A study that focused solely on the mechanism of neck retraction in Chelodina (pleurodire) versus that of Apalone (cryptodire), found an absence of the longissimus and iliocostalis systems and reduced epaxial musculature.

Epaxial musculature that functions in alternated forms of stepping and walking is minimized in turtles, due to their restricted stride lengths and heavily weighted shells.

[citation needed] Cryptodires evolved from pleurodires during the early Jurassic period, originating from South America and Southeast Asia.

[6] By the end of the Jurassic, cryptodires had almost completely replaced pleurodires in the lakes and rivers, while beginning to develop land-based species.

Meanwhile, pleurodires became the dominant freshwater testudines in the Cretaceous to Eocene of Europe,[7] and produced a family of marine species, the Bothremydidae.

These are, in turn, made up from some very basal groups, and the Centrocryptodira contain the prehistoric relatives of the living cryptodires, as well as the latter, which are collectively called Polycryptodira or Durocryptodira.