Not hot- nor cold-blooded, dinosaurs were 'in between'

Were dinosaurs hot-blooded like birds and mammals or cold blooded like reptiles? Well, they were somewhere "in between".

Scientists evaluated the metabolism of numerous dinosaurs using a formula based on their body mass.

"We found that dinosaurs had growth and metabolic rates that were actually not characteristic of warm-blooded or even cold-blooded organisms," said evolutionary biologist Brian Enquist from University of Arizona.

"Instead, they had growth rates and metabolisms intermediate to warm-blooded and cold-blooded organisms of today," he added.

The researchers called creatures with this medium-powered metabolism "mesotherms".

The study assessed 21 species of dinosaurs as well as a range of mammals, birds, bony fish, sharks, lizards, snakes and crocodiles.

"In short, they had physiologies that are not common in today's world," said Enquist.

Modern animals such as this leatherback turtle have a similar "in between" metabolism.

The study was published in the journal Science.