The brain-size issue also hits hard at bulk endothermy for theropods in another way. Walking dinosaur costume Bulk endothermy postulates that small dinosaurs had slow metabolisms, and that the metabolic rates of big species converged with those of big endotherms. This is simply not so, since the relatively big-brained small theropods almost certainly had faster metabolisms than reptiles of equal size. This means that the s2e-induced convergence in metabolic rates could not have occurred, and that there is no place for bulk endothermy in theropod metabolics.
Going to ever smaller detail in our look at dinosaur anatomy and physiology, we turn to bone histology-the internal fine structure of bones as revealed by sutting out thin sections and looking at them under a microscope. This ties into another critical factor, growth rates. Realistic dinosaur costume This is really an old line of work, for as far back as the 1800s it was noted that the insides of dinosaur bones were structured like those of birds and mammals, and quite different from those of reptiles. There has been a lot of debate about the similarities and differences between endothermic and reptilian bones, from which a consensus seems to have emerged. Armand Ricqles and Robin Reid show that most endotherms over 10 kg have well-developed “flbrolamellar” bone, while ectotherms do not. Animtronic Dinosaur costume The development of extensive fibrolamellar bone appears to stem from a hrgh rate of growth. we often despair over how fast our children grow. But humans really mature achingly slowly for mammals, perhaps because of our need for a long social education. Horses and ostriches reach adult size in only a year or so. on the other hand, crocodilians and giant tortoises take decades. Speed of growth is also size-related: usually, the bigger the creature, the slower it develops. And at any given size, most endotherms grow an order of magnitude more rapidly than ectotherms. so while elephantse and whales take about two or three decades to grow up, similarly gigantic ectotherms would take a couple of centuries or more to do the same.