DiagnosisIschnocnema henselii is a medium-sized species of the E. guentheri cluster sensu Heyer (1984). It is characterized by a prolonged advertisement call with a duration of about 10-25 sec, consisting of a series of more than 80 notes (up to 170). In other species of the guentheri cluster, the call is much shorter, consisting of 5-10 notes, with a maximum of 35 notes with a total duration of less than 3 sec. Ischnocnema henselii is a cryptic species that is not absolutely distinguishable morphologically from I. guentheri. Although I. henselii has a rounded, slightly protruding snout profile, the snout is more sloping in I. guentheri. The throat is usually white and unmottled in I. henselii but gray mottled in I. guentheri. Other Ischnocnema species occurring syntopically with I. henselii are I. manezinho. Ischnocnema henselii is distinguished from I. manezinho by the more slender body, smaller finger discs and longer hind legs (shank length about 68-69% snout-vent length in I. henselii; 58% snout-vent length in I. manezinho).