Figure 3.

Phylogeny of Gymnotiformes and evolution of heterocephaly. (a) Phylogenetic tree (based on Tagliacollo et al., 2015), trimmed to include 133 species examined for neurocranial morphology. Colored branches indicate heterocephalic variation with blue indicating more dolichocephalic and red more brachycephalic skull shapes (see inset). (b) Neurocrania of gymnotiform species in lateral view illustrating extreme brachycephalic and dolichocephalic morphologies. Note multiple independent evolutionary transitions to dolichocephalic and brachycephalic skull shapes