Parsimony and the analogy-versus-homology pitfall.
If we interpret the four–chambered hearts of birds and mammals as homologous instead of analogous and use no other
information, the tree in (a) appears to be the more parsimonious tree.
In fact, abundant evidence supports the hypothesis that birds and lizards are more closely related than birds and mammals are
and that four–chambered hearts evolved more than once, supporting the tree in (b).