It has long been thought that all dinosaurs were cold blooded but recent research suggests that this may not hold true for all species. Birds, that evolved from dinosaurs, are warm blooded but when the transition from warm to cold blooded occurred isn’t known.
Cold-blooded creatures can’t regulate their own body temperature internally and as a result have to behave in certain ways such as bathing in the sun to stay warm. These are also known as ectotherms. Warm-blooded organisms, or endotherms, on the other hand, can regulate their body temperature internally through a series of pathways. Ectotherms generally have a slower metabolism than endotherms because the reactions that break down food into energy are slower because they occur at lower temperatures.
The new finding suggests that two groups of dinosaurs, one part of the titanosaurs and the other part of the oviraptors, were more warm-blooded than most other dinosaurs. Titanosaurs were huge herbivorous dinosaurs with trademark long necks. Oviraptors were smaller dinosaurs that walked on two legs.
Research was conducted on portions of eggshells, which naturally contain isotopes. These Heavier isotopes tend to cluster together in colder temperature so this makes it possible to estimate body temperature in the egg. The body temperature in the titanosaurs was about 37 degrees Celsius and 32 degrees in the oviraptor. This isn’t as high as body temperatures in modern day birds but is much higher than in cold-blooded dinosaurs. According to the researchers, this doesn’t prove that these dinosaurs were completely endothermic but were a step in that direction.
Oviraptors are fairly closely related to the first birds that evolved so being warm-blooded probably emerged in dinosaurs and was passed onto birds. The titanosaurs, however are not as closely related to early birds. This may prove that being warm-blooded evolved more than once in dinosaurs. There may even be several other dinosaurs that were warm-blooded and that there is probably a spectrum and not a distinct difference between being an endotherm and an ectotherm.
“The temperatures we measured suggest that at least some dinosaurs were not fully endotherms [warm-blooded] like modern birds,” said Robert Eagle of the University of Los Angeles and head of the study, “They may have been intermediate — somewhere between modern alligators and crocodiles and modern birds.”
The research opens the doors for more studies about the evolution of traits in dinosaurs and the transitions of dinosaurs into birds.