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[[ Genus Cathorops Jordan & Gilbert ]]
The genus Cathorops Jordan & Gilbert, 1882 includes species of small size, reaching a maximum length 360 mm TL, that occur mainly in estuarine and freshwater habitats from southern Mexico to Central and South America (Kailola & Bussing, 1995; Marceniuk & Ferraris, 2003). The species assigned to Cathorops can be easily distinguished from the species belonging to the remaining genera of Ariidae by the absence of vomerine tooth plates (with the exception of C. dasycephalus ), presence of one pair of oval-shaped accessory tooth plates, molariform teeth on accessory plates, adipose-fin remarkably short, and lateral line not bifurcated on caudal region. Cathorops constitutes a natural group, with its monophyletic condition well defined (Marceniuk, 1997; Betancur-R., 2003; Marceniuk, 2003; Betancur-R. et al., 2004). Recently, Marceniuk & Menezes (2007) presented a revision for the genera of the family Ariidae, redefining Cathorops through six exclusive and eleven non-exclusive anatomical characters, whereas Betancur-R. et al. (in press) supported its monophyly by ten morphological and two amino acid synapomorphies. The genus Cathorops comprises 13 species (Marceniuk & Ferraris, 2003; Betancur-R. et al., in press), of which seven occur exclusively in the Pacific portion of America: Cathorops dasycephalus ( Guenther , 1864) , C. fuerthii (Steindachner, 1877) , C. hypophthalmus (Steindachner, 1877) , C. multiradiatus ( Guenther , 1864) , C. steindachneri (Gilbert & Starks, 1904) , C. taylori (Hildebrand, 1925) , and C. tuyra (Meek & Hildebrand, 1923) .
The great similarity in external morphology and coloration, and lack of knowledge of ontogenetic and intersexual differences, often hinders correct identification of Cathorops species (Marceniuk, 1997; Marceniuk, in press). Since its description, Cathorops multiradiatus ( Guenther , 1864) has been recognized and differentiated from its congeners by the large number of anal-fin rays (25-27), a characteristic considered to be exclusive until the present (Eigenmann & Eigenmann, 1890; Jordan & Evermann, 1896; Regan, 1906; Meek & Hildebrand, 1923; Hildebrand, 1946; Kailola & Bussing, 1995). The diversity of the genus and taxonomic status of nominal species from western America were recently examined by Allen & Robertson (1994), Bussing & López (1994), Kailola & Bussing (1995), Chirichigno & Vélez (1998), Castro-Aguirre et al. (1999), Marceniuk & Ferraris (2003) and Nelson et al. (2004).
In the present work, C. manglarensis , a new species with a similar number of anal-fin rays to Cathorops multiradiatus , is described. C. multiradiatus is redescribed and intersexual differences of both species evaluated.