Skull variation and the shape of the sagittal premaxillary crest in anhanguerid pterosaurs (Pterosauria, Pterodactyloidea) from the Araripe Basin, Northeast Brazil

Abstract

Sagittal cranial crests are evident in several groups of pterosaurs, although their exact function has still not been determined. One of the most distinctive features of the Anhangueridae is a sagittal premaxillary crest on the anterior portion of the skull. A comparison of the skulls of anhanguerids revealed that they all have similar skull and crests shapes. In this paper, six anhanguerids from Araripe Basin were analysed using bidimensional geometric morphometrics. As a result, the taxa were arranged in two groups and two isolated taxa in the morphospace: elongated skulls, with crests high and expanded, representing 40% of the skull length; and median size skulls; and low and short crests starting posteriorly on the region of the seventh and fourth pairs of alveoli. Some of these groupings also share a phylogenetic relationship. Despite this separation in morphospace, the difference between the morphology of the crest was not as striking as in other pterodactyloid pterosaurs. Crest variation in Anhangueridae presented in this paper is considered as non-specific, with some patterns of similarity, such as the shape and the beginning of this structure on the premaxilla. In addition, the presence of positive allometric growth in the skull was observed and no trend in sexual dimorphism could be pointed.