A study published in the journal Science reveals that many dinosaur fathers spent quality time baby-sitting the kids. This means that we need to give dinosaurs an extreme make-over from thinking of them as coldblooded, pea-brain tyrants to warmblooded, empathetic partners.

Statistical comparisons with birds and analysis of leg bones found on top of nests containing unhatched eggs, have led a team of paleontologists to conclude, at least three distinct types of dinosaur males did the brooding and incubating. The scientists examining fossilized leg bones of troodon and citipati adults found on top of nests, (in one case still in the brooding position) found, the bones had features characteristic of male, not female animals. From the above lines of evidence, researchers deduce the females built the clutch over days or possibly weeks, while the males guarded the eggs and, subsequently, incubated them.

This helps to shed light on the origins of parental care systems in birds, wherein males protect or support offspring in more than 90% of bird species, it is a distinctly rare attribute to be found in the animal world. As for mammals, only 5% males of species, provide parental care, getting even rarer in reptiles.

Researchers led by David J. Varricchio of Montana State, conducted an examination of three genuses of meat-eating dinosaurs i. e. troodon, oviraptor and citipati, all of which they found to have distinctly birdlike reproductive habits. Not only did they lay their eggs sequentially over time, instead on in large batches like the turtles, their eggs were asymmetrical rather than round in shape, with multi-layered shells like bird eggs. As well, the three dinosaur types also produced large clutches of eggs, up to as many as 30 in a nest.

Comparing the mass of the adult dinosaur bodies and the mass of the eggs in a clutch to more than 400-modern bird species, including numerous species of alligators and crocodiles that are the birds' closest living relatives, it was found that dinosaur ratios most closely matched a group of primitive birds like ostriches, rheas and emus, who all have a 'paternal model' for caring for the eggs and the hatchlings. The ratios were least similar to songbirds, in which both parents tend to the offspring.

While, the evolutionary advantage of stay-at-home fathers is not known, Montana State University paleontologist Frankie Jackson, one of the researchers has a theory, about how females needed to consume large amounts of food, especially calcium rich food, so that they could produce the large number of eggs seen in the oviraptor and troodon nests. This meant a lot of long-distance foraging and long periods of time away from home, leading to the males tending the eggs, so that the female dinosaurs were free to look after her own nutrition and possibly to mate with other males.

An intriguing hypothesis, it still needs to be substantiated with more evidence to support it.