Which Dinosaurs Were Warm Blooded or Cold Blooded?

In summary, the research group found indications that some dinosaurs were warm blooded (endothermic), while others (Stegosauri and Triceratops) were apparently reverted to being cold blooded (ectothermic). Additionally, it seems that the flying non-avian reptiles were also warm blooded.
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In another well directed chemical analysis of fossils, a research group has indications that some but not all dinosaurs were warm blooded (endothermic), although some (Stegosauri and Triceratops) had apparently reverted to being cold blooded (ectothermic). In addition, it seems that the flying non-avian reptiles were also warm blooded.
They did this by testing sections of fossilized femurs in a variety of known and extinct animals (all were amniotes, animals with eggs protected by a shell that could be laid on land (amphibians are not amniotes)) and determined the relative amounts of metabolic lipoxidation signals using in situ Raman and Fourier-transform infrared spectroscopy. The amounts of these chemicals are expected to reflect the warm or cold blooded state of the animals. This was confirmed by examining fossils of extent (still around) animals.
This paper is open access and available here.

Here is their phylogenetic diagram summarizing their findings:

Screen Shot 2022-05-25 at 5.28.13 PM.png


How to read the phylogenetic diagram:
  • Time goes left to right (scale at the bottom).
  • Color of the lines in the phylogeny are colored (temp. scale upper left)
  • Lines that go all the way to the right are still alive. Those ending more to the left are extinct.
  • Changes in the temperature trait are indicated by small circles on the lines of the phylogenetic diagram (yellow: transitioning cold to warm blooded, blue: transitioning warm to cold blooded).
  • Birds are at the top and branch off from the dinosaurs near the raptors (Deinonychous).
  • Hadrosaur = the group of duck billed dinosaurs (more cold blooded than their close relatives).
  • The flying non-avian reptiles (Pterodons (they are in Jurassic world for example) and Phanphorhinchoid) branch off from pre-dinosaurs just before they become dinosaurs. they are warm blooded.
  • Plesioaurs (long necked large aquatic reptiles with paddle-like feet) were somewhat warm blooded. Not sure where mososaurs (large whale-like extreme carnovores, also in Jurassic world) would fit in. Maybe they were not tested.
Its thought that being warm blooded would provide a more sustained higher rate of metabolism, which would have some advantages.
On the other hand, its not entirely clear why some of them would switch back to being cold blooded, but being warm blooded continuously requires a lot of energy (unless hibernating like some mammals can do).
 
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If you're a carnivore / omnivore, being warm blooded is a big advantage in a world full of cold-blooded stuff: You can simply ... graze on them when they're down at night or in the winter. Ask e.g. the hedgehog...

Re. reverting: Obviously, when you're living in a constantly warm environment, like equatorial rainforest, or subtropical forests (not deserts - those get really cold at night), the "warm-bloodedness" advantage disappears, so keeping the metabolic rate as low as possible becomes advantageous again.
 
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FAQ: Which Dinosaurs Were Warm Blooded or Cold Blooded?

What evidence is there to support the idea that some dinosaurs were warm blooded?

There are several lines of evidence that support the idea that some dinosaurs were warm blooded. One is the presence of feathers, which are typically found on warm blooded animals. Additionally, some dinosaurs had a high growth rate and active lifestyles, which are characteristics of warm blooded animals. Finally, the structure of some dinosaur bones suggests a high metabolic rate, which is also associated with warm blooded animals.

What evidence is there to support the idea that some dinosaurs were cold blooded?

There is evidence to suggest that some dinosaurs were cold blooded, or ectothermic. This includes the presence of scales, which are typically found on cold blooded animals. Additionally, some dinosaurs had a slow growth rate and were found in environments that would have been too cold for warm blooded animals to survive. Finally, the structure of some dinosaur bones suggests a low metabolic rate, which is associated with cold blooded animals.

How do scientists determine if a dinosaur was warm blooded or cold blooded?

Scientists use various methods to determine if a dinosaur was warm blooded or cold blooded. These include analyzing the structure and growth rates of bones, examining the presence of feathers or scales, and studying the environments in which the dinosaurs lived. Scientists also use computer models and comparisons to living animals to make inferences about the metabolism and body temperature of dinosaurs.

Were all dinosaurs either warm blooded or cold blooded, or were there some that were in between?

There is evidence to suggest that some dinosaurs may have had a mix of warm blooded and cold blooded traits, making them mesothermic. This means that they were able to regulate their body temperature to some extent, but not as efficiently as warm blooded animals. This is supported by the presence of both feathers and scales on some dinosaurs, as well as their varying growth rates and environments.

Is there a consensus among scientists about which dinosaurs were warm blooded or cold blooded?

There is ongoing debate and research among scientists about the metabolic rates and body temperatures of dinosaurs. While some evidence points to certain dinosaurs being warm blooded or cold blooded, there is not yet a consensus about all species. New discoveries and advancements in technology continue to shed light on this topic and may lead to a better understanding in the future.

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