It has long been unclear how oviraptorosaurs, flightless bird-like dinosaurs, incubated their eggs. A new study published in Frontiers in Ecology and Evolution sheds light on the phenomenon by examining the nesting behaviors and incubation patterns of oviraptorosaurs. Researchers in Taiwan reported that they combined heat transfer simulation and practical experiments to better understand how these dinosaurs incubated their eggs. They also compared their findings with the incubation of modern birds. To do this, they built a life-size model of an oviraptorosaur dinosaur and a real nest to test how heat transfers through the eggs. Dr. Tzu-Roy Yang, lead researcher and head of the vertebrate paleontology department at the National Museum of Natural Sciences in Taiwan, explained that the experiment revealed differences in the hatching patterns of oviraptorosaur eggs, noting that this difference was due to the relative position of the adult female brooding the eggs. The study's first author, Chun-Yu Su, added that, furthermore, the efficiency of oviraptorosaur egg incubation was estimated to be much lower than that of modern birds. The model was based on 'Huanansaurus huangi,' a type of oviraptorosaur that lived between 70 and 66 million years ago in what is now China. This dinosaur was about 1.5 meters long and weighed about 20 kilograms, building semi-open nests with eggs arranged in multiple rings. To reconstruct this creature, the researchers built the torso using polyurethane foam and a wooden frame, then added cotton, bubble wrap, and fabric to simulate soft tissues.
Arranging the eggs in a circle means the adult bird could not touch all the eggs at once. Therefore, it is likely that these dinosaurs and the environmental temperature worked together, making them shared incubators. Although this method was less efficient than that of modern birds, it may have suited their nesting style, which appears to have transitioned from buried nests to semi-open ones. In conclusion, modern birds are not better at incubating eggs. This suggests that in warm climates, sunlight may have helped to equalize temperatures and affect hatching patterns. Additionally, researchers compared oviraptorosaur incubation with modern bird incubation. Most birds rely on contact incubation, where the adult bird sits directly on the eggs and provides heat. For this method to be successful, the adult bird must touch all the eggs, be the primary heat source, and maintain a stable temperature. It is noted that oviraptorosaurs likely could not meet these conditions. In experiments, two groups of eggs were arranged in double rings to simulate fossil evidence. The research team also tested how the presence of adults and environmental conditions affected egg temperatures and hatching outcomes. In cold conditions, with a brooding adult present, temperatures varied in the outer ring of eggs by up to 6 degrees Celsius. These differences can also lead to asynchronous hatching, where eggs in the same nest hatch at different times. Modern birds and oviraptorosaurs follow a completely different method of incubation, or rather, parental care. In warm environments, this variation decreased to about 0.6 degrees Celsius. The eggs were made of epoxy resin.
