Convergent approaches, evolutionary novelties and the origin of the turtle carapace

Abstract

The origin of the turtle carapace has been for a long time an evolutionary mystery. Historically,
two main hypotheses about its emergence disputed the interests of researchers: the composed origin
proposed its genesis by the successive accumulation of osteoderms and their posterior fusion with the
ribs and trunk vertebrae neural arches; the de novo origin, considered the carapace as a novel structure,
derived from intense modification of the ribs and neural arches. In this review, I will show how recent
advances on evolutionary developmental biology and new paleontological findings favored the latter
hypothesis, filling the gaps about the origin and supporting the carapace as an evolutionary novelty,
illustrating how integrative approaches can provide more detailed views on the evolutionary process.