Abstract of poster presented at June 2000 meeting of the American Society of Ichthyologists and Herpetologists in La Paz, Baja California, México

Rodiles Hernández, Rocío, Curator of Ichthyology, El Colegio de la Frontera Sur (ECOSUR), San Cristóbal de Las Casas, Chiapas, México,

Carr. Panamericana y Periférico sur s/n, San Cristóbal de Las Casas

Chiapas 29290, México (Phone: 967 81883 ext. 5103, E-mail: rrodiles@scic.ecosur.mx)

Hendrickson, Dean A., Curator of Ichthyology, University of Texas, Texas Natural History Collections, PRC 176 / R4000, 10100 Burnet Road, Austin, TX 78758-4445, USA (Phone (512) 471-9774, deanhend@mail.utexas.edu)

Lundberg, John G., Curator and Chair, Department of Ichthyology, The Academy of Natural Sciences, 1900 Benjamin Franklin Parkway, Philadelphia, PA 19103, USA, (Phone (215) 405-5069, lundberg@acnatsci.org)

Alves Gomes, José A., Pesquisador Titular, Instituto Nacional de Pesquisas da Amazônia - C.P.B.A., C.P. 478, Manaus – AM, 69083-000, Brasil (Pone 55 92 643-3249, puraque@inpa.gov.br)

A new siluriform family from southern México

During 1996-1998, the first author collected specimens of a new, relatively large (up to 463 mm SL) catfish from fast flowing, turbulent, foothill rivers and streams of the Usumacinta drainage in Chiapas, southern México. Three other siluriform family groups occur in the region, ariids, ictalurids and pimelodids. The new catfish lacks all derived features of ariids and the heptapterine pimelodid Rhamdia. It has a nasal barbel on the posterior naris, a derived feature shared with modern ictalurids and many old world taxa. Although resembling ictalurids (most closely Noturus and Pylodictis), its invariant and plesiomorphic pelvic ray count of 6 is unknown in that family, and the pelvic girdle appears plesiomorphic compared to the fossil Astephus + living ictalurids. Furthermore, the apomorphic jaw adductor muscle insertions on the skull roof and associated sculpturing and sagittal crest of ictalurids are lacking. The sphenotic, rather than the frontal (as in modern ictalurids), bears the bifurcation and exit for the infraorbital lateralis canal. Although preliminary, available morphological characters and mtDNA sequences (12s and 16s), do not allow us to assign this previously unseen fish to any described family. Phylogenetic hypotheses for the new species, based on morphology and DNA sequence data, will be presented.

Keywords: SILURIFORMES, MEXICO, CHIAPAS, RIO USUMACINTA, PHYLOGENETIC STUDIES, NEW FAMILY