One of the most distinctive phyletic lines among the diverse Neotropical hylid frogs is composed of a group of 40 species placed in the genus _Phyllomedusa_ (Funkhouser, 1957) or in two or three different genera (Goin, 1961; Lutz, 1966). These species differ from all other Neotropical hylids by possessing a vertical, instead of horizontal, pupil. The only other hylids having a vertical pupil belong to the Papuan genus _Nyctimystes_. Goin (1961) erroneously stated that _Nyctimantis_ and _Triprion_ have vertical pupils.

Although limited information is available on the cytotaxonomy of hylids, the data show that phyllomedusine species have _n_=13 (2_n_=26) chromosomes. _Acris_ has _n_=11 (2_n_=22) (Cole, 1966). Members of the _Hyla leucophyllata_, _microcephala_, and _parviceps_ groups have _n_=15 (2_n_=30), _Gastrotheca ceratophrys_ has a haploid number of 14, the Papuan hylid genus _Nyctimystes_ and all but one of the Australo-Papuan _Hyla_ for which the numbers are known have a haploid number of 13, and all other New World hylids studied have _n_=12 (2_n_=24) (Duellman and Cole, 1965; Duellman, 1967).