The lack of large terrestrial vertebrate predators and the highly oxygenic atmosphere at that time probably enabled them to grow so large.

Marine faunas became fairly modern, as did terrestrial vertebrate fauna on the northern continents.

It uses its flexible toes to grab prey -- large arthropods and small to mid-sized terrestrial vertebrate.

Sometimes known as perching birds or, less accurately, as songbirds, the passerines form one of the most diverse terrestrial vertebrate orders, with over 5,000 identified species.

For example mammaliformes (almost mammals) and then mammals existed throughout the reign of the dinosaurs, but could not compete for the large terrestrial vertebrate niches which dinosaurs monopolized.