Thread: Classifying Dinosaurs

Reptiles are air-breathing, cold-blooded vertebrates that have skin covered in scales as opposed to hair or feathers. They are tetrapods (having or having descended from vertebrates with four limbs) and amniotes, whose embryos are surrounded by an amniotic membrane.

By this definition, I think it is safe to point out that Dinosaurs don't quite fit in this category. Especially after it has been found that most of them were warm blooded and more and more discoveries support that more and more species of them have been discovered to have had feathers.

While I agree with the consensus to place most dinosaurs in the same class as birds, I'm not sure what to think about species of tetrapods such as Brachiosaurus and triceratops, and other dinosaurs utilizing all four of their legs for walking.

I don't think you can classify all dinosaurs as one species just as you can't classify all mammals as one species. Some would be classified under birds as well some would be classified under reptiles and a host of other classifications. I think you need to narrow your topic down to specific types of dinosaurs. As with those large four legged dinosaurs such as Brachiosaurus and Diplodocus I'm not too sure what classification they'd be under. Most likely Lizard. The big meat eaters such as Tyranosaurus Rex and Albertosaurus should be classified under birds in my opinion. How about ankylosaurus? I think they should be classified under lizards and Triceratops and Styracosaurus in my opinion should be labbeled under mammals.

One defining characteristic of dinosaurs is the shape of their hip-bones. The hind legs point downwards, instead out sideways and then down (crocodiles). Birds share this feature and lizards do not.

Isn't it established that there are a few different dinosaur lineages, some of which group with birds and others which don't?

that doesn't matter - it has been established that Dinosauria is a perfectly good, monophyletic clade if you include birds, a paraphyletic one if you don't

for a more inclusive term you could use "Archosauria", which would also include crocodiles, pterosaurs and "thecodontia"

There has been recent discoveries that dinosaurs in fact has a different mode of metabolism, most evident in its mode of thermoregulation, than modern organisms.

For years scientists have been debating whether dinosaurs are cold-blooded or warm-blooded. From new data (such as the fact that dinosaurs have higher metabolic rate than modern cold-blooded reptiles, which is not characteristic of ectotherms) it appears to be somewhere in between.

Based on this alone, dinosaur is neither reptiles nor birds, so it most likely belongs to a separate class.

Many cold-blooded species are capable of maintaining a higher temperature.

The great white shark for instance. It's not even a reptile. Not even a bony fish.

Tunafish.

I'm afraid that cold-warm bloodedness isn't really a black and white area. Lots of grey.