In turtle embryos, the CR appears at stage 14 of the embryonic stages of turtle development. The CR forms on both sides of the embryo dorsal to the limbs and looks like an outgrowth of the body surface. At this first stage of development, the CR isn’t yet a continuous margin across the neck to the base of the tail. In subsequent stages, it grows both anteriorly and posteriorly and becomes continuous over the base of the tail and the cervical region. When the formation of the embryo is complete, after stage 16 the CR forms a continuous margin delimiting the upper shell.