Dinosaurs May Have Been Warm-Blooded After All

dinosaur femur

Is the debate over dinosaur “blood” finally over?

Generations of scientists previously believed — and generations of schoolchildren were taught — that dinosaurs were cold-blooded, like fish, amphibians, and reptiles. Then some scientists began to argue that dinosaurs were warm-blooded, like birds and mammals. Meanwhile, other researchers hypothesized that dinos were “mesotherms,” not quite hot-blooded and not quite cold-blooded either.

But now a new paper — essentially a reanalysis of a 2014 study putting forth the mesothermy theory — argues that dinosaurs’ metabolisms and growth rates were strikingly similar to those of modern-day mammals. In other words, they were warm-blooded after all.

“I was surprised to see how well dinosaurs fit within our concept of what it means to be a warm-blooded animal today,” Dr. Michael D’Emic, a paleontologist at Stony Brook University in New York who wrote the paper, told The Huffington Post in an email. “Dinosaurs are a really diverse group of animals that lived over a very long period of time, so I expect that as we study more dinosaurs’ growth, we will find more variability in how fast they grew and what their metabolism was like.”

Not hot, not cold. The original mesothermy study, which D’Emic was not involved in, included an assessment of 21 dinosaur species — such as Tyrannosaurs, long-necked Apatosaurus, duck-billed Tenontosaurus, and bird-like Troodon — as well as a range of mammals, birds, bony fish, sharks, lizards, snakes, and crocodiles, Reuters reported.

The study suggested that the growth rates of dinosaurs’ bones were not characteristic of either warm-blooded or cold-blooded animals, so the prehistoric creatures must have been mesotherms.

Sizing up bones. But D’Emic’s reanalysis of the data showed that the 2014 study had underestimated growth rates for some of the dinosaurs. —> Read More