Why didn't the small reptiles when the dinosaurs did?

Answer 1

There were small reptiles in the time of the dinosaurs, they just weren't the most dominant form of reptile on the planet. According to the theory of evolution, following the Cambrian period, most land animals were primitive reptiles that still had amphibian traits and habits. Over time, protein requirements, and the higher oxygen content of the atmosphere on earth millions of years ago, made them grow bigger and bigger. Also dinos were not true reptiles; they were a life form that was a cross between a reptile and a bird, dinosaurs were in fact a primitive species of bird, most of them featherless, hence they ressembled reptiles, but they weren't. Scientists have theorized as much, because skeletal remains of dinos have been found in places of the world were cold blooded animals simply could not have survived, not even in that earlier era.