The dinosaurs proper had hollow bones and other indicators of being warm-blooded, and belonging to aves, not sauria.

Glendoor – If you manage to catch and kill a living dinosaur, please send me a sample of the resultant barbecue.

Dogu – Well, there is some speculation regarding smell – I think T-rex smelled terrible, personally.

Though they were reptiles the way they lived and functioned is more like that of present day birds and mammals and it is best to look to them for clues on how the dinosaurs lived, especially birds but obviously a bird finch is a very different animal from a triceratops, but then we have rhinos to look at for that sort of comparison.

Well first of all I phrased it undiscovered reptiles and put “dinosaurs” in quotes. I’m aware of some of the research suggesting that some dinosaurs might have had metabolisms closer to warm-blooded.

However most of the evidence I have seen hews to the old cold-blooded model. At Champlain you start getting sightings when the temperature rises to 70 or so in the spring and then they drop to zero when the temperature goes below 70 in the fall. (This observation first made my Dennis Hall, I believe.) That follows the model of a cold-blooded animal that hybernates, like the smaller known reptiles at Champlain.

The other sightings of “living dinosaurs” seem to be in very warm tropical or sub-tropical areas, so that doesn’t disagree with the cold-blooded model. That doesn’t rule out warm-bloodedness, though.

CryptoInformant 2.0 -

See the reply to maslo63.

One of the most interesting (to me) departures from the biology I learned in elementary school is precisely this division of animals into warm-blooded and cold-blooded, with birds and mammals being warm-blooded and reptiles, amphibians, and fish being cold-blooded. But some mammals (such as the naked mole rat, and if I remember correctly, to a lesser extent the manatee) are barely warm-blooded at all. On the other hand, the tuna is a “warm-blooded” fish. The distinction is not as black-and-white as it used to be. Besides, a large sauropod probably had a low metabolism (to reduce how much it had to eat, to allow the food to ferment in its stomach, and because it did not need to run from predators) but would still be more challenged with getting rid of heat than with generating it.

But perhaps the best illustration of the difference between the traditional picture of dinosaurs and recent thinking is given by this website.

It is generally agreed upon that dinosaurs or at least some dinosaurs were not cold blooded. Though they were reptiles the way they lived and functioned is more like that of present day birds and mammals and it is best to look to them for clues on how the dinosaurs lived, especially birds but obviously a bird finch is a very different animal from a triceratops, but then we have rhinos to look at for that sort of comparison. I imagine the larger herbivores were most likely dull, like modern large mammals. Crested hadrosaurs and certopsians may have had display colors on their head ornamentation. Carnivores were likely camouflaged, smaller species may have been colorful.

Terrell–”Those ridiculous dino-bird pictures always make me smile…

So I guess the duck billed platypus is becoming a duck, or a maybe a beaver! Or maybe a snake (the males do have venom). Maybe collagen should be seriously considered as the reason for the ‘dino-fuzz’, I mean come on, those pictures just look ridiculous.”

Evidently this is a comment made from someone who just is not familiar with the fossil evidence for feathered dinosaurs. Current finds go way beyond dino fuzz and into secondary feathers extending from the arms and display feathers on the tails. Species such as Microraptor were gliding animals with wings on all four limbs. You may see them as ridiculous but they were real, like it or not.