Dinosaurs (Oviraptor, Troodon) Males Incubated Eggs

A research team from Montana State University and other institutions has announced that it is highly likely that males of the small theropod dinosaurs Oviraptor and Troodon from the Late Cretaceous (95 million to 65 million years ago) incubated the eggs.

To determine the sex, they examined traces of a tissue called "medullary bone." Female birds create medullary bone in their hind legs before laying eggs to store calcium for the eggshells. Traces of this have also been found in fossils of Tyrannosaurus and other dinosaurs.

When they examined the medullary bone of Oviraptor and Troodon fossils found in a brooding posture, they found no traces of it. This suggests that the individuals brooding the eggs were "individuals that had never laid eggs." It was found that they were not "mothers." According to the research team, they infer that it is highly likely that the "fathers," or males, were the ones incubating the eggs.