Neblinichthys brevibracchium Taphorn & Armbruster & López-Fernández & Bernard 2010, new species

Neblinichthys brevibracchium, new species Fig. 1 Holotype. CSBD 1653 (ex ROM 83772), 73.3 mm SL, presumably male, Guyana, upper Mazaruni River drainage, mouth of a small creek with cut banks and primary forest, lower Kukui River at Jawalla, 05°39’10”N 60°28’57”W, 20 Apr 2008, H. López-Fernández, D. C. Taphorn, E. Liverpool, K. Kramer & C. Thierens. Paratypes. All from Guyana, upper Mazaruni River drainage, collected by H. López-Fernández, D. Taphorn, E. Liverpool, K. Kramer & C. Thierens: ROM 83684, 4, 19.5-30.9 mm SL, AUM 50302, 1, 78.8 mm SL, Kukui River upstream of Philipai, 05°22’05”N 60°21’59”W, 16 Apr 2008. ROM 83692, 4, 58.1- 79.9 mm SL, Kukui River in and around Philipai, 05°21’37”N 60°22’18”W, 16 Apr 2008. ROM 83695, 1, 68.0 mm SL, Kukui River at Philipai, 05°21’37”N 60°22’18”W, 16 Apr 2008. AUM 50303, 1, 57.3 mm SL, ROM 83697, 3, 35.6-62.0, Kukui River around Philipai, 05°21’37”N 60°22’18”W, 16 Apr 2008. AUM 50304, 2, 47.7-60.8 mm SL, ROM 83713, 5, 29.0- 65.6 mm SL, Kukui River upstream from Philipai, 05°21’37”N 60°22’18”W, 17 Apr 2008. ROM 83739, 2, 40.9-56.9 mm SL, Mazaruni River, sandy beach at the confluence of the Mazaruni River and the Kukui River, 05°40’21”N 60°28’59”W, 17 Apr 2008. ROM 83785, 2, 58.8-60.3 mm SL, Waruma River, riffles and shallow rapids, 05°28’32”N 60°46’47”W, 20 Apr 2008. ROM 83816, 1, 60.4 mm SL, Waruma River, shallow pool, 05°28’32”N 60°46’47”W, 21 Apr 2008. ROM 83828, 1, 63.6 mm SL, rapids on Paikwa River, 05°29’00”N 60°43’56”W, 22 Apr 2008. ROM 83841, 1, 54.1 mm SL, rapids on Paikwa River, 05°29’10”N 60°43’57”W, 22 Apr 2008. ROM 83853, 1, 61.2 mm SL, Paikwa River drainage, Sedaa creek, at lowermost rapids, 05°41’18”N 60°40’43”W, 23 Apr 2008. Diagnosis. Neblinichthys brevibracchium can be separated from all congeners except N. echinasus by lacking odontodes on the opercle (rarely one odontode present, vs. the exposed portion of the opercle completely covered in odontodes), by completely lacking the iris operculum (vs. iris operculum small or at least the dorsal rim of the pupil straight), and internares width/head length ratio (5.0-8.5% vs. 7.6-15.5%, see Tables 1-2), and by having irregular gray spots and vermiculations on the abdomen of adults (vs. no markings); from N. roraima by having one to two preadipose plates (vs. more than four); and from N. echinasus by a smaller dorsalfin base length/SL ratio (18.1-22.8% vs. 24.3-27.0%), a larger dorsal-anal distance/SL ratio (13.7-18.3% vs. 11.9-12.5%), by having the snout decreasing in steep arc just anterior to eyes and then flattening in area anterior of nares (vs. snout tapering shallowly and continuously from eyes to snout tip; Fig. 1), and by having the adpressed dorsal fin not reaching the anterior preadipose plate (vs. reaching anterior preadipose plate). Description. Morphometrics presented in Table 1. Meristics based on 11 individuals, from total of 29 examined. Largest specimen: 79.9 mm SL. Nuptial males not observed. Body relatively deep, not particularly dorsoventrally flattened as in other species of Neblinichthys. Caudal peduncle laterally compressed. Profile from tip of snout to nares concave, angled up at about 45 o, slightly convex to dorsal-fin origin. Orbits slightly elevated above head profile. Deepest point of body just anterior to dorsal fin. Profile straight or gently concave to adipose-fin origin, then slightly concave to base of upper caudal-fin spine. Ventral surface flat or slightly concave from just behind oral disk to anal-fin origin then straight to base of lower caudal spine. Eyes widely separated, laterally oriented, not visible from below. Dorsal profile of head as shown in Fig. 1. Body widest just anterior to dorsal-fin origin, narrowing slightly until posterior margins of pelvic fins, and then quickly tapering to end of caudal peduncle. Anterior margin and dorsal surface of snout with small odontodes. No large hypertrophied odontodes present in any specimens examined. Cheek plates only moderately evertible (not reaching to 90° from head), cheek odontodes short, tiny, and very numerous. Snout tip wide and with protuberant patch of odontodes, odontode bearing raised crests extend along margins of snout, and down dorsal midline of snout. Another elevated patch of odontodes extending short distance anterior from orbit. Iris operculum absent, making dorsal rim of pupil round. Mouth moderate in size with narrow premaxillary and dentary tooth cups forming gentle arcs. Premaxillary teeth 32-58; dentary teeth 30-72. Teeth villiform and bicuspid with very short cusps (medial cusp longer than lateral). Edge of oral disk scalloped, and extending to vertical through anterior margin of eye, not extending beyond lateral margins of head. Enlarged central papilla present in buccal cavity. Maxillary barbel very short, not reaching base of evertible cheek plates. Ventral surface of lips papillose. Papillae largest in center of lower lip, decreasing radially. No enlarged papillae located behind dentary teeth. Dorsal fin II,7; dorsal-fin spinelet flat platelet with short odontodes. Dorsal fin short, not reaching preadipose plate when adpressed. First dorsal-fin ray slightly longer than dorsal-fin spine. Pectoral fin I,6. Pectoral-fin spine short (about equal to pelvic-fin spine) not reaching pelvic fin when adpressed; relatively weak, numerous odontodes of equal size present along entire length. Anterior pectoral-fin rays longer than pectoral-fin spine, decreasing to about half of length of spine posteriorly, covered with odontodes, largest on dorsal surface. Pelvic fin I,5; thickened and covered with odontodes, reaching into anterior third of anal-fin base when adpressed; anterior pelvic-fin rays longer than pelvic-fin spine with posterior margin of fin curving out beyond posterior tip of spine.Anal fin I,5; all anal-fin rays slightly longer than odontode-covered weak spine. First anal-fin pterygiophore not exposed to form platelike structure. Adipose-fin spine straight to slightly curved posteriorly with adipose membrane extending beyond posterior extent of spine. Caudal fin I,14,I; upper caudal-fin spine shorter than first two upper rays, lower spine longer than all rays, and much longer than upper spine. Dorsal procurrent caudal-fin rays five (six in one specimen), ventral procurrent caudal-fin rays three. Posterior caudal-fin margin slightly concave. Rays of all fins supporting small odontodes. Median plate series with 21-23 plates, not counting those on base of caudal fin. Ventral plates forming gentle arc on caudal peduncle and not forming strong rounded keel. Plates in mid-ventral row weakly arched submedially forming low ridge from cleithrum to posterior insertion of pelvic fin. Three rows of plates on caudal peduncle (mid-dorsal plate series ending at level of adipose fin). Abdomen naked. Coloration in alcohol. Head, dorsum of body and sides tan to dark brown with irregular, darker brown or black spots and blotches. No individuals showing regular rows of spots. Ventrum light colored, whitish or light tan with irregular spots and vermiculations, pattern strongest anteriorly just behind oral disk. Oral disk with inner papillated surfaces pale tan; upper lip’s outer anterior margin darkly mottled.All fin spines and rays with alternating wide dark and narrow light bands (pattern evident in all fins of most individuals); fin membranes hyaline, not pigmented. Dark spot present at base of anteriormost dorsal-fin membrane (Fig. 1). Sexual dimorphism. Presumed males appear to have either recently lost hypertrophied snout odontodes, or are just gaining them. The area at the tip of the snout has enlarged papillae that appear to presage the development of hypertrophied odontodes in ancistrins (JWA, pers. obs.). There is a small region, about one and a half eye diameters, that is without noticeable odontode hypertrophication and is followed by region of about one and a half eye diameters with mildly hypertrophied odontodes (holotype has two very long odontodes on the left side in this region), followed by a region preceding the gill opening where we observe a very slight increase in size of odontodes (Fig. 1). The preorbital ridge appears thickened and has some relatively elongate odontodes suggesting that this area may also develop hypertrophied odontodes. Given the presence of two very long odontodes on the snout of the holotype, we presume that nuptial males have more extensive ornamentation. Distribution. Known from upper Mazaruni River, Essequibo drainage, Guyana (Fig. 2). Etymology. From the Latin words brevis which means short, and bracchium meaning forearm, in reference to the relatively short pectoral spines present in Neblinichthys. Epithet used as a noun in apposition, in masculine form.

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