Two new species of Pseudancistrus (Siluriformes, Loricariidae) from the Amazon basin, northern Brazil Author Silva, Gabriel S. C. Author Roxo, Fabio F. Author Oliveira, Claudio text ZooKeys 2015 482 21 34 http://dx.doi.org/10.3897/zookeys.482.6909 journal article http://dx.doi.org/10.3897/zookeys.482.6909 1313-2970-482-21 0069EEE37654461AA817EDD23EA4470A Taxon classification Animalia Siluriformes Loricariidae Pseudancistrus asurini sp. n. Figures 3, 4, Table 1 Pseudancistrus sp. L17: Covain and Fisch-Muller 2012 : 232−233 (Table 1), 235 (Fig. 2), 237 (Fig. 3), 242 (Fig. 4). - Silva et al. 2014 : 6 (Fig. 2), 14 (Fig. 6), 16 (Table 3), 17 (Fig. 7). Pseudancistrus sp. L67: Lujan et al. 2015 : 281 (Fig. 3). Holotype. MZUSP 116323, male, 195.8 mm SL. Brazil: Para State: municipality of Altamira: rio Xingu (Amazon basin), Cachoeira do Espelho, 03°39'05"S , 52°22'42"W , 18 November 2011, OT Oyakawa, JLO Birindelli, C Moreira, A Akama, LMS Souza. Paratypes . All from Brazil: Para State: municipality of Altamira: Amazon basin. AUM 65640, 2, 79.1−82.9 mm SL, rio Xingu, Cachoeira da Mucucura, 03°24'31"S , 51°44'40"W , 09 November 2011, OT Oyakawa, JLO Birindelli, C Moreira, LMS Souza . LBP 16551, 2, 75.6−101.4 mm SL, rio Xingu, 03°15'24"S , 52°05'47"W , 28 September 2012, C Oliveira, R Britzke, LMS Sousa. MZUSP 107174, 4, 45.9−123.4 mm SL, rio Xingu, Cachoeira de Mucura, 03°24'51"S , 51°44'23"W , ECIX team. MZUSP 107179, 2, 62.3−68.7 mm SL, rio Xingu, Cachoeira do Mucura, 03°24'51"S , 51°44'23"W , 07 July 2010, ECIX team. MZUSP 107435, 3, 74.6−105 mm SL, rio Xingu, 03°10'40"S , 51°36'58"W , 26 September 2007, FCT Lima, AK Zeinad. MZUSP 111285, 2, 84.4−106.6 mm SL, rio Iriri (trib. rio Xingu) Cachoeira Grande, 03°50'37"S , 52°44'02"W , OT Oyakawa, JLO Birindelli, C Moreira, A Akama, LMS Souza. MZUSP 111441, 6, 49.5−152.3 mm SL, rio Xingu, Cachoeira da Mucucura, 03°24'31"S , 51°44'40"W , 09 November 2011, OT Oyakawa, JLO Birindelli, C Moreira, LMS Souza. MZUSP 111558, 1, 91.4 mm SL, collected with holotype. Diagnosis. The new species differs from all congeners by having the dorsal-and caudal-fin tips whitish (Fig. 4) (vs. entirely dark). It further differs from Pseudancistrus reus and Pseudancistrus kayabi by having conspicuous whitish spots on the body (vs. body mottled or with bars in Pseudancistrus reus and with whitish spots that fade along the body and can cover more than one plate in Pseudancistrus kayabi ). It is also distinguishable from Pseudancistrus depressus and Pseudancistrus barbatus by having the snout with yellowish odontodes (vs. reddish-brown) (see Fig. 3 in De Chambrier and Montoya-Burgos 2008 for comparison) and from Pseudancistrus nigrescens , Pseudancistrus corantijniensis , and Pseudancistrus zawadzkii by having smaller whitish spots covering the body which increase gradually in size on the head (diameter 0.3−0.8 mm) and further on the body (diameter 0.7−1.3) (vs. spots abruptly increasing size between the head (diameter 1.1−1.3) and the body (diameter 2.6−2.3 mm). In addition, the new species is distinguished by a shorter predorsal length, 39−43% SL (vs. 43−46% in Pseudancistrus zawadzkii and 43−45% in Pseudancistrus nigrescens ), a smaller dorsal pectoral depth, 23−27% SL (vs. 27−31% in Pseudancistrus zawadzkii ); a smaller caudal peduncle depth, 9−11% SL (vs. 13−14% in Pseudancistrus zawadzkii and 13% in Pseudancistrus nigrescens ), a shorter barbel, 5−9% HL (vs. 10−11 in Pseudancistrus nigrescens ), and head depth, 57−66% SL, which is smaller than in Pseudancistrus zawadzkii (67−73%) but greater than in Pseudancistrus barbatus (41−53%). Figure 3. Pseudancistrus asurini , holotype, MZUSP 116323, male 195.8 mm SL, from rio Xingu (Amazon basin), municipality of Altamira, Para State, Brazil. Figure 4. Pseudancistrus asurini , paratype, LBP 16551, female 100.5 mm SL, from rio Xingu (Amazon basin), showing the dorsal and caudal fins tips whitish. Description. Morphometric data is presented in Table 1. In lateral view, dorsal profile convex from snout tip to dorsal-fin origin; straight, gradually descending from dorsal-fin origin to posterior insertion of adipose fin; straight, steeply ascending to insertion of caudal fin; ventral profile flat from snout tip to anal-fin origin; shallowly concave from anal-fin insertion to lower caudal-fin spine; greatest body depth at dor sal-fin origin. In dorsal view, greatest body width across cleithral region; snout broadly elliptical; body decreasing in width from opercular region to caudal fin. Cross-section of body between pectoral and pelvic fins rounded dorsally and flattened ventrally; cross-section of caudal peduncle ellipsoid. Body almost entirely covered with plates, except on ventral portions of head, abdomen, and dorsal-fin base. Five lateral rows of dermal plates, dorsal plates 21−22, lateral mid-dorsal plates 18−22, lateral median plates 22−23, lateral mid-ventral plates 23−24, lateral ventral plates 18−19. Three predorsal plates; seven plates below dorsal-fin base; four plates between dorsal fin and adipose fin; five rows of plates on caudal peduncle. Dorsal spinelet present. Body plates and cleithrum with minute odontodes. Odontodes gradually getting larger towards tips on pectoral-fin spines. Numerous whitish hypertrophied odontodes along lateral margins of head including snout; homogenous in length excepting in anterior portion of snout where odontodes are smaller; longest odontodes on posteriormost portion of non-evertible cheek plates. Eye small (orbital diameter 13−10% HL), dorsolaterally positioned. Oral disk transversely ellipsoid. Lower lip not reaching transverse line between gill openings. Lower lip covered with numerous small papillae. Maxillary barbel poorly developed. Mouth relatively large. Premaxillary teeth 38−77 per ramus; dentary teeth 39−86 per ramus. Teeth bifid, medial cusp large and rounded, lateral cusp minute and rounded. Jaws wide, dentaries forming oblique angle, premaxillaries almost co-linear. Dorsal fin II,7, origin approximately at midpoint between pectoral- and pelvic-fin origins, last dorsal-fin ray not reaching adipose-fin when depressed. Pectoral fin I,6, spine tip not curved inward; depressed tip reaching one-third length of pelvic-fin spine. Pelvic fin I,5, spine tip curved inward, almost reaching anal-fin origin when depressed. Anal-fin I,5, spine tip straight, reaching fifth plate posterior to its origin. Caudal fin I,7-7I, distal margin concave, inferior lobe longer than superior. Adipose fin with almost straight spine, preceded by single median preadipose plate. Color in alcohol. Ground color dark brown on back and sides of body, and lighter brown ventrally. Anterior portion of head to posterior margin of orbits with many small, crowded, white spots; spots increasing slightly and gradually in size between snout to body. Dorsal plate series usually with two or three spots per plate in anterior portion of body and one spot on posterior portion of body. Mid-dorsal plates usually with two or three spots per plate. Lateral median plates with one or two spot per plate. Mid-ventral plates and ventral plates with two or three spots per plate. Dorsal-fin spine, rays and membranes with small round spots. Adipose fin with three small spots on spine and membrane. Pectoral, pelvic, anal and caudal fins with numerous and white spots of equal size. Dorsal and caudal fin tips whitish. Hypertrophied odontodes along head margin yellowish. Color in life. Similar to pattern described for alcohol individuals, but with ground color dark greenish-brown, and with yellow spots on body and on tips of dorsal and caudal fins. Sexual dimorphism. Males possess a papilla posterior to urogenital opening, an attribute absent in females. Both sexes in Pseudancistrus asurini exhibit highly hypertrophied odontodes along snout margin, as well as in others species of Pseudancistrus ( Armbruster 2004b ). Etymology. The specific name "asurini" is a reference to the Asurini indigenous peoples who inhabit the right margin and median portions of rio Xingu, close to the municipality of Altamira in Para State, Brazil. A noun in apposition. Distribution. Pseudancistrus asurini is known from the rio Xingu, municipality of Altamira, from the Xingu river basin, Para State, Brazil (Fig. 2b).