NAGOYA--Scientists have worked out the incubation style of dinosaur species by examining the type of sediment their fossilized eggs were found in.

Some are believed to have brooded their eggs, like present-day birds, while others apparently drew on solar, geothermal or fermentation heat to warm their eggs left in sandstone or mudstone.

The researchers from Nagoya University, Hokkaido University and other institutions also studied the distribution of locations where the fossilized eggs have been found.

“In addition to motor capabilities and metabolic capacity, incubating habits may also have been a key factor that affected the dinosaurs’ habitat distribution,” said Kohei Tanaka, a superlative postdoctoral fellow with Nagoya University Museum.

The scientists analyzed the sediment data from about 160 million to 66 million years ago, partly by studying available literature on the topic.

Fossilized eggs of sauropodomorphs, a group of long-necked dinosaurs that included the brachiosaur and measured up to more than 30 meters in length, have been found in sandstone.

That suggests they used to lay eggs in sand and relied on solar or geothermal heat, the researchers said.

Fossilized eggs of hadrosaurs, which looked like platypuses, have been found in mudstone, which is made of solidified soil containing fragments of microorganisms and plants.

They likely relied on heat from the fermentation of plant bodies, the researchers said.

In the meantime, eggs of oviraptorosaurs and troodontids, which resembled ostriches, have been found in equal proportions in mudstone and sandstone.

Their eggs are presumed to have been brooded by parents, regardless of the environment.

Eggs of dinosaur species that relied on solar or geothermal heat have been found only in mid-latitudes between 20 and 50 degrees north.

But fossilized eggs of dinosaur species that either relied on fermentation heat or brooded their eggs have been also found in the Arctic region, such as Siberia.

The research results have been published in Scientific Reports, a British science journal.