Data from: Heterochronic shifts and conserved embryonic shape underlie crocodylian craniofacial disparity and convergence

The distinctive anatomy of the crocodylian skull is intimately linked with
dietary ecology, resulting in repeated convergence on blunt- and
slender-snouted ecomorphs. These evolutionary shifts depend upon
modifications of the developmental processes which direct growth and
morphogenesis. Here we examine the evolution of cranial ontogenetic
trajectories to shed light on the mechanisms underlying convergent snout
evolution. We use geometric morphometrics to quantify skeletogenesis in an
evolutionary context and reconstruct ancestral patterns of ontogenetic
allometry to understand the developmental drivers of craniofacial
diversity within Crocodylia. Our analyses uncovered a conserved embryonic
region of morphospace (CER) shared by all non-gavialid crocodylians
regardless of their eventual adult ecomorph. This observation suggests the
presence of conserved developmental processes during early development
(before Ferguson stage 20) across most of Crocodylia. Ancestral state
reconstruction of ontogenetic trajectories revealed heterochrony,
developmental constraint, and developmental systems drift have all played
essential roles in the evolution of ecomorphs. Based on these
observations, we conclude that two separate, but interconnected,
developmental programs controlling craniofacial morphogenesis and growth
enabled the evolutionary plasticity of skull shape in crocodylians.