Ancient Ornithischia: Scales, Quills and Spikes

For many years very little was known about the external appearance of the earlier ornithischians, that were assumed to be simply scaly or armoured like many of their descendants.

However, the fossil findings in the Chinese Liaoning Province deposits have helped to get a first hand picture of the primitive ornithischians’ external appearance, and they were as extraordinary and complicated as their Saurischian counterparts. Many of the primitive members were quilled like porcupines. So the very old heterodontosaurs and primitive ceratopsians like Psittacosaurus demonstrate that quilled or insulated dinosaurs were right at the base of the evolution of Dinosauria.

We can’t call them precisely “protofeathery” like the Saurischians, but their peculiar range of outer coverings were also made of keratin and probably were as much used as defence, insulation and display as the Saurischians.

In fact, these quills probably evolved later into their massive armour and spikes, like the primitive armoured dinosaur Scelidosaurus shows.