Titanosaur eggshells from the latest Cretaceous of Patagonia, Argentina: implications for nesting at high latitude

Dinosaur egg remains are rarely found in areas of high palaeolatitudes, with Canada (approx. 57-60° N) and Siberia (approx. 70-75° N) yielding the most polarward occurrences. Here, we describe dinosaur eggshells from the Upper Cretaceous (Maastrichtian) Chorrillo Formation of southernmost Patagonia (Argentina), an area located at approximately 55-60° S palaeolatitude during that time interval. The more than 250 eggshell fragments collected are assignable to Fusioolithus oosp., an ootaxon known from Late Cretaceous Gondwana regions that probably belongs to titanosaur dinosaurs. The eggshells are shown to have a high porosity like those of titanosaur eggs studied previously, indicating the eggs were fully covered by nest substrate during incubation. The high latitude of the area in the Maastrichtian suggests the eggs were buried in a mound-style nest where microbial decay, rather than solar radiation, was the primary source of incubation heat. The Chorrillo Formation represents, to our knowledge, the highest palaeolatitude area to produce definitive dinosaur egg remains from the Southern Hemisphere and reveals that titanosaurs were nesting at higher latitudes than previously known.