单选题 Because dinosaurs were reptiles, scientists once assumed that, like all reptiles alive today, dinosaurs were coldblooded. The recent discovery of dinosaur fossils in the northern arctic, however, has led a number of researchers to conclude that at least some "dinosaurs might have been warmblooded. These researchers point out that only warm-blooded animals could have withstood the frigid temperature that are characteristic of arctic winters, whereas cold-blooded animal would have frozen to death in the extreme cold.
Which one of the following, if true, weakens the researchers' argument?