PROC. BIOL. SOC. WASH. 100(1), 1987, pp. 89-103 HEADSTANDERS OF THE NEOTROPICAL ANOSTOMID GENUS ABRAMITES (PISCES: CHARACIFORMES: ANOSTOMIDAE) Richard P. Vari and Ann M. Williams Abstract.— ThQ anostomid characiform genus Abramites Fowler (1906) is revised and two species are recognized. Abramites eques (Steindachner, 1878) occurs only in the Rio Magdalena basin of Colombia. Abramites hypselonotus (Gunther, 1868) is distributed through the Rio Orinoco, Rio Amazonas, and the Rio Paraguay-lower Rio Parana systems. The two species can be distin-guished via differences in pigmentation, meristics, and morphometries. Le-porinus solarii Holmberg (1887), Abramites microcephalus Norman (1926), Abramites ternetzi Norman (1926) and Leporinus nigripinnis Meinken (1935) are placed as synonyms of Abramites hypselonotus (Giinther). The genus is characterized by its deep body, postpelvic median keel, increased anal-fin ray count, and perhaps by a unique autogenous ossification on the dorsomedial surface of the fourth infrapharyngobranchial. A key is provided to the species oi Abramites. The genus Abramites comprises a small group of distinctive anostomid characi-forms whose common aquarium name of "headstanders" derives from their habit of resting in life with the body at a distinct angle with the head down (see Gery 1977: 177 for life photos showing this trait). Abramites species occur in the Rio Mag-dalena system of trans-Andean northwest-em South America, and in the Rio Orinoco, Rio Amazonas and the Rio Paraguay and lower Rio Parana systems of the cis-Andean slope of the continent. The two species we recognize as valid, Abramites hypselonotus (Giinther, 1868) and A. eques (Steindach-ner, 1878), were originally described as members of the large anostomid genus Le-porinus. Fowler (1906:331) advanced Abramites for A. hypselonotus, citing the longer anal-fin base in that species as a char-acter distinguishing it from the remainder of Leporinus. Eigenmann (1920a:31, 1920b: 16, 1923:1 17) expanded Abramites by add-ing Leporinus eques Steindachner of the Magdalena system in Colombia, a practice followed by Norman (1926:92-94). Boro-din (1929:287), apparently unaware of Ei-genmann's and Norman's publications, in-dependently noted that Leporinus eques Steindachner was closely aligned to L. hyp-selonotus. Although Borodin discussed two additional characters diagnostic for Abra-mites relative to Leporinus (sensu 5uictu>, he considered the two taxa to be congeneric. The synonymy oi Abramites into Leporinus was continued by some authors (e.g., Ei-genmann and Allen 1942:305 and 308), but most researchers have followed Fowler in recognizing a distinct Abramites for this readily distinguishable group of anostomid fishes. Although the overall body form readily delimits the genus, the number of recogniz-able species oi Abramites has not previously been analyzed in depth. Bohlke (1958:101-105) presented evidence for the synonymy of Abramites microcephalus Norman into A. hypselonotus (Gunther). The other nom-inal cis-Andean species have not been the subject of thorough systematic studies. Dif-
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