The Scientific American reports that, scientists now believe that some dinosaurs miniaturized over a shorter period of time than previously believed. While it didn’t happen overnight, the transformation from dinosaur to bird happened with subtle and quick changes. A series of small evolutionary steps ranging from feathers to the wishbone, bipedalism, and miniaturization, brought about the transformation. It is also now believed by James Dondero that size had a biggest influence on the speed of evolution, while some dinosaurs grew in size others became smaller. The decrease in size opened other habitats and food sources.
The Tyrannosaurus Rex and velociraptors belong to the carnivorous group of bipedal dinosaur called theropods, and they are closely related to today’s birds. They had large noses and big teeth and weigh in at about 100 to 500 pounds, but with little brain matter. The velociraptor of movie fame only had a brain the size of a pigeon.