9.9.15

Diferenciación entre morfotipos apendiculares de titanosaurios de Lo Hueco en el 63rd SVPCA



Entre los pósters presentados por el Grupo de Biología Evolutiva (GBE) en el 63rd Symposium for Vertebrate Paleontology (SVPCA) en Southampton esta semana pasada, se presentó uno sobre la variabilidad en el esqueleto apendicular de titanosaurios de Lo Hueco.

En el yacimiento se han encontrado docenas de huesos apendiculares de difícil atribución. Presentan una elevada variabilidad tanto en caracteres discretos como tamaño. Muchos de los fémures y humeros por ejemplo les faltan parte de los términos proximales y distales. Además se encuentran desarticulados. Para resolver esta serie de problemas que dificultan estudiar su afinidad, se propone un set de landmarks en una muestra de humeros y fémures.

Gracias al uso de técnicas de morfometría geometría se puede comprobar que existen diferencias entre dos morfotipos, así como confirmar observaciones realizadas sobre el material incompleto de diversos ejemplares.

Sigan atentos a más de los póster del GBE en el SVPCA meeting de Southampton.

Resúmen:

The Upper Cretaceous fossil site of Lo Hueco (Cuenca, Spain) has yielded several remains attributable to titanosaur sauropods. Among them, a high abundance and morphological disparity of appendicular bones is recognized. Most of this appendicular material is partially or totally disarticulated. In addition, several specimens lack the proximal or distal ends. These features make difficult its association with other bones corresponding to the same titanosaur individuals, and also its taxonomic assessment. The study of a sample composed by several femora and humeri from Lo Hueco, attributable to titanosaur sauropods, is done through 3D geometric morphometric techniques. It allows identifying two main morphotypes of each category of bone. These results are consistent with previous studies on cranial elements, and in a much more reduced set of femora. Principal Components also supports the differences observed in several characters between both morphotypes.
A robust and anteroposteriorly compressed morphotype of femora is recognized. The other one is a more slender type, with a high eccentric diaphysis. Concerning the humeri, a more robust and a slender and elongated morphotypes are identified. The generation of mean shape 3D models from the sample, related to each of the Principal component analysis (PCA), allows to visualize some morphological differences comparing incomplete specimens, related to the two morphotypes. For example, a difference is the presence of a more quadrangular humeral head, with a high deltopectoral crest, in the robust morphotype; but a more rounded humeral head, with a deep-ventrally directed stepwise deltopectoral crest, in the slender morphotype.