Variabilidad en los saurópodos de Lo Hueco: ¡La Tesis!

El pasado viernes 24 de enero, en el Salón de Grados del Edificio de Biología de la Universidad Autónoma de Madrid, Adrián Páramo defendió su memoria de tesis titulada "Análisis de la evolución neurocraneal en la radiación temprana de Eusuchia". El resultado, por supuesto, fue la obtención del título de Doctor en Ciencias, obteniendo además la calificación, Sobresaliente...

La tesis ha sido dirigida por José Luis Sanz de la Universidad Autónoma de Madrid (UAM) y Académico Numerario de la Real Academia de las Ciencias Exactas, Físicas y Naturales (RAC), y por Francisco Ortega, de la Universidad Nacional de Educación a Distancia (UNED). La finalización de este proceso de doctoramiento de Adrián supone el reconocimiento al duro esfuerzo y trabajo llevado a cabo en los últimos años en su labor de resolver el rompecabezas de elementos apendiculares de saurópodos titanosaurios que se conocen del yacimiento paleontológico de Lo Hueco. Aquí tenéis el abstract de la tesis:

In the current dissertation a revision of new data of the appendicular skeleton of the Campanian-Maastrichtian fossil site of Lo Hueco (Cuenca, Spain) is presented. This fossil site have yielded an abundant sample of specimens referable to titanosaur sauropods, with several individuals partially articulated and tens of isolated specimens. There has been identified a high morphological variability in each appendicular element and the presence of several small-sized specimens in this sample.

Until now, a single titanosaur exclusive form have been described, Lohuecotitan pandafilandi. However, the study of abundant isolated specimens from the fossil site have allowed to identify two main teeth morphotypes, two types of braincase, three morphotypes in the axial skeleton of the dorsal region, and four morphotypes among the caudal vertebrae.

The current study explores the high variability found in the sample of appendicular elements. For this matter, a series of analytical techniques related with modern machine learning and 3D geometric morphometrics are used with the objective of identifying the probable morphotypes that help explain the morphological variance. A 3D digitizing workflow of the specimens of study is herein proposed, with a new proposal for virtual restoration of fragmentary elements and its incorporation to statistical analyses. Using these techniques it has been identified two main appendicular morphotypes. Based on this morphotypes, the intraspecific variability has been quantified in each of them, the ontogenetic sequences have been identified and the variability related to transformations during titanosaur ontogenetic development.

Previous studies indicates that two titanosaur morphotype from Lo Hueco could have been pertain to two different guilds with two different types of feeding niche exploitation. In the current study, the implications of several morphological differences between both main morphotypes are discussed under the hypothesis of differences in the ecomorphological specialization. A statistical proxy model was created to test the relationships between main appendicular morphology with ecomorphological specialization related with the height of the feeding envelope among neosauropods. The results allow relating the two main morphotypes with two different feeding niche exploitation strategies congruent with previous analyses in the cranial material.

The observed intraspecific variability in each morphotype allows determining its impact on morphological character scoring. In the current dissertation it has been identified the presence of several ontogenetic sequences in each morphotype. The ontogenetic sequences have been comprehensively described for first time in this group, as well as the ontogenetic stage and relative time estimation of the morphological character changes with implications for character scorings.

Como es tradición en estos eventos de enorme felicidad y algarabía, al final del acto oficial de lectura y defensa de la tesis no pudo faltar la ya típica celebración. Sólo una cosa más: ¡enhorabuena Adrián!

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Más información:

• Referencia: Páramo Blázquez, A. 2019. The Appendicular Skeleton Variability of the Sauropoda Titanosauria from the Upper Cretaceous of Lo Hueco (Cuenca, Spain). Tesis Doctoral. UAM, Madrid.
• Imágenes: Arriba, Adrián Páramo al comienzo de la defensa de su tesis; abajo, el ya doctor junto a sus directores y a los miembros de tribunal instantes después de dar por concluido el acto.