HECHENLEITNER Esteban Martin
congresos y reuniones científicas
A new titanosaur nesting site from the Los Llanos Formation (Late Cretaceous, La Rioja, Argentina)
MARTÍN HECHENLEITNER; LUCAS FIORELLI; GERALD GRELLET-TINNER; GIORGIO BASILICI; LÉA LEUZINGER
Congreso; XXIX Jornadas Argentinas de Paleontología de Vertebrados; 2015
Ten years after the first report, knowledge on Cretaceous titanosaur dinosaurs from La Rioja (Argentina) has been significantly increased through the study of the Los Llanos Formation. The key findings include a nesting site at the Sanagasta valley and several skeletal remains at the Tama locality. Here we report the discovery of the first eggs and egg-clutches found at Tama, in the same stratigraphic context of the Los Llanos Fm. At least 3 egg-clutches (CRILAR-Pv 530/1-3), several partially-preserved isolated eggs, and eggshell fragments were recovered in a single outcrop, in a sandy level within a cumulative paleosol profile. Although embryonic remains were not yet discovered, the egg shape, the mono-layered eggshells with densely packed nodular structures on their outer surfaces and eggshell units formed by acicular calcitic crystals radiating from nucleation centers, are features that closely resemble those of titanosaur eggs found worldwide. Interestingly, although all these characters are shared by the Sanagasta and Tama eggshells, they clearly differ in thickness, the latter being substantially thinner. As such, the morphological and sedimentological data at hand suggest that two different titanosaur species nested in La Rioja during the Cretaceous, using different nesting strategies. Moreover, the occurrence of these in situ preserved egg-clutches represents a new fossil dinosaur nesting site, which adds to a series of paleontological discoveries, namely semi-articulated tetrapod and sauropod specimens, and a microfossils assemblage, that further strengthens previous interpretations of the Los Llanos Formation, in southern La Rioja, as Late Cretaceous.