Evolution of dinosaurs?

Question

1. How long did it take for dinosaurs to evolve, what proof have we? And how come they evolved so big?

Answer 1

There is no proof on dinosaurs really doing a major change with evolving, however there are many different versions of dinosaurs such as, or Example:

Tyrannosaurus REX

Tyrannosaurus BATAAR

Tyrannosaurus LANPINGENSIS  

Tyrannosaurus LUANCHUANENSIS  

Answer 2

Since life appeared 3.8 billion years ago, and dinosaurs as such came around 230 million years ago, then it took 3.6 billion years or so for bacteria to evolve into multi-celled organisms, then those to go notochords, and vertebrate, fish, amphibians, primitive reptiles and finally dinosaurs.

Proof? Fossils.

Not all dinosaurs were big, some were the size of rats, for instance. But smaller creatures do not leave big bones that are easy to recover a couple of million years later.

Admittedly, some dinosaurs were much bigger than present day elephants, and it is believed this gigantism was allowed by the fact that, back then, the air contained 30% oxygen (as opposed to about 21% today).  The missing oxygen was probably fixated by the raging fires that followed the asteroid impact that wiped out the large beasts.

Answer 3

life started about 1 billion years ago and dinosaurs appeared about 350 million years ago, so it took about 650 million years.

Proof: various kinds of dating techniques, carbon, potassium, uranium, etc...

One idea on why the plant eaters got so big is that the plant life was not very nutritious so they had to eat huge quantities to get nutrients.  The largest dinosaurs were basically moving fermentation vats.  Then carnivores had larger meals so could get larger.

Answer 4

hmmm,, i don't believe with the evolution of dinosaurs, if you're going to ask me why, i can't even imagine how those creatures came and gone after a big comet phenomenon, then how those dinosaurs exist herein the world without any proof