Figure 1.

Time‐calibrated phylogeny of the casque‐headed lizards (Corytophanidae), and sexual dimorphism in head structure among extant species. (a) The sexual dimorphism in the head anatomy is evidenced by the crest structure, which is present in most members (=basiliscus, plumifrons, and vittatus) of Basiliscus. (b) Mesh deformation plots are the result of forcing female head landmarks into those of the males for each species; members of Corytophanes and Laemanctus show almost no deformation, while this is well developed in Basiliscus. The inclusion of the corytophanid fossils Babibasiliscus alxi and Geiseltaliellus maarius in the estimation of the chronogram has almost doubled the inferred ages of the crown and genus‐level divergences in Corytophanidae (previous estimates are indicated in the top‐left blue phylogeny). Nodal support (i.e., ML bootstrap support ≥ 60) is provided by values above lines and high support (i.e., ML support = 100) are indicated by an (*). The skulls are examples of each genus modified from (Conrad, 2015); the red overlay corresponds to the parietal crest bone and a question mark (?) indicates that the evidence of a crest is inconclusive. We propose two alternative evolutionary trajectories of this structure: ornamental (Basilicus) and biomechanical (Corytophanes); while this bone in Laemanctus shows an intermediate state