new synonymy:
Acrobrycon ipanquianus (Cope, 1877)
is a senior synonym of
Acrobrycon tarijae Fowler, 1940

published in:
Arcila, D., R.P. Vari & N.A. Menezes (2013):
Revision of the neotropical genus Acrobrycon (Ostariophysi: Characiformes: Characidae) with description of two new species.
Copeia 2013 (4): 604-611

abstract (from publication):
Acrobrycon, a genus of Neotropical freshwater fishes from the western Amazon and northwestern portions of the La Plata basin, is revised. The genus is found to include three species, two of which are new to science. Acrobrycon ipanquianus is distributed from the western portions of the Rio Amazonas through to the northwestern region of the Rio de La Plata basin; A. starnesi, new species, in the southwestern portion of the Amazon basin in Bolivia; and A. ortii, new species, in the northwestern Rio de La Plata basin in Argentina. Members of the genus are distinguished from each other on the basis of the depth at the dorsal-fin origin, the horizontal eye diameter, the least interorbital width, and the numbers of perforated lateral-line scales, anal-fin rays, and horizontal scales around the caudal peduncle. The analysis found that A. tarijae, described from the Rio Lipeo in Bolivia, cannot be distinguished morphologically from A. ipanquianus; thus, A. tarijae is placed into the synonymy of A. ipanquianus.

The authors erroneously report the new species Acrobrycon ortii as being found in Argentina in the abstract, introduction and key of species (pers.comm. D. Arcila). The only so far known material is from Bolivia as mentioned in the list of type specimens.