Lamontichthys filamentosus (LaMonte, 1935)

Fig. 10

Harttia filamentosa LaMonte, 1935: 5-6, fig. 4 [original description; type locality: Brazil, Amazonas, rio Juruá drainage, vicinity of mouth of rio Embira, tributary of the rio Tarauacá, 7°30’S 70°15’W]; Conci & Michelangeli, 1974: 226 [listed].

Lamontichthys filamentosa: Miranda-Ribeiro, 1939: 12 [original description of genus; designation of typespecies]; Gosline, 1945: 108 [listed]; Barzanti & Oldani, 1976: 130-137 [incorrect identification; based on four specimens of probably, Loricaria sp., Loricariinae; Argentina, rio Paraná basin - specimens not examined].

Harttia filamentissima Eigenmann &Allen, 1942: 211, 445, pl. VIII figs. 1 and 2 [original description; type locality: Peru, Loreto, río Huallaga; Fowler, 1945: 109 [listed; Peru]; Gosline, 1945: 108 [listed]; Tovar Serpa, 1967: 222 [listed; Peru]; Ovchynnyk, 1968: 258 [Chicherota, near the mouth of the río Bobonaza, tributary of the upper río Pastaza, specimen not examined].

Lamontichthys filamentosus: Ovchynnyk, 1968: 258 [Eastern Ecuador]; Isbrücker & Nijssen, 1976: 121-122 [7 branched pectoral-fin rays as diagnostic for Lamontichthys; Harttia filamentissima presumed to be a synonym of L. filamentosus]; Isbrücker & Nijssen, 1978b: 57-80, fig. 1-4, 7, 10a,c, 14, table Ia, IIa-h, IIIa [redescription; Harttia filamentissima as synonym of L. filamentosus; photographs of types of both species; specimens not examined]; Isbrücker, 1978: 88 [listed]; Isbrücker, 1980: 91 [listed]; Ortega & Vari 1986: 17 [literature compilation; Peru]; Burgess, 1989: 426-427, 440 [description]; Barriga, 1991: 66 [eastern drainages of Ecuador]; Lauzanne et al., 1991: 70, 73, table I and IV [Bolivia, upper rio Madeira basin, rio Chapare; specimens not examined]; Eschmeyer, 1998: 578 [listed]; Chernoff et al., 1999a, 1999b: 59 [Bolivia, upper río Orthon basin]; Sarmiento et al., 1999: 92 [Bolivia, Pando, río Tahuamanu]; Machado-Allison et al., 1999: 50 [Bolivia, Pando, upper and middle río Tahuamanu, specimens not examined]; Begossi et al., 1999: 79, table I [Brazil, Acre, upper rio Juruá; common name]; Silvano et al., 2001: 158- 159 [Brazil, Acre, upper rio Juruá; common name; photograph]; Isbrücker, 2001: 27, 29 [listed]; Ferraris Jr., 2003: 336 [listed]; Buckup et al. 2007:88 [listed]; Ferraris Jr., 2007: 263 [listed].

Parasturisoma filamentosa: Boeseman, 1971: 9 [listed].

Parasturisoma filamentissima: Boeseman, 1971: 9 [listed].

Diagnosis. Specimens of Lamontichthys filamentosus larger than 60 mm SL are distinguished from all congeners by having the pectoral-fin spine extending into a very long filament that may exceed four times the length of the first branched pectoralfin ray (vs. not extending into a long filament in the remaining species of Lamontichthys) (Fig. 10). The pectoral-fin filament is very fragile, breaks off easily, and it is frequently damaged in preserved specimens.

Lamontichthys filamentosus is further distinguished from all other Lamontichthys species, except L. llanero, by having the dorsal-fin spine prolonged into a long filament that may reach the posterior margin of the caudal fin (vs. dorsal-fin spine not extending into a long filament) and by the lower lip with a semicircular shape (Fig. 9a) (vs. semi-oval, Fig. 9b). Lamontichthys filamentosus is further distinguished from L. llanero by having a broader head (97.4-111.1%, vs. 82.6-96.9% HL).

Lamontichthys filamentosus is distinguished from L. maracaibero, L. stibaros, and L. parakana by having fewer lateral plates on the mid-ventral series (14 to 18, vs. 18 to 20). The presence of more than one plate between the base of the innermost pelvic-fin ray and the anterior margin of the anus further distinguishes Lamontichthys filamentosus from L. maracaibero, which has only one plate (Figs. 1 and 5).

Lamontichthys filamentosus is further distinguished from L. stibaros, L. avacanoeiro, and L. parakana by having the anterior portion of the snout almost totally covered with plates (vs. anterior portion of the snout with a large nude area lacking plates) and by the teeth with short cusps (vs. long) (Fig. 3). The longer first branched dorsal-fin ray further distinguishes Lamontichthys filamentosus from L. avacanoeiro (27.8-39.9%, vs. 20.5-26.0% SL). Morphometric and meristic data are presented in Table 1.

Geographic distribution. Upper and middle rioAmazonas basin (Fig. 2). Lamontichthys filamentosus occurs in sympatry with L. stibaros in the drainages of río Ucayali and río Marañón (upper rio Amazonas basin).

Comments. Specimens smaller than 80 mm SL differ from adults in having various poorly defined transversal bands on the back, between the base of the last dorsal-fin ray and the base of the caudal fin.

Fins of specimens from the upper rio Madeira (FMNH 107021, 1, 119.6 mm SL), upper rio Juruá (MZUSP 50379 and 50497, 3, 158.3- 172.5 mm SL) and one specimen from upper rio Purus basin (MCP 28834, 154.9 mm SL) have gray and light brown small spots, forming short transversal bands more evident on the pectoral-fin spine and unbranched pelvic-fin ray. In addition, the specimens from the upper rio Madeira basin (FMNH 107021) and upper rio Purus basin (MCP 28834) also have the head relatively larger than the other specimens of similar size (18.2-19.3%, vs. 16.5-18,0% SL, n = 13, 119.4- 172.5 mm SL). Isbrücker & Nijssen (1978b) previously reported on the variation of color pattern in specimens of L. filamentosus from the río Chapare, upper rio Madeira basin in Bolivia, and suggested that those specimens could represent a distinct subspecies or species. Although some differences were observed in specimens from the upper rio Juruá, rio Purus and rio Madeira basins, the reduced (n = 6) number of specimens from these localities do not allow to infer if these differences are significant, and we therefore chose to conservatively assign them to L. filamentosus .

Although the holotype of Harttia filamentissima Eigenmann &Allen (1942: 211) was not examined, information from the literature and photographs (available at www.calacademy.org) allowed us to confirm the synonymy of this species with L. filamentosus, previously proposed by Isbrücker & Nijssen (1978b).

Material examined (63 specimens; 38.8-172.5 mm SL): Bolivia: FMNH 107021, 1, 119.6, upper rio Madeira, Pando, 1.5 km above mouth of río Muyumanu . Brazil: Acre: MZUSP 50379, 1, 172.5, upper rio Juruá, Colocação São João ; MZUSP 50497, 2, 158.3- 158.7, upper rio Juruá, mouth of rio Tejo; MCP 28834, 2, 154,9- 168,8, upper rio Purus, Bujari, igarapé Antimari, BR 364, 58 km SE of Sena Madureira. Amazonas: MZUSP 57463, 1, 62.3, rio Amazonas, below rio Madeira; MZUSP 75367, 1, 38.8, rio Amazonas, below rio Negro; INPA 17927, 2, 75.8-79.4; MZUSP 57460, 1, 65.9, rio Solimões, below rio Purus . Ecuador: FMNH 104334, 1, 155.7, Napo, río Napo . Peru: Amazonas: LACM 41724-9, 10, 120.2-150.8, Marañón, río Santiago; LACM 41705- 9, 11, 130.7-153.3; LACM 41729-29, 13, 128.2-154.1, Marañón, río Santiago in La Poza ; LACM 41741-9, 13, 82.5-169.0, 1cs *, 119.4, LACM 42001-7, 1, 162.8, LACM 41740-13, 1, 167.4, confluence of río Marañon with río Nieva; LACM 42005-6, 1, 155.8, Marañón, near Caterpiza; LACM 39884-7, 1, 139.2, Marañón, Galilea, río Santiago .