Lokiceratops rangiformis gen. et sp. nov. (Ceratopsidae: Centrosaurinae) from the Campanian Judith River Formation of Montana reveals rapid regional radiations and extreme endemism within centrosaurine dinosaurs.

The Late Cretaceous of western North America supported diverse dinosaur assemblages, though understanding patterns of dinosaur diversity, evolution, and extinction has been historically limited by unequal geographic and temporal sampling. In particular, the existence and extent of faunal endemism along the eastern coastal plain of Laramidia continues to generate debate, and finer scale regional patterns remain elusive. Here, we report a new centrosaurine ceratopsid, Lokiceratops rangiformis, from the lower portion of the McClelland Ferry Member of the Judith River Formation in the Kennedy Coulee region along the Canada-USA border. Dinosaurs from the same small geographic region, and from nearby, stratigraphically equivalent horizons of the lower Oldman Formation in Canada, reveal unprecedented ceratopsid richness, with four sympatric centrosaurine taxa and one chasmosaurine taxon. Phylogenetic results show that Lokiceratops, together with Albertaceratops and Medusaceratops, was part of a clade restricted to a small portion of northern Laramidia approximately 78 million years ago. This group, Albertaceratopsini, was one of multiple centrosaurine clades to undergo geographically restricted radiations, with Nasutuceratopsini restricted to the south and Centrosaurini and Pachyrostra restricted to the north. High regional endemism in centrosaurs is associated with, and may have been driven by, high speciation rates and diversity, with competition between dinosaurs limiting their geographic range. High speciation rates may in turn have been driven in part by sexual selection or latitudinally uneven climatic and floral gradients. The high endemism seen in centrosaurines and other dinosaurs implies that dinosaur diversity is underestimated and contrasts with the large geographic ranges seen in most extant mammalian megafauna.

Complication reporting in trauma: An environmental scan and comparison of nationwide trauma registry data.

BACKGROUND: To explore variability in quality measurement, this study aimed to compare abstraction and definitions of complications reported across trauma registries in Canada. METHODS: A literature search was performed to identify active trauma registries used in Canadian hospitals. Registry characteristics, data abstraction, and reported complications and definitions based on registry data dictionaries were compared. RESULTS: Nine registries were included, most of which were provincial-level registries (67 â€‹%). A total of 53 individual complications were identified. Twenty-one (40 â€‹%) were recorded by only one registry each whereas 5 (9 â€‹%) were collected by all. Of the 32 complications collected by â€‹> â€‹1 registry, 18 (56 â€‹%) had different definitions. Of the 18 with different definitions, 12 (67 â€‹%), 5 (28 â€‹%), and 1 (6 â€‹%) had 2, 3, and 4 different definitions across registries, respectively. CONCLUSIONS: Complications reported by trauma registries are variable. Reliable benchmarking is likely challenging, and efforts to standardize complication reporting may be a valuable undertaking.

Nutritional support for the trauma and emergency general surgery patient: What you need to know.

ABSTRACT: Decades of research have provided insight into the benefits of nutritional optimization in the elective surgical patient. Patients who are nutritionally prepared for surgery enjoy reduced length of hospital and intensive care unit stays and suffer fewer complications. In the trauma and emergency general surgery patient populations, we are not afforded the preoperative period of optimization and patients often suffer longer lengths of hospital stay, discharge to nonhome destinations, and higher infectious and mortality rates. Nonetheless, ongoing research in this vulnerable and time critical diagnosis population has revealed significant outcomes benefits with the meticulous nutritional support of these patients. However, it is important to note that optimal nutritional support in this challenging patient population is not simply a matter of "feeding more and feeding earlier." In this review, we will address assessing nutritional needs, the provision of optimal nutrition, the timing and route of nutrition, and monitoring outcomes and discuss the management of nutrition in the complex trauma and emergency general surgery patient. LEVEL OF EVIDENCE: Literature Synthesis and Expert Opinion; Level V.

Prognostic factors associated with risk of stroke following blunt cerebrovascular injury: A systematic review and meta-analysis.

BACKGROUND & OBJECTIVES: Blunt cerebrovascular injury (BCVI) includes carotid and/or vertebral artery injury following trauma, and conveys an increased stroke risk. We conducted a systematic review and meta-analysis to provide a comprehensive summary of prognostic factors associated with risk of stroke following BCVI. METHODS: We searched the EMBASE and MEDLINE databases from January 1946 to June 2023. We identified studies reporting associations between patient or injury factors and risk of stroke following BCVI. We performed meta-analyses of odds ratios (ORs) using the random effects method and assessed individual study risk of bias using the QUIPS tool. We separately pooled adjusted and unadjusted analyses, highlighting the estimate with the higher certainty. RESULTS: We included 26 cohort studies, involving 20,458 patients with blunt trauma. The overall incidence of stroke following BCVI was 7.7 %. Studies were predominantly retrospective cohorts from North America and included both carotid and vertebral artery injuries. Diagnosis of BCVI was most commonly confirmed with CT angiography. We demonstrated with moderate to high certainty that factors associated with increased risk of stroke included carotid artery injury (as compared to vertebral artery injury, unadjusted odds ratio [uOR] 1.94, 95 % CI 1.62 to 2.32), Grade III Injury (as compared to grade I or II) (uOR 2.45, 95 % CI 1.88 to 3.20), Grade IV injury (uOR 3.09, 95 % CI 2.20 to 4.35), polyarterial injury (uOR 3.11 (95 % CI 2.05 to 4.72), occurrence of hypotension at the time of hospital admission (adjusted odds ratio [aOR] 1.32, 95 % CI 0.87 to 2.03) and higher total body injury severity (aOR 5.91, 95 % CI 1.90 to 18.39). CONCLUSION: Local anatomical injury pattern, overall burden of injury and flow dynamics contribute to BCVI-related stroke risk. These findings provide the foundational evidence base for risk stratification to support clinical decision making and further research.

Guidance for assessment of the inflammation etiologic criterion for the GLIM diagnosis of malnutrition: A modified Delphi approach.

BACKGROUND & AIMS: The Global Leadership Initiative on Malnutrition (GLIM) approach to malnutrition diagnosis is based on assessment of three phenotypic (weight loss, low body mass index, and reduced skeletal muscle mass) and two etiologic (reduced food intake/assimilation and disease burden/inflammation) criteria, with diagnosis confirmed by fulfillment of any combination of at least one phenotypic and at least one etiologic criterion. The original GLIM description provided limited guidance regarding assessment of inflammation and this has been a factor impeding further implementation of the GLIM criteria. We now seek to provide practical guidance for assessment of inflammation in support of the etiologic criterion for inflammation. METHODS: A GLIM-constituted working group with 36 participants developed consensus-based guidance through a modified-Delphi review. A multi-round review and revision process served to develop seven guidance statements. RESULTS: The final round of review was highly favorable with 99 % overall "agree" or "strongly agree" responses. The presence of acute or chronic disease, infection or injury that is usually associated with inflammatory activity may be used to fulfill the GLIM disease burden/inflammation criterion, without the need for laboratory confirmation. However, we recommend that recognition of underlying medical conditions commonly associated with inflammation be supported by C-reactive protein (CRP) measurements when the contribution of inflammatory components is uncertain. Interpretation of CRP requires that consideration be given to the method, reference values, and units (mg/dL or mg/L) for the clinical laboratory that is being used. CONCLUSION: Confirmation of inflammation should be guided by clinical judgement based upon underlying diagnosis or condition, clinical signs, or CRP.

Guidance for assessment of the inflammation etiologic criterion for the GLIM diagnosis of malnutrition: A modified Delphi approach.

BACKGROUND: The Global Leadership Initiative on Malnutrition (GLIM) approach to malnutrition diagnosis is based on assessment of three phenotypic (weight loss, low body mass index, and reduced skeletal muscle mass) and two etiologic (reduced food intake/assimilation and disease burden/inflammation) criteria, with diagnosis confirmed by fulfillment of any combination of at least one phenotypic and at least one etiologic criterion. The original GLIM description provided limited guidance regarding assessment of inflammation, and this has been a factor impeding further implementation of the GLIM criteria. We now seek to provide practical guidance for assessment of inflammation. METHODS: A GLIM-constituted working group with 36 participants developed consensus-based guidance through a modified Delphi review. A multiround review and revision process served to develop seven guidance statements. RESULTS: The final round of review was highly favorable, with 99% overall "agree" or "strongly agree" responses. The presence of acute or chronic disease, infection, or injury that is usually associated with inflammatory activity may be used to fulfill the GLIM disease burden/inflammation criterion, without the need for laboratory confirmation. However, we recommend that recognition of underlying medical conditions commonly associated with inflammation be supported by C-reactive protein (CRP) measurements when the contribution of inflammatory components is uncertain. Interpretation of CRP requires that consideration be given to the method, reference values, and units (milligrams per deciliter or milligram per liter) for the clinical laboratory that is being used. CONCLUSION: Confirmation of inflammation should be guided by clinical judgment based on underlying diagnosis or condition, clinical signs, or CRP.

Internal and external validation of an updated ICD-10-CA to AIS-2005 update 2008 algorithm.

BACKGROUND: Administrative data are a powerful tool for population-level trauma research but lack the trauma-specific diagnostic and injury severity codes needed for risk-adjusted comparative analyses. The objective of this study was to validate an algorithm to derive Abbreviated Injury Scale (AIS-2005 update 2008) severity scores from Canadian International Classification of Diseases (ICD-10-CA) diagnostic codes in administrative data. METHODS: This was a retrospective cohort study using data from the 2009 to 2017 Ontario Trauma Registry for the internal validation of the algorithm. This registry includes all patients treated at a trauma center who sustained a moderate or severe injury or were assessed by a trauma team. It contains both ICD-10-CA codes and injury scores assigned by expert abstractors. We used Cohen's kappa (𝜅) coefficient to compare AIS-2005 Update 2008 scores assigned by expert abstractors to those derived using the algorithm and the intraclass correlation coefficient to compare assigned and derived Injury Severity Scores. Sensitivity and specificity for detection of a severe injury (AIS score, ≥ 3) were then calculated. For the external validation of the algorithm, we used administration data to identify adults who either died in an emergency department or were admitted to hospital in Ontario secondary to a traumatic injury (2009-2017). Logistic regression was used to evaluate the discriminative ability and calibration of the algorithm. RESULTS: Of 41,869 patients in the Ontario Trauma Registry, 41,793 (99.8%) had at least one diagnosis matched to the algorithm. Evaluation of AIS scores assigned by expert abstractors and those derived using the algorithm demonstrated a high degree of agreement in identification of patients with at least one severe injury (𝜅 = 0.75; 95% confidence interval [CI], 0.74-0.76). Likewise, algorithm-derived scores had a strong ability to rule in or out injury with AIS ≥ 3 (specificity, 78.5%; 95% CI, 77.7-79.4; sensitivity, 95.1; 95% CI, 94.8-95.3). There was strong correlation between expert abstractor-assigned and crosswalk-derived Injury Severity Score (intraclass correlation coefficient, 0.80; 95% CI, 0.80-0.81). Among the 130,542 patients identified using administrative data, the algorithm retained its discriminative properties. CONCLUSION: Our ICD-10-CA to AIS-2005 update 2008 algorithm produces reliable estimates of injury severity and retains its discriminative properties with administrative data. Our findings suggest that this algorithm can be used for risk adjustment of injury outcomes when using population-based administrative data. LEVEL OF EVIDENCE: Diagnostic Tests/Criteria; Level II.

Neurosensory anatomy and function in Dimetrodon, the first terrestrial apex predator.

Dimetrodon is among the most recognizable fossil taxa, as well as the earliest terrestrial amniote apex predator. The neuroanatomy and auditory abilities of Dimetrodon has long been the subject of interest, but palaeoneurological analyses have been limited by the lack of three-dimensional endocast data. The first virtual endocasts reveal a strongly flexed brain with enlarged floccular fossae and a surprisingly well-ossified bony labyrinth clearly preserving the semicircular canals, along with an undifferentiated vestibule and putative perilymphatic duct. This first detailed palaeoneurological reconstruction reveals potential adaptations for a predatory lifestyle and suggests Dimetrodon was able to hear a wider range of frequencies than anticipated, potentially being sensitive to frequencies equal to or higher than many extant sauropsids, despite lacking an impedance matching ear. Ancestral state reconstructions support the long-standing view of Dimetrodon as representative of the ancestral state for therapsids, while underscoring the importance of validating reconstructive analyses with fossil data.

Calvarial suture interdigitation in hadrosaurids (Ornithischia: Ornithopoda): Perspectives through ontogeny and evolution.

Lambeosaurine hadrosaurids exhibited extreme modifications to the skull, where the premaxillae, nasals, and prefrontals were modified to form their iconic supracranial crests. This morphology contrasts with their sister group, Hadrosaurinae, which possessed the plesiomorphic arrangement of bones. Although studies have discussed differences between lambeosaurine and hadrosaurine skull morphology and ontogeny, there is little information detailing suture modifications through ontogeny and evolution. Suture morphology is of particular interest due to its correlation with the mechanical loading of the skull in extant vertebrates. We quantify and contrast the morphology of calvarial sutures in iguanodontians and ontogenetic series of Corythosaurus and Gryposaurus to test whether the evolution of lambeosaurine crests impacted the mechanical loading of the skull. We found that suture interdigitation (SI) increases through ontogeny in hadrosaurids, although this increase is more extreme in Corythosaurus than Gryposaurus, and overall suture complexity (i.e., overall shape) remained constant. Lambeosaurines also have higher SI than other iguanodontians, even in crestless juveniles, suggesting that increased sinuosity is unrelated to the structural support of the crest. Hadrosaurines and basal iguanodontians did not differ. Similarly, lambeosaurines have more complexly shaped sutures than hadrosaurines and basal iguanodontians, while the latter two groups do not differ. Taken together, these results suggest that lambeosaurine calvarial sutures are more interdigitated than other iguanodontians, and although suture sinuosity increased through ontogeny, the suture shape remained constant. These ontogenetic and evolutionary patterns suggest that increased suture complexity in lambeosaurines coincided with crest evolution, and corresponding modifications to their facial skeleton altered the distribution of stress while feeding.

Neurosensory anatomy and function in Seymouria.

Seymouria is among the best-known stem amniotes and holds an important phylogenetic position for discussions of amniote evolution. Previous work has focused primarily on the osteology of Seymouria, with recent interest turning to the application of computed tomography (CT) to study the internal features. We utilized neutron CT to reconstruct the first virtual cranial endocast and the first complete otic endocasts of Seymouria, revealing previously unrecognized details of its palaeoneuroanatomy. The brain and inner ear of Seymouria are largely plesiomorphic relative to later-diverging crown amniotes, showing no indication of increased encephalization or braincase ossification. Our results also clarify the plesiomorphic condition for carotid artery morphology in amniotes, with Seymouria showing a similar condition to basal members of both the synapsid and sauropsid lineages. The reconstructed neuroanatomy also indicates that Seymouria did not possess any particular neuroanatomical specializations, despite the probable presence of an impedance matching hearing system.

Reconstructing locomotor ecology of extinct avialans: a case study of Ichthyornis comparing sternum morphology and skeletal proportions.

Avian skeletal morphology is associated with locomotor function, including flight style, swimming and terrestrial locomotion, and permits informed inferences on locomotion in extinct taxa. The fossil taxon Ichthyornis (Avialae: Ornithurae) has long been regarded as highly aerial, with flight similar to terns or gulls (Laridae), and skeletal features resembling foot-propelled diving adaptations. However, rigorous testing of locomotor hypotheses has yet to be performed on Ichthyornis, despite its notable phylogenetic position as one of the most crownward stem birds. We analysed separate datasets of three-dimensional sternal shape (geometric morphometrics) and skeletal proportions (linear measurements across the skeleton), to examine how well these data types predict locomotor traits in Neornithes. We then used this information to infer locomotor capabilities of Ichthyornis. We find strong support for both soaring and foot-propelled swimming capabilities in Ichthyornis. Further, sternal shape and skeletal proportions provide complementary information on avian locomotion: skeletal proportions allow better predictions of the capacity for flight, whereas sternal shape predicts variation in more specific locomotor abilities such as soaring, foot-propelled swimming and escape burst flight. These results have important implications for future studies of extinct avialan ecology and underscore the importance of closely considering sternum morphology in investigations of fossil bird locomotion.

Theropod dinosaur facial reconstruction and the importance of soft tissues in paleobiology.

Large theropod dinosaurs are often reconstructed with their marginal dentition exposed because of the enormous size of their teeth and their phylogenetic association to crocodylians. We tested this hypothesis using a multiproxy approach. Regressions of skull length and tooth size for a range of theropods and extant varanid lizards confirm that complete coverage of theropod dinosaur teeth with extraoral tissues (gingiva and labial scales) is both plausible and consistent with patterns observed in living ziphodont amniotes. Analyses of dental histology from crocodylians and theropod dinosaurs, including Tyrannosaurus rex, further indicate that the most likely condition was complete coverage of the marginal dentition with extraoral tissue when the mouth was closed. This changes our perceptions about the appearance and oral configuration of these iconic predators and has broad implications for our interpretations of other terrestrial animals with large teeth.

Association between prealbumin, all-cause mortality, and response to nutrition treatment in patients at nutrition risk: Secondary analysis of a randomized controlled trial.

BACKGROUND: Because of the shorter half-life as compared with albumin, serum prealbumin concentrations have been proposed to be useful nutrition biomarkers for the assessment of patients at nutrition risk. In a post hoc analysis of patients at nutrition risk from a randomized controlled nutrition trial, we tested the hypothesis that (1) prealbumin is associated with higher all-cause 180-day mortality rates and that (2) individualized nutrition support compared with usual-care nutrition more effectively improves survival at 30 days in patients with low prealbumin levels compared with patients with normal prealbumin levels. METHODS: We performed a prespecified cohort study in patients included in the pragmatic, Swiss, multicenter randomized controlled EFFORT trial comparing the effects of individualized nutrition support with usual care. We studied low prealbumin concentrations (<0.17 g/L) in a subgroup of 517 patients from one participating center. RESULTS: A total of 306 (59.2%) patients (mean age 71.9 years, 53.6% men) had low admission prealbumin levels (<0.17 g/L). There was a significant association between low prealbumin levels and mortality at 180 days (115/306 [37.6%] vs 47/211 [22.3%], fully adjusted hazard ratio [HR]=1.59, 95% CI 1.11-2.28; P = 0.011). Prealbumin levels significantly improved the prognostic value of the Nutritional Risk Screening total score regarding mortality prediction at short- and long-term. The difference in mortality between patients receiving individualized nutrition support and usual-care nutrition was similar for patients with low prealbumin levels compared with patients with normal prealbumin levels (HR=0.90 [95% CI=0.51-1.59] vs HR=0.88 [95% CI=0.35-2.23]) with no evidence for interaction (P = 0.823). CONCLUSION: Among medical inpatients at nutrition risk, low admission prealbumin levels correlated with different nutrition markers and higher mortality risk, but patients with low or high prealbumin levels had a similar benefit from nutrition support. Further studies should identify nutrition markers that help further personalize nutrition interventions.

Rare juvenile material constrains estimation of skeletal allometry in Gryposaurus notabilis (Dinosauria: Hadrosauridae).

In studying the skeletal allometry of any vertebrate, it is important to sample the ontogenetic extremes to ensure the accuracy of parameter estimation; this is particularly true for fossil taxa, where sampling of ontogenetic series is incomplete and sporadic. Previous studies have examined allometry in the skull of the duck-billed dinosaur Gryposaurus notabilis, but these did not include individuals smaller than ~65% the maximum known size (based on linear dimensions). Here, we report on the two smallest known examples of this species (a mostly complete skeleton and a partial skull), which are ~37% the known maximal size of G. notabilis. Osteohistology indicates that these represent individuals ~2 years of age. Allometric analysis demonstrates that most aspects of the skull of G. notabilis grew isometrically, although the height of the nasal arch grew with positive allometry. Early in the ontogeny of G. notabilis, the dentary teeth possessed secondary ridges, which were lost later in life. This finding has important bearing on hadrosaurid tooth taxonomy. The limb proportions of G. notabilis largely grew isometrically (or with weak negative allometry, at most), like some other hadrosaurids, suggesting that the species did not undergo a gait shift with increasing age (unless it occurred very early in ontogeny). We argue that the lack of significant locomotory performance compensation exhibited by young hadrosaurids helps to explain why they apparently formed small, mutualistic aggregations, presumably for protection from large predators.

Postcranial description of Wendiceratops pinhornensis and a taphonomic analysis of the oldest monodominant ceratopsid bonebed.

The early centrosaurine ceratopsid, Wendiceratops pinhornensis, was discovered in Alberta, Canada in a medium density monodominant bonebed from the Oldman Formation (mid-Campanian, ~79 Ma). The bonebed contains abundant, well-preserved, adult-sized and some juvenile-sized postcranial material, allowing for the first description of a number of elements of the postcrania of this basal centrosaurine ceratopsid. The postcranial elements described are generally consistent with postcrania described for more derived centrosaurine taxa. However the rectangular-shaped distal terminus of the ischium previously considered to be an apomorphy of Wendiceratops. is shown to also be present in Medusaceratops, and thus may be a synapomorphy of basal centrsaurines. The bonebed represents a lag deposit within a mudstone-bearing overbank facies and contains individuals from multiple age classes. It contains over 95% ceratopsid remains, with all identifiable elements referable to Wendiceratops. The elements are completely disarticulated, but have undergone little weathering or abrasion (both Stage 0), although the ends of long bones and processes capped by cartilage in life frequently exhibit evidence of wet rot and breakage by hydrological reworking after decomposition. The taphonomy of the bonebed is consist with other monodominant centrosaurine bonebeds that have been interpreted as mass death assemblages preserving evidence of gregarious (herding) behavior. At approximately 79 million years old, the Wendiceratops bonebed is approximately two million years older than other ceratopsid bonebeds indicating that this bonebed is the oldest documented evidence of herding behavior in a ceratopsid.

Description of the first definitive Corythosaurus (Dinosauria, Hadrosauridae) specimens from the Judith River Formation in Montana, USA and their paleobiogeographical significance.

Despite the long history of research in the late Campanian Judith River Formation in northern Montana, most of the vertebrate fossils are represented by fragmentary remains, making precise taxonomic identifications difficult. Contrary to this, the partially contemporaneous Dinosaur Park Formation, Alberta, Canada is known for its tremendous fossil preservation, permitting rigorous studies of dinosaur diversity, evolution, and biostratigraphy. Hadrosaurids comprise one of the most abundant dinosaur clades in the Dinosaur Park Formation, but taxonomic affinities of hadrosaurid specimens remain poorly understood in the Judith River Formation. Corythosaurus is the most common hadrosaurid in the Dinosaur Park Formation and, to date, has been restricted to this formation. This study reports the first definitive Corythosaurus specimens from the Judith River Formation, which were discovered on two private ranches in northern Montana. The attribution of the most complete skeleton to Corythosaurus is indicated by: wide crest-snout angle, presence of premaxilla-nasal fontanelle, dorsoventrally expanded nasal, laterally exposed ophthalmic canal of the laterosphenoid, and tall neural spines. A second specimen preserves a large ilium that can be positively identified as Corythosaurus based on its associated skull, which is now in private hands. The specimens were recovered from the Coal Ridge Member of the Judith River Formation, which is approximately time equivalent to the Dinosaur Park Formation. Thus, the discovery of Corythosaurus in the Judith River Formation extends the biogeographic range of this genus and establishes a framework for future interformational biostratigraphic studies of Late Cretaceous dinosaur faunas in North America.

Endocasts of the basal sauropsid Captorhinus reveal unexpected neurological diversity in early reptiles.

Captorhinids are a group of Paleozoic amniotes that represents one of the earliest-diverging clades of eureptiles. Although captorhinids are one of the best-known and most well-studied clades of early amniotes, their palaeoneuroanatomy has gone largely unexamined. We utilized neutron computed tomography to study the virtual cranial and otic endocasts of two captorhinid specimens. The neurosensory anatomy of captorhinids shows a mixture of traits considered plesiomorphic for sauropsids (no expansions of the cerebrum or olfactory bulbs, low degree of encephalization, low ossification of the otic capsule) and those considered more derived, including moderate cephalic and pontine flexures and a dorsoventrally tall bony labyrinth. The inner ear clearly preserves the elliptical, sub-orthogonal canals and the short, rounded vestibule, along with an unusually enlarged lateral canal and a unique curvature of the posterior canal. The reconstructed neurosensory anatomy indicates that captorhinids were sensitive to slightly higher frequencies than many of their contemporaries, likely reflecting differences in body size across taxa, while the morphology of the maxillary canal suggests a simple, tubular condition as the plesiomorphic state for Sauropsida and contributes to the ongoing discussions regarding the phylogenetic placement of varanopids. This study represents the first detailed tomographic study of the brain and inner ear of any basal eureptile. The new data described here reveal that the neuroanatomy of early sauropsids is far more complex and diverse than previously anticipated, and provide impetus for further exploration of the palaeoneuroanatomy of early amniotes.

Palaeopathological evidence for intraspecific combat in ankylosaurid dinosaurs.

Ankylosaurid dinosaurs were heavily armoured herbivores with tails modified into club-like weapons. These tail clubs have widely been considered defensive adaptations wielded against predatory theropod dinosaurs. Here we argue instead that ankylosaurid tail clubs were sexually selected structures used primarily for intraspecific combat. We found pathological osteoderms (armour plates) in the holotype specimen of Zuul crurivastator, which are localized to the flanks in the hip region rather than distributed randomly across the body, consistent with injuries inflicted by lateral tail-swinging and ritualized combat. We failed to find convincing evidence for predation as a key selective pressure in the evolution of the tail club. High variation in tail club size through time, and delayed ontogenetic growth of the tail club further support the sexual selection hypothesis. There is little doubt that the tail club could have been used in defence when needed, but our results suggest that sexual selection drove the evolution of this impressive weapon. This changes the prevailing view of ankylosaurs, suggesting they were behaviorally complex animals that likely engaged in ritualized combat for social dominance as in other ornithischian dinosaurs and mammals.