Acanthodactyus sp., (Merre 1820) extant, commonly referred to as a fringe-fingered lizard, is smaller than most Tupinambis, but the two are sisters derived from a sister to Eolacerta.
Distinct from Tupinambis, the skull of of Acanthodactylus is shorter with larger orbits, as befitting its reduced size. The parietals are flatter and wider, reducing the upper temporal fenestra to specks. The postfrontal also extends posteriorly to fill the former gap. The rostrum is shorter. The naris is larger. The teeth are small, like those in Eolacerta. The retroarticular process angles down. The internal nares are mere slits against the maxillae. The basisphenoid is greatly enlarged.