Pimelodella serrata, Eigenmann, 1917

Complementary description of Pimelodella serrata View in CoL

Below we provide a morphological description of Pimelodella serrata , based on examination of 12 specimens (1 c&s) from Colombia, and photographs and radiographs of the holotype (housed at FMNH) .

Morphometric data summarized in Table 2 View TABLE 2 . Body moderately deep and elongated, deeper at dorsal-fin origin. Dorsal profile of body rises straight and upward to supraoccipital process origin, then convex to dorsal-fin origin; dorsal-fin base convex, straight and downward from posterior end of dorsal fin to adipose-fin end, 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 ( Fig. 3 View FIGURE 3 ).

Head conical. Mouth subterminal, upper jaw more pronounced than lower jaw. Premaxilla with two or three rows of villiform teeth and dentary with three or four rows of similar teeth. Anterior naris tubular. Posterior naris rounded, slightly closer to anterior ocular margin than to anterior naris, and anteromedially bordered by a fleshy margin. Nares disposed in a rectangular or slightly trapezoidal arrangement. Barbels thin, elliptical in cross-section. Maxillary barbel surpassing base of caudal fin, extending to anterior third of lower lobe. Outer mental barbel slightly surpassing origin of pelvic fin ( Fig. 3 View FIGURE 3 ). Inner mental barbel reaching pectoral-fin base. Eye placed dorsolaterally, slightly elliptical, its greatest diameter along horizontal axis. 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. Pseudotympanum large and oval, dorsal to posterior process of cleithrum and extending to vertical through dorsal-fin origin. Branchiostegal rays six. Gill rakers on first gill arch 17–20 (9); 14 gill rakers associated to anterior margin of ceratobranchial, one on cartilage between ceratobranchial and epibranchial, and five on epibranchial (verified in one c&s specimen).

Dorsal fin with spinelet, spine, and six branched rays (9), originating approximately above posterior end of pseudotympanum. Distal margin of dorsal fin slightly convex. Spinelet large with wide base and slightly rounded distal tip. Dorsal-fin spine straight, slender, pungent, shorter than first branched ray (15.5–18.3% of SL) and slightly curved towards distal end. Anterior margin of dorsal spine smooth; posterior margin with serrae along distal third, and small, straight to retrorse dentations along middle third of its length. Anteriormost dorsal-fin pterygiophore inserted above complex vertebra; posteriormost dorsal-fin pterygiophore located anterior to neural spine of vertebra 11.

Pectoral fin with distal margin slightly convex, consisting in one unbranched and eight (1), nine (3) or ten (5) branched rays. First pectoral-fin ray curved with basal portion ossified, forming a spine, and distal tip flexible and segmented. Roughly all anterior margin of pectoral-fin spine with small, but well-defined antrorse dentations (35–39), plus 2 or 3 distal serrations; posterior margin of pectoral-fin spine bearing 26–30 large, retrorse dentations, extending along almost entire margin ( Fig. 4 View FIGURE 4 ).

Pelvic fin with distal margin convex. 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 (9); first ray distinctly shorter than second and third rays (first and second branched rays, respectively).

Anal-fin margin rounded, with iv, 8 rays (9). First and second anteriormost anal-fin rays embedded in a thick skin fold. Anal-fin origin at vertical through middle of adipose-fin base. Anal-fin adpressed terminus between verticals through 70 and 75% 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 anterior to hemal spine of vertebra 28.

Adipose-fin long (40.2–43.8% of SL), almost in contact with dorsal fin; forming ascending curve in lateral profile with deepest point approximately at vertical through anal-fin origin. Posterior limit of adipose fin as a rounded free lobe. Origin of adipose fin posterior to mid-length of trunk, and approximately at vertical through vertebral centrum 23. Adipose-fin terminus at vertical through vertebral centrum 37.

Caudal fin deeply forked, lower caudal-fin lobe slightly longer than upper lobe, and both lobes with pointed tips. Upper lobe with one unbranched and six (1) or seven (8) branched principal rays. Lower lobe with one unbranched and eight branched principal rays (9). Seven rays articulated to dorsal caudal-fin plate (six to hypurals 3+4 and one to hypural 5), and eight rays articulated to ventral caudal-fin plate (five to hypurals 1+2 and three to parhypural). Parhypural not fused to hypurals 1 and 2. Hypurals 1 and 2 completely fused into single caudal plate. Hypurals 3 and 4 completely fused. Hypural 5 free. Middle caudal-fin ray of upper lobe not articulated to caudal plate. Total vertebrae 43 (c&s). Ribs eight (c&s).

Supraorbital canal with seven sensory pores: s1, s2, s3, s4, s6 (epiphyseal), s7 and s8 (parietal). Pore s1 located anteromedial to anterior nare. Pore s2 at end of short membranous tube on internarial space (slightly closer to posterior nare). Pores s3 and s4 emerging from canal segment between posterior portion of nasal and anterior portion of frontal. Contralateral epiphyseal branches (s6) fused, anterior to epiphyseal bar, at posterior margin of anterior fontanel. Pore s8 emerging dorsally to parieto-supraoccipital bone, from posteriorly directed osseous canal. Supraorbital and infraorbital canals connected posterior to anterior nare. Pore i1 located posterior to anterior nare. Pore i3 lateral to posterior nare. Pore i4 adjacent to ventral margin of eye, at vertical through anterior ocular margin. Pore i5 ventrally to eye, at end of posteroventrally directed membranous tube. Pore i6 placed behind eye, at end of posteriorly directed membranous tube. Preoperculomandibular canal with 11 sensory pores. Postotic canal with three sensory pores. Pore po2 emerging from a posteriorly directed membranous tube, ending dorsally to dorsal corner of branchial opening. Pore po3 at end of posteriorly directed membranous tube, dorsal to lateral line canal of trunk, and located dorsally to pectoral-fin base. Lateral line canal of trunk long, extending to basal third of interradial membrane between innermost caudal-fin rays.

Color in alcohol

Background body coloration pale yellow. Ventral region of abdomen whitish. Dorsal surface of head with dense concentration of dark brown chromatophores, extending from snout tip to posterior process of cleithrum. A conspicuous dark spot on spinelet. Dorsal surface of maxillary barbel darker than ventral surface. Mental barbels yellow. A faint and narrow brown midlateral stripe, extending from pseudotympanum, fading posteriorly along caudal peduncle, and ending in caudal-fin base. Dorsal, pectoral, adipose, anal, and pelvic fins hyaline. Lower lobe of caudal fin slightly dark, pigmented only along fin-rays.