Ontogenetic variability of the intertympanic sinus distinguishes lineages within Crocodylia.

The phylogenetic relationships within crown Crocodylia remain contentious due to conflicts between molecular and morphological hypotheses. However, morphology-based datasets are mostly constructed on external characters, overlooking internal structures. Here, we use 3D geometric morphometrics to study the shape of the intertympanic sinus system in crown crocodylians during ontogeny, in order to assess its significance in a taxonomic context. Intertympanic sinus shape was found to be highly correlated with size and modulated by cranial shape during development. Still, adult sinus morphology distinguishes specimens at the family, genus and species level. We observe a clear distinction between Alligatoridae and Longirostres, a separation of different Crocodylus species and the subfossil Malagasy genus Voay, and a distinction between the Tomistoma and Gavialis lineages. Our approach is independent of molecular methods but concurs with the molecular topologies. Therefore, sinus characters could add significantly to morphological datasets, offering an alternative viewpoint to resolve problems in crocodylian relationships.

The endocast of the insular and extinct Sylviornis neocaledoniae (Aves, Galliformes), reveals insights into its sensory specializations and its twilight ecology.

Sylviornis neocaledoniae (Galliformes, Sylviornithidae), a recently extinct bird of New-Caledonia (Galliformes, Sylviornithidae) is the largest galliform that ever lived and one of the most enigmatic birds in the world. Herein, for the first time, we analyze its neuroanatomy that sheds light on its lifestyle, its brain shape and patterns being correlated to neurological functions. Using morphometric methods, we quantified the endocranial morphology of S. neocaledoniae and compared it with extinct and extant birds in order to obtain ecological and behavioral information about fossil birds. Sylviornis neocaledoniae exhibited reduced optic lobes, a condition also observed in nocturnal taxa endemic to predator-depauperate islands, such as Elephant birds. Functional interpretations suggest that S. neocaledoniae possessed a well-developed somatosensorial system and a good sense of smell in addition to its specialized visual ability for low light conditions, presumably for locating its food. We interpret these results as evidence for a crepuscular lifestyle in S. neocaledoniae.

The neuroanatomy of Zulmasuchus querejazus (Crocodylomorpha, Sebecidae) and its implications for the paleoecology of sebecosuchians.

The endocranial structures of the sebecid crocodylomorph Zulmasuchus querejazus (MHNC 6672) from the Lower Paleocene of Bolivia are described in this article. Using computed tomography scanning, the cranial endocast, associated nerves and arteries, endosseous labyrinths, and cranial pneumatization are reconstructed and compared with those of extant and fossil crocodylomorphs, representative of different ecomorphological adaptations. Z. querejazus exhibits an unusual flexure of the brain, pericerebral spines, semicircular canals with a narrow diameter, as well as enlarged pharyngotympanic sinuses. First, those structures allow to estimate the alert head posture and hearing capabilities of Zulmasuchus. Then, functional comparisons are proposed between this purportedly terrestrial taxon, semi-aquatic, and aquatic forms (extant crocodylians, thalattosuchians, and dyrosaurids). The narrow diameter of the semicircular canals but expanded morphology of the endosseous labyrinths and the enlarged pneumatization of the skull compared to other forms indeed tend to indicate a terrestrial lifestyle for Zulmasuchus. Our results highlight the need to gather new data, especially from altirostral forms in order to further our understanding of the evolution of endocranial structures in crocodylomorphs with different ecomorphological adaptations.

Cranial evolution in the extinct Rodrigues Island owl Otus murivorus (Strigidae), associated with unexpected ecological adaptations.

Island birds that were victims of anthropic extinctions were often more specialist species, having evolved their most distinctive features in isolation, making the study of fossil insular birds most interesting. Here we studied a fossil cranium of the 'giant' extinct scops owl Otus murivorus from Rodrigues Island (Mascarene Islands, southwestern Indian Ocean), to determine any potential unique characters. The fossil and extant strigids were imaged through X-ray microtomography, providing 3D views of external and internal (endocast, inner ear) cranial structures. Geometric morphometrics and analyses of traditional measurements yielded new information about the Rodrigues owl's evolution and ecology. Otus murivorus exhibits a 2-tier "lag behind" phenomenon for cranium and brain evolution, both being proportionately small relative to increased body size. It also had a much more developed olfactory bulb than congeners, indicating an unexpectedly developed olfactory sense, suggesting a partial food scavenging habit. In addition, O. murivorus had the eyes placed more laterally than O. sunia, the species from which it was derived, probably a side effect of a small brain; rather terrestrial habits; probably relatively fearless behavior; and a less vertical posture (head less upright) than other owls (this in part an allometric effect of size increase). These evolutionary features, added to gigantism and wing reduction, make the extinct Rodrigues owl's evolution remarkable, and with multiple causes.