PROC. BIOL. SOC. WASH. 94(1), 1981, pp. 18-36 SYSTEMATICS AND VARIATION OF THE AZTEC SHINER, NOTROPIS SALLEI, A CYPRINID FISH FROM CENTRAL MEXICO Barry Chernoff and Robert Rush Miller Abstract. — Notropis sallei (Gunther) inhabits upper tributaries of the Rio Balsas, Rio Lerma, and Rio Panuco drainages, the Valley of Mexico, and the small endorheic basin of the Rio Grande de Morelia. The Aztec shiner has had a confusing taxonomic history, having been placed in no fewer than eight genera and 16 nominal taxa. There is much variation within popula-tions and overlap of ranges for most characters analyzed among disjunct populations, thus supporting our conclusion that recognition of only a single highly variable taxon, properly named Notropis sallei, is warranted. A re-description is presented and the generic assignment of the Aztec shiner is discussed. The Aztec shiner, Notropis sallei (Gunther), is one of the southernmost representatives of the American Cyprinidae. It is confined to the Rio Lerma system, including its former Pleistocene connectives within the geological limits of the Mesa Central of Mexico (West, 1964: Fig. 8). The species in-habits upper tributaries of the Rio Lerma, Rio Balsas, and Rio Panuco drainages, the Valley of Mexico, and the small endorheic basin of the Rio Grande de Morelia (Fig. 1). All of these are or have been tributary to the Pacific except the Rio Panuco, which flows to the Gulf of Mexico. Head-water erosion by the Rio Panuco into the Mexican Plateau (Segerstrom, 1962) has transferred the Aztec shiner and other Lerma basin fishes to the Atlantic Slope (Hubbs and Turner, 1939; Barbour, 1973; Barbour and Miller, 1978). The minnow populations here referred to Notropis sallei had a confusing taxonomic history over the last century, with assignment to no fewer than 8 genera, 7 species, and 16 nominal taxa (see below). Papers by Meek (1904), Regan (1906-08), de Buen (1940) and Alvarez (1970) failed to resolve the number of taxa represented by the Aztec shiner or to clarify their geograph-ical distributions. This situation resulted from inadequate study material and from different concepts of what constitute recognizable species and genera. Not enough was known to permit proper evaluation of traits that were thought to distinguish the Aztec shiner generically from its northern rela-tives, especially within the species-rich genus Notropis. Although we still need more information for confident generic assignments of American min-
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