A large accumulation of avian eggs from the Late Cretaceous of Patagonia (Argentina) reveals a novel nesting strategy in Mesozoic birds

MARIELA FERNÁNDEZ; RODOLFO GARCÍA; LUCAS ERNESTO FIORELLI; ALEJANDRO SCOLARO; RODRIGO SALVADOR; CARLOS N. COTARO; GARY W. KAISER; GARETH J. DYKE

PLOS ONE

PUBLIC LIBRARY SCIENCE

Lugar: San Francisco; Año: 2013 p. 1 - 22

1932-6203

We report the first evidence for a nesting colony of Mesozoic birds on Gondwana: A fossil accumulation in Late Cretaceous sediments mapped and collected from within the campus of the National University of Comahue, NeuquénCity, Patagonia (Argentina). Here, Cretaceous ornithothoracine birds, almost certainly Enanthiornithes, nested in an arid, shallow basinal environment among sand dunes close to an ephemeral water-course. We mapped 65 complete, near-complete, and broken eggs across an area of more than 55m2 that were laid either singly, or occasionally in pairs, onto a sandy substrate. All eggs were found apparently in, or close to, their original nest site; they all occur within the same bedding plane and almost certainly represent the product of a single nesting season. Although there is no evidence for nesting structures, all but one of the Comahue eggs were placed upright in the sand with their pointed end downwards, a position that would have exposed the pole containing the air cell and precluded egg turning. This egg position is not seen in living birds, with the exception of the basal galliform megapods who place their eggs within mounds of vegetation, and reveals a novel nesting behaviour in Mesozoic Aves.