The Clavicle and Interclavicle of Odontochelys – a proto-turtle

Today, a little snippet about the turtle shell and its origins.

The turtle plastron
(= lower shell) has its origins in the dermal bones of related reptiles. The interclavicle, renamed entoplastron (= gular) in turtles, is incorporated (Fig. 1) in Odontochelys (Li et al. 2008). The clavicles, renamed the epiplastra in turtles, are also incorporated. More can be learned with Proganochelys, a basal turtle, likewise from the Late Triassic.

Modern turtles
modify these patterns somewhat. Pleurodire turtles add an extra scute, the intergular).

Figure 1. Odontochelys in situ exposed ventrally. The interclavicle (in red) and clavicles (renamed epiplastra, in blue) are located here.

Figure 1. Odontochelys in situ exposed ventrally. The interclavicle (renamed entoplastron, in red) and clavicles (renamed epiplastra, in blue) are located here. Here the right clavicle is shown at full length, crushed into the transverse plane. The left clavicle may be likewise crushed into the transverse plane, but it is largely hidden beneath the plastron here. Both extended vertically in vivo.

Earlier we looked at the origin of turtles in Stephanospondylus, an early splinter from the pareiasaur lineage derived from millerettids. Turtle relationships, and many others, are clarified in the large reptile tree.

References
Li C, Wu X-C, Rieppel O, Wang L-T and Zhao L-J 2008. An ancestral turtle from the Late Triassic of southwestern China. Nature 456: 497-501.

wiki/Odontochelys

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