BBC Focus Magazine

[M Paul Lloyd]

By Jason Palmer Science and technology reporter, BBC News
One of the strongest lines of evidence that dinosaurs were cold-blooded, like modern reptiles, has been knocked down.
Prior studies of dinosaur bones uncovered what are known as "lines of arrested growth".
The creatures were presumed to be cold-blooded because modern cold-blooded animals show these same lines.
But scientists reporting in Nature have studied the bones of 41 modern mammal species from around the world, finding every one had these lines as well.
A number of discoveries in recent years have challenged the 40-year-old notion that dinosaurs were cold-blooded.
But because soft tissues such as organs and skin are not preserved, much of what is known about dinosaurs must be inferred from their bones, and comparisons made with modern animals that can be studied in greater detail.

More here.
http://www.bbc.co.uk/news/science-environment-18602965

[Shadowwolf]

Probably also stems from most modern reptiles being cold blooded and assuming that the dinos were most likely also cold blooded.

[MikeG]

Probably also stems from most modern reptiles being cold blooded and assuming that the dinos were most likely also cold blooded.

But since conventional wisdom believes that birds are the closest living relatives to dinosaurs, and birds are endothermic (warm-blooded), this should push the scales towards seeing dinosaurs as warm blooded as well. If however, they were in fact warm-blooded, they must have required massive amounts of food, especially given their huge size, to maintain a stable body temperature. So, if thats true, maybe their demise is partly due to collapsing populations. Once the meteorite hit, it may have tipped a delicate balance. The available plant material may have been somewhat reduced but not dramatically so. This however, was enough to affect the size of the herbivorous herds, which collapsed exponentially by pressure from the carnivores whose voracious appetites required them to feed more frequently than previously thought.

I call this theory the fast-food chain meltdown (because T-Rex had to be fast enough to chase down his meal)

[Lateralman]

There were so many various types of Dinosaur, living in a wide variety of environments all around the planet, could they have been both. Some species cold blooded and others warm?