Rocks in His Head by Carol Otis Hurst, James Stevenson
When Trilobites Ruled the World
The remains of trilobites, a diverse group of marine animals much older than dinosaurs, are remarkably well preserved, providing fresh insights of their anatomies and social behavior. Trilobites may be the archetypal fossils, symbols of an archaic world long swept beneath the ruthless road grade...
By the Middle Ordovician 470 million years ago life on Earth experienced a dramatic evolutionary radiation and the first jawless fishes arose. Having experienced a major extinction at the end of the Cambrian trilobites rebounded and reamained abundant and
An armoured jawless fish (a Cephalaspis, which is a kind of osteostracan). This creature evolved as it adapted to the transition from open sea to freshwater conditions in the Ludlow area towards the end of the Silurian.