A gravid marine fossil turtle from the Early Cretaceous reveals a different egg development strategy to that of extant marine turtles

Extant sea turtles develop and lay pliable (flexible)eggs; however, it is unknown whether they inherited thisreproductive strategy from their closer fossil relatives or if itrepresents an evolutionary novelty. Here, we describe the firstundisputable gravid marine fossil turtle ever found, from theearly Cretaceous of Colombia, belonging to Desmatochelyspadillai Cadena & Parham, which constitutes a representativeof the Protostegidae. Using thin sectioning of one of the eggs, aswell as scanning electron microscopy coupled with elementalcharacterization, cathodoluminescence, and computer tomography,we established that Desmatochelys padillai produced rigideggs similar to those associated with some extant and fossilfreshwater and terrestrial turtles. At least 48 spherical eggs werepreserved inside this gravid turtle. We suggest that the developmentof rigid eggs in the extinct marine turtle Desmatochelyspadillai resulted as an adaptation for egg-embryo requirementsdictated by the physical attributes of the nesting site.