Yet some dinosaurs did have yearly rings. A pair of Canadian paleontologists found them in the teeth of duckbill dinosaurs and tyrannosaurs and loudly declared their evidence proved the dinosaurs were cold-blooded.(dinosaur equipment) Their conclusion was hardly justifiable since they hadn’t taken into account the fact that growth rings are very common in the teeth of some warm-blooded mammals living in tropical habitats (lions and hyenas in East Africa have such rings) and that these mammals usually have more sharply defined rings in their teeth than in their bones. Moreover, if we compare the average condition of crocs and dinosaurs from any one habitat, the crocs invariably have better-defined growth rings and more of them, just as East African crocs today exhibit better rings than the mammals in the same locale. (lifelike dinosaur for sale)Finally, the Canadian dinosaurs actually showed the mammal-style pattern: rings in the teeth but not in the bones.
Some other scientists have found growth rings in the limb bones of dinosaurs in one specimen of Allosaurus, in one brontosaur from England, and in another excavated in Madagascar. (dinosaur costume)A great deal was made of each of these specimens with rings, but all the hundreds of dinosaur specimens with no rings whatever were ignored. Were some dinosaurs cold-blooded, then, while others were warm-blooded? A theoretical possibility. But the evidence from growth rings certainly does not prove, as orthodoxy would have it, that any dinosaur was cold-blooded. Growth rings merely prove that growth stopped during one part of the year.(dinosaur factory) The only useful way to derive evidence from them must come from a broad survey: If, on average, dinosaurs were more warm-blooded than crocs or turtles, then in any one fossil habitat more and better-defined growth rings should be found in the crocs and turtles. And that is exactly what is found. At Como Bluff, all the turtles and crocs display sharply defined growth rings, but the dinosaurs only rarely. The same is true in the Late Cretaceous deltas of Montana and Alberta.