The iguanid genera Diplolaemus, Leiosaurus, Aperopristis and Cupriguanus are discussed and several morphological characters such as palatine teeth, or sub-ocular, sub-digital and tail scales are analyzed. Some progressive evolutive trends from Aperopristis to Diplolaemus are pointed out, together with geographical distribution of the genera. The real geographical distribution of the Bell’s forms (Diplolaemus darwini and bibroni) is discussed and confirmed.