Redescription and variation of Hyophryne histrio Carvalho, 1954, an enigmatic microhylid frog from the Atlantic Rainforest of Brazil
Hyophryne histrio was described in 1954 as a new species and placed in its own genus based on a single juvenile specimen from Ilhéus, State of Bahia, northeastern Brazil. This species was known only from the holotype until 1999 when a series of specimens was collected 50 km from the type-locality. Herein, we provide a redescription of the species based on this new material and present new information on morphological variation in order to help with the recognition of this poorly known species. The diagnostic characters are: occipital skin fold present, interdigital membranes between the toes well developed, dark venter with white blotches, an arrow-shaped dorsal color pattern that begins just after the occipital fold, and a distinct pale line between the venter and dorsum. Dermal spines, which were found in all males and vary in the number of spines and location, are reported for the first time in this species; gravid females have dermal spines only in the pericloacal region. We also compare Hyophryne histrio to all other Neotropical microhylid genera.