Pachycephalosaurus

Its head had a thick, round dome.

Dinosaur Picture Book

The Beginning of the Dinosaurs — Triassic

• Herrerasaurus
• Eoraptor
• Eodromaeus
• Hyperodapedon
• Saurosuchus

Back Plates and Sharp Claws — Jurassic

• Allosaurus
• Stegosaurus
• Diplodocus
• Camarasaurus

Feathered Dinosaurs — Early Cretaceous

• Yutyrannus
• Changyuraptor
• Sinosauropteryx
• Psittacosaurus

Hunter of the Desert — Late Cretaceous

• Velociraptor
• Protoceratops
• Citipati
• Pinacosaurus

The Great Tyrannosaurus — End of the Cretaceous

• Tyrannosaurus rex
• Triceratops
• Edmontosaurus
• Pachycephalosaurus