Search

The Late Cretaceous dinosaur Tyrannosaurus rex was recently split into three species based on the premise that variation in the T. rex hypodigm is exceptional, indicating cryptic species and “robust” and “gracile” morphs. The morphs are based on proportional ratios throughout the skeleton. The species are claimed to be stratigraphically separate, with an early robust species followed by robust and gracile descendants. There are problems with the hypothesis: the taxon diagnoses are based on two features that overlap between the species; several skulls cannot be identified based on the diagnoses; proportional comparisons between Tyrannosaurus and other theropods are based on incomparable samples; the tooth data are problematic; the stratigraphic framework divides the Hell Creek Formation into thirds, without the stratigraphic position of each specimen, or independent age control showing the subdivisions are coeval over the entire geographic area; previous work found variation in T. rex, but it cannot be parsed into discrete categories. We tested for “gracile” and “robust” morphs by analyzing the femoral and tooth ratios that were published in the multiple species study using agglomerative hierarchical clustering. The results found that each set of ratios are explained by one cluster, showing that dimorphism is not supported. We tested for exceptional variation of the femoral ratio of Tyrannosaurus; we calculated the mean intraspecific robusticity for 112 species of living birds and 4 nonavian theropods. The results showed that the absolute variation in Tyrannosaurus is unexceptional and it does not indicate cryptic diversity. We conclude that “T. regina” and “T. imperator” are subjective junior synonyms of T. rex.

Across the evolution of powered flight, the ecological niche of aerial insectivore has been occupied by members of the three volant vertebrate clades-Aves and Chiroptera, and the first known volant vertebrates, pterosaurs. However, morphological and quantitative evidence to support pterosaurs exhibiting this ecology remains scant. Anurognathids are an unusual group of pterosaurs in which the skull exhibits the unique morphology of being mediolaterally expanded, so much so that their skulls may be wider than rostrocaudally long. Here, we conduct quantitative comparative cranial measurements and dental morphology in anurognathids against extant avian and chiropteran taxa, respectively, with ecologies and behaviors that are similar to predicted putative behaviors of anurognathids. Comparative analyses of both skull and dental morphology suggest anurognathid specimens in similar morphospaces as insectivorous crepuscular and nocturnal extant volant taxa. Our results support that this unique group of pterosaurs likely occupied a niche of mid-flight insectivorous capture in low-light conditions.

Gut contents are extremely important for inferring trophic interactions between extinct species. These are,however, very rare in the fossil record and it is not always possible to accurately identify both the carnivore and theconsumed organisms. Here we describe the remains of a small fossil mammal foot preserved inside the body cavity of theholotype specimen of the small feathered dinosaur Microraptor zhaoianus. This adds to the known diversity of diet forthis genus, which also consumed birds, fish, and lizards. Previous interpretations that Microraptor was an arboreal hunterof birds and adept hunter of fish are not supported. Although the various known stomach contents would be plausibleprey items based on size, there is no clear evidence that any of them were predated rather than scavenged, andMicroraptor likely did both and foraged in multiple habitats

Spinosaurids are among the most distinctive and yet poorly-known of large-bodied theropod dinosaurs, a situation exacerbated by their mostly fragmentary fossil record and competing views regarding their palaeobiology. Here, we report two new Early Cretaceous spinosaurid specimens from the Wessex Formation (Barremian) of the Isle of Wight. Large-scale phylogenetic analyses using parsimony and Bayesian techniques recover the pair in a new clade within Baryonychinae that also includes the hypodigm of the African spinosaurid Suchomimus. Both specimens represent distinct and novel taxa, herein named Ceratosuchops inferodios gen. et sp. nov. and Riparovenator milnerae gen. et sp. nov. A palaeogeographic reconstruction suggests a European origin for Spinosauridae, with at least two dispersal events into Africa. These new finds provide welcome information on poorly sampled areas of spinosaurid anatomy, suggest that sympatry was present and potentially common in baryonychines and spinosaurids as a whole, and contribute to updated palaeobiogeographic reconstructions for the clade.

The tails of non-avialan dinosaurs varied considerably in terms of overall length, total number of vertebrae, and gross form and function. A new dataset confirms that there is little or no consistent relationship between tail length and snout-sacrum length. Consequently, attempts to estimate one from the other are likely to be very error-prone. Patterns of changes in centra lengths across the caudal series vary among non-avian dinosaurs. However, some overarching patterns do emerge. A number of taxa show (anterior to posterior) a series of short centra, followed by a series of longer centra, with the remainder of the tail consisting of a long series of centra tapering in length. This pattern is consistent with functional constraints, and the anterior series of longer centra are coincident with the major attachments of femoral musculature. This pattern is not present in many basal taxa and may have evolved independently in different dinosaurian groups, further suggesting functional importance.

Socio-sexual selection is predicted to be an important driver of evolution, influencing speciation, extinction and adaptation. The fossil record provides a means of testing these predictions, but detecting its signature from morphological data alone is difficult. There are, nonetheless, some specific patterns of growth and variation which are expected of traits under socio-sexual selection. The distinctive parietal-squamosal frill of ceratopsian dinosaurs has previously been suggested as a socio-sexual display trait, but evidence for this has been limited. Here, we perform a whole-skull shape analysis of an unprecedentedly large sample of specimens of Protoceratops andrewsi using a high-density landmark-based geometric morphometric approach to test four predictions regarding a potential socio-sexual signalling role for the frill. Three predictions—low integration with the rest of the skull, significantly higher rate of change in size and shape during ontogeny, and higher morphological variance than other skull regions—are supported. One prediction, sexual dimorphism in shape, is not supported, suggesting that sexual differences in P. andrewsi are likely to be small. Together, these findings are consistent with mutual mate choice or selection for signalling quality in more general social interactions, and support the hypothesis that the frill functioned as a socio-sexual signal in ceratopsian dinosaurs.

The giant theropod Spinosaurus was an unusual animal and highly derived in many ways, and interpretations of its ecology remain controversial. Recent papers have added considerable knowledge of the anatomy of the genus with the discovery of a new and much more complete specimen, but this has also brought new and dramatic interpretations of its ecology as a highly specialised semi-aquatic animal that actively pursued aquatic prey. Here we assess the arguments about the functional morphology of this animal and the available data on its ecology and possible habits in the light of these new finds. We conclude that based on the available data, the degree of adaptations for aquatic life are questionable, other interpretations for the tail fin and other features are supported (e.g., socio-sexual signalling), and the pursuit predation hypothesis for Spinosaurus as a “highly specialized aquatic predator” is not supported. In contrast, a ‘wading’ model for an animal that predominantly fished from shorelines or within shallow waters is not contradicted by any line of evidence and is well supported. Spinosaurus almost certainly fed primarily from the water and may have swum, but there is no evidence that it was a specialised aquatic pursuit predator.

In a recent paper, the contention that spinosaurine theropods were semi-aquatic was supported by Arden et al., (2019) and they provided a hypothetical sequence of acquisition of traits that had evolved in line with this lifestyle. However, we find that the presented traits were either loosely defined and/or are clearly distinct from those traits seen in extant animals with adaptations to life in water. Some spinosaurs may have spent extensive time in water, but the data to support this is currently insufficient and other hypotheses for their behaviour also fit the available data.

The ‘positive allometry hypothesis’ predicts that ornaments and weapons of sexual selection will scale steeply when among-individual variation in trait size is compared with variation in overall body size. Intuitive and striking, this idea has been explored in hundreds of contemporary animal species and sparked controversy in palaeobiology over the function of exaggerated structures in dinosaurs and other extinct lineages. Recently, however, challenges to this idea have raised questions regarding the validity of the hypothesis. We address this controversy in two ways. First, we suggest the positive allometry hypothesis be applied only to morphological traits that function as visual signals of individual body size. Second, because steep scaling slopes make traits better signals than other body parts, we propose that tests of the positive allometry hypothesis compare the steepness of the scaling relationships of focal, putative signal traits to those of other body parts in the same organism (rather than to an arbitrary slope of 1). We provide data for a suite of 29 extreme structures and show that steep scaling relationships are common when structures function as signals of relative body size, but not for comparably extreme structures that function in other contexts. We discuss these results in the context of animal signalling and sexual selection, and conclude that patterns of static scaling offer powerful insight into the evolution and function of disproportionately large, or extreme, animal structures. Finally, using data from a ceratopsid dinosaur and a pterosaur, we show that our revised test can be applied to fossil assemblages, making this an exciting and powerful method for gleaning insight into the function of structures in extinct taxa.

Mammalian carnivores show a higher degree of prey bone utilization relative to non-avian theropod dinosaurs, with this major ecological difference reflected in the frequency and morphology of tooth marks in modern and Cenozoic assemblages relative to Mesozoic ones. As such, prey bone utilization (i.e., gnawing, bone-breaking, osteophagy) may represent a key ecological strategy repeatedly exploited by mammalian carnivores but rarely in theropod dinosaurs. Here we describe an isolated adult-sized hadrosaurid pedal ungual (III-4) from the Dinosaur Park Formation (Campanian) of southern Alberta which shows a unique pattern of bite marks from a small- to medium-sized theropod dinosaur. Thirteen distinct tooth marks occur in a restricted area of the ungual, and the pattern suggests up to six repeated, high-power bites delivered to the bone. The tracemaker cannot be definitively identified, but was likely a dromaeosaurid or very young tyrannosaurid. Tooth marks on at least four other Dinosaur Park Formation hadrosaur pedal unguals are reported, but the overall frequency of occurrence in unguals (< 1%) is much lower than that reported for other bones. The pattern of tooth marks on this specimen deviates from most described theropods tooth marks, and given the low volume of meat associated with the ungual, may represent theropod prey bone utilization as part of late-stage carcass consumption, and a behavior similar to mammalian gnawing.

There has been considerable debate about whether the controversial tyrannosauroid dinosaur ‘ Nanotyrannus lancensis ’ from the uppermost Cretaceous of North America is a valid taxon or a juvenile of the contemporaneous Tyrannosaurus rex . In a recent Cretaceous Research article, Schmerge and Rothschild (2016) brought a new piece of evidence to this discussion: the morphology of the dentary groove, a depression on the lateral surface of the dentary that houses neurovascular foramina. They argued that an alleged ‘ Nanotyrannus ’ specimen, which possesses a groove, cannot be referable to Tyrannosaurus rex , which they considered as lacking the groove, and they hypothesized that ‘ Nanotyrannus ’ is closely related to albertosaurine tyrannosauroids, which also are said to possess the groove. However, we show that the groove is a widespread feature of tyrannosauroids that is present in T . rex and many other specimens, and that it is an ontogenetically variable feature that changes from a sharp, deeply-impressed groove to a shallower sulcus as an individual matures. As a result, the presence or absence of a dentary groove does not clarify the validity of ‘ Nanotyrannus ’ or its phylogenetic position among tyrannosauroids. We consider it most parsimonious that ‘ Nanotyrannus’ specimens belong to juvenile T . rex .

Despite strong evidence for sexual selection in various display traits and other exaggerated structures in large extinct reptiles, such as dinosaurs, detecting sexual dimorphism in them remains difficult. Their relatively small sample sizes, long growth periods, and difficulties distinguishing the sexes of fossil specimens mean that there are little compelling data on dimorphism in these animals. The extant gharial (Gavialis gangeticus) is a large and endangered crocodylian that is sexually dimorphic in size, but males also possesses a sexually selected structure, the ghara, which has an osteological correlate in the presence of a fossa associated with the nares. This makes the species a unique model for potentially assessing dimorphism in fossil lineages, such as dinosaurs and pterosaurs, because it is a large, slow-growing, egg-laying archosaur. Here we assess the dimorphism of G. gangeticus across 106 specimens and show that the presence of a narial fossa diagnoses adult male gharials. Males are larger than females, but the level of size dimorphism, and that of other cranial features, is low and difficult to detect without a priori knowledge of the sexes, even with this large dataset. By extension, dimorphism in extinct reptiles is very difficult to detect in the absence of sex specific characters, such as the narial fossa.

A cervical vertebra of the large, pelagic pterodactyloid pterosaurPteranodonsp. from the Late Cretaceous Niobrara Formation of Kansas, USA is significant for its association with a tooth from the large lamniform shark,Cretoxyrhina mantelli. Though the tooth does not pierce the vertebral periosteum, the intimate association of the fossils—in which the tooth is wedged below the left prezygapophysis—suggests their preservation together was not mere chance, and the specimen is evidence ofCretoxyrhinabitingPteranodon. It is not possible to infer whether the bite reflects predatory or scavenging behaviour from the preserved material. There are several records ofPteranodonhaving been consumed by other fish, including other sharks (specifically, the anacoracidSqualicorax kaupi), and multiple records ofCretoxyrhinabiting other vertebrates of the Western Interior Seaway, but until now interactions betweenCretoxyrhinaandPteranodonhave remained elusive. The specimen increases the known interactions between large, pelagic, vertebrate carnivores of the Western Interior Seaway of North America during the Late Cretaceous, in addition to bolstering the relatively small fossil record representing pterosaurian interactions with other species.

The leading edge and shape of the pterosaur wing is constrained by the skeleton. Although it has long been known that at least some pterosaurs had posteriorly curved distal wing phalanges, affecting the shape of the wingtip, this has been little studied despite that this may have profound effects on flight performance. Here we examine the evidence for curved wingtips in pterosaurs and evaluate the possible aerodynamic and aeronautical effects. Curved wingtips are shown to be common in both pterosaurs likely to have inhabited terrestrial environments, and those which were strongly pelagic. The recently described genus Bellubrunnus provides new anatomical novelty for pterosaurs having anteriorly directed wingtips and thus likely had a different flight profile to all previously known pterosaurs.

In fossilised vertebrates, the presence of soft tissues is the most obvious way to determine aspects of anatomy and functional morphology; however, occurrences are rare and other lines of evidence must be sought to indicate its extent and strength. For example, pterosaurs possessed a large wing membrane that enabled powered flight but other tissues are not widely preserved. A semi-quantitative analysis comparing skeletal articulation and completeness of the pterodactyloid Pterodactylus and non-pterodactyloid pterosaur Rhamphorhynchus from Solnhofen-type deposits implies there were anatomical differences between soft-tissue structure and attachments articulating skeletal joints of each. Typically, skeletons of Pterodactylus disarticulate to a greater extent than those of Rhamphorhynchus, which in turn suggests decay progressed to more advanced states in the former. However, this generalisation masks a mosaic of differences between different body parts, for example Rhamphorhynchus tends to lose the wings as complete units but retains a complete and still articulated tail in a greater number of specimens than Pterodactylus.

Animal flight is ecologically important and has a long evolutionary history. It has evolved independently in many distantly related clades of animals. Powered flight has evolved only three times in vertebrates, making it evolutionarily rare. Major recent fossil discoveries have provided key data on fossil flying vertebrates and critical insights regarding the evolution and different arrangements of animal flight surfaces. Combined with new methodologies, these discoveries have paved the way for potentially expanding biomimetic and biologically inspired designs to incorporate lessons from fossil taxa. Here, we review the latest knowledge and literature regarding flight performance in fossil vertebrates. We then synthesise key elements to provide an overview of those cases where fossil flyers might provide new insights for applied sciences.

Reconstructing the possible behaviours of long extinct species, and especially those with no close living relatives, are naturally fraught with difficulty: data are often limited and hard to interpret. However, the field of palaeoethology has not been helped by a poor understanding of the range and plasticity of the behaviour of extant organisms, coupled with a tendency to generalize and over-interpret the limited information available. Here we attempt to construct a framework for the establishment of viable hypotheses about the behaviour of extinct organisms and the generation of support for, or testing of, these hypotheses. We advocate that it is preferable to under-interpret available data, than to suggest problematic hypotheses that may become accepted as correct.

The Early Cretaceous Jehol Biota of northeastern China has become famous over the last two decades as a source of feathered avialan and non-avialan theropods, preserved alongside an array of other fossil vertebrates, invertebrates, and plants. Still more recently, a rich assemblage referred to in this paper as the Daohugou Biota has begun to emerge from Jurassic strata in the same region. Like their counterparts from the Jehol Biota, Daohugou Biota vertebrate specimens are typically preserved in fine-grained lacustrine beds and often retain feathers and other soft-tissue features. At present, 30 vertebrate taxa (five salamanders, one anuran, two lizards, 13 pterosaurs, five dinosaurs, and four mammals) are known from the Daohugou Biota, which was first recognized at the Daohugou locality in Inner Mongolia. The presence of the salamander Chunerpeton tianyiensis, proposed in this paper as an index fossil for the Daohugou Biota, links the Daohugou locality to five other fossil-producing areas in the...

The highly pneumatic skeleton of the extinct flying pterosaurs suggests that they would float high up on open water, but in a posture rather different to that of birds. However, the exact posture of the body and head remains unknown and would be critical for an ocean going pterosaur forced onto the waters' surface or animals that alighted to feed. Using computational methods with recent models and body mass estimates for four pterosaur genera—Dimorphodon, Rhamphorhynchus, Pteranodon and Dsungaripterus we show that the floating posture of pterodactyloid pterosaurs led to the head, neck and body being horizontal with the ventral 1/4 to 1/3 being immersed, and the external nares being almost at, or potentially partially below, the waterline that could have left them vulnerable to drowning. The floatation methods were verified using a model of a Canada goose (Branta canadensis) that is able to successfully replicate the expected orientation and depth of immersion of the bird. While there is convincing ev'idence for a number of pterosaurs foraging in marine and freshwater environments, these results suggest that many did not regularly rest on the surface of the water and if immersed would need to take off again rapidly. The high numbers of fossils of juvenile pterosaurs compared to the terrestrial Mesozoic dinosaurs suggest that this may be linked to their floating posture.

Azhdarchid pterosaurs have been known since 1972 from upper Campanian deposits of Alberta, Canada. Originally represented by only very fragmentary remains tentatively assigned to the genus Quetzalc...

Summary The horned, ceratopsid dinosaurs can be easily split into two major groups based on their cranial structures, but now a new discovery shows that at least one genus ‘switched sides' and convergently evolved the form of the other clade.

We present an annotated and illustrated catalogue of all original fossils, casts, and sculpted replicas of pterosaur specimens from the Upper Jurassic Solnhofen limestones of southern Germany that are housed at Carnegie Museum of Natural History (Pittsburgh, Pennsylvania, U.S.A.). The museum obtained its substantial Solnhofen pterosaur fossil collection—almost certainly the largest currently held outside of Europe—as part of its purchase of the vast private collection of the Belgian Baron Ernest de Bayet in 1903. Original fossils include six partial to nearly complete skeletons and a beautifully preserved skull of the rhamphorhynchine Rhamphorhynchus muensteri (Goldfuss, 1831), two skeletons of the ctenochasmatid pterodactyloid Aurorazhdarcho micronyx (von Meyer, 1856), and one large pterodactyloid partial appendicular skeleton of indeterminate affinity. Three of the fossils preserve significant soft tissues, and one of these is also among the very few specimens of Rhamphorhynchus von Meyer, 1847...

The partial skeleton of an immature azhdarchoid pterosaur from the Santana Formation (Early Cretaceous) of NE Brazil is described, where breaks across several of the three dimensionally preserved postcranial elements have permitted the thickness of the cortex to be accurately measured. Air-space proportions (ASP) are shown to be comparable to those observed in sauropod dinosaurs. The pterosaurian pneumatic system, prevalent throughout these animals, is shown to be well developed in even non-adult animals and is inferred to have penetrated into even the smallest of bones.

The hypothesis that the exaggerated structures in various non-avialan dinosaurs (e.g. horns, crests, plates) primarily functioned in species recognition, allowing individuals of a species to recognize one another, is critically examined. While multifunctionality for many such structures is probable given extant analogues, invoking species recognition as the primary selective mechanism driving the evolution of such structures is problematic given the lack of evidence for this in extant species. Furthermore, some of the evidence presented does not support the hypothesis as claimed or is equivocal or erroneous. Suggestions that certain evolutionary patterns of diversification in these exaggerated structures are indicative of a role in species recognition are unreliable, as both a degree of phylogenetic directionality and of randomness are seen in extant species where similar structures function in sexual selection. Claims that an absence of sexual dimorphism in the exaggerated structures of non-avialan dinosaurs rule against a role in sexual selection ignores the possible existence of mutual sexual selection and is also sometimes limited in view of sample sizes. The suggestion that the existence of species recognition is supported by the presence of exaggerated structures in sympatric, closely related relatives is also erroneous because adorned dinosaur species sometimes exist in the absence of unadorned relatives. We conclude that species recognition was not the evolutionary mechanism most likely to be driving the appearance and persistence of exaggerated structures in non-avialan dinosaurs.

Many fossil animals bear traits such as crests or horns that probably functioned as sexually selected signals or weapons. Interpretations of these structures as functioning in mate choice or intrasexual contests are often controversial, with interpretations based on biomechanics or physiology being favoured by many. Although testing hypotheses based on sexual selection can be difficult, especially given that there is no single, reliable means of recognising sexual selection, we argue that it is not impossible; indeed, there are now several cases where sexual selection is strongly supported. In other cases, a careful study of features such as sexual dimorphism, ontogeny, and allometry, coupled with testing of alternative hypotheses, will be necessary to distinguish between possible explanations for exaggerated features.

In a recent Cretaceous Research article, Schmerge and Rothschild (2016) argued that the controversial tyrannosauroid dinosaur ‘ Nanotyrannus lancensis ’ from the uppermost Cretaceous of North America is a valid taxon, as originally proposed by Bakker et al. (1988). There has been considerable debate recently about the affinities of ‘ Nanotyrannus ’, with some authors considering it a distinct taxon (e.g., Currie, 2003; Larson, 2013), but most tyrannosauroid specialists regarding its holotype skull (CMNH 7541) and other possibly referred specimens (e.g., BMRP 2002.4.1) as belonging to juveniles of the contemporaneous Tyrannosaurus rex (e.g., Carr, 1999; Brochu, 2003; Carr and Williamson, 2004; Holtz, 2004; Brusatte et al., 2010; Brusatte and Carr, 2016). These latter authors have recognized differences between purported ‘ Nanotyrannus ’ specimens (which are clearly juveniles based on bone histology and possession of characters seen in the early growth stages of other tyrannosauroids: Carr, 1999; Erickson, 2005) and large specimens of T. rex, but explain them as ontogenetically variable features that changed as juveniles grew into massive, deep-skulled, strong-biting adults. * Corresponding author. E-mail address: Stephen.Brusatte@ed.ac.uk (S.L. Brusatte). http://dx.doi.org/10.1016/j.cretres.2016.02.007 0195-6671/ © 2016 Elsevier Ltd. All rights reserved. Please cite this article in press as: Brusatte, S.L., et al., Dentary groove morphology does not distinguish ‘ Nanotyrannus ’ as a valid taxon of tyrannosauroid dinosaur. Comment on: “Distribution of the dentary groove of theropod dinosaurs: Implications for theropod phylogeny and the validity of the genus Nanotyrannus Bakker et al., 1988 ”, Cretaceous Research (2016), http://dx.doi.org/10.1016/j.cretres.2016.02.007 Please cite this article in press as: Brusatte, S.L., et al., Dentary groove morphology does not distinguish ‘ Nanotyrannus ’ as a valid taxon of tyrannosauroid dinosaur. Comment on: “Distribution of the dentary groove of theropod dinosaurs: Implications for theropod phylogeny and the validity of the genus Nanotyrannus Bakker et al., 1988 ”, Cretaceous Research (2016), http://dx.doi.org/10.1016/j.cretres.2016.02.007 Schmerge and Rothschild (2016) bring a new piece of evidence to the debate: the morphology of the dentary groove, a depression that extends anteroposteriorly across part of the lateral surface of the dentary and houses neurovascular foramina below the tooth alveoli. Based on the distribution of this feature, they argue that the alleged ‘ Nanotyrannus ’ specimen BMRP 2002.4.1, which possesses a groove, cannot be referable to Tyrannosaurus rex, which is said to lack this feature. They furthermore hypothesize that ‘ Nanotyrannus ’ is not particularly closely related to Tyrannosaurus rex, but groups with the albertosaurine tyrannosaurids (Albertosaurus and Gorgosaurus), which also are said to possess the groove. These interpretations hinge on Schmerge and Rothschild's (2016) correct identification of the groove in tyrannosauroid specimens, their assertion that the groove is not an ontogenetically variable feature, and their contention that a single anatomical feature can be a ‘key’ characteristic for elucidating phylogenetic relationships. In this response, we challenge these points. We show that the groove is a widespread feature of tyrannosauroids, and that it is ontogenetically variable. As a result, the presence or absence of a dentary groove does not clarify the validity of ‘ Nanotyrannus ’ or its phylogenetic position among tyrannosauroids. Institutional Abbreviations &horbar; AMNH , American Museum of Natural History, New York, NY, USA; BMRP, Burpee Museum of Natural History, Rockford, IL, USA; BYU, Brigham Young University, Provo, Utah, USA; CMN, Canadian Museum of Nature, Ottawa, Ontario, Canada; CMNH, Cleveland Museum of Natural History, Cleveland, OH, USA; FMNH, Field Museum of Natural History, Chicago, IL, USA; IGM, Institute of Geology, Ulaan Baatar, Mongolia; LH, Long Hao institute of Geology and Paleontology, Hohhot, China; MOR, Museum of the Rockies, Bozeman, Montana, USA; NMMNHS, New Mexico Museum of Natural History and Science, Albuquerque, NM, USA; PIN, Paleontological Institute, Moscow, Russia; RMM, Red Mountain Museum, McWane Center, Birmingham, Alabama, USA; ROM, Royal Ontario Museum, Toronto, Ontario, Canada; TMP, Royal Tyrrell Museum of Palaeontology, Drumheller, Alberta, Canada; ZCDM, Zhucheng Dinosaur Museum, Shandong, China; ZPAL, Instytut Paleobiologii PAN, Warsaw, Poland. 2. The dentary groove as a phylogenetic character Schmerge and Rothschild (2016:26) insinuate that the dentary groove had yet to be ‘anatomically defined’ and only recently had been included in phylogenetic character datasets, beginning with the tyrannosauroid-specific study of Brusatte et al. (2010). How- ever, this is incorrect. There is a long legacy of phylogenetic characters relating to the dentary groove, and it has appeared in several iterations of the Theropod Working Group (TWiG) dataset, a 20+ year project that has conducted increasingly larger and more inclusive analyses of theropod phylogeny (e.g., Norell et al., 2001: character 73; Turner et al., 2007: character 71; Turner et al., 2012: character 69; Brusatte et al. 2014: character 69). Part of this confusion stems from our (Brusatte and Carr's) error in not attributing the historical usage of this character in our 2010 study. The TWiG character was inspired by Currie's (1987) description of the derived bird-like theropod Troodon, in which he noted that the primary neurovascular foramina on the lateral dentary were set into a groove. Additional comparisons by the TWiG team revealed that nearly all troodontids had this morphology, in which the neurovascular foramina are embedded into a sharp, dorsoventrally shallow, deeply impressed groove that is more pronounced across the middle and posterior regions of the dentary but becomes much more shallowly impressed as it dissipates anteriorly, in the symphyseal region and underneath the first several alveoli. This differs from the condition in other theropods, which early versions of the TWiG dataset described as having ‘superficial’ neurovascular foramina. Later TWiG studies revealed that some dromaeosaurids (Buitreraptor, Austroraptor, Shanag), some early birds (e.g., Pengornis, Yanornis), the basal alvarezsauroid Haplocheirus, and some basal tyrannosauroids (Guanlong, Proceratosaurus, Sinotyrannus, Yutyrannus) also possessed the deep groove of troodontids. This led Brusatte et al. (2010) to include the character in their tyrannosauroid-specific dataset, which was later merged into the larger TWiG dataset by Brusatte et al. (2014). In doing so, Brusatte et al. (2010) redefined the character states so that they were more descriptive. The primitive ‘superficial’ condition, seen in most theropods, was defined as one in which the foramina are ‘distinct or set into a shallow groove posteriorly’. The derived condition, seen in troodontids and the handful of other theropods mentioned above, was defined as one in which the foramina are ‘set into a deep and sharp groove across the middle and posterior regions of the dentary’. Among tyrannosauroids, the derived, deeply impressed, troodontid-style groove is present only in the basal clade Proceratosauridae. It is absent in all other tyrannosauroids, and is scored that way in the Brusatte et al. (2010, 2014) datasets, and in the recently published update of our tyrannosauroid dataset (Brusatte and Carr 2016). That is not to say that other tyrannosauroids do not have any type of groove on the dentary, just that they do not possess the distinctive troodontid-style condition. Indeed, many of them have shallower grooves that fall into the ‘superficial’ category. Schmerge and Rothschild (2016), on the other hand, consider some derived tyrannosauroids like Albertosaurus, Gorgosaurus, Dryptosaurus, and putative specimens of ‘ Nanotyrannus ’ to possess what they consider as a ‘dentary groove’. Their concept of a dentary groove is much more inclusive than the strictly-defined feature in the TWiG dataset, and seems to be a catch-all that combines the troodontid condition (as seen in proceratosaurids) and the more shallow grooves that are commonly seen in other tyrannosauroids (see below). 3. Dentary grooves are widespread among tyrannosauroids We prefer to distinguish between troodontid-style grooves and shallow grooves using the TWiG definitions, and will continue to do so in our phylogenetic analyses (e.g., Brusatte and Carr, 2016). However, in the following discussion, we employ Schmerge and Rothschild's (2016) more inclusive definition of a ‘dentary groove’, considering it as any longitudinal depression on the lateral surface of the dentary that includes a series of neurovascular foramina underneath the tooth row. Schmerge and Rothschild (2016) identify this type of groove in the BMRP 2002.4.1 skull of ‘ Nanotyrannus ’, and also in Albertosaurus, Gorgosaurus, Dryptosaurus, and proceratosaurids. However, they consider it absent in all other tyrannosauroids, including Bistahieversor, Alioramus, Tarbosaurus, and Tyrannosaurus. In most cases these assessments were based on examination of published photographs, mostly of holotype specimens only, as Schmerge and Rothschild (2016:27) wanted to ‘avoid controversy as to taxonomic assignment’. Please cite this article in press as: Brusatte, S.L., et al., Dentary groove morphology does not distinguish ‘ Nanotyrannus ’ as a valid taxon of tyrannosauroid dinosaur. Comment on: “Distribution of the dentary groove of theropod dinosaurs: Implications for theropod phylogeny and the validity of the genus Nanotyrannus Bakker et al., 1988 ”, Cretaceous Research (2016), http://dx.doi.org/10.1016/j.cretres.2016.02.007 In fact, a neurovascular groove on the lateral surface of the dentary is widespread among tyrannosauroids, although often it is shallow or even very shallow (particularly anteriorly in the symphyseal region) and can easily be missed in photographs. Contra to Schmerge and Rothschild (2016), it is present in specimens of Raptorex (LH PV18; Sereno et al., 2009: fig. 1), Appalachiosaurus (RMM 6670; Carr et al. 2005: fig. 12), Bistahieversor (Fig. 1 G-H; NMMNHS P-27469, P-25049; Carr and Williamson, 2010: fig. 1), Alioramus (IGM 100/1844; Brusatte et al., 2012: fig. 32), Teratophoneus (BYU 9398; Carr et al., 2011: fig. 2; Loewen et al. 2013: fig. 3), Daspletosaurus (Fig. 1 E-F; MN 8506; TMP 1994.143.001; Currie, 2003: fig. 33), Tarbosaurus (Fig. 1 A-B; e.g., PIN 551-2/1, 551- 12/1, 4216/3, 4216/1; ZPAL MgD-I/75, I/5), and Tyrannosaurus (Fig. 1 C-D; e.g., CMN 9380; MOR 008; AMNH FARB 5027; Osborn, 1912: pl. 1, although we do concur with Schmerge and Rothschild [2016] that some Tyrannosaurus specimens like FMNH PR 2081 have such a shallow groove that it is essentially absent). We have personally observed and studied all of these specimens, and photographs of some of the more salient ones are shown in Fig. 1. The groove is also present on the tyrannosaurids Lythronax (Loewen et al., 2013: fig. 2) and Zhuchengtyrannus (ZCDM V0031; Hone et al., 2011: fig. 3), which were not considered by Schmerge and Rothschild (2016). In some of these cases, we are considering the same specimens as Schmerge and Rothschild (2016) but our observations are at odds (e.g., Raptorex, Appalachiosaurus, Bistahieversor, Alioramus, Teratophoneus). The most likely explanation is that all Schmerge and Rothschild (2016) scored all of these taxa based on figures in published literature, which often do not clearly convey the extent and morphology of shallow grooves. In other cases, however, our disagreements have to do with Schmerge and Rothschild's (2016) strategy of targeting holotypes or small samples of taxa known from many specimens. For example, they score Tarbosaurus as lacking the groove based on a photograph of a single specimen (MPC-D 107/7) with either an absent or very shallow groove, whereas we have examined numerous other specimens in the Warsaw (ZPAL) and Moscow (PIN) collections that have grooves of varying morphology, from very shallow to deeply impressed (Fig.1 A-B). Therefore, by looking primarily at holotypes rather than larger hypodigms, Schmerge and Rothschild (2016) minimize the chance of recognizing variation in this trait. To effectively demonstrate this trait exists in only one state within a species (i.e., that it does not vary by ontogeny, sexual dimorphism, individual variation, or other causes), one needs to examine a larger number of individuals. Our identification of a dentary groove in a wide variety of tyrannosauroids, including Tyrannosaurus rex, falsifies two main conclusions of Schmerge and Rothschild (2016): that the presence of a groove differentiates ‘ Nanotyrannus ’ from T. rex, and that the groove is unusually shared between ‘ Nanotyrannus ’ and albertosaurines (Albertosaurus and Gorgosaurus) to the exclusion of other taxa. Instead, the groove is a common character of tyrannosauroids, and indeed theropods in general, that all of these taxa plesiomorphically retain from their distant ancestors. Simple presence or absence of a groove appears to have no bearing on tyrannosauroid phylogeny, although as discussed above, the presence of a troodontid-style deep, sharp groove is a proceratosaurid synapomorphy (Brusatte et al., 2010, 2014; Brusatte and Carr, 2016). 4. Dentary grooves are ontogenetically variable in tyrannosauroids Schmerge and Rothschild (2016:31) also argue that the dentary groove is an ontogenetically invariant feature in tyrannosauroids, meaning that juveniles and adults of the same taxon would have the same condition (presence or absence of the groove). This is based on two points: 1) their identification of the groove as absent in juvenile, subadult, and adult specimens of Tyrannosaurus rex, and 2) a philosophical argument that a ‘dramatic change’ like ‘metamorphosis’ would be needed to explain the loss of the groove as an individual matured, because the groove corresponds to a system of nerves that they assume to be developmentally conservative. In fact, the morphology of the groove is highly ontogenetically variable in tyrannosauroids, and in some taxa clearly changes from a deeply-inset and pronounced structure in juveniles to a shallow and sometimes nearly indistinguishable sulcus in adults. This can be seen in the growth series of two tyrannosauroids. A remarkably preserved juvenile specimen of Tarbosaurus that died at two or three years of age has a deep, well-pronounced dentary groove (Tsuihiji et al., 2011: fig. 3). Much larger, subadult and adult Tarbosaurus retain dentary grooves, but they are much more shallowly impressed (Fig. 1 A-B; PIN 551-2/1, 551-12/1, 4216/3, 4216/1; ZPAL MgD-I/75, I/5). In the same vein, a juvenile Bistahieversor specimen has a deep groove across the middle and posterior portion of its dentary, which approaches the troodontid-condition in having well-defined dorsal and ventral margins that completely enclose the neurovascular foramina (Fig. 1G; NMMNHS P-25049; Carr and Williamson, 2010: fig. 1B). An adult, by contrast, has a much shallower groove that is better defined ventrally than dorsally. The neurovascular foramina are larger and channel upwards, breaching the dorsal margin of the groove and thus making the groove appear as a less discrete structure (Fig. 1H; NMMNHS P-27469; Carr and Williamson, 2010: fig. 1A). The ontogenetic trend from a deeply impressed to a shallow and indistinct groove is also seen in three taxa that were discussed by Schmerge and Rothschild (2016). First, in Gorgosaurus, a taxon they consider as possessing the groove, juveniles have sharp and well-defined grooves whereas adults have less discrete and shallower grooves just like those of adult Tarbosaurus and Bistahieversor (Fig. 1 I-J; juvenile condition: TMP 1986.144.0001 and ROM 1247, adult condition: CMN 2120). Second, the trend is seen in Albertosaurus (juvenile condition: TMP 1986.064.0001, adult condition: TMP 1999.050.0021). It is also worth noting that some non-ontogenetic variation is also seen in Abertosaurus and Gorgosaurus, as some adults have a deep groove like that of juveniles (TMP 2000.045.0084, AMNH FARB 5458, respectively). Third, although Schmerge and Rothschild (2016) argue that no specimens of T. rex possess the groove, we disagree and instead identify T. rex as undergoing the same ontogenetic trajectory as other tyrannosauroids. Our observations show that a groove is seen on the left side of the juvenile specimen LACM 28471, contra to Schmerge and Rothschild (2016), but heavy damage to the external bone surface obscures its depth, easily making it appear absent in photographs. There is also a groove in adult T. rex specimens (Fig. 1 C-D; AMNH FARB 5027; CM 9380; MOR 008), which is shallow, weakly inset, and houses large foramina that course dorsally, just as in other adult tyrannosaurids. The well- defined grooves of the two purported ‘ Nanotyrannus ’ specimens (CMNH 7541; BMRP 2002.4.1) are thus expected for juvenile T. rex filling an ontogenetic gap between the very small LACM 28471 and adults. The dentary groove, therefore, can be added to the list of features that are ontogenetically variable in large-bodied tyrannosauroids, which have been outlined in detail by Carr (1999) and Carr and Williamson (2004). Many of these other ontogenetic transformations in skull shape, robusticity, ornamentation, and sinuses are much more extreme than a shallowing of the neuro- vascular groove on the dentary, so there is no need to invoke biologically implausible mechanisms like metamorphosis to explain the latter. With that said, T. rex did undergo a major transformation as it grew from a tiny hatchling into a multi-ton, 13- meter-long, bone-crunching adult (Erickson et al., 2004). Subtle alterations in its neurovascular ornamentation were some of the least impressive changes as T. rex and other tyrannosauroids matured. Please cite this article in press as: Brusatte, S.L., et al., Dentary groove morphology does not distinguish ‘ Nanotyrannus ’ as a valid taxon of tyrannosauroid dinosaur. Comment on: “Distribution of the dentary groove of theropod dinosaurs: Implications for theropod phylogeny and the validity of the genus Nanotyrannus Bakker et al., 1988 ”, Cretaceous Research (2016), http://dx.doi.org/10.1016/j.cretres.2016.02.007 5. Key characters and phylogenetic analysis Even if Schmerge and Rothschild (2016) were correct and ‘ Nanotyrannus &rsquo, Published as part of Stephen L. Brusatte, Thomas D. Carr, Thomas E. Williamson, Thomas R. Holtz Jr., David W. E. Hone & Scott A. Williams, 2016, Dentary groove morphology does not distinguish ' Nanotyrannus' as a valid taxon of tyrannosauroid dinosaur. Comment on: " Distribution of the dentary groove of theropod dinosaurs: Im ..., pp. 232-237 in Cretaceous Research 65 on pages 1-5, DOI: 10.1016/j.cretres.2016.02.007, http://zenodo.org/record/3897669, {"references":["Schmerge, J. D., Rothschild, B. M., 2016. Distribution of the dentary groove of theropod dinosaurs: implications for theropod phylogeny and the validity of the genus Nanotyrannus Bakker et al., 1988. Cretaceous Research 61, 26 - 33.","Bakker, R. T., William, M., Currie, P., 1988. Nanotyrannus, a new genus of pygmy tyrannosaur, from the Latest Cretaceous of Montana. Hunteria 1, 1 - 28.","Currie, P. J., 2003. Cranial anatomy of tyrannosaurid dinosaus from the Late Cretaceous of Alberta, Canada. Acta Palaeontologica Polonica 48, 191 - 226.","Larson, P., 2013. The case for Nanotyrannus. In: Parrish, J. M., Molnar, R. E., Currie, P. J., Koppelhus, E. B. (Eds.), Tyrannosaurid Paleobiology. Indiana University Press, Bloomington, Indiana, pp. 14 - 53.","Carr, T. D., 1999. Craniofacial ontogeny in Tyrannosauridae (Dinosauria, Coelurosauria). Journal of Vertebrate Paleontology 19, 497 - 520.","Brochu, C. A., 2003. Osteology of Tyrannosaurus rex: insights from a nearly complete skeleton and high-resolution computed tomographic analysis of the skull. Journal of Vertebrate Paleontology Memoir 7, 1 - 138.","Carr, T. D., Williamson, T. E., 2004. Diversity of late Maastrichtian Tyrannosauridae (Dinosauria: Theropoda) from western North America. Zoological Journal of the Linnean Society 142, 479 - 523.","Holtz, T. R., 2004. Tyrannosauroidea. In: Weishampel, D. B., Dodson, P., Osmolska, H. (Eds.), The Dinosauria. University of California Press, Los Angeles, California, pp. 111 - 136.","Brusatte, S. L., Norell, M. A., Carr, T. D., Erickson, G. M., Hutchinson, J. R., Balanoff, A. M., Bever, G. S., Choiniere, J. N., Makovicky, P. J., Xu, X., 2010. Tyrannosaur paleobiology: new research on ancient exemplar organisms. Science 329, 1481 - 1485.","Brusatte, S. L., Carr, T. D., 2016. The phylogeny and evolutionary history of tyrannosauroid dinosaurs. Scientific Reports 6, 20252.","Erickson, G. M., 2005. Assessing dinosaur growth patterns: a microscopic revolution. Trends in Ecology and Evolution 20, 677 - 684.","Norell, M. A., Clark, J. M., Makovicky, P. J., 2001. Phylogenetic relationships among coelurosaurian theropods. In: Gauthier, J., Gall, L. F. (Eds.), New Perspectives on the Origin and Early Evolution of Birds. Peabody Museum of Natural History. Yale University, New Haven, CT, pp. 49 - 68.","Turner, A. H., Pol, D., Clarke, J. A., Erickson, G. M., Norell, M. A., 2007. A basal dromaeosaurid and size evolution preceding avian flight. Science 317, 1378 - 1381.","Turner, A. H., Makovicky, P. J., Norell, M. A., 2012. A review of dromaeosaurid systematic and paravian phylogeny. Bulletin of the American Museum of Natural History 371, 1 - 206.","Brusatte, S. L., Lloyd, G. T., Wang, S. C., Norell, M. A., 2014. Gradual assembly of avian body plan culminated in rapid rates of evolution across the dinosaur-bird transition. Current Biology 24, 2386 - 2392.","Currie, P. J., 1987. Bird-like characteristics of the jaws and teeth of troodontid theropods (Dinosauria, Saurischia). Journal of Vertebrate Paleontology 7, 72 - 81.","Sereno, P. C., Tan, L., Brusatte, S. L., Kriegstein, H. J., Zhao, X. - J., Cloward, K., 2009. Tyrannosaurid skeletal design first evolved at small body size. Science 326, 418 - 422.","Carr, T. D., Williamson, T. E., Schwimmer, D. R., 2005. A new genus and species of tyrannosauroid from the Late Cretaceous (Middle Campanian) Demopolis Formation of Alabama. Journal of Vertebrate Paleontology 25, 119 - 143.","Carr, T. D., Williamson, T. E., 2010. Bistahieversor sealeyi, gen. et sp. nov., a new tyrannosauroid from New Mexico and the origin of deep snouts in Tyrannosauroidea. Journal of Vertebrate Paleontology 30, 1 - 16.","Brusatte, S. L., Carr, T. D., Norell, M. A., 2012. The osteology of Alioramus, a gracile and long-snouted tyrannosaurid (Dinosauria: Theropoda) from the Late Cretaceous of Mongolia. Bulletin of the American Museum of Natural History 366, 1 - 197.","Carr, T. D., Williamson, T. E., Britt, B. B., Stadtman, K., 2011. Evidence for high taxonomic and morphologic tyrannosauroid diversity in the Late Cretaceous (Late Campanian) of the American Southwest and a new short-skulled tyrannosaurid from the Kaiparowits Formation of Utah. Naturwissenschaften 98, 241 - 246.","Loewen, M. A., Irmis, R. B., Sertich, J. J. W., Currie, P. J., Sampson, S. D., 2013. Tyrant dinosaur evolution tracks the rise and fall of Late Cretaceous oceans. PLoS One 8 (11), e 79420. http: // dx. doi. org / 10.1371 / journal. pone. 0079420.","Osborn, H. F., 1912. Cranial of Tyrannosaurus and Allosaurus; and integument of the iguanodont dinosaur Trachodon. Memoirs of the American Museum of Natural History 1 (1 - 2), 1 - 54.","Hone, D. W. E., Wang, K., Sullivan, C., Zhao, X. - J., Chen, S., Li, D., Ji, S., Ji, Q., Xu, X., 2011. A new, large tyrannosaurine theropod from the Upper Cretaceous of China. Cretaceous Research 32, 495 - 503.","Tsuihiji, T., Watabe, M., Togtbaatar, K., Tsubamoto, T., Barsbold, R., Suzuki, S., Lee, A. H., Ridgely, R. C., Kawahara, Y., Witmer, L. M., 2011. Cranial osteology of a juvenile specimen of Tarbosaurus bataar from the Nemegt Formation (Upper Cretaceous) of Bugin Tsav, Mongolia. Journal of Vertebrate Paleontology 31, 497 - 517.","Erickson, G. M., Makovicky, P. J., Currie, P. J., Norell, M. A., Yerby, S. A., Brochu, C. A., 2004. Gigantism and comparative life-history parameters of tyrannosaurid dinosaurs. Nature 430, 772 - 775.","Kluge, A. G., 1989. A concern for evidence and a phylogenetic hypothesis of relationships among Epicrates (Boidae, Serpentes). Systematic Zoology 38, 7 - 25.","Fowler, D. W., Woodward, H. N., Freedman, E. A., Larson, P. L., Horner, J. R., 2011. Reanalysis of \" Raptorex kriegsteini \": a juvenile tyrannosaurid dinosaur from Mongolia. PLoS One 6 (6), e 21376.","Carr, T. D., Henderson, M., Erickson, G. M., Peterson, J., Williams, S., Currie, P., Scherer, R., Harrison, B., 2015. A subadult Tyrannosaurus rex and its bearing on the Nanotyrannus hypothesis. Journal of Vertebrate Paleontology 35, 101 A."]}

The allometry in the frill and jugal bosses of the small ornithischian dinosaur Protoceratops andrewsi are assessed. An analysis of 37 specimens, encompassing four distinct size classes of animal, shows that the frill (in both length and width) undergoes positive allometry during ontogeny, while the jugals also show a trend towards an increase in relative size. In conjunction with other data, this provides support that these features were under selection as socio-sexual dominance signals.

Of all the processes of the science of palaeontology, the actual preparation of fossil specimens to a condition suitable for display, research, and education is perhaps the least recognised and understood by the general public. Documentaries and popular books feature the excavation of specimens and their final status but rarely mention the critical, and often long and detailed, intervening work. Recently the authors embarked on a series of posts on the blog of DWEH which narrated the process of preparing a largely complete tyrannosaur specimen by DHT from opening the jack- et to a finished display- and research-quality specimen. Here we review this outreach process and discuss the benefits of such a scheme. While this series has not to date attracted a large audience, it does nevertheless provide a model for future projects and is readily accessible and permanently archived as a source of information online.

A new anurognathid pterosaur specimen from the Middle Jurassic Tiaojishan Formation of Qinglong, northern Hebie Province is described. The new specimen is referred to Dendrorhynchoides, based on the general morphology of the skeleton, but it represents a new species, named here as Dendrorhynchoides mutoudengensis sp. nov.. It is characterized by the presence of short, robust and straight teeth, and bearing wing metacarpal approximately 40% of the length of humerus. The new specimen provides further osteological information for anurognathid pterosaurs, especially the presence of a relatively elongate tail.

In the years since the first description of a pterosaur specimen in 1784, pterosaur research has inevitably advanced considerably. However the last decade has arguably seen a much greater increase in our knowledge than the preceding two centuries. Since the turn of the new millennium, more than 40 new pterosaur genera and species have been described and whole new clades have been discovered, in addition to much new data being developed on pterosaur anatomy, functional morphology, palaeobiology, systematics, ecology and more. We are perhaps at the start of a golden age of pterosaur research and much as the dinosaurs underwent a revolution in the 1970s through to the early 1990s, now the Pterosauria are taking their turn. There is also a new and wider interest in pterosaur work as it attracts both more researchers and greater public interest. Pterosaurs appear to be an increasingly popular aspect of paleontology in popular culture and of interest to the media, both mainstream and digital.

A previously undescribed and near-complete specimen of the non-pterodactyloid pterosaur Rhamphorhynchus is briefly described. Although purchased in 1878 and held in a public collection in Dublin, Ireland ever since, this specimen has never been described and was not even mentioned in the literature until 2010.

Estimating the mass of an extinct organism is naturally difficult. Practicality and simplicity means that often some linear measurement is used as a proxy. In the case of non-avian dinosaurs, the total length of the animal (from the snout to the tip of the tail) is sometimes used for this purpose. However, the total length of the tail is unknown in all but very few dinosaurian taxa. Tail length data taken from specimens and the literature are shown here to have remarkable variation both between and within clades (and even within single species). Comparison with body length data shows that total length (including the tail) is therefore a less reliable measure of size than using the snout-vent length of the animal. ‘Snout-sacrum’ lengths are suggested as a more reliable alternative. Total length should not be abandoned, however, both to provide a comparison with older works and specimens lacking complete presacral axial columns, and for communication with the general public.

Stomach contents preserved in fossil specimens provide direct evidence for the diet of extinct animals. Such exceptional fossils remain rare for predatory non-avian dinosaurs and each can add significantly to our understanding of trophic interactions between various taxa. Here we present evidence for the dromaeosaurid theropod Velociraptor scavenging on the carcass of an azhdarchid pterosaur, with a long bone of the pterosaur being found as gut contents of the dinosaur. Despite previous inferences of dromaeosaurs as hyper-predators, scavenging appears to have been an important part of their ecology.

Hone, D.W.E., Naish, D. & Cuthill, I.C. 2011: Does mutual sexual selection explain the evolution of head crests in pterosaurs and dinosaurs? Lethaia, Vol. 45, pp. 139–156. Cranial ornamentation is widespread throughout the extinct non-avialian Ornithodira, being present throughout Pterosauria, Ornithischia and Saurischia. Ornaments take many forms, and can be composed of at least a dozen different skull bones, indicating multiple origins. Many of these crests serve no clear survival function and it has been suggested that their primary use was for species recognition or sexual display. The distribution within Ornithodira and the form and position of these crests suggest sexual selection as a key factor, although the role of the latter has often been rejected on the grounds of an apparent lack of sexual dimorphism in many species. Surprisingly, the phenomenon of mutual sexual selection – where both males and females are ornamented and both select mates – has been ignored in research on fossil ornithodirans, despite a rich history of research and frequent expression in modern birds. Here, we review the available evidence for the functions of ornithodiran cranial crests and conclude that mutual sexual selection presents a valid hypothesis for their presence and distribution. The integration of mutual sexual selection into future studies is critical to our understanding of ornithodiran ecology, evolution and particularly questions regarding sexual dimorphism. □Behaviour, Dinosauria, ornaments, Pterosauria, sexual selection.

Resumen en: We describe theropod bite marks on the tibia of a hadrosaurine ornithopod recovered northwest of Coahuila, Mexico. Based on the size and shape of the bit...

Tyrannosaurids are primarily gigantic, predatory theropod dinosaurs of the Cretaceous. Here we report a new member of the tyrannosaurid clade Tyrannosaurinae from the Upper Cretaceous Wangshi Group of Zhucheng, Shandong Province, China, based on a maxilla and associated dentary. The discovery of this animal, here named Zhuchengtyrannus magnus gen. et sp. nov., adds to the known diversity of tyrannosaurids in Asia. Z. magnus can be identified by a horizontal shelf on the lateral surface of the base of the ascending process, and a rounded notch in the anterior margin of the maxillary fenestra. Several additional features contribute to a unique combination of character states that serves to further distinguish Z. magnus from other taxa. Comparisons with other tyrannosaurids suggest that Zhuchengtyrannus was a very large theropod, comparable in size to both Tarbosaurus and Tyrannosaurus.

It has recently been argued that the elongate necks of sauropod dinosaurs evolved primarily through selection for their use as sexual and dominance signals, and not as an adaptation for accessing a large ‘feeding envelope’ as traditionally thought. Here we explore this idea and show that all six arguments that have been advanced in support of the sexual selection hypothesis are flawed: there is no evidence for sexual dimorphism in the necks of sauropods; neither is there any evidence that they were used in dominance displays; long necks provided significant survival benefits in allowing high browsing and energetically efficient grazing; their fitness cost was likely less than has been assumed; their positive allometry through ontogeny is uninformative given that ontogenetic allometry is common in animals; apparent lack of correlation between neck and leg length across phylogeny is illusory due to over-representation of mamenchisaurids in a previously analysed dataset, and in any case is not informative as the unique morphology of sauropod necks suggests they, rather than legs, may have been cheaper to elongate when evolving increased vertical reach. In no speciose, morphologically varied, longlived tetrapod clade has sexual selection consistently acted on a single part of the body, and it is unlikely that Sauropoda is the exception to this. In summary, there is no convincing evidence that sexual selection was the primary force driving the evolution of sauropod necks. While a subsidiary role for sexual selection cannot be discounted, the traditional hypothesis that sauropod necks evolved primarily due to the feeding benefits that they conferred is, by comparison, far better supported.

The shape and extent of the membranous brachioptagium in pterosaurs remains a controversial topic for those attempting to determine the aerodynamic performance of the first vertebrate fliers. Various arguments in favour of the trailing edge terminating against either the torso or hip, the femur, the ankle, or different locations for various taxa, has resulted in several published reconstructions. Uncertainty over the correct model is detrimental to both aerodynamic and palaeoecological studies that are forced to simultaneously consider multiple and highly variable configurations for individual taxa. A review of relevant pterosaur specimens with preserved soft tissues or impressions of the wing membrane, however, strongly suggests that the trailing edge of the wing extended down to the lower leg or ankle in all specimens where the brachiopatagium is completely preserved. This configuration is seen across a phylogenetically broad range of pterosaurs and is thus likely to have been universally present throug...

Sixteen isolated theropod teeth were discovered in two areas in the upper Middle-lower Upper Jurassic Shishugou Formation of the Xinjiang Uyghur Autonomous Region, northwest China. This sample can be divided on the basis of qualitative features and simple quantitative metrics into seven tooth morphotypes, each of which probably represents a distinct taxon. Three of the morphotypes may be attributable to theropods already known from the Shishugou Formation, namely the alvarezsauroid Haplocheirus and the basal tetanurans Monolophosaurus and Sinraptor. The other four morphotypes, however, appear to represent new taxa, taking the known theropod diversity of the Shishugou Formation from six species to at least ten. One of the new taxa is probably a dromaeosaurid. Another appears to represent a troodontid or a relative of the potentially troodontid-like Paronychodon, itself so far known only from isolated teeth. Of the remaining two taxa, one appears to be a basal tetanuran or tyrannosauroid, whereas the other either belongs to one of these same groups or represents a ceratosaur. The probable deinonychosaurian teeth in our sample are among the oldest fossils known for this clade, and highlight the diversity of coelurosaurs in the Shishugou Formation.