Hemipenes in females of the Mexican viviparous lizard Barisia imbricata (Squamata: Anguidae): an example of heterochrony in sexual development.

The sexual development of saurians follows a similar pattern to that described for other amniotes. Changes in the timing or sequence of development events are known as heterochrony. We describe the pattern of sexual development in the viviparous Mexican lizard Barisia imbricata and report heterochrony in the regression of hemipenes in this lizard.