Data from: Evidence for heterochrony in the cranial evolution of fossil crocodyliforms

The southern supercontinent of Gondwana was home to an extraordinary
diversity of stem-crocodylians (Crocodyliformes) during the Late
Cretaceous. The remarkable morphological disparity of notosuchian
crocodyliforms indicates that this group filled a wide range of ecological
roles more frequently occupied by other vertebrates. Among notosuchians,
the distinctive cranial morphology and large body sizes of Baurusuchidae
suggest a role as apex predators in ecosystems in which the otherwise
dominant predatory theropod dinosaurs were scarce. Large-bodied
crocodyliforms, modern and extinct, are known to have reached large sizes
by extending their growth period. In a similar way, peramorphic
heterochronic processes may have driven the evolution of the similarly
large baurusuchids. To assess the presence of peramorphic processes in the
cranial evolution of baurusuchids, we applied a geometric morphometric
approach to investigate ontogenetic cranial shape variation in a
comprehensive sample of notosuchians. Our results provide quantitative
morphological evidence that peramorphic processes influenced the cranial
evolution of baurusuchids. After applying size and ancestral ontogenetic
allometry corrections to our data, we found no support for the action of
either hypermorphosis or acceleration, indicating that these two processes
alone cannot explain the shape variation observed in Notosuchia.
Nevertheless, the strong link between cranial shape variation and size
increase in baurusuchids suggests that peramorphic processes were involved
in the emergence of hypercarnivory in these animals. Our findings
illustrate the role of heterochrony as a macroevolutionary driver, and
stress, once more, the usefulness of geometric morphometric techniques for
identifying heterochronic processes behind evolutionary trends.