View article

We studied the morphology, development, and the terminology of a lobe over the iris present in three genera of South American cycloramphid frogs (Cycloramphus, Thoropa, and Zachaenus). This research is based on dissections and a macroscopic survey of the eyes of tadpoles, post-metamorphosed, and adults of all six species of Thoropa, nine species of Cycloramphus (3 with adults only, and 6 with tadpoles and adults), and Zachaenus parvulus and Zachaenus carvalhoi (only adults). Because at least three distinctive names are associated with a similar lobe on the iris of frogs from different families, we also discuss the properties that guarantee the observed variations of the involved morphologies as homologues. Lastly, we discuss the possibility that structure present in Cycloramphidae may be the first morphological synapomorphy for the family.