The discovery of Pappochelys provides strong support for the placement of turtles within Diapsida, a hypothesis that has long been suggested by molecular data, but never previously by the fossil record.

The gastralia (rib-like bones covering the abdomen) are tightly packed and occasionally fused together, forming a structure similar to the plastron of turtles.

[1][3] Fossils of Pappochelys come from a rock group in Germany called the Lower Keuper, which dates to the Ladinian stage of the Middle Triassic, approximately 240 million years ago (Ma), and are restricted to a 5 to 15 centimetres (2 to 6 in) layer of organic-rich claystone in an outcrop of the Erfurt Formation in the town of Vellberg.

In 2015, Schoch and Sues incorporated Pappochelys, Eunotosaurus, and Odontochelys into a phylogenetic analysis along with parareptiles, turtles, and many other reptilian taxa to elucidate their relationships.

Below is a cladogram or evolutionary tree showing the results of their analysis, with stem-turtles denoted by the green bracket:[1] Seymouriidae Diadectomorpha Synapsida Parareptilia Captorhinidae Paleothyris Araeoscelida Claudiosaurus Younginiformes Archosauromorpha(archosaurs: crocodilians, birds, and relatives) Kuehneosauridae Rhynchocephalia Squamata(lizards and snakes) Sauropterygia Eunotosaurus Pappochelys Odontochelys Testudines(turtles) In their description of Chinlechelys, Lichtig & Lucas (2021) criticized Schoch & Sue's hypothesis of turtle origins, particularly the idea shells evolved from broadening ribs with no osteoderms involved (as Pappochelys apparently indicates).

Although Pappochelys lacked a fully formed shell like modern turtles, its thickened bones may have helped reduce the body's buoyancy, making it a more adept swimmer.