Studies of fossil nests and nesting sites provide information on the reproductive biology of the egg-laying taxon that, otherwise, could not be evaluated by the study of skeletal remains. However, only dinosaur and turtle nests and nesting sites have been described to date. Here we report a hitherto unknown crocodylomorph nesting site in the Upper Cretaceous Adamantina Formation at Jales, Southeastern Brazil. At least twenty egg clutches were found in four distinct stratigraphic layers within an area of ≈0.15 km2. Morphological analyses of the eggs and eggshells showed that all eggs can be assigned to the same egg type. Most of the egg clutches were collected from the same layer, whereas few were collected from three other layers, respectively 1.09 m under and 0.71 and 0.99 m above the main egg layer. The minimum distance among egg clutches in the same layer is 1.8 m. The terrestrial mesoeucrocodylian Baurusuchus was the only vertebrate recovered from the outcrop, with three partially articulated specimens and several scattered remains found in close association with the egg clutches. The maximum number of preserved eggs per clutch is five, and all have been found with the main axis parallel to the ground. Eggshell fragments are frequent inside the nests, randomly distributed within the egg clutches (concave up and concave down percentages of 59% and 41%, respectively). Within the most complete eggs several stacked eggshell fragments where found. These are interpreted as hatched eggs in which the opening hole made by the hatchling also cracked the eggshell, producing additional eggshell fragments that fell within the egg as the shell membrane detached from the inner surface of the egg. These data suggest that: a) most of the egg clutches were preserved in situ, without any transport; b) this crocodylomorph species nested in colonies, returning to the same nesting site periodically, and; c) nest fidelity in crocodylomorphs may have been present as far back as the Late Cretaceous.
|Translated title of the contribution||A crocodylomorph nesting site from the Upper Cretaceous Adamantina Formation of Brazil|
|Title of host publication||Society of Vertebrate Paleontology 69th Annual Meeting, Bristol|
|Number of pages||1|
|Publication status||Published - 2009|
Bibliographical noteConference Proceedings/Title of Journal: Journal of Vertebrate Paleontology v29(3)
Conference Organiser: Society of Vertebrate Paleontology / University of Bristol