Name: Renan dos Santos Brandão
Type: MSc dissertation
Publication date: 31/07/2018
Advisor:
Name |
Role |
|---|---|
| Taissa Rodrigues Marques da Silva | Advisor * |
Examining board:
| Name |
Role |
|---|---|
| Bruno Cavalcanti Vila Nova de Albuquerque | External Alternate * |
| Elisandra de Almeida Chiquito | Internal Examiner * |
| Felipe Lima Pinheiro | External Examiner * |
| Taissa Rodrigues Marques da Silva | Advisor * |
| Yuri Luiz Reis Leite | Internal Alternate * |
Summary: ABSTRACT
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 and Principal Component
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.
KEYWORDS: Pterosauria, Ontogeny, Morphometry, Sexual Dimorphism
