The fusioolithid dinosaur eggshells from Poyos (Campanian–Maastrichtian, Guadalajara, Spain) and its implications for the interpretation of the variability of Fusioolithus baghensis

Resumen

A considerable portion of the fusioolithid oological remains from the Poyos site (Villalba de la Sierra Fm., central Spain) show the diagnostic features of Fusioolithus baghensis. However, the thickness of most Poyos eggshells is at the lower end or even below the diagnosed thickness range of F.baghensis, with a portion of them showing an increased presence of anastomosed structures and larger internodal spaces than most specimens from other sites. Though eggshell thickness is a highly variable feature and many known eggshells of the Villalba de la Sierra Fm. (both Megaloolithidae and Fusioolithidae) share this low thickness (compared to specimens from coeval formations), comparing its spherolith dimensions with published F.baghensis thin sections reveals signicant statistical dierences between the latter and both subsets from Poyos. Therefore, if all these Poyos eggshells belong to F.baghensis, this ootaxon exhibits higher variability than previously recognized. The signicance of these dierences in a widespread genus such as F.baghensis (including the specimens from Poyos) could possibly be related to biotic conditions (i.e.having dierent productors), abiotic conditions, (i.e. denoting dierent environmental conditions) and/or methodological biases (i.e. ambiguous diagnosis producing a wastebasket ootaxon eect); and should therefore be carefully assessed in the future.