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Palaeontology

Were dinosaurs warm or cold-blooded ?

By T.K. Randall
June 2, 2015 · Comment icon 26 comments

Were the dinosaurs warm or cold-blooded ? Image Credit: CC BY 2.5 Brian Engh
A new study has suggested that the prehistoric reptiles were more likely to be warm-blooded like mammals.
The question over whether the dinosaurs were cold-blooded like today's reptiles and fish or warm-blooded like mammals and birds has remained a topic of controversy and debate for years.

While many experts have settled on the idea that dinosaurs were actually somewhere in the middle with both cold-blooded and warm-blooded traits, a new study has this week thrown another spanner in the works by suggesting that they were in fact almost certainly warm-blooded.

"Upon re-analysis, it was apparent that dinosaurs weren't just somewhat like living mammals in their physiology," said study author and palaeontologist Michael D'Emic of Stony Brook University.

"They fit right within our understanding of what it means to be a ‘warm-blooded' mammal."
D'Emic's re-analysis focused on two main aspects of the original study with the first being the scaling of yearly growth rates to daily ones in an attempt to standardize comparisons, a discrepancy that he contends failed to take in to account variable growth rates throughout the year.

In addition D'Emic also argues that birds, which are now commonly believed to be the modern-day descendants of dinosaurs, are warm-blooded and that therefore dinosaurs probably were too.

"Separating what we commonly think of as 'dinosaurs' from birds in a statistical analysis is generally inappropriate, because birds are dinosaurs - they're just the dinosaurs that haven't gone extinct," he said.

While his findings are unlikely to be sufficient on their own to prove that dinosaurs really were warm-blooded his efforts will no doubt fuel further study in to this 65 million-year-old mystery.

Source: Discovery News | Comments (26)




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Recent comments on this story
Comment icon #17 Posted by TheGreatBeliever 9 years ago
Obviously warm. If im not wrong there was no ice during the dinos time..
Comment icon #18 Posted by adke 8 years ago
This videos pretty good.
Comment icon #19 Posted by shadowsot 8 years ago
There was a paper recently that argued that marine reptiles were warm blooded due to the isotopes in their teeth. Don't remember it at the moment. The huge sauropods were supposedly to be warm blooded, the theory is that they were instead gigantothermic. Being warm blooded is one of the size limiters for mammals. The bigger you are, the more surface area you need to bleed off heat. Smaller dinosaurs were probably warmblooded, certainly theropods like velocirapter or Tyrannosaurus.
Comment icon #20 Posted by DieChecker 8 years ago
I'd imagine that a sauropod would be one shape that would increase the surface area at the same time increasing size. Many of the largest ones were almost snake shaped in their neck and tail length.
Comment icon #21 Posted by Taun 8 years ago
"Were dinosaurs warm or cold-blooded?"... Yes...
Comment icon #22 Posted by third_eye 8 years ago
Maybe they;re more alike the Great White or Mako ~ endotherms ~ Most sharks are cold-blooded. Some, like the Mako and the Great white shark, are partially warm-blooded (they are endotherms). These sharks can raise their temperature about the temperature of the water; they need to have occasional short bursts of speed in hunting. link ~ Or meet Opah : Meet the Comical Opah, the Only Truly Warm-Blooded Fish Posted Thu, 05/14/2015 nat geo link ~
Comment icon #23 Posted by SlippySlug 8 years ago
The original article is a year old, but I thought it was pretty much accepted long ago that dinosaurs were warm-blooded, at least the therapods. I might be remembering things completely wrong because it was about ten years ago, but didn't paleontologist Mary Schweitzer basically prove that T-Rex was warm-blooded by studying blood vessels in from its fossilized thigh bone? If that name sounds familiar, she was all over the news for discovering "soft tissue" in about a 65 million year old fossil. You'd still have to wonder about the sauropods and whatnot. This... I don't know of any other clade ... [More]
Comment icon #24 Posted by shadowsot 8 years ago
I'd imagine that a sauropod would be one shape that would increase the surface area at the same time increasing size. Many of the largest ones were almost snake shaped in their neck and tail length. It's surface area to internal volume. If you're warm blooded you need a certain ratio of skin to internal meats to disperse excess body heat. Sauropods were probably to large to do that successfully.
Comment icon #25 Posted by Emma_Acid 8 years ago
Firstly, dinosaurs weren't a single species. Secondly, the binary notion of warm vs cold is a scientific categorization, and like all such things, not always representative of what actually happens in nature. Plenty of animals fall in between the warm/cold category, and its possible dinosaurs did too. Remember, this isn't really about the temperature of the blood, it's about how the species regulates its body temperature. Tuna use both internal regulation and external warming depending on where in the ocean they are.
Comment icon #26 Posted by DieChecker 8 years ago
It's surface area to internal volume. If you're warm blooded you need a certain ratio of skin to internal meats to disperse excess body heat. Sauropods were probably to large to do that successfully. But look at them. It appears a long sauropod would have a much larger surface to weight ratio then any land mammal alive today. If they had lots of large veins near the surface on their neck and tail, they'd be able to shed a Lot of heat.


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