Data from: The convergent evolution of snake-like forms by divergent evolutionary pathways in squamate reptiles

Convergent evolution of phenotypes is considered evidence that evolution
is deterministic. Establishing if such convergent phenotypes arose through
convergent evolutionary pathways is a stronger test of determinism. We
studied the evolution of snake-like body shapes in six clades of lizards,
each containing species ranging from short-bodied and pentadactyl to
long-bodied and limbless. We tested whether body shapes that evolved in
each clade were convergent, and whether clades evolved snake-like body
shapes following convergent evolutionary pathways. Our analyses showed
that indeed species with the same numbers of digits in each clade evolved
convergent body shapes. We then compared evolutionary pathways among
clades by considering patterns of evolutionary integration and shape of
relationship among body parts, patterns of vertebral evolution, and models
of digit evolution. We found that all clades elongated their bodies
through the addition, not elongation, of vertebrae, and had similar
patterns of integration. However, patterns of integration, the body parts
that were related by a linear or a threshold model, and patterns of digit
evolution differed among clades. These results showed that clades followed
different evolutionary pathways. This suggests an important role of
historical contingency as opposed to determinism in the convergent
evolution of snake-like body shapes.