First evidence of a mandibular crest in Brasileodactylus Kellner, 1984 (Pterosauria, Pteranodontoidea, Anhangueridae), with comments on pterosaur headcrests.

Abstract

Brasileodactylus araripensis Kellner, 1984, is a toothed pterosaur from the Lower Cretaceous Romualdo Formation of the Araripe Basin, Brazil. Traditionally regarded as crestless, the species has been central to debates on anhanguerid taxonomy, as most members of the clade possess well-developed sagittal cranial or dentary crests. Here we describe a nearly complete lower jaw (MCT.R.1473) that reveals, for the first time, the presence of a sagittal dentary crest in Brasileodactylus araripensis. The specimen was examined through high-resolution computed tomography and incorporated into the most comprehensive phylogenetic dataset for Pterosauria, which recovered it within Anhanguerinae in close association with Brasileodactylus Kellner, 1984. The new specimen shares many diagnostic features of the taxon, including accessory sulci, paired occlusal foramina, and a sharp odontoid process, confirming its referral. Comparative data indicate that crested individuals of Brasileodactylus represent the largest known specimens of the taxon, tentatively suggesting that crest development occurred late in ontogeny (potentially following a size-related pattern, as seen in other anhanguerids) and was possibly influenced by sexual dimorphism. The discovery of a crested Brasileodactylus araripensis challenges the assumption that crest absence can be used as a diagnostic feature, reinforcing the role of ontogeny and sexual selection in shaping pterosaur cranial morphology and underscoring the need for caution in taxonomy based primarily on crest variation.