PROC. BIOL. SOC. WASH. 92(1), 1979, pp. 10-22 SOME PHYLOGENETIC IMPLICATIONS OF A DISCOVERY OF ASPIDORAS PAUCIRADIATUS (PISCES: SILURIFORMES: CALLICHTHYIDAE) FROM THE RIO NEGRO IN BRAZIL Stanley H. Weitzman and Martha H. Balph Abstract. — Aspidoras pauciradiatus is redescribed on the basis of 10 specimens collected from the Rio Negro near Tapurucuara, Amazonas, Bra-zil. The occurrence oi Aspidoras nearly 3,000 river kilometers beyond the previously known range of the genus brings into question statements by H. Nijssen and I. J. H. Isbriicker concerning the distribution and relationships of Aspidoras and Corydoras. Substantial variability in size of the frontal cranial frontanel may invalidate the use of this character to separate Aspi-doras from Corydoras, although the two genera still may be distinct on the basis of the supraoccipital fossa. Additional collecting is needed to test further the hypothesis that Aspidoras and Corydoras should be recognized as separate genera. Aspidoras pauciradiatus (Weitzman and Nijssen) has been known from two type specimens collected in 1961 from the Rio Araguaia near Aruana, State of Goias, Brazil (Weitzman and Nijssen, 1970) and from three aquar-ium specimens without known locality (Nijssen and Isbriicker, 1976). The objectives of this paper are: (1) to report on what may be 10 additional specimens of this species (Figs. 1-3) collected in 1972 from the Rio Negro near Tapurucuara, State of Amazonas, Brazil, over 3,000 river kilometers from the type locality and nearly that far out of the previously known range of the genus Aspidoras von Ihering; and (2) to discuss relationships between populations of A. pauciradiatus and between Aspidoras and Corydoras Lacepede in the light of this discovery. Aspidoras pauciradiatus (Weitzman and Nijssen) Figs. 1-3, Table 1 Synonymy. — See Nijssen and Isbriicker (1976:114). Specimens examined. — 1, holotype, National Museum of Natural Histo-ry, United States National Museum (USNM) 191625, SL 23.2 mm, Brazil, State of Goias, Rio Araguaia, near Aruana (14°58'S, 51°04'W), H. R. Ax-elrod, 1960. 1, paratype, USNM 204363, SL 22.6 mm, same data as holo-type. Ten distributed in museums as follows: 2, Academy of Natural Sci-ences, Philadelphia (ANSP) 136687; 2, British Museum (Natural History)
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