Conorhynchos nelsoni Systematics of the family Ariidae (Ostariophysi, Siluriformes), with a redefinition of the genera. Alexandre P. Marceniuk Naércio A. Menezes Zootaxa 2007 1416 1 126 4M38W 419349 Actinopterygii Ariidae Potamarius Animalia Siluriformes 98 Chordata species nelsoni  (fig. 84)   Conorhynchos nelsoniEvermann & Goldsborough, 1902: 140, fig. 1. Type locality:  rioUsumacinta, Montecristo,  Yucatan, Mexico. Holotype:  USNM50001.  Paratypes:  USNM52963.  Distribution: Usumacinta River basin. Countries: Mexico and Guatemala.  Habitat: Freshwater.    FIGURE87. Potamarius izabalensis, UMMZ 177252. Dorsal view of neurocranium. Scale bar = 10 mm. FR - frontal; LET - lateral ethmoid; LN - lateral horn; MS - mesethmoid.   Maximumsize: 390 mm TL.  Material examined:   AMNH25684(2 al, 217-233 mm TL), Guatemala, Peten, rio de la Passion, Altos de los Sacrificios. 923907214 USNM Mexico rio Usumacinta, Montecristo USNM 50001 Yucatan Holotype 923907212 USNM Mexico rio Usumacinta, Montecristo USNM 52963 Yucatan Paratype 923907187 AMNH Guatemala rio de la Passion, Altos de los Sacrificios AMNH 25684 Peten