Dinosaur cold-blood theory in doubt

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.

The idea that dinosaurs are cold-blooded, or ectothermic, goes back to the 19th Century. But a number of discoveries 1960s have been challenging that notion.

Because soft tissues such as organs and skin are not preserved (with a few notable exceptions), 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.