Desde las primeras fases de excavación de Lo Hueco (Cretácico Superior de Fuentes, Cuenca), se ha considerado que su fauna contiene (al menos) dos tipos de saurópodos titanosaurios diferentes... esto es (al menos): dos tipos de dientes, dos tipos huesos apendiculares y dos morfotipos craneales. El primero de estos tipos cráneales fue identificado como una forma cercana al titanosaurio francés Ampelosaurus y, de hecho, como ya comentamos aquí, determinado como Ampelosaurus sp.
Llega ahora el turno de aproximarse al segundo morfotipo de titanosaurio del yacimiento. Se ha preentado en el 73rd annual Meeting of the Society of Vertebrate Paleontology, celebrado a principios de Noviembre en Los Angeles (California. Estados Unidos), el análisis de la caja cráneana de uno de los individuos recogidos en Lo Hueco. Los resultados consideran preliminarmente que presenta semejanzas con uno de los titanosaurus del tipo Jainosaurus del Maastrichtiense de la India. Habrá que ajustar un poco más la determinación, pero poco a poco se va precisando la estructura de la fauna de Lo Hueco.
Ahí dejamos el resumen:
The Spanish Late Cretaceous (Campanian or Maastrichtian) site of “Lo Hueco” has yielded a wealth of sauropod bones. However, only two braincases are represented among these specimens. One presents certain similarities (but also differences) with the braincase of Ampelosaurus atacis from the Campanian of France. It has been recently described in detail as Ampelosaurus sp.
The new specimen enhances our knowledge of European titanosaur cranial anatomy, which remains poor despite recent improvements. It is short and deep in overall morphology. The frontal is rostrocaudally short. A ventrally curved process (? prefrontal) projects from its rostrolateral corner. The parietal is characterized by two crescentic crests on both sides of the median plan. The supraoccipital is a small, rounded bone. The caudal surface of the otoccipital is fairly flat. The paroccipital process is aliform and strongly arches ventrally. The basioccipital is a relatively high but short bone. In caudal view of the braincase, the parabasispenoid makes up the very ventral extremity of the basicranium, just beneath the basal tubera. Both basipterygoid processes are broken near their base. However, it can be inferred from what remains that they probably diverged from one another in a widening U-shaped fashion. The adductor chamber is partially filled with matrix on both sides, largely concealing the prootic. The chamber is very short rostrocaudally and the prootic is even shorter. As in other dinosaurs, a conspicuous trigeminal foramen pierces the lateral wall of the braincase. The laterosphenoid is characterized by a thin capitate process. The orbitosphenoid is carinate.
A flat occiput is a phylogenetically restricted character within titanosaurs. The same condition is found in both Ampelosaurus and Jainosaurus septentrionalis from the Maastrichtian of India. Nevertheless, the new specimen presents several features (such as a dorsoventrally elliptical foramen magnum) suggesting that it did not pertain to the same species as the other titanosaur braincase from “Lo Hueco”. It appears so close to the “Jainosaurus morph” braincase that a phylogenetic proximity with Jainosaurus is likely.
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