Taxonomic treatment Open Access

Pseudohemiodon almendarizi Provenzano-Rizzi & Argüello & Barriga-Salazar 2022, new species

Provenzano-Rizzi, Francisco; Argüello, Pablo; Barriga-Salazar, Ramiro

Pseudohemiodon almendarizi new species

Figures 1, 2, 3, Table 1

urn:lsid:zoobank.org:act: BBE0CAE9-D73F-4728-9AC1-33E62A3146D7

Holotype. MEPN 17903, 87.9 mm SL, Ecuador, Orellana Province, Aguarico River, near Puerto Loja, Napo River system, approx. 00°52’57”S 75°13’30”W, 24 July 1998, R. Barriga & D. J. Stewart.

Paratype. MEPN 19491, 80.3 mm SL, same data as holotype.

Diagnosis. Pseudohemiodon almendarizi can be distinguished from all its congeners by the combinations of the following characters: abdomen totally covered with small to medium-sized, irregularly shaped plates (vs. abdomen partially covered, in P. platycephalus and P. amazonum or covered by one central row of plates wide and rectangular, in P thorectes); absence of small, bony plates, anterior to gill openings (vs. presence of one to three small plates in front of the gill openings, in P. lamina); 12–15 coalescing lateral scutes (vs. 20–21 in P. thorectes); thoracic plates (between pectoral and pelvic fins) fold sideways (vs. thoracic plates do not fold in P. amazonum); eyes relatively smaller, its diameter without notch fits 12.0–12.7 times in HL (vs. 8.3–11.8 times in HL in P. apithanos, 7.1–9.0 times in HL in P. lamina, 8.2–8.7 times in HL in P. laticeps and 8.1–9.2 times in HL in P. unillano); body less wide at anal-fin origin 10.4%–12.0% SL (vs. 13.4%–17.7% SL in P apithanos, 12.8%–13.9% SL in P. laticeps, 11.9%–17.1% SL in P. unillano); six or seven wide and dark transverse bands, posterior to dorsal-fin (vs. bands absent in P. laticeps, P. unillano, and medium to large sized P. lamina (over 60 mm SL) or no more than three or four transverse dark bands posterior to dorsal-fin in P. apithanos, or up to eight in very small sized (below 55 mm SL) of P. lamina.

Description: Morphometric data presented in table 1. Head and body very depressed, caudal peduncle long, narrow and very depressed, without adipose-fin (Fig. 1). Maximum body depth at dorsal-fin origin, or slightly ahead and maximum width at cleithrum, becoming narrower posteriorly, gradually, to caudal-fin origin. Dorsal profile of body from tip of snout through anterior border of eye, straight and scarcely sloping up, from this point to dorsal-fin origin, straight and gently inclined or gently convex, then descending straight to caudal-fin origin. Ventral profile of body flat and straight. Pectoral-fin insertions at vertical through posterior margin of orbit. Dorsal-fin origin opposite pelvic-fin insertions. Anal-fin origin at lateral plate number 11 (Fig. 1)

Head shape in dorsal view an acute triangle with straight edges. Snout little projected, with rounded tip (Figs 1, 2, 3). Eyes located dorsally, orbits with shallow, ventral and posterior notches. Keels weak with parallel path, from nostrils, through eyes to anterior tip of supraoccipital. Over the supraoccipital, keels convergent posteriorly, becoming closer and again parallel to posterior tip of supraoccipital. Pre-dorsal area with three single plates, first and second with low parallel keels, third with single low keel at midline (Fig. 1).

Ventral surface of head naked except for plates along border and snout, no plates anterior to the gill openings. Branchiostegal membrane smooth and uniform, without wrinkled flap on anterior margin or any protuberance or fold (Fig. 2). Mouth ventral with lips laminar and thin. Upper lip very narrow, imperceptible, its border with conical, small, elongated, unbranched barblets, decreasing in size toward middle. Surface of upper lip with sparse small papillae laterally. Border of upper lip continuous with maxillary barbels that extend to gill opening. Maxillary barbel with small, conical, unbranched barblets. Lower lip wide, its edge with elongated, branched, and conical barblets; barblets slightly shorter at middle. Lower lip surface covered with short, fleshy, thick papillae, sometimes slightly elongated (Fig. 2). Teeth present in both jaws, minute but evident, same length, asymmetrical bicuspids with medial cusp more developed and spoon-shaped, lateral cusp very small, sometimes not visible, pointed, apex yellow or golden, stalk white. Premaxillary teeth 2–5, dentary teeth 5–7 (Fig. 2). Buccal ornamentation composed of two or three small, fleshy, cylindrical, elongate and unbranched barblets, at distal side of each premaxillae. Inside mouth, behind premaxillaries, just at middle, with single long, fleshy, cylindrical and unbranched barblet (Fig. 2).

Abdomen completely covered with irregularly polygonal-shaped plates, plates small to medium-sized, smaller near pectoral girdle. Anus projected as very small tube, urogenital papilla not visible, apparently attached to posterior surface of anal tube. Anus delimited by a narrow naked area, surrounded by plates (Fig. 2).

Body with 33 plates in median lateral series, 13 coalescent plates (double keel) and 20 posterior plates (one keel). Seven to eight thoracic plates (between posterior end of pectoral-fin base and origin of pelvic-fin base). Postdorsal plates 20–22 and post-anal plates 17–20. Four plates border dorsal-fin base; and two or three border anal-fin base. Dorsal-fin rays i,7; pectoral-fin rays i,6; pelvic-fin rays i,5; anal-fin rays i,5; and caudal-fin rays i,10,i. Tip of pelvic-fin surpasses anal-fin origin. Caudal-fin slightly bifurcated, with unbranched rays longer than branched. Upper unbranched caudal-fin rays projecting as long filaments (but broken in both specimens). In available material, first unbranched rays (spines) of dorsal, pectoral, pelvic and anal-fins not elongated as filaments (Fig. 1).

Color in alcohol: In specimens preserved in 70% alcohol, dorsal surface of head and body brown or yellowish brown, uniform. On head to end of dorsal-fin base, light and dark areas randomly positioned (Fig. 1). Six or seven dark, transverse bands, decreasing in width and intensity posteriorly located from posterior end of dorsal-fin base to caudal peduncle. Ventral surface of head and body, whitish or yellowish, uniform (Fig. 1). Dorsal and pectoral-fins rays and interradial membrane dark blackish. Pectoral-fin spine paler brown or yellow with four diffuse (faint) dark bands. Pelvic-fin rays and interradial membranes light brown or yellow with dark area at middle. Anal-fin whitish or yellowish, uniform. Caudal-fin rays dark brown becoming pale brown, posterior as the interradial membrane.

Geographical distribution: The two specimens came from Aguarico River, near Puerto Loja, Napo River system, Amazon River Basin, approx. 00°52’57”S 75°13’30”W (Fig. 6).

Etymology: The specific name honors Ana de Lourdes Almendáriz, in recognition of her significant contributions to the Ecuador herpetofauna knowledge, and her enthusiasm and friendship for many years. Noun in apposition.

Published as part of Provenzano-Rizzi, Francisco, Argüello, Pablo & Barriga-Salazar, Ramiro, 2022, The genus Pseudohemiodon (Siluriformes, Loricariidae) in Ecuador, with the description of a new species, pp. 77-91 in Zootaxa 5129 (1) on pages 79-81, DOI: 10.11646/zootaxa.5129.1.4, http://zenodo.org/record/6488189
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