Two new species of Pseudancistrus (Siluriformes, Loricariidae) from the Amazon basin, northern Brazil

Abstract Two new species of Pseudancistrus, a genus diagnosed by non-evertible cheek plates and hypertrophied odontodes along the snout margin, are described from two drainages of the Brazilian Shield: Pseudancistrus kayabi from the rio Teles Pires (rio Tapajós basin) and Pseudancistrus asurini from the rio Xingu. The new species are distinguished from congeners (Pseudancistrus barbatus, Pseudancistrus corantijniensis, Pseudancistrus depressus, Pseudancistrus nigrescens, Pseudancistrus reus, and Pseudancistrus zawadzkii) by the coloration pattern. Pseudancistrus kayabi has dark bars on the dorsal and caudal fins which are similar to that of Pseudancistrus reus from the Caroní River, Venezuela. Pseudancistrus asurini is unique among Pseudancistrus in having whitish tips of the dorsal and caudal fins in juveniles to medium-sized adults.


Introduction
With 892 species, the suckermouth armoured catfish family Loricariidae is the fifth most species-rich family of vertebrates and one of the most species-rich groups among Neotropical fishes (Eschmeyer and Fong 2014). The loricariids are easily distinguished by having a ventral oral disk, the body covered with ossified dermal plates, and the presence of small external teeth known as odontodes. Within this family, all species that have highly evertible clusters of cheek odontodes are placed within the subfamily Hypostominae, the tribe Ancistrini (Armbruster 2004a(Armbruster , 2008. Morphology-based studies by Armbruster (2004aArmbruster ( , 2008 showed Ancistrini as a monophyletic group; however, recent molecular studies supported the conclusion that the tribe was polyphyletic (e.g. Covain and Fish-Muller 2012;Lujan et al. 2015). Ancistrini was redefined by Lujan et al. (2015) and currently includes only ten valid genera but stays the second most genus-rich of the nine tribe-level clades of Hypostominae.
Pseudancistrus Bleeker, 1862 was known to contain 15 valid species (Eschmeyer and Fong 2014) but recent publications (e.g. Chambrier and Montoya-Burgos 2008;Covain and Fisch-Muller 2012;Silva et al. 2014;Lujan et al. 2015) revealed that the genus is not monophyletic and that the type species, P. barbatus (Valenciennes, 1840), is closely related only with four species known as the P. barbatus species group: P. corantijniensis de Chambrier & Montoya-Burgos, 2008, P. depressus (Günther, 1868), P. nigrescens Eigenmann, 1912, andP. zawadzkii Silva, Roxo, Britzke &Oliveira, 2014, the latter being the only species described to date from rivers flowing from the Brazilian Shield into the Amazon. Other species not included in these works were considered to possibly belong to Pseudancistrus: P. guentheri (Regan, 1904) P. kwinti Willink, Mol &Chernoff, 2010 (Covain andFisch-Muller 2012), and P. reus Armbruster & Taphorn, 2008(Lujan et al. 2015. This last work retained P. reus as the only species belonging to this group from the eastern Orinoco basin. The genus Pseudancistrus is diagnosed by a combination of characters state as follows: a depressed body, hypertrophied odontodes along the lateral margin of the snout (regardless of either sex or season), and hypertrophied cheek odontodes which are evertible to less than 45° from the body (Lujan et al. 2015).
Recently, an examination of the fish collections at the LBP (Laboratório de Biologia e Genética de Peixes de Botucatu) and MZUSP (Museu de Zoologia da Universidade de São Paulo) revealed the existence of two undescribed species of Pseudancistrus from the rio Xingu (the first species of Pseudancistrus for this basin) and the rio Teles Pires (the second species of Pseudancistrus for rio Tapajós basin), both of which are tributaries of the Amazon basin draining the Brazilian Shield. In the present paper these two new species are described.

Material and methods
After capture, fishes were anesthetized using 1% benzocaine in water, fixed in 10% formaldehyde, and preserved in 70% ethanol. Vouchers and tissues were deposited in the collection of AUM (Auburn University Natural History Museum, Auburn, USA), LBP (Laboratório de Biologia e Genética de Peixes, Botucatu, Brazil), and MZUSP (Museu de Zoologia da Universidade de São Paulo, São Paulo, Brazil). Measurements and counts were taken from the left side. Body plate follows Schaefer (1997) and measurements were taken point to point to the nearest 0.1 mm using digital calipers on left side of specimens following Armbruster (2003). Morphometrics are given as percentages of standard length (SL), except for subunits of the head region that are expressed as percentages of head length (HL). Dorsal-fin ray counts include the spinelet as the first unbranched ray. Zoological nomenclature follows the International Code of Zoological Nomenclature (International Commission on Zoological Nomenclature 1999).
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 dorsalfin 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 dorsalfin 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 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 P. 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.
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 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 pelvicfin 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 P. 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 Pará State, Brazil. A noun in apposition.

Discussion
The two new species, P. kayabi and P. asurini, are typical Pseudancistrus (sensu Chambrier and Montoya-Burgos 2008), recognized by non-evertible cheek plates and the presence of hypertrophied odontodes along the snout margin. This last character is shared with species of Lithoxancistrus and Pseudolithoxus. However, in Pseudancistrus, the odontodes along the snout are quite well developed, especially in P. kayabi. Additionally, Pseudolithoxus (Armbruster and Provenzano 2000) can be distinguished from Pseudancistrus by the presence of three rows of plates on the caudal peduncle (vs. five), and Lithoxancistrus can be distinguished from Pseudancistrus by the presence of three buccal papillae (vs. one; Isbrücker et al. 1988).
The most conspicuous character used to distinguish the two new species from all other described Pseudancistrus is the coloration pattern. Pseudancistrus kayabi has a pattern of dark bars on dorsal and caudal fins (Fig. 1) as in P. reus from the Caroní River, Venezuela. However, P. reus possesses dark brown bars also on the body. This character is absent in P. kayabi, which has a dark brown base color with whitish spots fading posterior to the dorsal fin and are large enough to cover more than one lateral body plate, a pattern that is similar to that found in P. nigrescens.
Pseudancistrus asurini has whitish tabs on the dorsal-and caudal-fin tips (Fig. 4) in juveniles and medium-sized adults (to approximately 100 mm SL), a pattern unique among Pseudancistrus. This character is similar to that found in Baryancistrus xanthellus (Py Daniel et al. 2011) andB. chrysolomus (Py Daniel et al. 2011), both of which are also from the rio Xingu basin and live sympatrically with P. asurini. Additionally, the new species P. asurini has a color pattern consisting of spots that increase in size from the head (diameter 0.3−0.8 mm) to posterior part of body (diameter 0.7−1.3). The species P. nigrescens, P. corantijniensis, and P. zawadzkii present a similar coloration pattern; however, the size of the spots increase abruptly from the head (diameter 1.1−1.3) to posterior part of body (diameter 2.6−2.3 mm).