Estudio de la variabilidad morfológica en tortugas fósiles europeas: ¡La Tesis!

El pasado viernes 26 de enero de 2024, en la Facultad de Humanidades de la UNEd, tuvo lugar la defensa de tesis doctoral titulada "Study of the morphological variability in European fossil turtles" a cargo de Andrea Guerrero Bach-Esteve. El resultado fue la obtención del título de Doctora en Ciencias, obteniendo además la calificación de Sobresaliente...

Esta tesis ha sido dirigida por Adán  Pérez-García y Francisco Ortega, ambos de la Universidad Nacional de Educación a Distancia (UNED). A lo largo de su trabajo de doctorado, Andrea ha estudiado, gracias al análisis de una amplia muestra de caparazones de tortugas fósiles, la variabilidad morfológica presente en diferentes linajes de Testudinata: pleurostérnidos, dortókidos, botremídidos y podocnemídidos. Así, ha logrado caracterizar la variación intraespecífica (ontogenia, polimorfimos, dimorfismo sexual y anomalias) de varios taxones pertenecientes a estos linajes, ampliando considerablemente el conocimiento que se tenía hasta el momento en el grupo de las tortugas. El abstract de la tesis es el siguiente:

Turtles (i.e., the members of Testudinata) represent a very diverse lineage of reptiles characterized by a conservative Bauplan, in which the presence of a shell stands out. However, although it is present for the different taxa, this structure often displays significant intraspecific variability, considering both the bones and the scutes arrangement. Despite the shells are relatively well-preserved in the fossil record, only a few studies have detailed addressed the intraspecific variation. This scarcity is primarily attributed to the limited sample sizes for most species, but also to other aspects, such as the poor preservation of the remains attributed to many of them. Consequently, many studies on extinct turtles are focused on the systematic characterization, frequently based on one or only a few specimens, with scarce or no consideration relative to the intraspecific morphological diversity. In addition, the limited literature available about the Testudinata intraspecific variability mainly focuses on pan-cryptodiran representatives due to their greater abundance and diversity of this clade relative to Pan-Pleurodira. As a result, the frequent absence of consideration of this important factor in the representatives of the crown Pleurodira generally causes errors or considerably limits in knowledge about the anatomical and even systematic characterization.

In this context, the interspecific variability between some of the best-represented extinct pleurodiran taxa from Europe, and the intraspecific variability that affects each of them, and more precisely, to the Iberian Peninsula representatives, have been studied as part of this PhD Thesis. This research aims to improve our understanding of the different typologies of intraspecific variability (i.e., polymorphisms, ontogeny, sexual variation, and anomalies) in some members of the most relevant pan-pleurodiran groups. Specifically, the analyzes of the morphological variability performed here are primarily focused on the shell.

The present PhD Thesis Project is structured into three main parts: the first one encompasses the main introduction of the four primary lineages under examination; the second part is dedicated to the analysis of these groups (i.e., Pleurosternidae, Dortokidae, Bothremydidae, and Podocnemididae) and presents the key findings; and the third part corresponds to the discussion and conclusions of each of the four main groups analyzed.

Y como es costumbre al acabar este tipo de eventos, tras el acto oficial de lectura y defensa de la tesis tuvo lugar la típica celebración con la que compartimos la alegría de la nueva doctora. ¡Enhorabuena Andrea!

----- 

Más información:

• Referencia: Guerrero Bach-Estevez, A. 2024. Study of the morphological variability in European fossil turtles. Tesis Doctoral. UNED, Madrid.
• Imágenes: Arriba, Andrea durante la defensa de su tesis; abajo, la ya doctora junto a sus directores y los miembros de tribunal poco después de dar por concluido el acto.