ALT Plot in the centre shows the first two PC axes in the phylomorphospace of variation in theoretical shape of ornithopod limb bones. Different colours indicate different groups (non-ornithopod neoornithiscians in grey, non-styracosternan ornithopods in green, non-hadrosaurid styracosternans in yellow and hadrosaurids in purple). Bipedal taxa are shown as diamonds and those of indeterminate habit as circles. The vertical axis represents PC2, and the model on the left indicates landmark displacement between the two end members (low displacement in blue; high displacement in red; see scale at bottom). Model on the right shows a similar picture for the horizontal, PC2 axis.