Clytoctantes atrogularis Lanyon, Stotz and Willard, 1990 (Thamnophilidae) is one of the most mysterious and poorly known birds of the Neotropics. Endemic to Amazonian Brazil, it was known only from the holotype and two sight records at the type locality in Rondônia, and a sighting of a pair with a recording on the Sucunduri River in Amazonas. Here we review the distribution and report five new records in the states of Mato Grosso, Amazonas, and Rondônia, considerably increasing the known range of the species. We present the first detailed descriptions of males, for which the plumage was previously unknown. The records presented herein were made in terra firme forest with understories dominated by Lepidocaryum palms and also with sparse Guadua spp. of bamboo, demonstrating that the bird species occurs in habitats other than those previously described. Stomach contents of six individuals included mostly ants and their eggs, possibly obtained by opening stems of Guadua spp. The high rate of deforestation that characterizes a large part of the range of C. atrogularis could be causing declines in local populations.