La gran variabilidad de Megaloolithus siruguei y las preguntas que plantea en el XX Annual Meeting de la EAVP

El foco de la línea de investigación en biología reproductiva del equipo del Grupo de Biología Evolutiva de la UNED deja tranquilo (por ahora) al yacimiento de Poyos para centrarse en Megaloolithus siruguei, una de las ooespecies presentes en otros yacimientos de la Formación Villalba de la Sierra, como Portilla y Zafra de Záncara. El registro de esta ooespecie en la Formación muestra una elevada variabilidad en su grosor y morfología de sus nodos que excede tanto la variabilidad representada en otros yacimientos publicados como la esperable en los huevos producidos por un único taxón. Esto plantea una serie de preguntas que fueron presentadas en el 20th EAVP Meeting con el trabajo titulado “Unusual Megaloolithus siruguei eggshells from the Villalba de la Sierra Fm. (Upper Cretaceous, Cuenca, Spain)”, cuyo resumen podéis encontrar a continuación:

Megaloolithus siruguei is to date the single megaloolithid oospecies recognized at two Campanian–Maastrichtian sites of the Villalba de la Sierra Fm. (Central Iberian Ranges): Portilla and Zafra de Záncara. This oospecies has also been reported at similarly aged sites in Southern France and the Tremp Fm. (Southern Pyrenees), and as M. aff. siruguei at the coeval Sierra Perenchiza Fm. (Southeastern Iberian Ranges). Interestingly, specimens from Villalba de la Sierra Fm show an uncommon combination of eggshell thickness and node shape that may represent extreme cases among this oospecies variability. The morphometric data obtained from measuring published thin sections from France, Southern Pyrenees, and Southeastern Iberian Ranges suggest that, overall, the eggshell units from specimens of the same site or formation show a similar range of spherolith width and height (and therefore eggshell thickness). Additionally, although its nodes can be bell-shaped, wave-shaped or dome-shaped, the latter morphology is seemingly the most common. The Portilla specimens, however, show a range of thickness variation comparable to all the considered French sites altogether, and the thickness of the Zafra de Záncara specimens is below the reported thickness range of the oospecies. The dome-shaped nodes are notably less frequent in the Villalba de la Sierra Fm. specimens, and bell-shaped nodes are the dominant morphology in Zafra de Záncara. The morphological data obtained from the specimens of this Formation may contribute to the understanding of the variability of this widespread European ootaxon and its relationship with biotic and abiotic factors.

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Más información:

• Referencia: Sanguino, F., de Celis, A., Pérez-García, A., Ortega, F. 2023. Unusual Megaloolithus siruguei eggshells from the Villalba de la Sierra Fm. (Upper Cretaceous, Cuenca, Spain). In: Alba, D.M., Marigó, J., Nacarino-Meneses, C., Villa, A. (Eds.), Book of Abstracts of the 20th Annual Conference of the European Association of Vertebrate Palaeontologists, 26th June– 1st July 2023. Palaeovertebrata, Special Volume 1-2023: 22. DOI: 10.18563/pv.eavp2023 (p. 236).