A gigantic feathered dinosaur from the lower cretaceous of China

Numerous feathered dinosaur specimens have recently been recovered from the Middle-Upper Jurassic and Lower Cretaceous deposits of northeastern China, but most of them represent small animals. Here we report the discovery of a gigantic new basal tyrannosauroid, Yutyrannus huali gen. et sp. nov., based on three nearly complete skeletons representing two distinct ontogenetic stages from the Lower Cretaceous Yixian Formation of Liaoning Province, China. Y. huali shares some features, particularly of the cranium, with derived tyrannosauroids, but is similar to other basal tyrannosauroids in possessing a three-fingered manus and a typical theropod pes. Morphometric analysis suggests that Y. huali differed from tyrannosaurids in its growth strategy. Most significantly, Y. huali bears long filamentous feathers, thus providing direct evidence for the presence of extensively feathered gigantic dinosaurs and offering new insights into early feather evolution.     

Baryonyx, a remarkable new theropod dinosaur

An extremely large claw bone, some 30 cm long, was found in Wealden (Lower Cretaceous) deposits in a Surrey claypit in January 1983. This led to the discovery the following month of the well-preserved skeleton of a new large theropod dinosaur. Only one other theropod specimen comprising more than a few bones had ever been found in Britain, and that discovery was more than a century ago. Indeed, no large theropod, reasonably complete, had previously been discovered in Lower Cretaceous rocks anywhere in the world. Our study so far suggests that the Surrey dinosaur was a typical large theropod in certain respects, resembling, for example Allosaurus. In several other respects, however, it differs sufficiently from all known dinosaurs to merit designation as the representative of a new species, genus and family.     

Pterosaurs as part of a spinosaur diet

A remarkable specimen has been discovered of an Early Cretaceous pterosaur that has a tooth embedded in one of its cervical vertebrae: the tooth has been identified as one from a spinosaurid theropod dinosaur. This fossil is direct evidence that spinosaurs included items other than fish in their diet.     

Branched integumental structures in Sinornithosaurus and the origin of feathers

The evolutionary origin of feathers has long been obscured because no morphological antecedents were known to the earliest, structurally modern feathers of Archaeopteryx. It has been proposed that the filamentous integumental appendages on several theropod dinosaurs are primitive feathers; but the homology between these filamentous structures and feathers has been disputed, and two taxa with true feathers (Caudipteryx and Protarchaeopteryx) have been proposed to be flightless birds. Confirmation of the theropod origin of feathers requires documentation of unambiguously feather-like structures in a clearly non-avian theropod. Here we describe our observations of the filamentous integumental appendages of the basal dromaeosaurid dinosaur Sinornithosaurus millenii, which indicate that they are compound structures composed of multiple filaments. Furthermore, these appendages exhibit two types of branching structure that are unique to avian feathers: filaments joined in a basal tuft, and filaments joined at their bases in series along a central filament. Combined with the independent phylogenetic evidence supporting the theropod ancestry of birds, these observations strongly corroborate the hypothesis that the integumental appendages of Sinornithosaurus are homologous with avian feathers. The plesiomorphic feathers of Sinornithosaurus also conform to the predictions of an independent, developmental model of the evolutionary origin of feathers.     

The distribution of integumentary structures in a feathered dinosaur

Non-avian theropod dinosaurs with preserved integumentary coverings are becoming more common; but apart from the multiple specimens of Caudipteryx, which have true feathers, animals that are reasonably complete and entirely articulated that show these structures in relation to the body have not been reported. Here we report on an enigmatic small theropod dinosaur that is covered with filamentous feather-like structures over its entire body.     

The smallest known non-avian theropod dinosaur

Non-avian dinosaurs are mostly medium to large-sized animals, and to date all known mature specimens are larger than the most primitive bird, Archaeopteryx. Here we report on a new dromaeosaurid dinosaur, Microraptor zhaoianus gen. et sp. nov., from the Early Cretaceous Jiufotang Formation of Liaoning, China. This is the first mature non-avian dinosaur to be found that is smaller than Archaeopteryx, and it eliminates the size disparity between the earliest birds and their closest non-avian theropod relatives. The more bird-like teeth, the Rahonavis-like ischium and the small number of caudal vertebrae of Microraptor are unique among dromaeosaurids and improve our understanding of the morphological transition to birds. The nearly completely articulated foot shows features, such as distally positioned digit I, slender and recurved pedal claws, and elongated penultimate phalanges, that are comparable to those of arboreal birds. The discovery of these in non-avian theropods provides new insights for studying the palaeoecology of some bird-like theropod dinosaurs.     

Basic avian pulmonary design and flow-through ventilation in non-avian theropod dinosaurs

Birds are unique among living vertebrates in possessing pneumaticity of the postcranial skeleton, with invasion of bone by the pulmonary air-sac system. The avian respiratory system includes high-compliance air sacs that ventilate a dorsally fixed, non-expanding parabronchial lung. Caudally positioned abdominal and thoracic air sacs are critical components of the avian aspiration pump, facilitating flow-through ventilation of the lung and near-constant airflow during both inspiration and expiration, highlighting a design optimized for efficient gas exchange. Postcranial skeletal pneumaticity has also been reported in numerous extinct archosaurs including non-avian theropod dinosaurs and Archaeopteryx. However, the relationship between osseous pneumaticity and the evolution of the avian respiratory apparatus has long remained ambiguous. Here we report, on the basis of a comparative analysis of region-specific pneumaticity with extant birds, evidence for cervical and abdominal air-sac systems in non-avian theropods, along with thoracic skeletal prerequisites of an avian-style aspiration pump. The early acquisition of this system among theropods is demonstrated by examination of an exceptional new specimen of Majungatholus atopus, documenting these features in a taxon only distantly related to birds. Taken together, these specializations imply the existence of the basic avian pulmonary Bauplan in basal neotheropods, indicating that flow-through ventilation of the lung is not restricted to birds but is probably a general theropod characteristic.     

Dinosaur locomotion from a new trackway

Ardley Quarry in Oxfordshire, UK, contains one of the most extensive dinosaur-trackway sites in the world, with individual trackways extending for up to 180 metres. We have discovered a unique dual-gauge trackway from a bipedal theropod dinosaur from the Middle Jurassic in this locality, which indicates that these large theropods were able to run and that they used different hindlimb postures for walking and running. Our findings have implications for the biomechanics and evolution of theropod locomotion.     

Biomechanics (Communication arising): prey attack by a large theropod dinosaur

Prey-capture strategies in carnivorous dinosaurs have been inferred from the biomechanical features of their tooth structure, the estimated bite force produced, and their diet. Rayfield et al. have used finite-element analysis (FEA) to investigate such structure-function relationships in Allosaurus fragilis, and have found that the skull was designed to bear more stress than could be generated by simple biting. They conclude that this large theropod dinosaur delivered a chop-and-slash 'hatchet' blow to its prey, which it approached with its mouth wide open before driving its upper tooth row downwards. We argue that this mode of predation is unlikely, and that the FEA results, which relate to an 'overengineered' skull, are better explained by the biomechanical demands of prey capture. Understanding the mechanics of predation is important to our knowledge of the feeding habits of carnivorous dinosaurs and for accurate reconstruction their lifestyles.     

A new carnivorous dinosaur from the Late Jurassic Solnhofen archipelago

Small Late Jurassic theropod dinosaurs are rare worldwide. In Europe these carnivorous dinosaurs are represented primarily by only two skeletons of Compsognathus, neither of which is well preserved. Here we describe a small new theropod dinosaur from the Late Jurassic period of Schamhaupten in southern Germany. Being exquisitely preserved and complete from the snout to the distal third of the tail, the new fossil is the best-preserved predatory, non-avian dinosaur in Europe. It possesses a suite of characters that support its identification as a basal coelurosaur. A cladistic analysis indicates that the new taxon is closer to maniraptorans than to tyrannosauroids, grouping it with taxa often considered to be compsognathids. Large portions of integument are preserved along its tail. The absence of feathers or feather-like structures in a fossil phylogenetically nested within feathered theropods indicates that the evolution of these integumentary structures might be more complex than previously thought.     

Cranial design and function in a large theropod dinosaur

Finite element analysis (FEA) is used by industrial designers and biomechanicists to estimate the performance of engineered structures or human skeletal and soft tissues subjected to varying regimes of stress and strain. FEA is rarely applied to problems of biomechanical design in animals, despite its potential to inform structure-function analysis. Non-invasive techniques such as computed tomography scans can be used to generate accurate three-dimensional images of structures, such as skulls, which can form the basis of an accurate finite element model. Here we have applied this technique to the long skull of the large carnivorous theropod dinosaur Allosaurus fragilis. We have generated the most geometrically complete and complex FEA model of the skull of any extinct or extant organism and used this to test its mechanical properties and examine, in a quantitative way, long-held hypotheses concerning overall shape and function. The combination of a weak muscle-driven bite force, a very 'light' and 'open' skull architecture and unusually high cranial strength, suggests a very specific feeding behaviour for this animal. These results demonstrate simply the inherent potential of FEA for testing mechanical behaviour in fossils in ways that, until now, have been impossible.     

A gigantic bird-like dinosaur from the Late Cretaceous of China

An evolutionary trend of decreasing size is present along the line to birds in coelurosaurian theropod evolution, but size increases are seen in many coelurosaurian subgroups, in which large forms are less bird-like. Here we report on a new non-avian dinosaur, Gigantoraptor erlianensis, gen. et sp. nov., from the Late Cretaceous Iren Dabasu Formation of Nei Mongol, China. Although it has a body mass of about 1,400 kg, a phylogenetic analysis positions this new taxon within the Oviraptorosauria, a group of small, feathered theropods rarely exceeding 40 kg in body mass. A histological analysis suggests that Gigantoraptor gained this size by a growth rate considerably faster than large North American tyrannosaurs such as Albertosaurus and Gorgosaurus. Gigantoraptor possesses several salient features previously unknown in any other dinosaur and its hind limb bone scaling and proportions are significantly different from those of other coelurosaurs, thus increasing the morphological diversity among dinosaurs. Most significantly, the gigantic Gigantoraptor shows many bird-like features absent in its smaller oviraptorosaurian relatives, unlike the evolutionary trend seen in many other coelurosaurian subgroups.     

Tooth loss and alveolar remodeling in Sinosaurus triassicus (Dinosauria: Theropoda) from the lower jurassic strata of the Lufeng Basin, China

Pathological or traumatic loss of teeth often results in the resorption and remodeling of the affected alveoli in mammals. However, instances of alveolar remodeling in reptiles are rare. A remodeled alveolus in the maxilla of the Chinese theropod Sinosaurus (Lower Jurassic Lower Lufeng Formation) is the first confirmed example of such dental pathology in a dinosaur. Given the known relationship between feeding behavior and tooth damage in theropods (teeth with spalled enamel, tooth crowns embedded in bone) and the absence of dentary, maxillary, and premaxillary osteomyelitis, traumatic loss of a tooth is most likely the cause of alveolar remodeling. Based on the extent of remodeling, the injury and subsequent tooth loss were non-fatal in this individual.     

Dinosaurian growth rates and bird origins

Dinosaurs, like other tetrapods, grew more quickly just after hatching than later in life. However, they did not grow like most other non-avian reptiles, which grow slowly and gradually through life. Rather, microscopic analyses of the long-bone tissues show that dinosaurs grew to their adult size relatively quickly, much as large birds and mammals do today. The first birds reduced their adult body size by shortening the phase of rapid growth common to their larger theropod dinosaur relatives. These changes in timing were primarily related not to physiological differences but to differences in growth strategy.     

Cursoriality in bipedal archosaurs

Modern birds have markedly foreshortened tails and their body mass is centred anteriorly, near the wings. To provide stability during powered flight, the avian centre of mass is far from the pelvis, which poses potential balance problems for cursorial birds. To compensate, avians adapted to running maintain the femur subhorizontally, with its distal end situated anteriorly, close to the animal's centre of mass; stride generation stems largely from parasagittal rotation of the lower leg about the knee joint. In contrast, bipedal dinosaurs had a centre of mass near the hip joint and rotated the entire hindlimb during stride generation. Here we show that these contrasting styles of cursoriality are tightly linked to longer relative total hindlimb length in cursorial birds than in bipedal dinosaurs. Surprisingly, Caudipteryx, described as a theropod dinosaur, possessed an anterior centre of mass and hindlimb proportions resembling those of cursorial birds. Accordingly, Caudipteryx probably used a running mechanism more similar to that of modern cursorial birds than to that of all other bipedal dinosaurs. These observations provide valuable clues about cursoriality in Caudipteryx, but may also have implications for interpreting the locomotory status of its ancestors.     

A bizarre predatory dinosaur from the Late Cretaceous of Madagascar

Here we report the discovery of a small-bodied (approximately 1.8 m) predatory dinosaur from the Late Cretaceous (Maastrichtian) of Madagascar. Masiakasaurus knopfleri, gen. et sp. nov., represented by several skull elements and much of the postcranial skeleton, is unique in being the only known theropod with a highly procumbent and distinctly heterodont lower dentition. Such a derived dental morphology is otherwise unknown among dinosaurs. Numerous skeletal characteristics indicate that Masiakasaurus is a member of Abelisauroidea, an enigmatic clade of Gondwanan theropods. Previously, small-bodied abelisauroids were known only from Argentina. The occurrence of Masiakasaurus on Madagascar suggests that small-bodied abelisauroids, like their larger-bodied counterparts, were more cosmopolitan, radiating throughout much of Gondwana and paralleling the diversification of small coelurosaur theropods in Laurasia.     

An exceptionally preserved Lower Cretaceous ecosystem

Fieldwork in the Early Cretaceous Jehol Group, northeastern China has revealed a plethora of extraordinarily well-preserved fossils that are shaping some of the most contentious debates in palaeontology and evolutionary biology. These discoveries include feathered theropod dinosaurs and early birds, which provide additional, indisputable support for the dinosaurian ancestry of birds, and much new evidence on the evolution of feathers and flight. Specimens of putative basal angiosperms and primitive mammals are clarifying details of the early radiations of these major clades. Detailed soft-tissue preservation of the organisms from the Jehol Biota is providing palaeobiological insights that would not normally be accessible from the fossil record.     

福斯特对马克思生态思想的论证及其现代意蕴

许多自命为生态马克思主义的学者,都承认马克思对生态问题有深刻的见解。但有争论的是,他们认为生态问题只是马克思工作的边缘部分,马克思并没有留下显著的生态文化遗产,给未来的社会主义者思考,或是没有相关的生态学方面的后续发展。文章在认真研读福斯特的有关著作和参阅有关福斯特文献资料的基础上,解读福思特对马克思生态思想的论证及构建生态学马克思主义的重要意义,以便为我们如何对待和解决生态问题提出了解决方案。     

Pre-<Emphasis Type="Italic">Archaeopteryx</Emphasis> coelurosaurian dinosaurs and their implications for understanding avian origins

The last two decades have witnessed great advances in reconstructing the transition from non-avian theropods to avians, but views in opposition to the theropod hypothesis still exist. Here we highlight one issue that is often considered to raise problems for the theropod hypothesis of avian origins, i.e. the “temporal paradox” in the stratigraphic distribution of theropod fossils — the idea that the earliest known avian is from the Late Jurassic but most other coelurosaurian groups are poorly known in the Jurassic, implying that avians arose before their supposed ancestors. However, a number of Jurassic non-avian coelurosaurian theropods have recently been discovered, thus documenting the presence of most of the major coelurosaurian groups in the Jurassic alongside, or prior to, avians. These discoveries have greatly improved the congruence between stratigraphy and phylogeny for derived theropods and, effectively, they reject the “temporal paradox” concept. Most importantly, these discoveries provide significant new information that supports the relatively basal positions of the Tyrannosauroidea and Alvarezsauroidea among the Coelurosauria. Indeed, they imply a new phylogenetic hypothesis for the interrelationships of Paraves, in which Archaeopteryx, the Dromaeosauridae, and the Troodontidae form a monophyletic group while the Scansoriopterygidae, other basal birds, and probably also the Oviraptorosauria, form another clade. Mapping some of the salient features onto a temporally-calibrated theropod phylogeny indicates that characteristics related to flight and arboreality evolved at the base of the Paraves, earlier than the Late Jurassic.     

Evolution of ecological differences in the Old World leaf warblers.

Sympatric species that belong to the same ecological guild usually differ in their behaviour and morphology, and these differences are often interpreted as adaptations to having to make use of different resources. Evidence supporting this interpretation comes from association between ecology and morphology among species, in which an a priori functional relationship is reasonable. But one problem with such comparisons is that members of a guild may be closely related, so the more closely related species can share a greater similarity in their morphology and ecology simply as a result of the lingering legacy of a common ancestor. In principle, the importance of historical legacy can be evaluated from phylogenetic relationships and times since divergence for all species, but this is rarely possible because these data are not available. Here we use a phylogeny for eight sympatric species of warbler in the genus Phylloscopus, based on their mitochondrial DNA sequences, to remove the effects of historical legacy. Without these effects, we find strong support for adaptive interpretations of among-species variation in habitat selection, prey-size choice and feeding method. Ecological variation along any of these three niche axes is associated with predictable morphological variation. We also find evidence for historical legacy in that more closely related species are often more similar behaviourally and morphologically. This paradoxical result can be reconciled because the most closely related species tend to differ along only one niche axis, habitat choice. In contrast, the evolution of prey-size choice and feeding method occurred rapidly and early in the diversification of this group. Once a new ecological zone was occupied, subsequent morphological change along these niche axes was limited, accounting for the similarity of closely related species.