Could it be possible that over a course of millions of years if the asteroid never hit, some basal iguanodontian dinosaurs could evolve the limb bones and structure to become a better quadrupedal runner like today's gazelle and horses?

Could any ornithopod dinosaurs run quadrupedally similar in a way to what I described?

Some ornithopods were obligate quadrupeds- they could only walk on all four legs. It's perfectly reasonable to assume that they could have been pretty adept at running, though it's unlikely ever to have become like a gazelle or horse simply because the muscles and bones aren't arranged the same.

If you mean simply 'as fast' as gazelles and horses, well, I don't think there's been enough research to say for sure, but they could probably run pretty quickly to escape predators.

Last edited by Peter Falkingham (29th Oct 2014 13:57:39)