Dinosaurs are animals that live in the lost cities. The elves make sure that no species go extinct, and dinosaurs are not an exception. In the book, it is shown that dinosaurs are still alive. The elves prevented them from going extinct by keeping them in preserves, in order to hide them from humans.
The lambeosaurus was not encountered by Sophie in the lost cities but was in the museum where Fitz found her. Sophie recited the museum's information about this species after Mr. Sweeney accused her of not paying attention.
The Albertosaurus is a dinosaur covered in deep violet feathers. Sophie first met Fitz under a green, scaly model of one, and he commented that it seemed absurd that they would have looked like that. She also gave him a toy of one for midterms, thanking him for showing her what dinosaurs really looked like.
There is a Tyrannosaurus rex living at Havenfield named Verdi. Verdi has huge yellow eyes, sharp claws, and a pointed snout, as well as sharp fangs and neon green feathers. Verdi is also described as being "twice the size of an elephant." (Details on Verdi are in Book 1, page 202, e-book version)
Eckodons are amphibious dinosaurs mentioned in Neverseen. Six of them help to transport Sophie and her friends to Alluveterre for the first time. They have slightly pointed noses, long necks, and gills lining their cheeks.
There is also an undisclosed number of dinosaurs living in the mountain reserve.