Lamontichthys parakana, Paixão & Toledo-Piza, 2009

Paixão, Andrea de Carvalho & Toledo-Piza, Mônica, 2009, Systematics of Lamontichthys Miranda-Ribeiro (Siluriformes: Loricariidae), with the description of two new species, Neotropical Ichthyology 7 (4), pp. 519-568 : 531-535

Lamontichthys parakana , new species

Fig. 13

Holotype. INPA 3010, 112.7 mm SL, Brazil, Pará, lower rio Tocantins basin, rio Tocantins, below dam of Tucuruí , 31 Ago 1984,

Ichthyology team of INPA.

Paratype. INPA 31251 , 2 , 72.2 -119.0 mm SL, same data as holotype .

Diagnosis. Lamontichthys parakana differs from all other species of the genus in the more anterior position of the analfin (anal-fin origin situated anterior to the vertical through the distal tip of the last dorsal-fin ray, vs. anal-fin originating posteriorly).

Lamontichthys parakana further differs from the other species of Lamontichthys , except L. avacanoeiro and L. stibaros , in the lack of plates on the anterior tip of the snout (vs. snout entirely covered with plates or with an inconspicuous naked area), in the teeth with long cusps (vs. short) ( Fig. 3), and in the longer dentary in specimens larger than 50 mm SL (20.1-22.6%, vs. 11.5-19.1% HL).

The semi-oval shaped lower lip further distinguishes Lamontichthys parakana from L. filamentosus and L. llanero that have the lower lip semicircular shaped ( Fig. 9).

Among the species of Lamontichthys , L. parakana is more similar to L. avacanoeiro and L. stibaros , from which it may be distinguished by the broader head (101.3-106.1%, vs. 78.9-101.4% HL) and the greater orbital diameter (16.6-17.3%, vs. 13.7-15.5% HL), in specimens larger than 100 mm SL.

Lamontichthys parakana also differs from L. avacanoeiro in the longer length of the first branched dorsal-fin ray (26.4- 31.0%, vs. 20.5-26.7% SL).

Description. Morphometric and meristic data presented in Table 3. Largest specimen 119.0 mm SL (n = 3). Head and trunk totally covered with plates. Body depressed, deeper at vertical through dorsal-fin origin, gradually more depressed posteriorly, to caudal-fin base and anteriorly, to snout tip. Head ellipse shaped in dorsal view, with slight prominence at anterior tip. Dorsal profile of head slightly convex. Dorsal profile of body slightly convex from posterior tip of supraoccipital to dorsal-fin origin, posteroventrally slanted from latter point to vertical through tip of last anal fin ray, straight to caudal-fin base. Largest body width at cleithrum, gradually narrower to 18 th to 19 th lateral plate of median series more abruptly so posteriorly, into base of caudal-fin. Caudal peduncle long, narrow and very depressed. Ventral profile of head and body straight from snout tip into base of caudal-fin. Pectoral-fin origin at vertical through posterior border of orbit. Dorsal-fin origin immediately anterior of vertical through pelvic-fin origin. Base of last anal-fin ray at vertical through distal tip of last dorsal-fin ray.

Eyes located dorsally, anterior to vertical through pectoralfin origin. Interorbital distance shorter or equal to distance from orbit to exposed borders of cleithrum. Mouth ventral. Upper and lower lip semi-oval shaped. Lower lip extending short of vertical through anteriormost margin of orbit, covered with small papillae on ventral surface and along its border. Dorsal surface of lower lip smooth. Upper lip narrower, with small papillae on ventral surface (internal) and with small round plates covered with odontods on dorsal surface (external). Maxillary barbel inconspicuous, united by membrane to lateral border of lower lip.

Teeth setiform, long, hook-shaped and bicuspid. Tooth cusps long, flattened and unequal, with round tips, darker than rest of tooth. Median cusp slightly longer and broader than lateral cusp. Number of jaw teeth increasing with growth. Number of premaxillary teeth approximately 16% greater than number of dentary teeth. Emergent teeth placed in two irregularly arranged rows; teeth gradually smaller laterally. Replacement teeth oriented at 90 degrees relative to emergent teeth and covered with skin.

Anteroventral tip of snout without plates, with distinguishable naked portion, approximately oval shaped, covered with stiff connective tissue. Anterior border of head with small, flexible plates between snout tip and anterolateral margin of upper lip. Lateral border of head covered with larger dorsal plates anteroventrally curved.

Three inconspicuous horizontal keels along body, from plates 6 to 14 or 16. Last plate of median lateral series diminutive and triangular, located on caudal-fin base, between two slightly larger plates of similar shape (one upper and one lower, upper plate slightly larger than lower plate). Lateral plates of median series, 32-33. Small ventral thoracic plates lozenge shaped, arranged in irregular, oblique rows. Longest row with 7 to 8 plates delimited by lateroventral thoracic plates. Region of abdomen anterior to anus covered with small, lozenge shaped plates, followed by one larger plate that form anterior border of anus.

Pectoral- and dorsal-fin spines, unbranched pelvic- and anal-fin rays not projecting into long filaments. Unbranched caudal-fin rays of both specimens damaged, except lower unbranched caudal- fin ray from one specimen which projects as long filament. Branched caudal-fin rays gradually longer toward upper and lower unbranched rays. Dorsal most branched caudal-fin ray slightly longer than ventral most ray. Unbranched pelvic-fin ray reaching vertical through anterior border of first ventral plate posterior to base of anal fin. Unbranched anal-fin ray reaching eighth ventral plate posterior to base of anal fin.

Dorsal-fin rays II,7; pectoral-fin rays I,7; pelvic-fin rays i,5; anal-fin rays i,5; caudal-fin rays i,12,i.

Color in alcohol. Coloration of paratype faded, uniform yellow. Color pattern based only on holotype. Ground coloration of head and body brown or yellow. Ventral region of head and body lighter, uniform yellow. Dorsal region of upper lip dark brown. Straight unpigmented median stripe from last anal-fin ray to base of unbranched lower caudal-fin ray. Dorsal region of body with three longitudinal, dark brown bands extending from base of dorsal fin to base of caudal fin. Two of these bands extending ventrally to cover lateral plates. Third band extending along dorsal midline of body, from dorsal-fin base to caudal-fin base. Bands gradually narrower posteriorly. A transversal, dark brown band between bases of pectoral-fins, with anterior margin at posterior tip of supraoccipital. Dorsal portion of head dark brown with slightly lighter areas. All fin rays with dark brown pigmentation. Anterior half of dorsalfin dark brown, remaining of fin hyaline. Paired fins and analfin dark brown. Caudal-fin base and three upper most and lower most branched rays dark brown.

Etymology. The species name, parakana, is in reference to the Parakanã, inhabitants of the margins of the lower rio Tocantins, in the State of Pará. Parakanã, an American group that historically inhabited the area of the lower rio Tocantins, drainage from which the examined specimens of the species in this study originated.

Geographic distribution. Known from the type locality at lower rio Tocantins, below Tucuruí Dam ( Fig. 2) .