Pachyrhinosaurus follows two separate stories: the discovery of Pachyrhinosaurus fossils at Pipestone Creek in northwestern Alberta, and the story of a single Pachyrhinosaurus herd and the events that led to its abrupt demise 76 million years ago. Each story is compellingly told and accompanied by dynamic illustrations and photographs.

Pachyrhinosaurus, one of the rarest, least understood horned dinosaurs, lived during the second half of the Cretaceous Period, the last period in the 150-million-year Age of Dinosaurs. Pachyrhinosaurus was different in a striking way. Instead of the sweeping lances found on fossil Triceratops and Centrosaurus faces, gnarly platforms of bone covered Pachyrhinosaurus's nose and eyebrows. These bony fossil shields gave the dinosaur its name: Pachyrhinosaurus means "thicknose reptile."