Researchers from the University of New Mexico found that not all dinosaurs were warm-blooded - a handful of the species' bodies were somewhere between warm and cold.

Reptiles such as lizards and snakes are cold-blooded animals allowing their body temperature to change according to their environment. Mammals and birds, on the other hand, are warm-blooded animals allowing their bodies to regulate its own temperature despite of changes in the environment. For years, scientists believed that dinosaurs were cold-blooded animals just like modern day reptiles.

But this theory was challenged by new findings proving that dinosaurs were neither cold-blooded nor warm-blooded.

"Dinosaurs do not fit comfortably into either the cold-blooded or warm-blooded camp - they genuinely explored a middle way," said John Grady, lead author of the study and a theoretical ecologist from the University of New Mexico, told LiveScience.

Grady and his team looked at the growth rings of fossilized bones of different animal species to gather data on their metabolism. The team studied bones of both living and extinct species that included both warm-blooded and cold-blooded animals. They found out that in general, cold-blooded animals tend to metabolize 10 times faster than warm-blooded animals. However, warm-blooded animals could grow up to 10 times faster than cold-blooded animals.

An analysis of fossilized dinosaur bones revealed that they were neither warm-blooded nor cold-blooded. The researchers found out that the dinosaurs were capable of mesothermy, a rare ability that allowed them to grow and reproduce faster than reptiles, making them a strong predator. At the same time, mesothermy allowed dinosaurs to survive for extended periods of time even if when food source is scarce.

"For instance, it is doubtful that a lion the size of T. rex would be able to eat enough wildebeests or elephants without starving to death," Grady told LiveScience. "With their lower food demands, however, a real T. rex was able to get by just fine."

Further details of the study were published in the June 13 issue of Science.