Variação ontogenética e dimorfismo sexual em pterossauros Pteranodontidae

• Autor(a) principal: Brandão, Renan dos Santos
• Data de Publicação: 2018
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: Repositório Institucional da Universidade Federal do Espírito Santo (riUfes)
• Texto Completo: http://repositorio.ufes.br/handle/10/10681
• topic: Ontogeny; Morphometry; Sexual Dimorphism; Zoologia; Pterossauro; Ontogenia; Dimorfismo sexual; Morfometria; 57

Pteranodon is a genus of pterosaurs exclusive to North America, whose main features are the absence of teeth and the presence of a frontal crest. Although well known, with over a thousand fossil fragments already discovered, its taxonomy at the family level is still controversial. Bennett (1994) in his review of the family accepted only two species as valid: Pteranodon longiceps and P. sternbergi. Recently, Kellner (2010) reviewed the group and recognized four species, erecting two new ones: Dawndraco kanzai and Geosternbergia maiseyi. Aiming to revise the taxonomy of this family, this work proposed a) to recognize the diagnostic characters of the different species and genera of Pteranodontidae; b) perform a two-dimensional geometric morphometrics analysis, allowing to infer which are the intra- and interspecific morphological variations responsible for the differences in size and shape of the skulls; and c) to compare the results of the morphometric analyzes with pterodactyloid pterosaurs whose sexual dimorphism is evident, testing if it occurs in Pteranodon. 20 specimens of pteranodontids composed of cranial material were analyzed, and as most of them are incomplete, reconstruction of the skulls in lateral view were made, especially the rostrum, frontal crest and cranial openings. 51 homologous landmarks were designated for all skulls using the TPSDig2 software. Three rounds of morphometric tests were made: 1. using all landmarks; 2. without using the landmarks of the frontal crest and 3. excluding the landmarks of the curvature of the rostrum (keeping its length). With assistance of the MorphoJ program, the Procrustes Fit, the Principal Component Analyses and Canonical Variates Analyses were performed. The arrangement of UALVP 24238 and KUVP 967 in the morphospace in at least one Principal Component for each of the three tests allowed us to conclude that both are considered as a distinct species, Dawndraco kanzai, proposed by Kellner (2010). Linear regression analysis tested the allometric growth in these pterosaurs, and in all tests allometry was positive (p <0.05). It is remarkable the division of the skulls by size and shape, with the largest skulls bearing the largest crests, which are distinct in shape between them. Therefore the taxonomic revision indicated three valid species in two genera: Pteranodon longiceps, Pteranodon sternbergi and Dawndraco kanzai. As with pterodactyloid pterosaurs such as Caiuajara dobruskii and Hamipterus tianshanensis, in which the largest individuals with the largest cranial crests are considered males, we infer the same pattern for Pteranodon, under the influence of sexual selection. Therefore, we considered as adult males specimens DMNH 1732, FHSM 339, YPM 2473 and YPM 2594, besides AMNH 5099 as a young male. Regarding D. kanzai, the position of the holotype (UALVP 24238) on regression graphics provides evidence of possibly being a adult male, as proposed by Kellner (2017). Based on the sexual dimorphism present in Pteranodon, the referred specimen to D. kanzai (KUVP 967) would correspond to a young male