An ancestral turtle from the Late Triassic of southwestern China

Odontochelys specimens IVPP V 15639, V 13240 and V 15653 preserve a developed plastron with expanded ribs and neural plates but no complete carapace; plastron-first assembly, basal topology and habitat remain interpretations.

The atlas uses the approximately 220 Ma Odontochelys sample to anchor the older edge of its turtle-line Testudines navigation envelope and living turtles at 0 Ma for the younger edge; Odontochelys is treated as stem evidence, not a crown-Testudines global first appearance or direct ancestor.

Li et al. place Odontochelys basal to the known fossil and living turtles in their analysis, while the broader Mesozoic turtle matrix of Joyce samples 45 fossil and 22 living species; this profile retains Testudines as a navigation route rather than a single resolved stem-to-crown topology.

The documented turtle-line samples include Odontochelys from Late Triassic marine deposits in southwestern China and Pappochelys from the Middle Triassic Vellberg deposits of Germany; these named localities do not establish a global Testudines distribution.

The cited turtle-line sample records complementary shell mosaics: Odontochelys has a developed plastron, expanded ribs and neural plates without a complete carapace, whereas Pappochelys has broadened ribs and robust paired gastralia without a fused plastron or complete carapace.

Li et al. interpret the marine deposits yielding Odontochelys as marginal sea or river-delta settings, while the cited Pappochelys shell study addresses anatomy and shell evolution; these observations do not establish diet, body size or a single ecological guild for Testudines.