Paedomorphosis (juvenile characteristics remaining in adults) is a really neat mechanism for producing radically different-looking animals in a short time.

In the short span of ~30,000 years, we've managed to turn wolves into corgis that look like puppies their entire lives. We ourselves are often said to be a result of paedomorphosis from other primates -- now with less hair, bigger heads, and weaker muscles.

Yes, indeed. For humans, it's somewhat just a change in developmental timing. As we age, we start looking more like adult chimpanzees/bonobos.

Simple version: The amount of Oxygen in the air decreased, giving the Dino-birds less energy. so they became smaller.

Also air with less Oygen is lighter, another good reason for Dino-birds to loose weight.

On the contrary: The amount of CO₂ decreased. I see more of a correlation between CO₂, big plants (food supplies) and animals.

Why is 10 million years a blip in evolutionary time when you see the massive chamges that can happen on Islands in 100s of years?

You can see some chang s over 100's of years. Nothing as dramatic as this. I wouldn't call 10 million years quite a blip though. But dinosaurs were around for almost 200 million years! Some animals have not evolved much in hundreds of millions of years, like sharks and crocodiles.

Yeah, it's a remarkable thing that Homo Sapiens is closer in time to Tyrannosaurus Rex than T. Rex is in time to Stegosaurus.

Just so.