A new cranial reconstruction of Coelurosauravus elivensis Piveteau, 1926 (Diapsida, Weigeltisauridae) and its implications on the paleoecology of the first gliding vertebrates

ABSTRACT

The cranial skeleton of the enigmatic gliding neodiapsid reptile Coelurosauravus elivensis (Lower Sakamena Formation, Lopingian, Southwestern Madagascar) is re-described in detail. All previously referred specimens are re-examined under both direct observations and Reflectance Transformation Imaging. Their exquisite preservation yields detailed three-dimensional information on the outline of individual bones and their osteological relationships, which are missing in the Laurasian remains. In contrast to previous studies, the ontogenetic maturity of all specimens is re-affirmed. Previously unidentified elements of the palate, braincase and mandible are described, and a novel reconstruction is proposed, including the first palatal reconstruction in a weigeltisaurid reptile. C. elivensis has the smallest skull of all weigeltisaurids and differs from other species in its facial ornamentation, parietosquamosal frill and larger anterior maxillary dentition. We also provide extensive comparisons with contemporaneous reptiles, possibly closely related taxa and more recent analogs, as well as a preliminary discussion of the functional anatomy of the peculiar cranial morphology of weigeltisaurids. The cranial skeleton is a truss construction with large orbits and temporal fenestrae. By analogy with extant chamaeleonids, the elongate parietosquamosal frill is associated with an increase in length and diameter of the temporal jaw adductors, resulting in an increased gape and/or bite force and speed. Additionally, the spikes and frills of weigeltisaurids most likely served as a display and defensive structure.

ACKNOWLEDGMENTS

We thank N.-E. Jalil (MNHN) for access to the MNHN specimens and for his constructive comments on the manuscript. Many thanks to C. Letenneur (MNHN) for her life reconstruction of Coelurosauravus. We thank O. Béthoux (MNHN) for his help in RTI methodology and loaning the necessary hardware to V.B., and P. Loubry (CNRS) and D. Germain (MNHN) for their help in photography. Many thanks to J.-M. Pacaud (MNHN) for his help in nomenclature. We also thank J. Falconnet (MNHN), A. Pritchard (VMNH) and H.-D. Sues (NMNH) for constructive discussions on weigeltisaurids and Permo-Triassic reptiles. Finally, we thank G. Sobral and an anonymous reviewer for their constructing reviews, and H.-D. Sues for his editorial work. This work is supported by the French Ministry of Superior Education and Research (annual credits of the CR2P and Ph.D. grant to V.B.).

DATA AVAILABILITY

The data underlying this article are available in Zenodo, at http://doi.org/10.5281/zenodo.4300212.