Various Examples of Joe Heller's Illustrations
from "Danger, Dinosaurs" © 1989 Center Stage Productions

Among the first living things with a backbone and an internal skeleton, the Jamoytius became the ancestor for the modern lamprey. It lived 400 million years ago.
An example of the first fish, the jawless Pteraspis lived 430 million years ago. It's characteristic bony head grew throughout its life. This species was extinct before the more ferocious bonefish evolved (who definately had a jaw).
Although the Stegosaurus grew to be 30 feet, it's brain was only the size of a walnut. Yet, it is believed it was not a lumbering tank, as it is comically portrayed in "Danger, Dinosaurs". This illustration shows the modern interpretation: lifted tail, light on its feet, agile. The "armored" plates were probably used to regulate body temperature.