Determining dino size

摘要

Whether a stable body temperature via metabolism (endo-thermy) or outside temperatures (ectothermy) determined the size limits of dinosaurs is a source of controversy among paleontologists. Brian McNab pro-rnposes that the availability of food resources was more important than thermal biology in determining a dinosaur's ultimate size. Like couch potatoes sitting within easy reach of high-calorie foods, the size of dinosaurs likely stems from the abundance of resources coupled with low energy ex-rnpenditures. The author developed a model that describes a vertebrate's energy expenditures and takes into account an organism's mass and food habits. Applying the model to existing and extinct mammals, McNab noted that the model successfully predicted the large size of baleen whales, as compared to an ancient rhinoceros and today's elephant. The model also reflected the difference in body size between mammals and large reptiles. Noting that thermal biology differences are easily seen in small organisms, McNab suggests that dinosaurs were neither ecto-thermic nor endothermic, but maintained an intermediate temperature between mammals and reptiles, a feat enabled by their large mass.