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Head-biting behavior in theropod dinosaurs: Paleopathological evidence

Authors:
  • Royal Tyrrell Museum of Palaeontology

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Cranial material of Sinraptor dongi (Upper Jurassic, Xinjiang, China), Gorgosau- rus libratus, Daspletosaurus torosus (Upper Cretaceous, Alberta, Canada), and other large theropod dinosaurs exhibit similar paleopathological anomalies indicative of aggressive in- tra- or interspecific biting. Tooth strike trauma includes osseous lesions caused by solitary or multiple tooth punctures, or by dragging or gouging the tooth tips across the surfaces of cranial elements. Many of these lesions were undergoing active healing at the time of death. One isolated tyrannosaurid dentary bears a broken off and embedded tooth tip of another ty- rannosaur. Comparison with unhealed large theropod toothmarks on prey bone suggests that sublethal wounds of these types were caused by other large theropods, possibly rival conspecifics. This may indicate aggressive head or face-biting behavior in certain theropod families. Other associated traumatic osteopathy typified as localized rib and fibula fractures were observed but cannot be directly correlated with violent intra- or interspecific behavior. Healed and healing bite wounds of the head may be related to a number of factors. Establish- ment of dominance within a pack and territorial behavior are considered as two of the most likely causes. Study of paleopathologies is demonstrated to be a useful tool for understand- ing dinosaur behavior.
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... Because they are known from a great number of specimens across ontogenetic stages, representing one of the best fossil records of any theropod group, and they occupy a phylogenetic position midway between basal dinosaurs and birds, tyrannosaurids are the ideal clade to study the presence, frequency, and nature of agonistic behavior in the theropod ancestry of birds. Further, the widespread occurrence of healed or partially healed cranial lesions (hereafter "lesion") interpreted as intraspecific bite marks (Tanke and Currie 1998;Peterson et al. 2009;Bell and Currie 2010;Dalman and Lucas 2021) in tyrannosaurs offers a unique opportunity to study direct evidence of intraspecific aggression in this clade. Whereas previous research largely concentrated on articulated/associated skulls (Tanke and Currie 1998) or single individuals/elements (Peterson et al. 2009;Bell and Currie 2010;Hone and Tanke 2015;Dalman and Lucas 2021), we greatly expand the dataset by adding previously undescribed articulated/ associated skulls and a vast number of isolated and bone bed elements from individuals of different size/age categories, drastically increasing sample size and the ontogenetic and taxonomic range under investigation. ...
... Further, the widespread occurrence of healed or partially healed cranial lesions (hereafter "lesion") interpreted as intraspecific bite marks (Tanke and Currie 1998;Peterson et al. 2009;Bell and Currie 2010;Dalman and Lucas 2021) in tyrannosaurs offers a unique opportunity to study direct evidence of intraspecific aggression in this clade. Whereas previous research largely concentrated on articulated/associated skulls (Tanke and Currie 1998) or single individuals/elements (Peterson et al. 2009;Bell and Currie 2010;Hone and Tanke 2015;Dalman and Lucas 2021), we greatly expand the dataset by adding previously undescribed articulated/ associated skulls and a vast number of isolated and bone bed elements from individuals of different size/age categories, drastically increasing sample size and the ontogenetic and taxonomic range under investigation. ...
... Bones were examined to determine the presence or absence of healed or partially healed lesions consistent with tyrannosaurid tooth marks. Previous studies on these features have used the terms "tooth-strike lesion," "osseous lesion," "lesion mark," "lesion," "injury," and "bite mark" (Tanke and Currie 1998;Peterson et al. 2009;Bell 2010;Hone and Tanke 2015;Dalman and Lucas 2021). Here the terms "tooth-strike lesion" or "lesion" are used to avoid confusion with unhealed bite or tooth marks more consistent with predation or scavenging. ...
Article
Intraspecific aggression, or agonism, is a widespread intrasexual selective behavior important to understanding animal behavioral ecology and reproductive systems. Such behavior can be studied either by direct observation or inferred from wound/scar frequency in extant species but is difficult to document in extinct taxa, limiting understanding of its evolution. Among extant archosaurs, crocodylians display extensive intrasexual aggression, whereas birds show extreme visual/vocal intersexual display. The evolutionary origin of this behavioral divergence, and pattern in non-avian dinosaurs, is unknown. Here we document the morphology, frequency, and ontogeny of intraspecific facial bite lesions (324 lesions) in a large sample of tyrannosaurids (202 specimens, 528 elements) to infer patterns of intraspecific aggression in non-avian theropods. Facial scars are consistent in position and orientation across tyrannosaurid species, suggesting bites were inflicted due to repeated/postured behavior. Facial scars are absent in young tyrannosaurids, first appear in immature animals (~50% adult skull length), are present in ~60% of the adult-sized specimens, and show aggressor:victim size isometry. The ontogenetic distribution of bite scars suggests agonistic behavior is associated with the onset of sexual maturity, and scar presence in approximately half the specimens may relate to a sexual pattern. Considered in a phylogenetic context, intraspecific bite marks are consistent and widely distributed in fossil and extant crocodyliforms and non-maniraptoriform theropods, suggesting a potential plesiomorphic behavior in archosaurs. Their absence in maniraptoriform theropods, including birds, may reflect a transition from boney cranial ornamentation and crocodylian-like intrasexual aggression to avian-like intersexual display with the evolution of pennaceous feathers.
... 2004). Tanke and Currie (1998) reported severe head and face injuries caused by bites from likely intraspecific aggression in no fewer than nine species of carnivorous dinosaurs occurring from the Late Triassic, in the basalmost theropod, Herrerasaurus ischigualastensis Reig (Sereno and Novas 1993;Currie 1997), to the Late Cretaceous, in the much more highly derived Tyrannosaurus rex (Holtz 2001). Aggressive head or face biting between conspecific nonavian theropod dinosaurs was, it seems, a widespread behavior shared by a broad spectrum of nonavian theropods, occurring over essentially the entire 150-million-year time span of their Mesozoic evolution and existence. ...
... If nonavian theropods commonly fed in aggregations, as we propose, and if these aggregations were contentious and frequently cannibalistic like those of the ora, it is possible that the common and widespread facial injuries reported by Tanke and Currie (1998) were sus-tained in intraspecific clashes over carcasses. The high incidence of bite injuries by conspecifics to the sides of the face, lower jaws, and snouts of many nonavian theropods (Tanke and Currie 1998) could have occurred when, feeding in such aggregations, these predators would often have had their faces near one another. ...
... If nonavian theropods commonly fed in aggregations, as we propose, and if these aggregations were contentious and frequently cannibalistic like those of the ora, it is possible that the common and widespread facial injuries reported by Tanke and Currie (1998) were sus-tained in intraspecific clashes over carcasses. The high incidence of bite injuries by conspecifics to the sides of the face, lower jaws, and snouts of many nonavian theropods (Tanke and Currie 1998) could have occurred when, feeding in such aggregations, these predators would often have had their faces near one another. Feeding too close to or failing to yield to an aggressive, agonistic conspecific may have provoked a brief but explosive displacement attack. ...
Article
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Since the 1969 description of Deinonychus antirrhopus Ostrom, cooperative pack hunting behavior for this species and, subsequently, for many other nonavian theropods, has attained wide acceptance. In this paper we assess the hypothesis of mammal-like cooperative pack hunting in D. antirrhopus and other nonavian theropods by examining the behaviors of extant diapsids. Through phylogenetic inference and character optimization, we conclude that this hypothesis is both unparsimonious and unlikely for these taxa and that the null hypothesis should therefore be that nonavian theropod dinosaurs were solitary hunters or, at most, foraged in loose associations. Moreover, we present new evidence from the D. antirrhopus type locality of probable intraspecific aggression in this species. Additionally, our study suggests that some evidence that has previously been proposed in support of highly gregarious, mammal-like behavior in nonavian theropods (e.g., certain theropod-dominated fossil assemblages, preserved bite-mark injuries on some specimens, and the preponderance of theropod trackways at some sites) may alternatively be interpreted as evidence that nonavian theropod behavior was more agonistic, cannibalistic, and diapsid-like than has been widely believed.
... In contrast, osteopathologies are well documented in dinosaurs, crocodilians, mosasaurs, non-therapsid pelycosaurs, etc. (Buffetaut, 1983;Boucot, 1990;Rothschild and Martin, 1993;Mackness and Sutton, 2000;Tanke and Rothschild, 2002;Katsura, 2004;Lingham-Soliar, 2004;Reisz and Tsuji, 2006;Boucot and Poinar, 2011;Zammit and Kear, 2011;Rega et al., 2012;Bakker et al., 2015;Bastiaans et al., 2020), and the existence of paleopathologies in contemporaneous species is attested (Fernandez et al., 2013). Bite marks, in particular, have been documented in countless fossil mammals (e.g., Scott and Jepsen, 1936;Tanke and Currie, 1998;Chimento et al., 2019), pelycosaurs (Reisz and Tsuji, 2006;Bakker et al., 2015), and outside synapsids in, e.g., dinosaurs, crocodilians, mosasaurs, ichthyosaurs (Buffetaut, 1983;Boucot, 1990;Rothschild and Martin, 1993;Tanke and Currie, 1998;Mackness and Sutton, 2000;Tanke and Rothschild, 2002;Avilla et al., 2004;Katsura, 2004;Lingham-Soliar, 2004;Zammit and Kear, 2011;Bastiaans et al., 2020), but remain rarely reported in NMT. So far, bite marks have been described on the surface of the bones of two dicynodonts (Budziszewska-Karwowska et al., 2010;Fordyce et al., 2012) and one titanosuchid dinocephalian (Shelton et al., 2019). ...
... In contrast, osteopathologies are well documented in dinosaurs, crocodilians, mosasaurs, non-therapsid pelycosaurs, etc. (Buffetaut, 1983;Boucot, 1990;Rothschild and Martin, 1993;Mackness and Sutton, 2000;Tanke and Rothschild, 2002;Katsura, 2004;Lingham-Soliar, 2004;Reisz and Tsuji, 2006;Boucot and Poinar, 2011;Zammit and Kear, 2011;Rega et al., 2012;Bakker et al., 2015;Bastiaans et al., 2020), and the existence of paleopathologies in contemporaneous species is attested (Fernandez et al., 2013). Bite marks, in particular, have been documented in countless fossil mammals (e.g., Scott and Jepsen, 1936;Tanke and Currie, 1998;Chimento et al., 2019), pelycosaurs (Reisz and Tsuji, 2006;Bakker et al., 2015), and outside synapsids in, e.g., dinosaurs, crocodilians, mosasaurs, ichthyosaurs (Buffetaut, 1983;Boucot, 1990;Rothschild and Martin, 1993;Tanke and Currie, 1998;Mackness and Sutton, 2000;Tanke and Rothschild, 2002;Avilla et al., 2004;Katsura, 2004;Lingham-Soliar, 2004;Zammit and Kear, 2011;Bastiaans et al., 2020), but remain rarely reported in NMT. So far, bite marks have been described on the surface of the bones of two dicynodonts (Budziszewska-Karwowska et al., 2010;Fordyce et al., 2012) and one titanosuchid dinocephalian (Shelton et al., 2019). ...
... The absence of a drainage channel for pus or any other trace of infection suggests that an infection resulting from the bite was likely not the cause of death. In living animals, bites can be inflicted either during an act of predation or for social signaling (Poole, 1985;Tanke and Currie, 1998). Therefore, the two hypotheses that may account for the circumstances that led to the condition in SAM-PK-11490 are attempted predation or social signaling. ...
Article
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Despite their significance for paleobiological interpretations, bite marks have been rarely reported in non-mammalian therapsids (NMT). Here we describe, for the first time, the occurrence of a tooth embedded in the snout of a gorgonopsian. The tooth is surrounded by a bony callus, which demonstrates that the animal was still alive after the attack and healed. The identity of the attacker is unknown. Two hypotheses are discussed to account for this healed bite: failed predation (most likely by a biarmosuchian, therocephalian, or another gorgonopsian) and intraspecific social biting. Though predation cannot be ruled out, it has been hypothesized that gorgonopsians used their saber-like teeth for social signaling, which suggests that social biting may be the most likely scenario. The practice of social biting has long been hypothesized in NMT, but this is the first fossilized evidence of the behavior to be described.
... The tooth marks observed on BMR P2002.4.1 and BMR P2007.4.1 are Type 1 punctures (Jacobsen, 1998;Tanke and Currie, 1998), described as "punctures (partial and full penetration) are circular to oval in outline. In unhealed examples, plates of bone are folded down and inwards into the puncture hole. ...
... Bite marks and feeding traces attributed to theropod dinosaurs have been extensively studied (Fiorillo, 1991;Carpenter, 1998;Chure, Fiorillo & Jacobsen, 1998;Jacobsen, 1998;Tanke and Currie, 1998;Farlow & Holtz, 2002;Fowler & Sullivan, 2006;Happ, 2008;Bell & Currie, 2009;Peterson et al., 2009;Gignac et al., 2010;Peterson & Daus, 2019;Eberth & Currie, 2010;Hone and Rauhut, 2010;Hone & Watabe, 2010;Longrich et al., 2010;DePalma et al., 2013;Hone & Tanke, 2015;McLain et al., 2018;Drumheller et al., 2020). Whereas most studies discuss tooth marks attributable to adult theropods, the ability to observe multiple bitten specimens from a juvenile offer further insight into potential ontogenetic shifts in diet and behavior (e.g., Schroeder, Lyons & Smith, 2021). ...
... Whereas most studies discuss tooth marks attributable to adult theropods, the ability to observe multiple bitten specimens from a juvenile offer further insight into potential ontogenetic shifts in diet and behavior (e.g., Schroeder, Lyons & Smith, 2021). Bite marks specifically attributable to intraspecific aggression in theropods include Types 1 and 2 tooth marks to the maxilla, nasal, jugal, and dentary (Tanke and Currie, 1998;Bell & Currie, 2009;Peterson et al., 2009). In crocodylians, these injuries are produced during rapid biting motions directed at the face, which is covered in relatively thin integument and tissues, requiring less resistance from muscle prior to striking bone. ...
Article
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Background Bite marks attributed to adult Tyrannosaurus rex have been subject to numerous studies. However, few bite marks attributed to T. rex have been traced to juveniles, leaving considerable gaps in understanding ontogenetic changes in bite mechanics and force, and the paleoecological role of juvenile tyrannosaurs in the late Cretaceous. Methods Here we present bite force estimates for a juvenile Tyrannosaurus rex based on mechanical tests designed to replicate bite marks previously attributed to a T. rex of approximately 13 years old. A maxillary tooth of the juvenile Tyrannosaurus specimen BMR P2002.4.1 was digitized, replicated in dental grade cobalt chromium alloy, and mounted to an electromechanical testing system. The tooth was then pressed into bovine long bones in various locations with differing cortical bone thicknesses at varying speeds for a total of 17 trials. Forces required to replicate punctures were recorded and puncture dimensions were measured. Results Our experimentally derived linear models suggest bite forces up to 5,641.19 N from cortical bone thickness estimated from puncture marks on an Edmontosaurus and a juvenile Tyrannosaurus . These findings are slightly higher than previously estimated bite forces for a juvenile Tyrannosaurus rex of approximately the same size as BMR P2002.4.1 but fall within the expected range when compared to estimates of adult T. rex . Discussion The results of this study offer further insight into the role of juvenile tyrannosaurs in late Cretaceous ecosystems. Furthermore, we discuss the implications for feeding mechanisms, feeding behaviors, and ontogenetic niche partitioning.
... These observations suggest that infection was not the cause of the mandibular pathologies observed in FMNH PR2081 and tyrannosaurids in general. Tyrannosaurids and other theropods are known to engage in violent face-biting and other aggressive behaviors and the resultant wounds have been widely documented (Tanke and Currie, 2000;Brown et al., 2021). Bell and Currie (2009) reported a tyrannosaurid surangular TMP 1996.005.0013 with an imbedded tyrannosaurid tooth. ...
... Bell and Currie (2009) reported a tyrannosaurid surangular TMP 1996.005.0013 with an imbedded tyrannosaurid tooth. While face biting is well documented among tyrannosaurids (Tanke and Currie, 2000;Brown et al., 2021), the imbedded tooth confirmed that these injuries were the result of "intrafamilial (if not intraspecific) interaction between tyrannosaurs" (Bell and Currie, 2010, p. 1;Brown et al., 2021). Intraspecific aggression and dominance behavior (Le Boeuf and Mesnick, 1991) and courtship rituals or copulatory bites (Carpenter, 1961(Carpenter, , 1962Klimley, 1980) have been suggested as possible explanations for these injuries. ...
Article
Many tyrannosaurid specimens preserve unusual pathologies in the caudal half of the mandible that are of uncertain origin. The two main hypotheses put forth to date both suggest these pathologies are lesions resultant from infection either due to bacteria or protozoans. In light of this controversy, we provide a comparative anatomical study to characterize the pathophysiology of these enigmatic pathologies in order to elucidate their underlying cause. Human individuals that had been subjected to cranial trepanation and specimens of the late Triassic reptile Stagonolepis exhibiting healing fractures provide phylogenetic bracketing for investigating bone surface alterations induced by trauma in dinosaurs. Examination of mandibular pathologies in Tyrannosaurus rex FMNH PR2081 reveals all the characteristics of wound healing in the absence of infection. Additional evidence that refutes the previous hypothesis that these pathologies result from infection by the protozoan, Trichomonas gallinae, is discussed. Behavioral evidence suggests that these pathologies may be wounds induced through intraspecific combat.
... However, there is currently no evidence indicating head-butting in tyrannosaurids (Currie 2003a), and pathologies in the cranial roof due to such intraspecific combat are yet to be reported in this clade, unlike pachycephalosaurs (Peterson et al. 2013). Instead, numerous cases of bite marks in large theropod skulls strongly suggest facial biting was a ma-jor intraspecific aggression behavior (Tanke and Currie 1998;Peterson et al. 2009;Brown et al. 2021). Therefore, head-butting behavior seems to be an unlikely driving force of development of wide, deep cranial roof of large theropods, or at least in tyrannosaurids. ...
Article
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Tarbosaurus bataar is a sister taxon of the well-studied theropod dinosaur Tyrannosaurus rex, and numerous fossils of this tyrannosaurid have been discovered in the Upper Cretaceous Nemegt Formation of Mongolia. Although specimens of different sizes of Tarbosaurus bataar have been discovered since its initial description, few rigorous studies on its growth changes have been done. Here we examine growth changes in the frontal bones of seven Tarbosaurus bataar specimens using bivariate analyses and the Björk superimposition method to demonstrate trends in their ontogenetic allometry. The width and depth of the frontal undergoes positive allometry during growth, whereas the length shows a trend of negative allometry. The details of growth changes in Tarbosaurus bataar frontals are largely similar to those of Tyrannosaurus rex. Furthermore, generic allometric trends of tyrannosaurid frontals, including those of Tarbosaurus bataar, are shared with other large-bodied theropod clades and may represent a consequence of strengthening parts of the braincase as an anchor for the jaw musculature.
... The first documented instances of palaeopathologies are Marc Armond Ruffer's descriptions of spinal fusion in the early Miocene crocodilian Tomistoma and the Pleistocene bear Ursus spelaeus (Ruffer, 1921). The field of vertebrate palaeopathology has since identified various forms of osteologic pathologies, including destruction (e.g., Tanke and Currie 1998;Xing et al. 2018), volume change (e.g., Rothschild and Tanke 2005), deformation (e.g., Rothschild and Panza 2005), hyperostosis (e.g., Arbour and Currie 2011), and even tumours (e.g., Rothschild et al. 1999; Barbosa et al. 2016). Additionally, some abnormal vertebrate footprints have been interpreted as recording limb injuries and pedial lesions (e.g., Ishigaki 1986;Lockley et al. 1994). ...
... Although the bone remodeling documented here is extensive, there is no evidence of complete, circumferential fracture, or focal puncture (bite wound) in any of the affected elements of USNM 18313, either on the bone surfaces or in the radiological analyses. Theoretically, an armor-bearing carnivore such as a phytosaur would be better protected from bites than would theropod dinosaurs, which are the fossil group with the most extensively documented occurrences of skeletal traumarelated pathologies associated with bites (e.g., Tanke and Currie, 2000;Molnar, 2001;Tanke and Rothschild, 2002;Rothschild and Tanke, 2005, but note that some reinterpretation may be warranted in light of Wolff et al., 2009;Hone and Tanke, 2015). We have not observed any evidence of similar pathologies in the preserved dermal armor, but most of the remaining specimens are paramedian osteoderms that were arranged in two columns dorsal to the vertebral series, not over the limbs, which were generally covered with much smaller osteoderms (Camp, 1930). ...
Article
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Phytosaurs were a widespread clade of Triassic predatory archosauriforms whose skull anatomy is well known, but whose paleobiology is underexplored. Here we report on a well-preserved specimen from Adamanian (early-mid-Norian) strata in Arizona that includes not only the skull and lower jaws but much of the postcranial skeleton, which exhibits extensive evidence of pathologies. This specimen has a complex taxonomic history, and we verify its referral to Smilosuchus gregorii based on multiple cranial characters. The shafts of eight limb bones preserve extensive exostoses—more paleopathological elements than in any other Triassic archosauromorph. These exostoses are often centered on cavitations reminiscent of draining tracts. Extensive, irregular, proliferative lesions have completely engulfed the left deltopectoral crest and thoroughly altered the architecture of both femora. The animal’s presumed low metabolic rate would have allowed several months of lesion progression before it died of either nutritional deficiency or systemic infection. This is the fourth, and by far the most extensive, report of pathology in a phytosaur, and only the eighth in a non-dinosaurian Triassic archosauromorph. The character and location of the lesions evokes aspects of both osteomyelitis and hypertrophic osteopathy—though neither is fully consistent with the changes present, nor are these conditions well-explored in extant reptiles. The most likely cause of the pathologies exhibited here is osteomyelitis; indeed, this specimen bears more osteomyelitis-like paleopathological elements than any other fossil archosaur.
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