Pseudolithoxus kelsorum Lujan & Birindelli, 2011, new species
Creators: name: Lujan, Nathan K.
name: Birindelli, Jose L. O.
Publisher: name: Zenodo
Year: 2011
Subjects: Biodiversity
Taxonomy
Animalia
Chordata
Actinopterygii
Siluriformes
Loricariidae
Pseudolithoxus
Pseudolithoxus kelsorum

description: Pseudolithoxus kelsorum, new species
Figure 1. Table 1.
Holotype. MCNG 55357, 66.0 mm SL, Venezuela, Amazonas State, Orinoco River drainage, Orinoco River at Merey, 97.6 km N of San Fernando de Atabapo, 4°55'04''N, 67°49'58''W, J. Birindelli, N. K. Lujan & V. Meza, 18 April 2010.
Paratypes. Five specimens, collected with holotype. ANSP 182813, 1: 36.6 mm SL, AUM 51644, 2: 40.0, 52.4 mm SL; MCNG 55358, 1: 44.0 mm SL; MZUSP 108090, 1: 52.7 mm SL.
Diagnosis. Pseudolithoxus kelsorum is diagnosed from all other Pseudolithoxus by having dark brown to black base color with eight to 11 (usually nine) light yellowish vertical or oblique (tilted dorsoanteriorly) transversal bands between orbits and caudal fin, bands wide and rarely but sometimes incomplete or contorted as swirls (Fig. 1; vs. dark brown to black base color with 18 or more thin, light yellow, frequently contorted transversal bands between orbits and caudal fin in P. tigris, Fig. 2; black base color with small white spots in P. anthrax and P. n i c o i; and light brown base color with dark brown to black spots in P. dumus, Fig. 3).
Description. Morphometrics in Table 1. Largest specimen 66.0 mm SL. Head and body dorsoventrally flattened with body depth greatest at supraoccipital; dorsal and ventral profiles only slightly convergent caudally. Snout surface and body flanks armored with ossified dermal plates, each covered with small odontodes; plates absent from small region at posteroventral corner of pterotic and entire abdomen. Cheek plates bearing moderately to highly hypertrophied, distally-hooked odontodes (mean 35, range 27–42, holotype 42) evertible to approximately 90º from sagittal plane; longest odontodes extending to posterior exposed margin of opercle. Orbit positioned dorsally on head with opening sloped ventrolaterally at approximately 45º from sagittal plane in anterior view.
Oral disk occupying most of ventral surface of head anterior of cleithrum. Interpremaxillary and intermandiblar tooth row angle greater than 110º; premaxillary teeth 55–64 (average 61, holotype = 64); dentary teeth 47–57 (average 53, holotype 54). All teeth with gracile, flexible shafts and bicuspid heads bent inward at right angle to shaft. Maxillary barbel short and attached to lower lip along most of length; ventral surface of labial disk with hemispherical papillae decreasing in size distally and toward rictus; posterior margin of labial disk lacking fimbriae.
ILM Measurement Holotype Mean SD Min Max 1–20 Standard length 66.0 48.6 10.7 36.6 66.0 Percents of standard length
17–19 Adipose—upper caudal distance 14.2 14.1 1.2 11.9 15.3 15–19 Caudal peduncle depth 7.6 7.3 0.9 5.9 8.2 15–17 Adipose—lower caudal distance 19.3 19.2 1.2 17.4 20.8 14–17 Adipose—anal distance 19.3 19.0 1.3 17.0 20.3 Dorsal fin II,7; dorsal-fin spinelet small but visible, V-shaped; dorsal-fin lock functional; posteriormost dorsalfin ray free from body. Pectoral fin I,6; adpressed pectoral-fin spine reaching approximately halfway between anus and pelvic-fin origin; anterodorsal surfaces of spine with many hypertrophied odontodes increasing in length distally; odontodes longer an more numerous in larger specimens. Pelvic fin I,5; pelvic-fin spine extending to or past insertion of anal fin when adpressed. Anal fin I,4; second unbranched ray longest. Adipose-fin spine straight; adnate to caudal peduncle via fleshy membrane with concave or convex posterior margin. Caudal fin I,14,I; dorsal procurrent caudal-fin rays four; ventral procurrent caudal-fin rays four; caudal fin obliquely and asymmetrically emarginated, with ventral lobe longer than dorsal lobe.
Body broadest at cleithrum; posterior margin of exposed posterior process of cleithrum squared or tapering to a point. Lateral median plates 23–25 (mode 23, holotype 24), middorsal plates 20–23 (mode 23, holotype 20), midventral plates 22–25 (mode 23, holotype 23); anteriormost midventral plate strongly bent. Caudal peduncle plate rows three. One or two azygous preadipose plates (mode one, holotype one); predorsal plate rows two not including nuchal plate; interdorsal plate rows four or five (mode five, holotype four).
Color. Body with dark brown to black base color with eight to 11 (usually nine) light yellow vertical or oblique (tilted dorsoanteriorly) transversal bands between orbits and caudal fin; bands wide and rarely but sometimes incomplete or contorted as swirls (Fig. 1). Paired, dorsal, adipose, and caudal fins light with dark bands. Snout with light yellow longitudinal bands, small spots, or contortions. Abdomen pale; lower lip, ventral plated surfaces, ventral paired-fin spine surfaces, and anal fin uniformly light yellow to tan.
Distribution and habitat. Known only from a single site on the Orinoco River just above the Maipures rapids and approximately 60 km south of the Atures rapids (Fig. 4). Type material collected via rotenone and castnet from a single shoreline granite outcrop. Anecdotal reports (O. Lucanus pers comm. to NKL) suggest that the range of Pseudolithoxus kelsorum extends downstream into the Atures rapids. However, extensive ichthyological surveys of the Orinoco River further upstream by the first author and colleagues have failed to yield specimens of P. k e l s o r u m, suggesting that its distribution is limited to only more downstream reaches, possibly including the nearby and still poorly surveyed lower reaches of western tributaries of the Orinoco in Colombia.
Etymology. Named in honor of George and Carolyn Kelso whose generous contribution to Texas A&M University and to the Winemiller Aquatic Ecology Lab has facilitated important ichthyological discoveries, including this new species.
description: Published as part of Lujan, Nathan K. & Birindelli, Jose L. O., 2011, A new distinctively banded species of Pseudolithoxus (Siluriformes: Loricariidae) from the upper Orinoco River, pp. 38-46 in Zootaxa 2941 on pages 39-43, DOI: 10.5281/zenodo.278154