Warm Blooded Dinos?

I am not a paleontologist, but I am a big fan of scientific controversy. I love it when two sides argue about how flight originated or how new fossils may be related to our own hominid lineage. That’s why the recent findings that large bi-pedal dinosaurs like the beloved Tyrannosaurus rex may not have the typical large lizards we have long thought really caught my attention.

It’s generally consensus these days that some dinosaurs were birds rather than lizards, and the lineage has been split to include non-avian and avian branches. But there is still controversy among experts as to whether or not these dinos were warm-blooded like their birdy brethren or cold-blooded like their lizardy links. A new study published in the online scientific journal PLoS ONE on Nov. 11th brings to light some new information.

Say the study authors, endothermy, or warm-bloodedness, was widespread “in at least larger non-avian dinosaurs.” The results of their study seem to indicate that the ability to maintain a constant internal temperature may have originated earlier than previously believed.

What this essentially means is that once again we are rethinking how these extinct giants behaved. For the longest time, large dinosaurs like the T-rex were considered unwieldy, hulking and awkward. Now there’s evidence that there was more power and precision behind their lumbering movements.

So why is this such a point of contention? Because being warm-blooded and cold-blooded are very different and require different energy expenditures, different rates of respiration, and different natural histories altogether.

Cold-blooded animals (termed ectothermic), such as amphibians, reptiles and the ilk, rely on the environment to maintain body heat. They generally adapt behaviors to soak up as much heat and sun as possible to run their metabolic processes.

Warm-blooded animals are everything else—including birds (or avian dinosaurs). We can maintain homeostasis (i.e., regulate and maintain a constant body temperature through metabolism). But doing this requires much more energy consumption and output, and requires different anatomical and physical traits. It also means we can live anywhere, hunt for food anytime, and not have to worry about the environment to meet our temperature regulation needs.

So the fact that there is evidence for endothermy among dinosaurs has huge ramifications. We may need to reconsider how we classify them, and even how they became extinct.

Reptiles, a lineage of animals dating back over 300 million years, include organisms such as the extinct dinosaurs and the extant (still living) species of lizards, crocodilians, turtles. It was later expanded to include birds, based on genetic and molecular evidence. These new findings could also lead to more accurate phylogenies, or evolutionary trees.