Titanosaur eggshells from the Tremp Formation (Upper Cretaceous, Southern Pyrenees, Spain)

Abstract

Hundreds of megaloolithid eggshells have been found at the Costa de la Coma site (Tremp Fm, South-Central Pyrenees, Spain), the microstructural features (spherulitic eggshell units, thickness, ornamentation and pore system) of which agree with the Megaloolithus oogenus diagnosis. Comparisons with other megaloolithids from the Tremp Basin, southern France and South America, however, showed that these eggshells share many features with the South American oospecies Megaloolithus patagonicus. A cladistic analysis of the qualitative eggshell features of the main dinosaur taxa was performed. The results grouped the Costa de la Coma eggshells with Megaloolithus patagonicus, forming a clade separated from other megaloolithids, and revealed a polytomy of megaloolithids (associated with sauropods) and spheroolithids (associated with hadrosaurs). The finding of Megaloolithus cf. patagonicus in the Tremp Fm agrees with skeletal evidence provided by four indeterminate titanosaur forms from the Formation's late Cretaceous deposits. Other Megaloolithus oospecies of the Tremp Fm may belong to hadrosaurs, the skeletal remains of which are also abundant in the Tremp Basin.