The New Dinosaurs explores an imagined alternate version of the present-day Earth as Dixon imagines it would have been if the Cretaceous-Paleogene extinction event had never occurred. As in Dixon's previous work, After Man, ecology and evolutionary theory are applied to create believable creatures, all of which have their own binomial names and text describing their behaviour and interactions with other contemporary animals. Most of these animals represent surviving dinosaurs, pterosaurs and plesiosaurs, which Dixon discusses through biogeographic realms, divisions of the Earth's land surface based on distributional patterns of animals and other lifeforms.