June 28, 2012
Dinosaurs May Not Have Been Cold-Blooded After All
redOrbit Staff & Wire Reports - Your Universe Online
A new study, published Wednesday in the journal Nature, suggests that dinosaurs were warm-blooded creatures, not cold-blooded reptiles as previously thought.
According to BBC News Science and Technology Reporter Jason Palmer, researchers have disproven one of the primary bits of evidence supporting the four-decade-old theory that dinosaurs were cold blooded.
That evidence, skeletal markings on the creatures' bones known as "lines of arrested growth" or "LAGs," supposedly supported the notion that they were not warm-blooded because modern cold-blooded animals also had the same markings. However, the authors of the new study have discovered that 41 modern mammal species from various parts of the world also possessed the lines, Palmer said.
The background information of the study pointed out that the theory that dinosaurs did not generate internal heat was based on the presence of LAGs in bones, Elizabeth Lopatto of Bloomberg News said. However, the authors of the Nature study found those same skeletal markings on animals such as deer, and surmised that they actually indicate rain and food and water supply, not external temperature.
"The study we have carried out is very powerful, both in terms of the amount of material and the diversity of species with which we worked, but we did not design it to find a response to the thermophysiology of dinosaurs," Palaeontologist Dr. Meike Koehler of the Autonomous University of Barcelona, the institute behind the research, told Rob Waugh of the Daily Mail on Wednesday.
"It may seem surprising that until now there has not been a similar systematic study to prove or disprove whether it is only ectotherms that leave these marks in their bones during growth," Dr. Koehler added. "In fact, some previous studies had already questioned this hypothesis and among the international scientific community there has been increasing consensus about the idea that LAGs were not necessarily indicators of ectothermy“¦ This study conclusively closes the debate."
Ironically, Koehler told Palmer that the researchers did not set out to tackle this topic. She said that they were attempting to study how environmental changes affected bone growth in fossil and extant mammals, hoping to learn how creature may have coped with such issues in the past.