Paleontologists studying a species of feathered dinosaur, Cryolophosaurus, determined that the species was endothermic (warm-blooded). The researchers claim that this endothermy allowed Cryolophosaurus to inhabit high-altitude regions that would have been too cold for ectothermic (cold-blooded) reptiles.
Which finding, if true, would most directly lend credence to the researchers' assertion?
Fossils of Cryolophosaurus are often found alongside fossils of large, cold-blooded crocodiles.
The bone structure of Cryolophosaurus shows growth rings similar to those found in modern reptiles.
Cryolophosaurus fossils are abundant in rock layers corresponding to ancient mountain ranges, where no fossils of ectothermic reptiles have ever been found.
The global climate during the time Cryolophosaurus lived was significantly warmer than it is today.
Correct Answer: C
Choice C is the best answer. The claim is that endothermy (warm-bloodedness) allowed the dinosaur to live in cold, high-altitude regions. Finding Cryolophosaurus fossils in "ancient mountain ranges" (cold) where "no fossils of ectothermic reptiles" (cold-blooded, cannot survive cold) are found provides strong evidence that the dinosaur possessed a trait (endothermy) allowing it to survive where cold-blooded animals could not.
Choice A weakens the claim, as finding them with cold-blooded animals suggests the environment wasn't that cold. Choice B suggests similarity to reptiles (cold-blooded), which might weaken the endothermy claim. Choice D suggests the world was warm, which removes the need for endothermy to survive, weakening the specific argument about cold tolerance.