Lamontichthys stibaros Isbrücker & Nijssen, 1978

Fig. 14

Lamontichthys stibaros Isbrücker & Nijssen, 1978b: 66-69, figs. 8 and 9, 10d, 14, table Ic, Ii-j, IIIb [original description; type locality: Ecuador, “Prov. Pastaza, rio Amazon system, rio Bobonaza in Chicherota, 02°25’S 76°38’W, altitude aprox. 260-280 m, upper rio Pastaza ”]; Isbrücker, 1980: 92 [listed]; Ortega & Vari, 1986: 17 [literature compilation; Peru]; Burgess, 1989: 426-427 [listed; description]; Barriga, 1991: 66 [literature compilation; Oriental Ecuador]; Ferraris & Vari, 1992: 27 [type listed]; Eschmeyer, 1998: 1611 [listed]; Isbrücker, 2001: 29 [listed]; Ferraris Jr., 2003: 336 [listed]; Ferraris Jr., 2007:264 [listed]; Sullivan et al., 2006: [Siluriform higher-level relationships; molecular data, specimen not examined].

Diagnosis. Lamontichthys stibaros differs from all other species of the genus, with the exception of L. avacanoeiro and L. parakana, in the lack of plates on the anterior tip of the snout (vs. anterior portion of snout totally covered with plates or with an inconspicuous naked area), in the teeth with long cusps (vs. short) (Fig. 3), and in the lower lip semi-oval shaped (vs. semicircular) (Fig. 3).

Lamontichthys stibaros differs from L. avacanoeiro and L. parakana in the longer first branched dorsal-fin ray (29.7- 36.8%, vs. 22.6-31.0% SL), in specimens larger than 70 mm SL. It further differs from L. avacanoeiro in the longer first branched pectoral-fin ray (21.7-25.1%, vs. 19.2-22.0% SL) and from L. parakana in the narrower head (89.1-101.4%, vs. 101.3- 106.1% HL).

The presence of 19 to 20 lateral plates along the mid-ventral series (vs. 14 to 18) and the longer dentary (18.6-23.2%, vs. 11.5- 17.3% HL) in specimens larger then 70 mm SL also distinguishes L. stibaros from L. filamentosus and L. llanero . Lamontichthys stibaros differs from L. maracaibero in having more than one plate between the base of the last pelvic-fin ray and the anterior border of the anus (vs. one plate) (Figs. 1 and 5) and in the uniform color pattern of the fins (vs. with brown and gray spots). Morphometric and meristic data are presented in Table 3.

Geographic distribution. Upper rio Amazonas basin (Fig. 2). Lamontichthys stibaros occurs in sympatry with L. filamentous in the drainages of río Santiago, río Marañón and río Ucayali, in Peru.

Material examined (25 specimens; 27.2-172.8 mm SL): Peru: Amazonas: LACM 39897-1, 3, 42.2-89.5, río Santiago; LACM 39884-3, 2, 100.2-120.1, Marañón, río Santiago; LACM 39647-1, 1, 172.6, Marañón, río Cenepa, close to río Tujushiku. Ayacucho: ROM 47093, 2, 122.6-150.1, near to confluence between río Mantaro and Tambo Apurimac . Ucayali: FMNH 84137, 7, 27.2-58.2, río San Alejandro; FMNH 84131, 2, 43.8-47.3; FMNH 84112, 3, 63.3- 86.6, río San Alejandro; FMNH 84111, 6, 49.3-100.1, 1 cs *, 62.4, río San Alejandro .