Genidens Castelnau, 1855

(fig. 54)

Genidens Castelnau, 1855: 33. Type species: Bagrus genidens Valenciennes, 1840 (= Pimelodus genidens Cuvier, 1829). Type by absolute tautonymy. Gender: masculine.

Guiritinga Bleeker, 1858: 62 and 67. Type species: Pimelodus commersonii Lacépède, 1803. Type by monotypy. Gender: feminine.

Diagnosis. The combination of two unique (1 and 2) and eight shared (3 to 10) characters distinguishes the species of Genidens from all other genera of the Ariidae: (1) tooth plates associated with vomer movably attached to bone by ligamentous tissue (with exception of G. genidens); (2) lateral margins of orbitosphenoid converging anteroposteriorly; (3) posterior cranial fontanel reduced to a small opening [shared with Bagre, Brustiarius, Cathorops (with exception of C. dasycephalus), Galeichthys, Netuma and Plicofollis (with exception of P. platystomus)]; (4) temporal fossa very reduced or partially closed (shared with Bagre panamensis, B. pinnimaculatus, Brustiarius, Cathorops, Cephalocassis borneensis, Cryptarius, Galeichthys and Netuma bilineatus, Sciades); (5) proximal 2/3 of maxillary lateral margins parallel, distal 1/3 of bone narrower and posterior part truncate (shared with Carlarius heudelotii, Netuma thalassinus, Plicofollis and Sciades platypogon); (6) dentary teeth restricted to mesial 2/3 of bone (shared with Cephalocassis and Cryptarius); (7) posteroventral portion of opercle little pronounced posteriorly [shared with Bagre panamensis, Carlarius (with exception of C. heudelotii), Galeichthys, Ketengus, Plicofollis (with exception of P. platystomus) and Sciades (with exception of S. couma and S. felis)]; (8) lateral processes of urohyal short (fig. 55) [shared with Batrachocephalus, Cathorops, Cephalocassis borneensis, Cinetodus, Galeichthys, Ketengus, Osteogeneiosus, Pachyula and Plicofollis (with exception of P. platystomus)]; (9) urohyal lateral processes half as long as medial process (shared with Arius, Aspistor, Batrachocephalus, Cathorops, Cephalocassis borneensis, Cinetodus, Ketengus, Osteogeneiosus, Nedystoma, Nemapteryx, Netuma thalassinus and Pachyula); (10) posterior portion of second basibranchial short (fig. 56) (shared with Arius gagora, A. maculatus, Aspistor and Netuma).

Supplementary morphological characters. Cephalic shield granulated visible under the skin; lateral ethmoid and frontal limiting a small fenestra scarcely visible under the skin; medial groove of neurocranium very distinct, limited by frontals and/or on supraoccipital; posterior cranial fontanel very reduced closing completely with growth; fenestra limited by supraoccipital, pterotic and sphenotic absent; fossa limited by pterotic, supracleithrum and extrascapular very reduced; epioccipital not invading dorsal portion of cephalic shield; occipital process triangular moderately long and wide, narrower at posterior end; anterior and median nuchal plates fused and indistinct, forming a structure of semi-lunar aspect; tooth plates associated with vomer round or absent; accessory tooth plates with shape highly variable, bearing conical teeth; maxillary barbel fleshy and cylindrical; two pairs of mental barbels; base of adipose fin moderately long, about half as long as anal-fin base; lateral line not bifurcated at caudal region, reaching base of caudal-fin upper lobe; cleithrum wide, with second dorsal process on its upper portion; posterior cleithral process of moderate size, distinct from second dorsal process of cleithrum.

Remarks. The nominal genus Guiritinga is a junior synonym of Genidens based on the examination and analysis of its type-species Pimelodus commersonii Lacépède, 1803 (= Pimelodus barbus Lacépède, 1803). G. planifrons (Higuchi et al., 1982) was included on the basis of presence diagnostic external morphological features observed in specimens preserved in alcohol.

Distribution and habitat. Southeast of South America, marine and brackish waters.