops, T. horridus and T. prorsus, are stratigraphically separated within the HCF with the T. prorsus morphology recovered in the upper third of the formation and T. horridus found lower in the formation. Hypotheses that these morphospecies represent sexual or ontogenetic variation within a single species are thus untenable. Stratigraphic placement of specimens appears to reveal ancestor-descendant relationships. Transitional morphologies are found in the middle unit of the formation, a finding that is consistent with the evolution of Triceratops being characterized by anagenesis, the transformation of a lineage over time. Variation among specimens from this critical stratigraphic zone may indicate a branching event in the Triceratops lineage. Purely cladogenetic interpretations of the HCF dataset imply greater diversity within the formation. These findings underscore the critical role of stratigraphic data in deciphering evolutionary patterns in the Dinosauria.