Darren H. Tanke

Head-biting behavior in theropod dinosaurs: Paleopathological evidence

Cranial material of Sinraptor dongi (Upper Jurassic, Xinjiang, China), Gorgosaurus libratus, Daspletosaurus torosus (Upper Cretaceous, Alberta, Canada), and other large theropod dinosaurs exhibit similar paleopathological anomalies indicative of aggressive intraor 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 tyrannosaur. Comparison with unhealed large theropod tooth marks on prey bone suggests that sublethal wounds ofthese 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 intraor interspecific behavior. Healed and healing bite wounds ofthe head may be related to a numberoffactors. Establishment 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 understanding dinosaur behavior.

The facial integument of centrosaurine ceratopsids: morphological and histological correlates of novel skin structures.

The horned dinosaur Pachyhinosaurus possesses rugose bony bosses across the skull roof in lieu of the projecting bony horn cores seen in most ceratopsians. This elaboration of typical ceratopsian ornaments provides an opportunity to test hypotheses of ceratopsian facial skin morphology and function. We analyze bone morphology and histology associated with several classes of skin features in extant amniotes using a classification tree analysis. We isolate key osteological and histological correlates for unpreserved skin structures, including both a pattern of pitting and resorption characteristic of muskox (Ovibos) frontal horn boss, and a pattern of metaplastic ossification characteristic of rhinoceros nasal horn boss. We also describe correlates for other skin features, such as epidermal scales and horn sheaths. Dermatocranial elements from centrosaurine ceratopsians are then examined for the same osteological and histological correlates. From this comparison we propose that the rugose bosses that replace horn cores in many centrosaurine dinosaurs, most notably Achelousaurus and Pachyrhinosaurus, were covered by a thick pad of cornified skin derived from the caudodorsal side of the primitive horn sheath comparable to the horny boss of extant muskoxen (Ovibos). We examine extant taxa with skin morphologies similar to Pachyrhinosaurus for consistent adaptive relationships between structure and behavior. We determine that high‐energy headbutting is consistently associated with the acquisition of thick cornified pads, seen in muskoxen as well as helmeted hornbills [Buceros (=Rhinoplax) vigil] and African buffalo (Syncerus). The association of the bony ornaments of Pachyrhinosaurus with risky agonistic behaviors casts doubt on the role of species recognition as a primary selection pressure driving the diversity of all ceratopsian horns. We conclude that social selection (a broad form of intraspecific competition) is a more appropriate explanation for the diversity of centrosaurine ceratopsian ornaments in the Late Cretaceous. Anat Rec, 292:1370–1396, 2009.

A New Horned Dinosaur from an Upper Cretaceous Bone Bed in Alberta

October 1, 2008, Philip J. Currie, Wann Langston, Jr., and Darren H. Tanke unveiled for the first time the name of a newly discovered horned dinosaur species. In the first monographic treatment of a horned (ceratopsid) dinosaur in almost a century, this monumental volume presents one of the closest looks at the anatomy, relationships, growth and variation, behavior, ecology and other biological aspects of a single dinosaur species. The research, which was conducted over two decades, was possible because of the discovery of a densely packed bone bed near Grande Prairie, Alberta. The locality has produced abundant remains of a new species of horned dinosaur (ceratopsian), and parts of at least 27 individual animals were recovered. This new species of Pachyrhinosaurus is closely related to Pachyrhinosaurus canadensis, which is known from younger rocks near Drumheller and Lethbridge in southern Alberta, but is a smaller animal with many differences in the ornamental spikes and bumps on the skull. The adults of both species have massive bosses of bone in the positions where other horned dinosaurs (like Centrosaurus and Triceratops) have horns. However, juveniles of the new species resemble juveniles of Centrosaurus in having horns rather than bosses. Skull anatomy undergoes remarkable changes during growth and the horns over the nose and eyes of the Pachyrhinosaurus juveniles transform into bosses; spikes and horns develop on the top of and at the back of the frill that extends back over the neck. No cause has been determined for the apparent catastrophic death of the herd of Pachyrhinosaurus from the Grande Prairie area, but it has been suggested that such herds may have been migratory animals. In addition to the main descriptive paper, the volume includes information on the distribution of bones within the bone bed itself, and a cutting-edge digital treatment of CT-scan data of the fossils to reveal the anatomy of the animal’s brain! See below to view the Pachyrhinosaurus braincase, fading away to reveal the brain within. Courtesy of Witmer & Ridgely, Ohio University.

Evidence of Combat in Triceratops

Background The 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 Findings We 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/Significance This 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 centrosaurine from the Late Cretaceous of Alberta, Canada, and the evolution of parietal ornamentation in horned dinosaurs

In 1916, a centrosaurine dinosaur bonebed was excavated within the Campanian-aged deposits of what is now Dinosaur Provincial Park, Alberta, Canada. Specimens from this now-lost quarry, including two parietals, a squamosal, a skull missing the frill, and an incomplete dentary, were purchased by The Natural History Museum, London. The material was recently reprepared and identified herein as a previously unknown taxon, Spinops sternbergorum gen. et sp. nov. Based upon the available locality data and paleopalynology, the quarry lies in either the upper part of the Oldman Formation or the lower part of the Dinosaur Park Formation. The facial region of the partial skull is similar to putative mature specimens of Centrosaurus spp. and Styracosaurus albertensis, with short, rounded postorbital horncores and a large, erect nasal horncore. Parietal ornamentation is consistent on both known parietals and is unique among ceratopsids. Bilateral, procurved parietal hooks occupy the P1 (medial-most) position on the dorsal surface of the parietal and are very similar to those seen in Centrosaurus apertus. Epiparietals in the P2 or possibly P3 position (lateral to P1) manifest as extremely elongate, caudally directed spikes, unlike the condition in C. apertus, S. albertensis, or any other “derived” centrosaurine. Cladistic analysis suggests that S. sternbergorum is closely related to Centrosaurus and Styracosaurus. Historically, based upon the condition in Styracosaurus and related centrosaurines, it was assumed that the medial-most elongated spikes on centrosaurine parietals correspond to the P3 epiparietal position. The exception illustrated in the new taxon suggests that homologies of epiparietals among basal centrosaurines (e.g., Albertaceratops and Diabloceratops) and derived centrosaurines (e.g., Styracosaurus and “pachyrhinosaurs”) should be reconsidered. The medially-placed, caudally-directed “P3” process of basal centrosaurines may, in fact, be homologous with P2.

Vertebrate Ichnopathology: Pathologies Inferred from Dinosaur Tracks and Trackways from the Mesozoic

Literature concerning dinosaur footprints or trackways exhibiting abnormal gait or morphology reflecting pathology (ichnopathology) is rare. We report on a number of Jurassic and Cretaceous occurrences of theropod footprints from western North America with unusual morphologies interpreted herein as examples of inferred pathologies, or ichnopathologies. The majority of ichnopathologies are primarily manifested in the digit impressions and include examples of swelling, extreme curvature, dislocation or fracture, and amputation. A number of occurrences are single tracks on ex situ blocks with substantial deformation (inferred dislocation or fracture), or absence of a single digit impression. Two occurrences are from in situ natural mould trackways, one of which is a lengthy trackway of a presumed allosauroid with no noticeable deformation of the digits or feet but with strong inward rotation of the left footprint toward the midline and a pronounced, waddling limp. The other is a tyrannosaurid trackway consisting of three footprints (one right, two left) with the two left prints exhibiting repetitive ichnopathology of a partially missing Digit II impression.

Pre- and postmortem tyrannosaurid bite marks on the remains of Daspletosaurus (Tyrannosaurinae: Theropoda) from Dinosaur Provincial Park, Alberta, Canada

Trace marks on the bones of non-avian dinosaurs may relate to feeding by large carnivores or as a result of combat. Here the cranium and mandible of a specimen of Daspletosaurus are described that show numerous premortem injuries with evidence of healing and these are inferred to relate primarily to intraspecific combat. In addition, postmortem damage to the mandible is indicative of late stage carcass consumption and the taphonomic context suggests that this was scavenging. These postmortem bites were delivered by a large bodied tyrannosaurid theropod and may have been a second Daspletosaurus, and thus this would be an additional record of tyrannosaurid cannibalism.

Bone Lesions in Hadrosaurs: Computed Tomographic Imaging as a Guide for Paleohistologic and Stable-Isotopic Analysis

ABSTRACT High-resolution computed tomography (CT) scans through two fossilized lesions in hadrosaur bone guided paleohistological and stable-isotopic sampling to examine the stages and structures of bone repair in hadrosaurs. Two hadrosaur caudal neural spines from late Cretaceous bonebeds in Alberta, Canada, exhibit calluses produced during healing of traumatic fractures. In both CT scans and paleohistologic sections, these specimens display a combination of reptilian and non-reptilian characteristics in dinosaurian skeletal repairs. In one specimen the callus is dominated by a trabecular lattice that lacks signs of remodeling. Trabeculae in this callus are distinctively textured by clusters of densely packed, randomly oriented lacunae, two orders of magnitude larger than typical osteocyte lacunae and reminiscent of hypertrophic chondrocytes in cartilage of reptiles. The lattice represents early mineralization of callus tissue, and it preserves a &dgr;18O value in mineral phosphate 0.6‰ lower than adjacent non-pathologic cortex, suggesting that the repair site was ∼2.5°C warmer than uninjured tissue. The elevated temperature results from locally enhanced cellular activity around the fracture, a common consequence of bone injury in vertebrates. In the second specimen, the callus has been extensively remodeled, with several areas transformed to dense secondary Haversian bone typical of modern birds. Stable oxygen isotopes in bone phosphate of this callus show no isotopic offset, indicating that this injury had progressed further through the healing process before the animals death. High-resolution CT scans reveal tissue density and structure differences between the two lesions, suggesting that this technology could eventually be used to gauge relative healing without altering unique fossil specimens.

A history of Albertosaurus discoveries in Alberta, CanadaThis article is one of a series of papers published in this Special Issue on the theme Albertosaurus.

After many years of taxonomic uncertainty, Albertosaurus was established as a new genus in 1905, the year Alberta became a province of Canada. Gorgosaurus is a closely related tyrannosaurid from the Judithian beds of southern Alberta that was subsequently synonymized with Albertosaurus. Although most researchers consider the genera as distinct, there has been considerable confusion over the temporal and geographic range of Albertosaurus. Albertosaurus sarcophagus is only known from 13 skulls and (or) skeletons of varying completeness, and one (possibly two) bonebeds, all from the Horseshoe Canyon Formation (Campanian–Maastrichtian) of Alberta. Many of the major Albertosaurus specimens are scientifically compromised due to poor collection techniques, incomplete locality and stratigraphic information, politics, vandalism, accidents, gunplay, and landowner issues. The background of each specimen is discussed to eliminate some of the sources of confusion and to document how much of each specimen is preserved.

Spinal and rib osteopathy in Huehuecanauhtlus tiquichensis (Ornithopoda: Hadrosauroidea) from the Late Cretaceous in Mexico

Abstract Osteopathy from derived hadrosauroids has been extensively studied. However, little work has been done in the basal members of this group. Only two brief notes have recorded three examples of osteopathy in the basal hadrosauroids in Bactrosaurus, Gilmoreosaurus and Jeyawati. In the present manuscript, we found in the holotype of the basal hadrosauroid Huehuecanauhtlus tiquichensis (IGM 6253) from Mexico two dorsal ribs and a dorsal vertebra with unusual pathologic conditions. The injuries are described as possible premortem or perimortem anterior rib fracture, associated with a singular sclerosis and costo-vertebral ankyloses which probably originated by spinal and rib osteomyelitis. The vertebral lesion caused direct damage to the nervous system and possible back pain. This study represents the first study of palaeopathology in a Mexican hadrosauroid in which the bone abnormalities are extensively compared with previous studies and described in detail, their origins are interpreted, and the health implications for the individual are considered.