Quantitative assessment of the vertebral pneumaticity in an anhanguerid pterosaur using micro-CT scanning.

Research on the postcranial skeletal pneumaticity in pterosaurs is common in the literature, but most studies present only qualitative assessments. When quantitative, they are done on isolated bones. Here, we estimate the Air Space Proportion (ASP) obtained from micro-CT scans of the sequence from the sixth cervical to the fourth dorsal vertebra of an anhanguerine pterosaur to understand how pneumaticity is distributed in these bones. Pneumatisation of the vertebrae varied between 68 and 72% of their total volume. The neural arch showed higher ASP in all vertebrae. Anhanguerine vertebral ASP was generally higher than in sauropod vertebrae but lower than in most extant birds. The ASP observed here is lower than that calculated for the appendicular skeleton of other anhanguerian pterosaurs, indicating the potential existence of variation between axial and appendicular pneumatisation. The results point to a pattern in the distribution of the air space, which shows an increase in the area occupied by the trabecular bone in the craniocaudal direction of the vertebral series and, in each vertebra, an increase of the thickness of the trabeculae in the zygapophyses. This indicates that the distribution of pneumatic diverticula in anhanguerine vertebrae may not be associated with stochastic patterns.

The "χ" of the Matter: Testing the Relationship between Paleoenvironments and Three Theropod Clades.

The view of spinosaurs as dinosaurs of semi-aquatic habits and strongly associated with marginal and coastal habitats are deeply rooted in both scientific and popular knowledge, but it was never statistically tested. Inspired by a previous analysis of other dinosaur clades and major paleoenvironmental categories, here we present our own statistical evaluation of the association between coastal and terrestrial paleoenvironments and spinosaurids, along with other two theropod taxa: abelisaurids and carcharodontosaurids. We also included a taphonomic perspective and classified the occurrences in categories related to potential biases in order to better address our interpretations. Our main results can be summarized as follows: 1) the taxon with the largest amount of statistical evidence showing it positively associated to coastal paleoenvironments is Spinosauridae; 2) abelisaurids and carcharodontosaurids had more statistical evidence showing them positively associated with terrestrial paleoenvironments; 3) it is likely that spinosaurids also occupied spatially inland areas in a way somehow comparable at least to carcharodontosaurids; 4) abelisaurids may have been more common than the other two taxa in inland habitats.