Pimelodella longibarbata, Cortés-Hernández & Donascimiento & Ramírez-Gil, 2020

Cortés-Hernández, Miguel Ángel, Donascimiento, Carlos & Ramírez-Gil, Hernando, 2020, A new species of Pimelodella Eigenmann & Eigenmann, 1888 (Siluriformes: Heptapteridae) from the Orinoco River basin, Zootaxa 4808 (3), pp. 491-506 : 492-497

Pimelodella longibarbata , new species

( Figs. 1–4 , Table 1)

urn:lsid:zoobank.org:act:9003327E-9205-4685-B21F-B6E8D92FB37A

Holotype. IAvH-P 21920, 48.6 mm SL. Venezuela, Apure, El Amparo, NN creek, tributary of Caño Verde , 07°06’33.3”N 70°41’26.3”W, 2 Oct 2017, L. M. Mesa-Salazar. O. E. Castillo-G, J. M. Quiñones-Montiel.

Paratypes. Venezuela: IAvH-P 17879, 2 (48.7–60.3 mm SL), 1 c&s (48.8 mm SL), collected with the holotype. Colombia: IAvH-P 12039, 3 (57.7–71.8 mm SL), Arauca, Arauca, río Lipa , 06°46’48.3”N 71°01’20.3”W, L. Ortíz, 10 Mar 2013 ; IAvH-P 13025, 1 (45.4 mm SL), Arauca, Puerto Rondón, río Cravo , 06°30’26”N 70°45’14.9”W, L. Ortíz, 5 Dec 2014 ; IAvH-P 17212, 1 (56.9 mm SL), Casanare, Paz de Ariporo, laguna Las Brisas , 05°39’37.4”N 70°55’40.7”W, A. Urbano-Bonilla & A. Méndez-López, 17 Apr 2016 ; IAvH-P 17281, 4 (58.8–75.2 mm SL), 1 c&s (60.1 mm SL), Casanare, Paz de Ariporo, Tapa La Guayabera , 05°38’41.4”N 71°13’47.7”W, A. Urbano-Bonilla & A. Méndez-López, 20 Apr 2016 ; IAvH-P 17300, 3 (44.5–51.4 mm SL), Casanare, Paz de Ariporo, Tapa El Venado , 05°36’49.5”N 71°05’44.3”W, A. Urbano-Bonilla & A. Méndez-López, 7 Apr 2016 ; IAvH-P 17309, 2 (67.9–69.6 mm SL), Casanare, Paz de Ariporo, Tapa Los Hilariones , 05°36’34.4”N 71°11’13.3”W, A. Urbano-Bonilla & A. Méndez-López, 21 Sep 2016 ; IAvH-P 17321, 2 (48.7–56.7 mm SL), Casanare, Paz de Ariporo, Tapa El Venado , 05°36’49.5”N 71°05’44.3”W, A. Urbano-Bonilla & A. Méndez-López, 21 Sep 2016 ; IAvH-P 17365, 7 (43.9–58.6 mm SL), Casanare, Paz de Ariporo, Tapa Las Matas , 05°39’14.3”N 71°00’31.4”W, A. Urbano-Bonilla & A. Mé- ndez-López, 19 Sep 2016 ; IAvH-P 17389, 3 (32.4–58.6 mm SL), Casanare, Paz de Ariporo, caño La Hermosa , 05°42’20.8”N 71°01’11.3”W, A. Urbano-Bonilla & A. Méndez-López, 23 Sep 2016 ; IAvH-P 17463, 1 (56.3 mm SL), Casanare, Paz de Ariporo, laguna Las Brisas , 05°39’37.4”N 70°55’40.7”W, A. Urbano-Bonilla & A. Méndez-López, 24 Sep 2016 ; IAvH-P 21908, 3 (60.1–61.7 mm SL), Arauca, Arauca, caño Primores , 06°47’13.1”N 71°03’47.2”W, L. Ortíz, 12 Mar 2013 .

Diagnosis. Pimelodella longibarbata differs from all congeners, except P. cruxenti , P. howesi , P. humeralis , P. mucosa , and P. notomelas by having a long maxillary barbel that surpasses the tip of the dorsal lobe of the caudal fin (vs. maxillary barbel reaching between the origin of pelvic fin and the base of caudal fin). The new species is distinguished from P. cruxenti , P. howesi , and P. humeralis by having fewer total vertebrae (40–42 vs. 44 in P. howesi , 47–49 in P. cruxenti and P. humeralis ). Additionally, it can be differentiated from P. cruxenti and P. humeralis by having a shorter adipose fin (32.8–36.4% of SL vs. 48.7–51.3% in P. cruxenti ; 41.8–45.3% in P. humeralis ). Furthermore, P. longibarbata is distinguished from P. humeralis by lacking a dark anteriorly oblique blotch in the humeral region (vs. blotch present), and from P. howesi by having the ventral lobe of the caudal fin longer (vs. dorsal lobe slightly longer). Pimelodella longibarbata is distinguished from P. mucosa by having a longer adipose fin (32.8–36.4% of SL vs. 28.6%), shorter anal fin (8.7–12.0% of SL vs. 13.4%), background body coloration yellowish (vs. brown), faint and narrow midlateral stripe (vs. well-developed and wide midlateral band), and paired dorsal brown stripes absent (vs. present). Pimelodella longibarbata is distinguished from P. notomelas by lacking black pigmentation on distal third of dorsal fin (vs. distal third of dorsal fin dark brown to black).

Description. Morphometric data summarized in Table 1. Body elongate, deeper at dorsal-fin origin. Dorsal profile of body rises in a convex curve from snout to above orbit, then straight and upward to dorsal-fin origin, dorsal fin base convex, slightly concave from posterior end of dorsal-fin to adipose-fin origin, slightly convex along adipose-fin base, and concave along caudal peduncle. Ventral profile of body straight to slightly convex from jaw tip to pelvic-fin origin, slightly concave between pelvic-fin and anal-fin origin, anal-fin base straight and upward, and concave along caudal peduncle ( Figs. 1–2 ).

Head conical. Mouth subterminal, upper jaw more pronounced than lower jaw. Premaxilla and dentary with five or six rows of villiform teeth. Anterior naris tubular. Posterior naris rounded, slightly closer to anterior ocular margin than to anterior nares, anteromedially bordered by a fleshy margin. Nares disposed in trapezoidal arrangement. Barbels thin and slightly flattened, elliptical in cross section. Maxillary barbel surpassing upper caudal-fin lobe. Outer mental barbel reaching between distal end of pectoral-fin and pelvic-fin origin. Inner mental barbel reaching pectoral-fin base. Eye slightly elliptical, its greatest diameter along horizontal axis, placed dorsolaterally. Limits of eye well-defined by a free orbital rim. Supraoccipital process subrectangular in shape and long, reaching anterior nuchal plate. Branchiostegal membranes almost entirely free, united to isthmus only at medial apex and not joined to each other anteriorly. Branchiostegal rays six. Gill rakers on first gill arch 8–10, 6–7 associated to anterior margin of ceratobranchial, usually one on cartilage between ceratobranchial and epibranchial, and two on epibranchial.

Dorsal fin with spinelet, spine and six branched rays (18), originating approximately above posterior end of pseudotympanum. Distal margin of dorsal fin slightly convex. Spinelet large with wide base and rounded distal tip. Dorsal-fin spine straight, slender, pungent, shorter than first branched ray (14.7–18.2% of SL). Anterior margin of dorsal spine with serrae along distal third, posterior margin with serrae along distal third, and small, straight to retrorse dentations along second third of its length. Anteriormost dorsal-fin pterygiophore inserted above complex vertebra; posteriormost dorsal-fin pterygiophore located ahead of neural spine of vertebra 11.

Pectoral fin with distal margin slightly convex, with one unbranched and eight* (13) or nine (4) branched rays. First pectoral-fin ray curved with basal portion ossified, forming a spine, and short distal tip flexible and clearly segmented ( Fig. 3 ). Anterior margin of pectoral-fin spine with 20–25 small straight dentations covering two-thirds of margin (except for a smooth ridge near spine base), and 5–8 serrae along its distal third. Posterior margin with 12–18 retrorse dentations along its basal three-quarters ( Fig. 3 ).

Pelvic-fin with convex distal border. Pelvic-fin origin at vertical through base of last dorsal-fin ray. Tip of pelvic fin surpassing vertical through adipose-fin origin, but not exceeding first fourth of its base. Pelvic-fin rays i,5 (18), first ray distinctly shorter than second and third rays (first and second branched rays, respectively).

Anal-fin margin rounded, with iv,7 (4), 8* (10) or 9 (4) rays. Two or three anteriormost anal-fin rays embedded in thick skin fold. Anal-fin origin behind vertical through first fourth of adipose-fin base. Anal-fin adpressed terminus between verticals through 70 and 80% of adipose-fin base. Tip of anteriormost anal-fin pterygiophore inserted immediately posterior to hemal spine of vertebra 23. Tip of posteriormost anal-fin pterygiophore inserted immediately ahead of hemal spine of vertebra 28.

Adipose fin relatively short (32.8–36.4% of SL), forming ascending curve in lateral profile with deepest point approximately at midlength. Distance from dorsal fin to adipose fin less than length of dorsal-fin base. Origin of adipose fin posterior to midlength of trunk, and approximately at vertical through vertebral centrum 18. Adipose-fin terminus at vertical through vertebral centrum 36.

Caudal fin deeply forked, ventral caudal-fin lobe longer than dorsal lobe, both lobes with rounded contours. Dorsal lobe with 14 procurrent rays and one unbranched and seven branched principal rays. Ventral lobe with 16 procurrent rays and one unbranched and eight branched principal rays. Seven rays articulated to dorsal caudal-fin plate (five to hypurals 3+4 and two to hypural 5) and eight rays articulated to ventral caudal-fin plate (six to hypurals 1+2 and two to parhypural). Parhypural not fused to hypural 1 ( Fig. 4 ). Hypurals 1 and 2 completely co-ossified into single ventral caudal plate. Hypurals 3 and 4 completely fused to each other. Hypural 5 not fused to hypurals 3+4. Middle caudal-fin ray of dorsal lobe not articulated to caudal plate ( Fig. 4 ). Total vertebrae 40–42 (2). Ribs nine (2).

Cephalic laterosensory system with simple (unbranched) canals ending in single pores. Supraorbital canal continuous, connected anteriorly to infraorbital canal (forming complex s2+i2 pore), and posteriorly to the otic canal. Supraorbital canal with seven sensory pores: s1, s2+i2, s3, s4, s6 (epiphyseal branch), s7, and s8 (parietal branch). Contralateral epiphyseal branches fused to each other medially, ending in a single sensory pore (s6+s6). Paratype specimen of 65.0 mm SL (IAvH-P 17879) with unfused paired s6 pores, adjacent to each other at dorsal midline. Infraorbital canal with six sensory pores: i1, s2+i2, i3, i4, i5, and i6. Preoperculomandibular canal with 11 sensory pores, along dentary, subpreopercle and preopercle. Sensory pores of dentary and preopercle wide and corresponding foramina of preoperculomandibular canal large and externally conspicuous. Lateral line canal complete, extending to basal portion of middle caudal-fin rays.

Coloration in alcohol. Background body coloration yellowish. Ventral region of head and body lighter. Dorsal surface of head with dense concentration of dark brown chromatophores, more densely clustered delimiting supraorbital canal margins and snout portion of infraorbital canal. A conspicuous paired dark blotch, looking as a cloven hoof on occipital region. Dorsal surface of maxillary barbel darker than ventral surface. Mental barbels yellow. Conspicuous dark humeral blotch. A brown faint and narrow midlateral stripe extending from pseudotympanum, fading posteriorly along caudal peduncle, and ending as a spot at caudal-fin base ( Figs. 1–2 ). Dorsal-fin base darkly pigmented, from spinelet to posterior most interradial membrane ( Fig. 2 ). Adipose, anal, and caudal fins hyaline. Pectoral and pelvic fins with few dark chromatophores sparse along rays and interradial membranes hyaline.

Etymology. The specific epithet longibarbata is from the Latin adjectives longus for long and barbata for bearded and refers to the long maxillary barbel.

Distribution and habitat. Pimelodella longibarbata is known from piedmont tributaries of the Arauca, Casanare, and Meta River drainages, which are major Andean tributaries of the western Orinoco River basin ( Fig. 5 ). The water physicochemical parameters measured during the collection event of the paratypes are summarized in Table 2.

Figures

FIGURE 1. Pimelodella longibarbata, holotype, IAvH-P 21920, 48.6 mm SL. (A) Left lateral view, (B) dorsal view, (C) ventral view.

FIGURE 2. Pimelodella longibarbata, paratype, IAvH-P 17879, 65.0 mm SL. (A) Left lateral view, (B) dorsal view.

FIGURE 3. Ventral view of left pectoral-fin spine of Pimelodella longibarbata, paratype, IAvH-P 17281, 60.1 mm SL.

FIGURE 4. Caudal skeleton of Pimelodella longibarbata, paratype, IAvH-P 17879, 48.8 mm SL. cf, caudal artery foramen; epu, epural; hu1+hu2, hypurals 1 + 2; hu3+hu4, hypurals 3 + 4; hu5, hypural 5; ph, parhypural; pu1+u1, preural centrum 1 + ural centrum 1; pu2, preural centrum 2. Scale bar 2 mm.

FIGURE 5. Map of llanos region of Colombia and Venezuela, showing distribution of Pimelodella longibarbata. Star: type locality.