Dinosaurs were neither cold-blooded nor warm-blooded but somewhere in between. This is not that far-off a concept.
The latest research proves that during the period in prehistoric times when dinosaurs ruled the earth, the blood temperature they exhibited was a rare occurrence. At first, dinosaurs are classified as reptiles. And scientists thought for many years that dinosaurs were cold-blooded,
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But a dinosaur was neither warm-blooded like mammals and birds and nor was it cold-blooded like the reptiles you find basking in the sun today. The 135 million years they spent on the surface of the planet before they went extinct was an anomaly.
To resolve the years-old mystery of dinosaurs blood temperature, researchers used a new way to judge their metabolism. They found "dinosaurs do not fit comfortably into either the cold-blooded or warm-blooded camp — they genuinely explored a middle way," said lead study author John Grady, a theoretical ecologist at the University of New Mexico.
It is a known fact that today you either have warm-blooded creatures like men and ostriches which keep their body temperature normal by internal control. And then you have reptiles which take on the heat or cold levels of the surrounding atmosphere.
But the dinosaurs were giant saurian lizards that had a unique blood profile never seen in any other creature. Some scientists have said that they were in fact not reptiles but giant birds.
And conversely it is a truism that birds are the vestigial creatures leftover from the age of the dinosaurs. Somehow, it is a tough job to classify the dinosaurs in either one of the two pigeonholes of warm-blooded or cold-blooded.
They have a characteristic quality of their own which is hard to define. You just cannot pin them down as one or the other. The rate of bone growth that has occurred in extinct species is a proof of their blood profiles.
This method used by scientists resembles looking at the rings of a tree which tells us the age of the tree. The metabolic rates of the prehistoric creatures may be calculated from their fossils this way.
Warm-blooded creatures not only grow faster than cold-blooded ones, they metabolize food faster too. Dinosaurs however lie somewhere in between the extremes of mammals and reptiles. Very few animals resemble the profile of the dinosaurs today.
"For instance, tuna body temperature declines when they dive into deep, colder waters, but it always stays above the surrounding water. For instance, leatherback sea turtles are mesotherms, but smaller green sea turtles are not. Mako sharks are mesotherms, but whale sharks are regular ectotherms," Grady told Live Science.
"Gigantotherms like crocodiles rely on basking to heat up, so they are not mesotherms," Grady said. "Gigantotherms are slower to heat up and cool down, but if they rely on external heat sources like the sun, then they are not mesotherms. In general, mesotherms produce more heat than gigantotherms and have different mechanisms for conserving it."
The Great White Shark, Tuna and Leatherback Sea Turtle not to mention the Echidna are the only extant species that exhibit such a strange phenomenon. They are a reminder that once upon a time, not too long ago in the past, things were not as they are today.