Cheilonimata minuta, Provenzano-Rizzi, 2023

Provenzano-Rizzi, Francisco, 2023, A new genus and species of whiptail armored catfish (Siluriformes: Loricariinae) from southern Venezuela, Zootaxa 5315 (4), pp. 315-328 : 318-322

Cheilonimata minuta new species

Figs. 1–3 , Table 1

urn:lsid:zoobank.org:act:0A23FE54-7101-4F2A-B4E6-13F552406CEC

New genus and species “L3”. Provenzano, 2011:72–75, Figs 41–42.

Holotype MBUCV-V-32954, 54.3 mm SL, Orinoco River at sand island ca. 1/ 2 km upstream from Guachapana (Guachipana), approx. 03°54’30”N, 66°59’30”W, 08 March 1987, B. Chernoff, W.G. Saul, H. López-Rojas, J. Fernández, O. Castillo and M.E. Antonio, ( V87-3 ).

Paratypes ( All from Venezuela, Amazonas State) .

MBUCV-V-29154, 35.6 mm SL, same data as holotype. ANSP 162156 , 2 , 39.5–46.2 mm SL, same data as holotype. MBUCV-V-17551, 2 alc, 1 c&s, 54.6–54.8 mm SL, Orinoco River , at beach 1/2 h upstream from Temblador Island , approx. 03°10’05”N, 66°34’34”W, 10 March 1987, B. Chernoff, H. López-Rojas, W.G. Saul, O. Castillo, M.E. Antonio, J. Fernández and J. Moreno, ( V87-6 ). MBUCV-V-17580, 41.1 mm SL, Casiquiare River, approx. 7 km downstream from the mouth of the Pamoni River, small caño at E side, approx. 03°05’49”N, 65°53’46”W, 20 March 1987, B. Chernoff, H. López-Rojas, J. Fernández, O. Castillo and M.E. Antonio, ( V87-38 ). AUM 56760 , 4 , 65.4–74.3 mm SL, Orinoco River , beach in the middle of the river, upstream mouth of Ventuari River, 91 km ESE San Fernando de Atabapo, 03°42’09” N 66°57’18” W, 03 March 2005, N.K. Lujan, D. Werneke, M.H. Sabaj and M. Arce .

Diagnosis. As given for genus. In addition, C. minuta is very similar to C. papillosa , and can be distinguished by maxillary barbel reaches gill opening vs. maxillary barbel reaches middle of pectoral-fin in C. papillosa ; lateral series plates 29–32 (mode 32) vs. lateral series plates 27–29 and pectoral-fin with two or three transversal dark stripes on unbranched and branched rays vs. pectoral-fin with one wide stripe on unbranched and branched rays. Other differences related to the number teeth in upper jaw and body color pattern need to be confirmed with direct examination.

Description. Morphometric data is presented in Table 1 . Specimens small with fragile or delicate appearance. In lateral view, head and body very depressed, caudal peduncle without adipose-fin; body deeper at eye level and gradually tapering towards caudal-fin origin ( Fig. 1 ). Dorsal profile of body from tip of snout through anterior eye border straight and ascending with 45° slope approximately, from this point to caudal-fin origin descending straight. Ventral profile of head and body flat and straight ( Fig. 1 ). In dorsal view, head contour elliptical with sides gently convex; snout not projected, tip rounded; body wider at branchial opening or pectoral-fin insertion and tapering gradually and continuously to caudal-fin origin ( Fig. 1 ). Pectoral-fin insertion slightly posterior to vertical through posterior margin of orbit. Dorsal-fin origin opposite to pelvic-fin insertion. Anal-fin origin at lateral plate number nine or ten ( Fig. 1 ).

Eyes located dorsally, relatively large, orbit with shallow posterior notch, and with ventral extension; eyeball appears internally withdrawn from the ventral edge of the bone orbit.From nostrils until anterior edge of supraoccipital two parallel low keels pass between eyes. Then over supraoccipital, keels converge posteriorly becoming single keel, until ending at supraoccipital tip. Predorsal region with three unpaired plates, first and second plates double keeled, third with a single keel ( Fig. 1 ).

Ventral surface of head without plates.Abdomen, in larger specimens, nearly naked with only three longitudinal and discontinuous lines or rows of very minute, not clumped, irregularly shaped plates; plate rows include one midventral almost reaching anus, and two lateral rows between pectoral and pelvic fins. In small specimens, abdomen naked with only few and scattered very minute plates, difficult to observe with naked eye. Thoracic plates only observed in specimens more than 65.0 mm SL ( Fig. 2a ). Anus projected as very small tube, delimited by naked area. Urogenital papilla not visible, apparently attached to posterior surface of anal tube ( Fig. 2a ).

Mouth ventral; maxillary barbel reaches pectoral-fin spine origin. Upper lip border and maxillary barbel with elongated, cylindrical, unbranched, fleshy barblets embedded and interconnected by translucent membrane, leaving only barblet tips free ( Fig. 2b ). Translucent membrane occurs along upper lip margin and on proximal two thirds of maxillary barbel. Also, translucent membrane connects maxillary barbel with lower lip border, laterally and internally. Upper lip surface very narrow and continuous with maxillary barbel and has few elongated, cylindrical, unbranched fleshy barblets ( Fig. 2b ). Lower lip wide, its margin with unbranched barblets and its surface covered with elongated, cylindrical, unbranched fleshy barblets, which resemble filaments; some of these barblets surpasses lower lip margin ( Fig. 2b ). Palate with one elongate, cylindrical, unbranched, fleshy barblet behind premaxillaries at midline and one barblet with the same shape, lateral and external to each premaxilla ( Fig. 2b , 3 ).

Both jaws with very small, but visible teeth, with similar size in each jaw. Premaxillary with two to three teeth and dentary with four to five teeth ( Fig. 3 ). Teeth asymmetrically with outer cusp very small and pointed, sometimes not visible and inner cusp more developed, rounded; crown yellow or golden, stalk whitish ( Fig. 3 ).

Body sides with 29–32 (mode 32) plates in mid-lateral series, 17–20 (mode 18) coalescent plates and 9–14 (mode 14) posterior plates. Thoracic plates (between pectoral-fin to pelvic-fin, bases) 8–9 only observed in specimens with more than 65.0 mm SL. Post-dorsal plates 22–23; post-anal plates 19–20. Five plates along dorsal-fin base and three plates along anal-fin base. Dorsal-fin rays i,7, no spinelet nor vestigial bony plate observed; pectoral-fin rays i,6; pelvic-fin rays i,5; anal-fin rays i,5 and caudal-fin rays i,10,i. Pelvic-fin unbranched ray surpasses origin of anal-fin. Caudal fin with upper unbranched ray projected as filament (broken in holotype). First unbranched ray of dorsal, pectoral, pelvic and anal fins not elongated as filaments.

Color in alcohol. Dorsal surface of head and body light brown or yellowish, presence of six or seven transverse dark brown bands or stripes, sometimes faded, behind pectoral fin, first band at end of pectoral-fin base, second at dorsal-fin origin, third at end of dorsal-fin, remaining three or four, posterior to anal-fin base to caudal-fin origin ( Fig. 1 ). Ventral surface of head and body yellowish or creamy, uniform ( Figs 1–2a ). Dorsal, pectoral, pelvic and caudal-fins rays with dark bands; two longitudinal on dorsal fin, two or three transversal on pectoral fin, one on pelvic fin, sometime faded, and one on caudal fin, oblique; interradial membranes hyaline ( Fig.1 ). Anal-fin rays uniform, whitish or yellowish, interradial membrane hyaline ( Fig. 1 ).

Geographic distribution. Available records indicate C. minuta inhabits the upper Orinoco River and the Casiquiare River, Amazonas state, Venezuela ( Fig. 4 ). The information about capture sites indicates clear to black waters environments with sandy, rocky, gravel and pebbles bottoms. The water has low pH and conductivity levels, and little quantity of suspended sediments.

Etymology. minuta is taken from the Latin meaning small, which is a trait exhibited by the analyzed specimens.

Figures

FIGURE 1. Cheilonimata minuta, MBUCV-V-32954, 54.3 mm SL, holotype. Lateral, dorsal and ventral views. Scale bar 2 mm. Photos by C. Do Nascimiento.

FIGURE 2. Cheilonimata minuta, MBUCV-V-32954, 54.3 mm SL, holotype. a) Detail of ventral view to show: head contour, mouth and abdomen cover. b) Close-up of mouth, detail of lower lip cover and translucent membrane on upper lip margin (red arrows). Scale bar 2 mm. c) Photos by C. Do Nascimiento.

FIGURE 3. Cheilonimata minuta, ANSP 162156, 39.5 mm SL, paratype, detail of buccal ornamentation on mouth roof and behind premaxillaries (red arrow). Scale bar 1 mm. Photo by F. Provenzano.

FIGURE 4. Map of Venezuela showing the geographic distribution of Cheilonimata minuta, red star type locality.Some symbols may represent more than one lot.