rov1200, you plainly don't understand the basic principles of evolution.
Which species come about and which don't is decided by totally random mutations in the genetic code passed on from one generation to the next, followed by natural selection of those mutations that are viable and advantageous.
So even if the environment were still suitable for dinosaurs after they had become extinct, the probability of that long series of mutations needed to produce them occuring a second time is ridiculously and hopelessly small.