The Las Águilas site near Porvenir de Jalpa, Coahuila, Mexico, is extremely rich in tetrapod remains comprising both bones and trackways of several dinosaur taxa of late Campanian age. Within a 50 m thick section we identified at least nine layers with dinosaur bone assemblages. In one of these the dinosaur bones are associated with remnants of eusuchian crocodilians, turtles, plesiosaurs, pterosaurs, tyrannosaurids, dromaeosaurids, parksosaurid, hadrosaurids, ceratopsids, and ankylosaurs. This layer is also rich in coprolites of turtles, crocodilians and likely theropods, thus providing evidence for the wealth of Late Cretaceous vertebrate life in the area. 

Le premier Symposium International sur les ceufs de dinosaures et leurs petits a connu un francs succès, à Isona, en Catalogne (Espagne) en 1999. I1 faisait suite à la publication en 1994 d'un premier ouvrage "Dinosaurs eggs and babies" édité par K. Carpenter, K. Hirsch et J. Homer. Entre 1994 et 1999, les nouvelles découvertes ont augmenté significativement, notamment celles d'ceufs embryonnés, et le nombre de chercheurs impliqués dans ce domaine a accompagné cet accroissement. Jusque là, l'étude de ces objets, les coquilles d'ceufs, est restée longtemps marginale, faute d'une méthodologie scientifique appropriée. 

The reproductive biology of living birds differs dramatically from that of other extant vertebrates. Distinctive features common to most birds include a single ovary and oviduct, production of one egg at daily or greater intervals, incubation by brooding and extensive parental care. The prevalence of male parental care is most exceptional among living amniotes. A variety of hypotheses exist to explain the origin of avian reproduction. Central to these models are proposed transitions from a condition of no care to maternal, paternal or biparental care systems. These evolutionary models incorporate a number of features potentially preservable or inferable from the fossil record (integument, skeletal adaptations for flight, egg and clutch size, nest form, hatchling developmental stage, the number and function of oviducts, and the mode of egg incubation). Increasing availability of data on dinosaur reproduction provides a means of assessing these hypotheses with fossil evidence. We compare dinosaur data to a selection of models that emphasize maternal, paternal or biparental care. Despite some congruence with dinosaur features, no single model on the evolution of avian reproduction conforms fully to the fossil record, and the ancestral parental care system of birds remains ambiguous. Further investigation into dinosaur parental care, nest structures, clutch geometry, egg-pairing, eggshell porosity, and embryo identification may eventually resolve these issues.