El pasado viernes 10 de febrero, en el edificio de Biología de la Universidad Autónoma de Madrid, Elena Cuesta defendió su memoria de tesis titulada "Concavenator corcovatus (Theropoda, Dinosauria) from Las Hoyas fossil site (Early Cretaceous, Cuenca, Spain): Taphonomic, phylogenetic and morphofunctional analyses". El resultado, por supuesto, fue la obtención del título de Doctora en Biología, obteniendo además la máxima calificación, Sobresaliente cum laude.
La tesis ha sido dirigida por José Luis Sanz, de la Universidad Autónoma de Madrid (UAM), y por Francisco Ortega, de la Universidad Nacional de Educación a Distancia (UNED), y supone el broche de oro a 5 años de duro esfuerzo y trabajo por parte de la doctoranda (¡ahora ya Doctora!). Aquí tenéis el abstract de la tesis:
Theropods are a widely taxonomically, paleobiogeographically and morphologically diverse group that include the extant birds. The non-avian theropod record in the Iberian Peninsula is represented by Portuguese taxa and some fragmentary remains in Spain. However, the two taxa founded in Las Hoyas fossil site represent the most complete theropod inside the Iberian Peninsula and Europe.
Las Hoyas fossil site is a Konservat-Lagerstätte that is reconstructed as a subtropical wetland with a strong biannual seasonality. The fossils from Las Hoyas are characterized by their completeness, articulation and preservation of soft-tissues and colour patterns. Two non-avian theropods founded in this site, Pelecanimimus polyodon and Concavenator corcovatus, show these preservation features, which allow to perform an exhaustive paleoecological analysis.
Concavenator is the most complete dinosaur founded in the locality and, also, it represents the largest taxon preserved. Although its taphonomic features are coherent with the preservation framework of the Las Hoyas wetland, its terrestrial condition and size are infrequent in the fossil site, and thus, its presence raises issues about its processes of preservation. One of the aims of the current PhD thesis is reconstructing the taphonomic history that affect to Concavenator carcass. The methodology consists of several methods proposed in previous studies about the archosaurian preservation in Las Hoyas fossil site. The taphonomic analysis shows that Concavenator carcass suffered several processes as: early decay, dragging and slightly transport, rehydration and, finally, entombing into the microbial mats developed in Las Hoyas pools. These processes were consistent with the dynamic of the climate in Las Hoyas during the Lower Cretaceous. Therefore, the results not only clarify the processes produced on Concavenator, but it also sheds light on the understanding of mechanism acting in Konservat-Lagerstätten throughout the world.
The exquisite preservation of Concavenator allows to discern several anatomical features in the skeleton and soft-tissues impressions. In this PhD thesis, these soft-tissues impressions have been analysed and the results have determined a new conception of various anatomical structures, such as the avian podotheca. This podotheca is consisting of three types of scales, similar to those observed in the extant birds, plantar pads with an arthral disposition and corneous sheet around the ungual phalanges. Moreover, the completeness of the skeleton has allowed to carry out an exhaustive osteological description and phylogenetic analysis. Concavenator is a basal member of Carcharodontosauridae and has several synapomorphies within the clade as the lacrimal-postorbital contact or a peg-and-socket articulation between the ilium and ischium, among others. This phylogenetic position of Concavenator has the best obtained support value of branches until now.
Historically, carcharodontosaurids have been considered exclusively from Gondwana, however, recent discoveries show several taxa throughout Laurasia. The European position of Concavenator during the Early Cretaceous is key to understand the faunal interchanges between both continents.
Finally, two unusual and striking features are present in Concavenator, a series of bumps on the ulnar shaft and hypertrophied neurapophyses of the posterior dorsal and anterior caudal vertebrae. Both features have been analysed in the current thesis. The muscle reconstruction of the forearm suggests that the bumps are not related to myological origin. Regarding the axial skeleton, the unusual features of its vertebrae bestow stiffness during the locomotion and these features could be related to the presence of an axial structure in the pelvic area. These results propose new future research projects in order to determinate the functional morphology of both structures.
Por supuesto, al acto oficial de lectura y defensa de tesis siguió la tradicional celebración, jarana y algarabía, tan característicos de estos eventos. Solo nos queda añadir una vez más: ¡enhorabuena, Elena!
- Referencia: Cuesta Fidalgo, E. 2017. Concavenator corcovatus (Theropoda, Dinosauria) from Las Hoyas fossil site (Early Cretaceous, Cuenca, Spain): Taphonomic, phylogenetic and morphofunctional analyses. Tesis Doctoral. Universidad Autónoma de Madrid, Madrid.
- Imágenes: Arriba, Elena Cuesta al comienzo de la defensa de su tesis; en el medio, la doctoranda con sus dos directores (José Luis Sanz a la izquierda y Francisco Ortega a la derecha) y los miembros del tribunal (de izquierda a derecha: Oliver Rauhut, Jesús Marugán y Jorge Morales); abajo, la doctoranda junto a un nutrido grupo de paleontólogos de la UAM y la UNED.