The Earliest Pterodactyloid and the Origin of the Group

The cervical series is poorly known in several pterosaur clades despite the fact that distinct morphotypes of individual elements have been recognised. Among the least known is the neck of the Tapejaridae that until recently has received little attention. In order to provide further data on the tapejarid cervical anatomy, we describe three specimens from the Romualdo Formation (Lower Cretaceous, Brazil): AMNH 22568 comprises the last five cervical elements of a large individual, AMNH 24445 and MN 4728-V, both including three meso-cervical elements of small individuals. Despite size differences, AMNH 22568 and MN 4728-V are anatomically more similar to each another, showing a pattern of high, laterally flattened (bladelike) neural spines, short centra pierced by two lateral pneumatic foramina. AMNH 24445 presents a distinct anatomy, with low (but still evident) neural spines, more elongated centra with concave ventral surface, and only one lateral pneumatic foramen. Based on comparative studies we refer AMNH 22568 and MN 4728-V to the Thalassodrominae and AMNH 24445 to the Tapejarinae, helping to differentiate the cervical elements of these clades. Thalassodrominae cervical vertebrae can be distinguished by the presence of two lateral pneumatic foramina, a broad centrum (length/width ratio lower than two), and a flat ventral surface. Tapejarinae cervical vertebrae show only one lateral pneumatic foramen, the length/width ratio higher than two, and a concave ventral surface. Thalassodromine and tapejarine cervical vertebrae differ from those of azhdarchids in the presence of lateral pneumatic foramens, developed neural spine, and length/width ratio lower than three, and by being comparatively shorter.

The Late Jurassic to Early Cretaceous interval represents a time of environmental upheaval and cataclysmic events, combined with disruptions to terrestrial and marine ecosystems. Historically, the Jurassic/Cretaceous (J/K) boundary was classified as one of eight mass extinctions. However, more recent research has largely overturned this view, revealing a much more complex pattern of biotic and abiotic dynamics than has previously been appreciated. Here, we present a synthesis of our current knowledge of Late Jurassic-Early Cretaceous events, focusing particularly on events closest to the J/K boundary. We find evidence for a combination of short-term catastrophic events, large-scale tectonic processes and environmental perturbations, and major clade interactions that led to a seemingly dramatic faunal and ecological turnover in both the marine and terrestrial realms. This is coupled with a great reduction in global biodiversity which might in part be explained by poor sampling. Very few groups appear to have been entirely resilient to this J/K boundary 'event', which hints at a 'cascade model' of ecosystem changes driving faunal dynamics. Within terrestrial ecosystems, larger, more-specialised organisms, such as saurischian dinosaurs, appear to have suffered the most. Medium-sized tetanuran theropods declined, and were replaced by larger-bodied groups, and basal eusauropods were replaced by neosauropod faunas. The ascent of paravian theropods is emphasised by escalated competition with contemporary pterosaur groups, culminating in the explosive radiation of birds, although the timing of this is obfuscated by biases in sampling. Smaller, more ecologically diverse terrestrial non-archosaurs, such as lissamphibians and mammaliaforms, were comparatively resilient to extinctions, instead documenting the origination of many extant groups around the J/K boundary. In the marine realm, extinctions were focused on low-latitude, shallow marine shelf-dwelling faunas, corresponding to a significant eustatic sea-level fall in the latest Jurassic. More mobile and ecologically plastic marine groups, such as ichthyosaurs, survived the boundary relatively unscathed. High rates of extinction and turnover in other macropredaceous marine groups, including plesiosaurs, are accompanied by the origin of most major lineages of extant sharks. Groups which occupied both marine and terrestrial ecosystems, including crocodylomorphs, document a selective extinction in shallow marine forms, whereas turtles appear to have diversified. These patterns suggest that different extinction selectivity and ecological processes were operating between marine and terrestrial ecosystems, which were ultimately important in determining the fates of many key groups, as well as the origins of many major extant lineages. We identify a series of potential abiotic candidates for driving these patterns, including multiple bolide impacts, several episodes of flood basalt eruptions, dramatic climate change, and major disruptions to oceanic systems. The J/K t...

Cranial crests show considerable variation within the Pterosauria, a group of flying reptiles that developed powered flight. This includes the Wukongopteridae, a clade of non-pterodactyloids, where the presence or absence of such head structures, allied with variation in the pelvic canal, have been regarded as evidence for sexual dimorphism. Here we discuss the cranial crest variation within wukongopterids and briefly report on a new specimen (IVPP V 17957). We also show that there is no significant variation in the anatomy of the pelvis of crested and crestless specimens. We further revisit the discussion regarding the function of cranial structures in pterosaurs and argue that they cannot be dismissed a priori as a valuable tool for species recognition.