Rio de Janeiro antwren

The Rio de Janeiro antwren, Myrmotherula fluminensis, is a small bird of the typical antbird family Thamnophilidae and is endemic to Brazil. It is known only from a single specimen collected in 1988 in central Rio de Janeiro state, a handful of later observations beginning in 1994, and a few records from the Reserva Ecologica Guapiacu, which lies near the place where the specimen was taken. The bird is about 10 cm long and the type specimen weighed 9 g. The male has gray upperparts, a whitish ring around the eye with a stripe below it, white-tipped black wing coverts, and a black throat, breast and belly centre; the female has never been described. Its status is unsettled: several checklists accept it as a full species, but BirdLife International's handbook treats it as a color morph of the silvery-flanked antwren, and some authors suggest it could be a hybrid. Its diet is almost unknown, and sightings in secondary forest near old clearings have usually involved mixed-species foraging flocks close to the ground.