A standardized series of embryonic stages for the emydid turtle Trachemys scripta

Interspecific comparisons of embryological development in turtles have been confounded by differences in morphology, number of stages, and relative detail of information provided for stages. To mitigate this problem for the family Emydidae, the largest family of turtles, a 27-stage scheme is presented for Trachemys scripta. Because the earliest stages of development are comparable across all turtle taxa, only the latter portion of development (stages 12-26) is emphasized. Stages are defined on the basis of forelimb and claw morphological criteria described previously for Chelydra serpentina.