A NEW UPPER CRETACEOUS TITANOSAUR NESTING SITE FROM LA RIOJA (NW ARGENTINA), WITH IMPLICATIONS FOR TITANOSAUR NESTING STRATEGIES

CARLOS BUSTAMANTE

JOURNAL OF VERTEBRATE PALEONTOLOGY

SOC VERTEBRATE PALEONTOLOGY

Lugar: Lawrence; Año: 2016

0272-4634

Abstract: Cretaceous titanosaur nesting sites are currentlyknown only from Europe, Asia and South America. In thelatter, only the Auca Mahuevo and Sanagasta nesting siteshave been confidently assigned to this clade of sauropoddinosaurs. Here we report the discovery of the first eggs andegg clutches found at Tama, a new Upper Cretaceous fossiliferouslocality in the Los Llanos Formation, Sierra de Los Llanos(La Rioja, NW Argentina). At least five egg clutches,several partially preserved, isolated eggs and many eggshellfragments were discovered in a single outcrop of a sandstonehorizon which represents a cumulative palaeosol profile.Although the mechanical and digital preparation of eggs didnot reveal any embryonic remains in ovo, the morphology ofthe eggs and eggshells closely matches that of titanosaur eggsand eggshells found worldwide. The morphology and spatialgrouping of the titanosaur eggs from Tama, along withgeological observations support a burrow-nesting strategy forthese dinosaurs. Although the Sanagasta and Tama eggs werefound in the same stratigraphical unit and share severalmorphological characters, they clearly differ in shell thicknessand egg size. This, coupled with the interpretation ofdifferent sedimentary contexts for these nesting sites, stronglysuggests that at least two different titanosaur species nestedin La Rioja during the Late Cretaceous, using different nestingstrategies. The occurrence of this new titanosaur nestingsite in a semiarid palaeoenvironment represents aninteresting case study for the reproductive biology of thetitanosaur dinosaurs, particularly their labile nestingbehaviour.Key words: Tama, dinosaur eggs, burrow-nesting, nestingbehaviour.