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 kayabi sp. n. Figure 1, Table 1 Holotype. MZUSP 116322, male, 88.4 mm SL. Brazil: Mato Grosso State: municipality of Itauba : rio Teles Pires ( Tapajos River basin), 10°58'30"S , 55°44'03"W , 01 October 2007, JLO Birindelli, P Hollanda-Carvalho. Paratypes. All from Brazil: Mato Grosso State: rio Teles Pires ( Tapajos River basin): Amazon basin. AUM 65641 2, 74.5−80.3 mm SL, municipality of Itauba , 11°03'44"S , 55°19'08"W , 26 September 2007, JLO Birindelli, P Hollanda-Carvalho. LBP 19552, 2, 79.1−87.1 mm SL, municipality of Itauba , 11°03'44"S , 55°19'08"W , 26 September 2007, JLO Birindelli, P Hollanda-Carvalho. MZUSP 95851, 1, 60.9 mm SL, collected with holotype. MZUSP 95912, 54, 27.1−86.5 mm SL, municipality of Itauba , 11°03'44"S , 55°19'08"W , 26 September 2007, JLO Birindelli, P Hollanda-Carvalho. MZUSP 96157, 34, 29.5−85.8 mm SL, municipality of Paranaita , 09°26'58"S , 56°29'19"W , 28 September 2007, LMS Souza, AL Netto-Ferreira. Diagnosis. Pseudancistrus kayabi differs from all congeners except Pseudancistrus reus by having caudal and dorsal fins with dark bars (vs. with white spots in caudal and dorsal fins). Also, the new species differs from all Pseudancistrus except Pseudancistrus nigrescens by having a dark brown body with whitish spots that fade along the posterior portion of the dorsal fin and forming mottled pattern (vs. either dark brown with conspicuous rounded spots not covering more than one plate in Pseudancistrus barbatus , Pseudancistrus corantijniensis , Pseudancistrus depressus , Pseudancistrus asurini , and Pseudancistrus zawadzkii or with dark brown bars in Pseudancistrus reus ). It further differs from Pseudancistrus barbatus and Pseudancistrus depressus by having the snout with yellowish hypertrophied odontodes (vs. reddish-brown odontodes) (see Fig. 3 in De Chambrier and Montoya-Burgos 2008 for comparison). In addition, Pseudancistrus kayabi is distinguished by having a shorter pectoral spine, 22−30% SL (vs. 29−34% in Pseudancistrus nigrescens , 31−33% in Pseudancistrus zawadzkii , and 30−34% in Pseudancistrus barbatus ); a shorter dorsal-fin base, 20−28% SL (vs. 28−29% in Pseudancistrus nigrescens , 29−31% in Pseudancistrus zawadzkii , and 28−31% in Pseudancistrus barbatus ); a greater internares width, 13−19% HL (vs. 10.5−12.9% in Pseudancistrus nigrescens ); head depth, 60−66% HL, greater than in Pseudancistrus nigrescens (56−57%) and in Pseudancistrus barbatus (41−53%) but smaller than in Pseudancistrus zawadzkii (67−73%); and a greater adipose-anal distance (17−25% SL vs. 15−17% in Pseudancistrus nigrescens and 12−15% in Pseudancistrus barbatus ). Figure 1. Pseudancistrus kayabi , holotype, MZUSP 116322, male 88.4 mm SL, from rio Teles Pires (Amazon basin), municipality of Itauba , Mato Grosso State, Brazil. 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 dorsal-fin origin. In dorsal view, greatest body width across cleithral region; snout broadly elliptical; body progressively narrow 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 21−22, lateral median plates 22−23, lateral mid-ventral plates 21−22, lateral ventral plates 19−20. Three predorsal plates; eight plates below dorsal-fin base; four plates between dorsal fin and adipose fin; five rows of plates on caudal peduncle. Dorsal spinelet present. Table 1. Morphometric data for Pseudancistrus kayabi and Pseudancistrus asurini . SD = standard deviation.

Pseudancistrus kayabi n = 21				Pseudancistrus asurini n = 21
Holotype	Range	Mean	SD	Holotype	Range	Mean	SD
SL
Percentage of SL
Percentage of HL

Body plates and cleithrum with minute odontodes. Odontodes slightly hypertrophied on pectoral-fin spines, gradually larger towards tips. Numerous yellowish hypertrophied odontodes along lateral margins of head including snout; odontodes small on tip of snout increasing gradually in length from anterolateral margin of snout to cheeks ; longest odontodes on posteriormost portion of non-evertible cheek plates. Eye small (orbital diameter 13−20% 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 developed. Mouth relatively large. Premaxillary teeth 33−70 per ramus; dentary teeth 39−74 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 I,7, origin approximately at midpoint between pectoral- and pelvic-fin origins, last dorsal-fin ray reaching adipose fin when depressed. Pectoral fin I,6, spine tip slightly curved inward, covered with enlarged odontodes distally; 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 sixth plate posterior to its origin. Caudal fin I,7-7I, distal margin concave, inferior lobe longer than superior. Adipose fin with 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 getting abruptly larger on posterior portion of head, continuing on body, fading along posterior portion of dorsal fin and forming mottled pattern. Dorsal-fin spine rays and membranes with 6−7 dark bars. Pectoral, pelvic, anal with 4−5 dark bars and caudal-fin with four dark bars. Hypertrophied odontodes along head margin yellowish. Sexual dimorphism. Males possess a papilla posterior to urogenital opening, an attribute absent in females. Both sexes in Pseudancistrus kayabi exhibit highly hypertrophied odontodes along snout margin, as well as in other species of Pseudancistrus ( Armbruster 2004b ). Etymology. The specific name "kayabi" is a reference to the Kayabi indigenous people that inhabited the region of the rivers Arinos, dos Peixes and Teles Pires, in Mato Grosso State, Brazil. A noun in apposition. Distribution. Pseudancistrus kayabi is known from the rio Teles Pires, rio Tapajos basin, municipality of Itauba and Paranaita , Mato Grosso State, Brazil (Fig. 2a). Figure 2. Distribution maps. a Pseudancistrus kayabi . Star shows holotype locality, rio Teles Pires, 10°58'30"S , 55°44'03"W . Circle shows paratype locality b Pseudancistrus asurini . Star shows holotype locality, rio Xingu, 03°39'05"S , 52°22'42"W . Circles show paratypes localities.