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Re: Hot-blooded marine reptiles

You're right, Dann, but you have to see the data presented in this paper as additional evidence for endothermy in ichthyosaurs, plesiosaurs, and mosasaurs. Another interesting result is the body temperature variation within Ichthyosauria, compared to plesiosaurs and mosasaurs. Also, given what was known from ichthyosaur biology and functional anatomy, it was expected to find a lower body temperature in *Mixosaurus* than in Bristish thunnosaurs. These new results confirms this difference, even if the effect of size is still poorly understood AFAIK.

I expect future comparisons with Triassic taxa such as Shastasauria (*Shonisaurus* !), Eurhinosauria, or non-Ichthyosauria Ichthyopterygia (*Utatsusaurus* or Grippidia).

Regarding endothermy, it should not be forgotten that ichthyosaur high metabolic rates have probably been favoured by a global increase in size during Triassic, leading to higher thermic inerty ("gigantothermy). And that is why I am waiting eagerly for more investigations regarding giant forms (*Shonisaurus* and his relative *Himalayasaurus*).

Dann Pigdon a écrit :
The idea of high body temperatures in extinct marine reptiles isn't a complete surprise. Tuna and some sharks managed to maintain high internal temperatures by piping blood past their muscles like a biological central heating system. 'Waste' heat from muscle activity is thus used to heat the blood rather than actually being wasted. Bluefin tuna have a particularly efficient thermoregulatory system that keeps their internal temperature between 24 and 35 degrees celcius (depending on the temperature of the surrounding water). Who needs endothermy when you've got your own built-in central heating?