EARTH 7 Lecture Notes - Lecture 9: Ankylosaurus, Dermal Bone, Scelidosaurus
10/25/17
● ORNITHISCHIAN EVOLUTIONARY NOVELTIES
○ Reverse pubis
■ Derived condition
○ Predentary bone
○ Low jaw joint
● Evolutionary trends with ornithischia
○ Herbivory
○ Defense
○ Sociality
● Carnivores vs herbivores
○ Meat easy to digest
○ Plants not easy to digest
■ Solutions
● Large belly
● Lots of chewing
● Ornithischian trends: defense
○ Large size
○ Weapons
○ Armor
○ Numbers (herds)
● Ornithischian trends: sociality
○ Herds
○ male-male combat
○ Display
○ Communication
● Thyreophorans
○ Shield bearers
○ Dermal armor
■ Become scutes/osteoderms, and spikes in ankylosaurus
■ Become plates or spikes in stegosaurians
● Early thyreophorans
○ Dermal armor
○ Initially small and bipedal, later quadrupedal
● Scelidosaurus
○ The genus indicates what a common ancestor to stegosaurus and ankylosaurus
would have looked like (at least somewhat).
○ Described by Richard Owen in 1861, it’s also one of the earliest relatively
complete dinosaurs discovered.
● Stegosaurians & ankylosaurians
○ Stout forelimbs
○ Broad hands
