Interdigital cell death during limb development of the turtle and lizard with an interpretation of evolutionary significance.

Cell death accompanies the formation of free digits in birds and mammals. However, in species with webbing between the adult digits, little or no cell death occurs in the prospectively webbed region of the developing interdigit. Cell death does not occur during the formation of free digits in amphibians. In this paper we report that cell death accompanies the formation of the digits in snapping and painted turtles and in the skink (a lizard). We conclude that cell death accompanying the formation of free digits had its origin at the point of amniote emergence during evolution.