THE NESTING STRATEGIES OF THE TITANOSAUR DINOSAURS

HECHENLEITNER, ESTEBAN MARTÍN; GERALD GRELLET-TINNER; FIORELLI, LUCAS ERNESTO

Congreso; 4TH INTERNATIONAL PALAEONTOLOGICAL CONGRESS; 2014

Titanosauria is a clade of huge herbivorous dinosaurs whose representatives are known on all the continents, including Antarctica. Currently, the evidences suggest that this diverse group of sauropods seem to have used a variety of particular nesting sites worldwide. The overall rarity and nature of these nesting sites combined with their overwhelming abundance of egg clutches and eggs are enigmatic and have led to propose that sauropod dinosaurs were colonial nesters and migrated to the same selected locations (?nesting-site fidelity?) to lay their eggs. Historically the studies on nesting sites have focused on systematics, including diagnosis of eggs and eggshells fragments in a parataxonomic classification, an alternative that was held due to the fragmentary nature of their fossil record. Unfortunately, this trace fossil parataxonomy creates serious problems when trying to understand paleobiological aspects such as reproduction, as this classification scheme does not meet biological and evolutionary criteria. To date, no investigation delves on the ecological and geological bases for the selection of the nesting sites distributed worldwide. Our observations were performed on a series of well-known Cretaceous nesting sites in Argentina, South Korea, Romania, India, France and Spain. The simple reasoning, as well as preliminary observations, strongly suggest titanosaurs could not have used the classic ?sit-on-eggs? incubation strategy typical of most modern dinosaurs, thus must have relied on external environmental heat for incubating their egg clutches. Taking into account the clutch composition and geometry, the nature of the sediments and their properties, coupled with the eggshells structures and conductance, it would appear that they have adopted nesting behaviors comparable to those displayed by the modern megapodes. This family of birds shows a surprisingly wide and specific nesting strategies using burrow-nesting in diverse medium and mound building, which would possibly explain the lack description of true nesting traces, despite the overwhelming abundance of egg clutches in these nesting sites.