Talk:Auroran/@comment-5870856-20140214031039/@comment-5135903-20140214164220

They may appear like dinosaurs (or large birds; which actually have very similar physiologies to Theropods) because they have similar adaptations to dinosaurs, which, in turn, is because I determined that their natural environment would be most similar to the environment of the Earth during the Mesozoic Era.

The only evidence-based data we have about life in the universe is from Earth. The Mesozoic Era (in which dinosaurs were dominant) lasted for about 186 million years, while the Cenozoic Era (in which mammals are generally dominant, though even at the start of the Cenozoic most mammals were very small) has so far lasted for about 66 million years. Our (very narrow) evidence of life in the universe therefore seems to show that we are more likely to find dinosaur-like animals than mammal-like animals, if at all (though the Paleozioc, with its giant insects, lasted longer than both the Mesozoic and Cenozioc put together).

Dinosaurs are actually a whole classification of animals in themselves. I've seen species based on mammals, reptiles and even arthropods in GC; if basing extraterrestrial evolution on Earth evolution is acceptible, then why leave out those classifications of animals that happen to be no longer dominant Earth (that's right, there are still species around that match the classification)?

Dinosaurs are classed as archosaurs with limbs held erect beneath the body. 'Limbs held erect beneath the body' is a good adaptation for high gravities and, in some cases, leaves the front limbs free to use as arms (if the body is raised up high by the back legs). Archosaurs, meanwhile, are a classification of animal that stretches from birds to crocodiles.

So, is it really that surprising for an extraterrestrial to evolve that shares features with dinosaurs? I'd probably be more surprised to find an extraterrestrial that shares features with mammals.