A new species of hemiodontid has been described from the Rio Trombetas in Brazil.
Francisco Langeani of the Laboratory of Icthyology at the UNESP in Sao Paulo, described the new species as Hemiodus jatuarana in the latest edition of the systematics journal Zootaxa.
The new fish was found at Oriximina on the Rio Trombetas, one of the Amazon's tributaries. It brings the total number of described species in the genus Hemiodus to 18.
Most Hemiodus are hard to tell apart, with most of the obvious external differences being in their distinctive melanin patterns. H. jatuarana has a horizontally elongated black spot on the caudal peduncle, but no other markings on the body.
Langeani says that H. immaculatus also lacks dark markings on the body, but the species can be distinguished from H. jatuarana by its caudal fin lobes which lack longitudinal stripes, and by its differing number of gill rakers.
For more details see: Langeani, F. (2004) - Hemiodus jatuarana, a new species of Hemiodontidae from the Rio Trombetas, Amazon Basin, Brazil (Teleostei: Characiformes). Zootaxa 546:1-6.