Not all dinosaurs were giants, but, all the same, their ranks included the largest animals ever to walk the Earth. Supersaurus, Argentinosaurus, Futalognkosaurus, and more – these huge sauropod dinosaurs stretched over 100 feet long and weighed upwards of 45 tons, depending on the species.
No land-dwelling mammal has ever gotten close to such sizes. The biggest – a hornless rhino named Paraceratherium – was about 25 feet long and topped out around 20 tons. Why should this be so? Have mammals not evolved to the full range of their potential sizes, or is there something preventing them from becoming truly giant?
In the latest Royal Tyrrell Museum Speaker Series lecture, University of Calgary paleontologist Jessica Theodor draws from her recent research into mammal size to explain the size gap between giant dinosaurs and comparatively puny mammals. But the talk is more than that. The extinction of the non-avian dinosaurs gave mammals the chance to get big, but not all kinds of mammals did so. Looking around today, for example, elephants are much bigger than lions. What drove these changes and allowed herbivorous beasts to get big, but not giant? Watch to find out!