Re: What helped dinosaur eggs to hatch?

Greetings Australia!
I had to pick the brain of a Paleo-ecologist to answer your query:

That's a good question. Much of what we know about dinosaur nesting habits comes from evidence in Cretaceous rocks of Montana (approx 75 million years old). In Montana, fossil nests complete with dinosaur eggs and baby dinosaur bones (of the duckbilled dinosaur Maiasaura - "good mother lizard") have been found. Similar nests of the duckbilled dinosaur Hypacrosaurus have been found in southern Alberta.

Egg-hatching was one task that dinosaurs could not take lightly (excuse the expression). Try to imagine this. Eggs of the duckbilled dinosaurs in question were approximately the size of a large grapefruit, but the adults were approximately 7 metres long ! Obviously, the adult dinosaurs could not incubate their eggs by sitting on them because they would crush the eggs. So they had to come up with a different method of incubation.

In nests of Maiasaura, eggs are surrounded by mudstone containing a lot of plant material which had decomposed to some degree... and anyone with a composter at home can appreciate the fact that the decomposition of plant material generates heat. It is therefore thought that the eggs were incubated by heat generated by rotting remains of plant material brought to the nest by the parents. In other words, dinosaur nests (which measured up to 2 metres in diameter) would have looked like and worked like compost heaps ! Presumably, the parents would have cleared away this rotten stuff at hatching time.

It is emphasized that this method of incubation appears to have been used duckbilled dinosaurs, but may not have been used by other types of dinosaurs (we will have to find more nests in order to find this out).

Check out this book for the (possible) life story of a Maiasaura:

Title- Maia: A Dinosaur Grows up 
Authors- John ("Jack") P. Horner and J. Gorman
Publisher- Museum of the Rockies, Montana State University, Bozeman,
        Montana (1985).

Keep the questions coming !

-Dr. Cam Tsujita
The Department of Earth Sciences
University of Western Ontario