A DESCRIPTIVE AND MORPHOMETRIC STUDY OF THE SKULL OF THE Ramphastos toco (AVES: PICIFORMES)

Abstract The study of morphological traits and their biomechanical roles in the cranial structure of birds raises phylogenetic, taxonomic and morphofunctional debates. The aim of this study was to describe and analyze morphological and morphometric data of the skull of Ramphastos toco and to compare the results with the available bibliography. Thirteen adult skulls and one folmaldehyde-fixed dissected specimen were analyzed. For skeletal preparation, the carcasses were submitted to maceration with the removal of soft tissues, degreasing and bleaching in hydrogen peroxide (50%) and sodium hypochlorite (50%). The shape and size of the naso-frontal suture, the presence of the rostral and caudal intracapsular sesamoids in the quadratic joint and the presence of the orbital ligament were altogether elements that challenged the available data. It also challenges the strength transferring models proposed in kinetic studies for the species. The discussion that emerges is the possibility of these limiting characteristics of the cranial kinetics described on the specimens have, together, a single role promoting functional stability to a structure that has a dimensional nature that generates instability. The morphometric results also presented significant divergences when compared to the available bibliography, which may be related to variables such as allopatric speciation, hybridization and sampling.