The external anatomy of the bony carapace of testudinatans. Pholidosis is shown by the imprints (sulci) left by the borders of the corneous scutes. Kayentachelys aprix is the oldest known testudinatan that displays the complete mesochelydian plan: the general layout of bone plates and scutes that is preserved in the majority of living turtles, such as the emydid Malaclemys terrapin. Earlier testudinatans like Proganochelys quendstedti and Proterochersis porebensis (reconstructions) had more capacial scutes, and the series of marginal scutes did not meet in the posterior part of the carapace. Proterochersis also shows evidence of numerous irregular bone plates that are not present in mesochelydians; see Szczygielski & Sulej (2019) for details. Labelled elements are bone plates. Scute homologies are colour-coded. Thin lines represent bone plate sutures; thick lines represent sulci. The sutures in Proganochelys are unknown. Proganochelys after Gaffney (1990), Proterochersis after Szczygielski & Sulej (2019), Kayentachelys after Joyce (unpublished), Malaclemys by E.A.

  Part of: Ascarrunz E, Sánchez-Villagra MR (2022) The macroevolutionary and developmental evolution of the turtle carapacial scutes. Vertebrate Zoology 72: 29-46.