Prehistoric Life
Prehistoric
Secrets in Stone
The Earliest Fossils
The Silurian Reef
Trilobites
Fish
The Coal Forests
Early Reptiles and Amphibians
Sea Reptiles
Flying Reptiles
Hunting Dinosaurs
Biggest Dinosaurs
Two-Footed Plant Eaters
Plated and Armoured Dinosaurs
Horned Dinosaurs
The Mammal Age Dawns
Grassland Mammals
The Ice Age
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Shell Shapes
Some ammonite shells have ribs. Some have a distinct keel. Some, like Harpoceras have both.
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Book:
Prehistoric Life
Section:
Prehistoric
Chapter:
The Teeming Seas