Dinosaurs are still an enigma. Recent discoveries have revealed how they hatched eggs and take care of their children.
The magazine Journal of Vertebrate Paleontology has just published a study by the University of Zaragoza (Spain), where scientists explain how dinosaurs hatched eggs. The study has been leaded by Miguel Moreno Azanza, member of the group Aragosaurus-IUCA. They have also collaborated with the University of Liverpool.
The study has been realized with eggs of two very different specimens: a shell of Prismatoolithidae, a family related to Theropods, and a fragment of Hadrosaur eggshell (Maiasaur).
Different analyses (guidelines contrasts and electron backscattered diffraction) have allowed to know that Theropods (small, carnivores and with an average weight of 50-60 kilos) formed eggshells without using any organic control, similar to the formation of calcite in a stalactite, creating very stiff eggs, as eggs hen and allowing adults to sit on the egg. Of course, this demanded strong offspring that could break the shell.
However, the huge Hadrosaur (about 5 tonnes) never sat on the egg and they have immature offspring. Thus, the Maiasaur (means good mother) had to feed its children and to take care of them for a while. According to Moreno Azanza, dinosaurs could have a very social behavior.
The time spent by a dinosaur inside the egg before hatching is not known at the moment. Incubation in birds is a very variable period, which lasts 11 days in some small birds and about 85 days in the great albatross.
A small Maiasaur was born with a length of about 15 cm, but dinosaurs grew very fast and probably in the first year quadrupled its size. The adult size (ten years old) would be about 10 meters.
Theropods offspring would measure about 20 cm and adults 3 metres. They would reach maturity in just three or four years.
Dinosaur, a fascinating world!