Instantly recognizable by the seventeen bony plates along its back and the four-spiked tail it swung like a medieval mace. Its brain was famously the size of a walnut — yet Stegosaurus thrived for millions of years.
Length9 m
Height4 m
Weight5,000 kg
Top speed8 km/h
Field notes
- An Allosaurus vertebra was found with a Stegosaurus spike wound in it.
- Its back plates may have flushed with blood to change color.
- The spiked tail has an official name: the thagomizer, from a Far Side cartoon.