The first oviraptorosaur (Dinosauria: Theropoda) bonebed: Evidence of gregarious behaviour in a maniraptoran theropod

A monodominant bonebed of Avimimus from the Nemegt Formation of Mongolia is the first oviraptorosaur bonebed described and the only recorded maniraptoran bonebed from the Late Cretaceous. Cranial elements recovered from the bonebed provide insights on the anatomy of the facial region, which was formerly unknown in Avimimus. Both adult and subadult material was recovered from the bonebed, but small juveniles are underrepresented. The taphonomic and sedimentological evidence suggests that the Avimimus bonebed represents a perimortem gregarious assemblage. The near absence of juveniles in the bonebed may be evidence of a transient age-segregated herd or ‘flock’, but the behaviour responsible for this assemblage is unclear. Regardless, the Avimimus bonebed is the first evidence of gregarious behaviour in oviraptorosaurs, and highlights a potential trend of increasing gregariousness in dinosaurs towards the end of the Mesozoic

How to Live with Dinosaurs: Ecosystems Across the Mesozoic

We continue our trip back in time through the Mesozoic, visiting several different ecosystems across the planet. Each of these was strongly influenced by the continental breakup from a single landmass into several tectonic plates and associated landmasses during this period. We will visit localities on several continents, observe how their vertebrate faunas changed over time, and what external factors might have contributed to these differences. During the Cretaceous, we visit the Iberian Peninsula, where hadrosauroids replaced titanosaurs as the most abundant dinosaur taxon. On the other side of the planet, a succession of geologic formations in Australia shows a gradual change from aquatic to terrestrial faunas resulting from sea-level changes of a now non-existent inland ocean. A visit to two polar ecosystems indicates possible mutual exclusion between amphibians (temnospondyls) and reptiles (crocodylomorphs), because they occupied similar ecological niches. Observing the record of Cretaceous landscapes in what is now Mongolia shows how changes in environment and climate correlate with changes in faunal composition. Heading back, we check if there are distinct differences in vertebrate diversity in space and time in the Late Jurassic of North America. Then we move south, to Argentina, and back to the Middle and Early Jurassic. Here, we will try to understand where these Late Jurassic faunas originated and what influence the fragmentation of the supercontinent Pangea had on their evolution and diversity. Finally, we will stop our trip in the Late Triassic of Central Europe, examining a typical vertebrate fauna from the time when dinosaurs began their domination of the planet

On the Ancestry of Feathers in Mesozoic Dinosaurs

Over the last two decades, the dinosaur fossil record has revealed much about the nature of their epidermal structures. These data challenged long-standing hypotheses of widespread reptile-like scalation in dinosaurs and provided additional evidence that supported the deeply nested position of birds within the clade. Moreover, in recent years, the discovery of filamentous structures in numerous species across the dinosaurian evolutionary tree suggests a model of deep feather homology within dinosaurs, with the appearance of feathers hypothesised to coincide with the dinosaur origin. Thanks to phylogenetic comparative methods, these homologies can now be tested empirically and form the basis of this study. Based on a dataset of 77 dinosaur species that preserve integumentary structures, we undertake a series of model-fitting and ancestral state reconstruction analyses to interpret the evolutionary history and ancestral integumentary condition in dinosaurs. Our results provide the first empirical support for the evolution of feathers in an ordered fashion, but reveal that these evolutionary trends were not always towards ‘more complex’ conditions. Ancestral state reconstructions demonstrate that irrespective of the preferred phylogenetic framework, the ancestral pterosaur condition or whether any one major dinosaur lineage had a Late Triassic-feathered representative, support values for a filamentous/feathered dinosaur ancestor are low. More examples of feathered taxa from across the dinosaur tree, and in particular the discovery of as yet unknown feathered Triassic taxa, will be needed in order to overturn current support for a scaly dinosaurian ancestor