First record of the hypoptopomatine genus Eurycheilichthys Reis & Schaefer, 1993 (Siluriformes, Loricariidae) from Argentina

The Neotropical family Loricariidae is the largest within the Siluriformes and contains six subfamilies. The species included in the subfamily Hypoptopomatinae have a wide distribution from the Orinoco basin to the Rio de la Plata, with the largest number of small bodied hypoptopomatine genera distributed in Southeastern Brazil. Among the genera present in Southern Brazil, Eurycheilichthys Reis & Schaefer, 1993 is considered until now endemic to mountain rivers of Rio Grande do Sul State, occurring above 600 m of altitude. Eurycheilichthys pantherinus (Reis & Schaefer, 1992) lives in the Uruguay River basin and E. limulus Reis & Schaefer, 1998 inhabits the upper basin of the Jacui River. Recent samples revealed the presence of E. pantherinus in a small stream of the Uruguay River basin, in the province of Misiones. Thus, this is the first record of the species in the middle Uruguay of Argentina. The specimens examined were collected in the arroyo Garibaldi near San Pedro City (approx. 26°53′00″ S, 54°05′01″ W), a headwater of the arroyo Yaboti Guazu which flows into the Uruguay river (Figures 1 and 2). The stream has very clear, rapidly streaming water and stony bottom. The specimens were collected only in the rapids. Reis and Schaefer (1992) described E. pantherinus by the possession of several characteristics: an apomorphic character seven branched pectoral-fin rays; presence of greatly expanded lower lip (Figure 3); accessory ceratobranchial flange reduced to a slender uncinate process; loss of filamentous gill rakers from the oral surfaces of the hyoid skeleton; and very wide body, with cleithral width 27.5–31.8% SL. The collected specimens have these characteristics, although, one of the two cleared and stained specimens has a large accessory flange in the ceratobranchial. The males have a fleshy flap along the posterior margin of the thickened first pelvic-fin rays. Eurycheilichthys pantherinus also has an accessory series of unicuspid teeth in the maxilla and dentary not associated with the common bicuspid teeth. Reis and Schaefer (1992) commented that this type of unicuspid teeth appears in