The systematics of the South American characoid subfamily Anostominae is reviewed on the basis of 36 morphometric and meristic characters, and the osteology is described. A new genus, Pseudanos, is described for a monophyletic lineage previously assigned to Anostomus. Two new species, Anostomus intermedius dind Pseudanos irinae, are described. The subfamily consists of five genera, three of which are monotypic. A hypothesis of the phylogenetic relationships of the members of the Anostominae is presented, based primarily on their osteology. The monotypic genera together form a monophyletic assemblage. Zoogeographic interpretations are not attempted, since vast areas (particularly in the central Amazon basin) are as yet either not or inadequately sampled. Considerable distributional extensions and discovery of new forms are to be expected in the future. Abstracto La sistematica de los Characoides Sud-Americanos (Caracoides), subfamilia Anostominae es revisada en base a 36 caracteres morfometricos y meristicos, describiendo tambien su osteologia. Un nuevo genero, Pseudanos es descrito en un lineage monofiletico, anteriormente asignado a Anostomus. Dos nuevas especies son descritas: Anostomus intermedius y Pseudanos irinae. La subfamilia consiste de cinco generos, tres de los cuales son monotipicos. Se presento una hipotesis de la relacion filetica de los Anostominae, basada principalmente en su osteologia. Los generos monotipicos forman en conjunto un grupo monofiletico. Interpretaciones zoogeograficas no son intentadas, ya que regiones muy vastas (especialmente en la Cuenca Central del Amazona) no han sido aun, o solo parcialmente estudiadas. Una distribucion extensional mucho mayor y el descubrimiento de nuevas formas se esperan en el futuro. Although this paper is not concerned with the relationships of the entire family Anostomidae, I propose a new concept for the subfamily Anostominae (here conceived as encompassing the genera Anostomus, Pseudanos, Gnathodolus, Sartor and Synaptolaemus) on the basis of its monophyly (see the diagnosis of the subfamily, p. 4, and discussion, p. 48). Other genera I recognize in the family Anostomidae (but here exclude from the Anostominae) are Abramites, Anostomoides, Laemolvta, Leporellus, Leporinus, Rhytiodus and Schizodon, following Myers (1950) and Gery (1961, 1972/73). This number will probably be increased when further specimens make it possible to describe formally an anostomid with more than 65 lateral line scales from the vicinity of Manaus figured and described (but not named) by Gery (1972/73), and another form from the Essequibo River which has an incomplete lateral line (and is represented by three small specimens in the collections of the National Museum of Canada). After this paper had been accepted for publication, I received a copy of Gery's (1977) "Characoids of the world". In this work, Gery recognizes the family Anostomidae, and includes all the genera accepted here. However, we differ significantly in subsequent subdivision. Gery (op. cit.) recognizes a subfa...