Two new Amazonian species of armored catfishes (Siluriformes: Loricariidae): Ancistrus verecundus and Ancistrus parecis

Two new species Ancistrus are described: A. verecundus from the upper rio Madeira basin and A. parecis from the upper rio Juruena, rio Tapajós basin, Brazil. The two species differ from all congeners except A. jataiensis, A. reisi, and A. tombador in the absence of an adipose fin which is replaced by a series of median platelets forming a low postdorsal ridge. Ancistrus verecundus is further distinguished from these species, except A. tombador by the broad naked margin of the snout and reduced tentacle development. Ancistrus verecundus differs from A. tombador in various morphometric features, and in having the base of the first anal-fin pterygiophore covered by skin (vs. base of the first anal-fin pterygiophore exposed and forming a platelet-like element). Ancistrus verecundus and A. tombador have two or more dermal plates of the dorsal plate series between the end of the postdorsal ridge and the origin of the first plate-like procurrent caudal-fin ray, whereas the other species of the genus that lack an adipose fin, including A. parecis, have one or none. Ancistrus parecis is further distinguished from A. tombador and A. verecundus by the presence of tentacles in adults. It also differs from A. tombador in morphometric and meristic features and from A. jataiensis and A. reisi in the length of the mandibular tooth row, the number of teeth on dentary and premaxillary, and the caudal-peduncle depth. A key is provided for the identification of species of Ancistrus lacking an adipose fin.


Introduction
In July 2004, an expedition in the Brazilian states of Mato Grosso, Rondônia, Acre, and Amazonas, yielded, two new species of Ancistrus Kner, 1854 that lack an adipose fin.The loss of the adipose fin in the Hypostominae was recently discussed by Fisch-Muller et al. (2005), who described the first three species of Ancistrus with this condition: A. jataiensis, A. reisi, and A. tombador.In each of these species, the adipose fin is replaced by a series of small median, unpaired plates forming a low postdorsal ridge.This character was also observed in some other taxa, including Liptopterichthys Norman, 1935, Corymbophanes Eigenmann, 1909 (see also Armbruster et al., 2000), and Hemipsilichthys vestigipinnis Pereira & Reis, 1992.In addition to the absence of an adipose fin, one of the newly discovered species, along with Ancistrus tombador, lacks tentacles in both sexes or, as was discussed for A. tombador, shows a reduced development of these fleshy protuberances that are unique to the genus.Variation in the number, size, and distribution of tentacles in relation to reproductive condition, sex, and species, as well as the size of the naked margin of the snout where they occur, was extensively documented recently (Sabaj et al., 1999;Fisch-Muller, 1999;Fisch-Muller et al., 2005).Some species of Ancistrus were described as lacking tentacles; however, we never observed any species of Ancistrus completely devoid of tentacles.An example is A. gymnorhynchus Kner, 1854, the first species to be distinguished from A. cirrhosus (type species of the genus) by the purported absence of tentacles.Kner based his description on a single specimen, a large female (111.2mm SL) without tentacles.Several conspecific specimens, including females, have few, short tentacles along the naked margin of the snout, and a few other specimens probably in breeding condition have more developed tentacles (Fisch-Muller, 1999).
Ancistrus gymnorhynchus as well as other species with reduced tentacles had been placed in the genus Xenocara, a name that was initially proposed by Regan (1904) for all species presently placed in Ancistrus.This usage was disputed by Eigenmann (1905: 795) and the name was retained conditionally for some "Ancistroids without tentacles".Eigenmann (1910) restricted further the use of the name Xenocara to include A. gymnorhynchus and Chaetostomus latifrons Günther, 1869, with the latter designated as the type species of the genus.The name Xenocara was subsequently used for such species of Ancistrus "without tentacles" in several works and other catalogs (i.e.Gosline, 1945;Fowler, 1954), until it was subsequently synonymized with Ancistrus by Isbrücker (1980).
The objective of the present paper is to describe the two new species and to provide an identification key for the species of Ancistrus lacking an adipose fin.The descriptions of these species bring to thirty the number of described species of Ancistrus from the Amazon River drainage, but several other undescribed forms are known from this basin.

Material and Methods
Measurements and counts were taken as described by Fisch-Muller et al. (2001) on all specimens measuring 35 mm standard length (SL) or more.Morphometric characters are expressed as percents of SL except for subunits of the head, which are expressed as percents of head length (HL).The nomenclature of the dermal plates in lateral series follows Schaefer (1997).Vertebrae counts are taken from radiography specimens, and include the Weberian and ural complexes.The sex of specimens was determined by the width of the naked margin of the snout.Specimens are deposited in the Museu de Ciências e Tecnologia, Pontifícia Universidade Católica do Rio Grande do Sul, Porto Alegre (MCP) and in the Muséum d'histoire naturelle, Genève (MHNG).Comparative material includes the primary type specimens of all recognized and synonymized species of Ancistrus according to Fisch-Muller (2003), except for Hypostomus punctatus Jardine in Schomburgk, 1841 (holotype not preserved; invalid name, synonym of A. dolichopterus Kner, 1854, type material examined), A. mattogrossensis Ribeiro, 1912 (type material not found; type locality not stated), and A. galani Perez & Viloria, 1994 (Venezuelan cave species).

Ancistrus verecundus, new species
Figs. by a series of 3 to 5 median, unpaired platelets forming a low postdorsal ridge.Ancistrus verecundus differs from all congeners lacking an adipose fin, except for A. tombador, by the naked margin of snout broad and the reduced development of snout tentacles in both sexes (usually absent), and by the presence of two or more plates of the dorsal plate series between the end of the postdorsal ridge and the origin of the first dorsal procurrent caudal-fin spine (Fig. 4a) (vs.one or none).Ancistrus verecundus is distinguished from A. tombador by the head depth at supraoccipital (17.9-19.3 vs. 15.6-16.9%SL), cleithral width (31.4-33.1 vs. 27.5-31.2%SL), interorbital width (15.9-16.8 vs. 12.7-15.1%SL), and by the base of the first anal-fin pterygiophore covered by skin (vs.exposed).
Description.Morphometric and meristics in Table 1.Head and body depressed.Dorsal profile of head convex from tip of snout tip to posterior tip of supraoccipital, nearly straight to slightly convex from tip of supraoccipital to dorsal-fin origin, straight and posteroventrally slanted along dorsal-fin base, slightly concave from end of dorsal-fin base to median platelets replacing adipose fin, more concave from that point to last procurrent caudal-fin ray.Ventral profile straight, caudal peduncle slightly concave.Greatest width of body at cleithrum, with body narrowing progressively from cleithrum to end of caudal peduncle.Caudal peduncle very low and slender.Snout rounded with relatively broad naked margin in both sexes (much wider than distance between naked margin and nostril in specimens hypothesized to be males, including holotype; nearly as broad as distance between naked margin and nostril in specimens hypothesized to be females, including largest specimen examined).Thin median row of platelets extends up to, or nearly to, anterior extremity of snout.Tentacles usually absent in both sexes in specimens examined.
Eye small, dorsal margin of orbit slightly elevated, interorbital area slightly concave.Exposed part of opercle roughly triangular with posterior part slightly elongated; dermal plates of postopercular area never numerous, generally contiguous with pterotic-supracleithrum, sometimes few smaller plates anteriorly, leaving large naked area around opercle.Hypertrophied cheek odontodes numerous and short, none reaching posterior margin of adpressed opercle; base fleshy and sometimes thick.
Oral disk roughly circular, lips covered with minute papillae.Lower lip large but not reaching pectoral girdle, its border covered with very small papillae.Maxillary barbel short, about as long as buccal papilla.Mandibular tooth row short, pre- Supraoccipital with margins between surrounding bones and plates usually not clearly visible.Nuchal plate small and curved.Five series of lateral plates; mid-dorsal, and mid-ventral series ending at level of end of series of platelets replacing adipose fin.Last plate in median series rarely smaller than penultimate plate.Odontodes present on body plates except along dorsal-fin base, and on widely extended area below anal fin; odontodes generally short, only very slightly longer on ventral margin of opercle and on pectoral-fin spine of males.Abdomen entirely devoid of plates.Base of first anal-fin pterygiophore covered by skin (without preanal platelet-like element).
Dorsal-fin origin situated slightly anterior to vertical through pelvic-fin insertion; dorsal fin short, tip of adpressed fin not reaching series of median platelets.Area usually occupied by adipose fin covered by series of 3 to 5 small median platelets forming low postdorsal ridge.Two or more plates of dorsal plate series between end of postdorsal ridge and origin of first dorsal procurrent caudal-fin spine (Fig. 4a).Pectoral spine extending to anterior one-third of pelvic spine.Anal fin short.First anal-fin pterygiophore covered by skin.Caudal fin short, slightly concave.Fin-ray formulae: dorsal i,7 (7) or i,8 (1); pectoral i,6; pelvic i,5; anal i,4; caudal i,13,i (1) or i,14,i (7).Vertebrae: 27 (1).
Color in alcohol.Body reddish-brown, ventral portion of caudal peduncle paler.Body with irregularly distributed dark spots dorsally.Some specimens with numerous small and inconspicuous paler spots, limited to naked margin of snout (holotype), or more extending extensively on head.Lips yellowish.Ventral surface of head and abdomen plain or with coalescent spots forming thin and ill-defined whitish vermiculations.Fin rays generally reddish-brown with scattered dark-brown spots; membranes dark-brown when pigmented.Spots on distal one-half of dorsal and caudal fins sometimes forming bands (Fig. 2).
Distribution.Ancistrus verecundus was collected in a small river of the upper rio Madeira basin, in the state of Rondônia, Brazil (Fig. 1).
Etymology.From Latin, verecundus, meaning bashful, modest, in allusion to the absence or reduced development of tentacles on the snout.

Ancistrus parecis, new species
Figs. Description.Morphometric and meristics in Table 1.Dorsal profile of head convex from snout tip to posterior tip of supraoccipital, nearly straight to slightly convex from supraoccipital tip to dorsal-fin origin, straight and posteroventrally slanted along dorsal-fin base, slightly concave from end of dorsal-fin base to median platelets in area otherwise occupied by adipose fin, more concave from that point to last procurrent caudal-fin ray.Ventral profile straight, caudal peduncle slightly concave.Greatest width of body at cleithrum, body narrowing progressively from that point to near caudal peduncle.Snout rounded; plates delimiting posterior margin of naked area of snout irregularly placed; thin median row of platelets covering naked area up to or nearly to anterior extremity of snout.Naked margin of snout narrower than distance between naked margin and nostril in females, nearly as great as distance to nostrils in males, with fleshy tentacles (up to 30, in holotype).Tentacles placed along border of snout in two specimens; but also on dorsum of snout (only in holotype, 59.5 mm SL).Male of 44.4 mm SL with small tentacles arranged in one row bordering snout.Some tentacles branched in holotype.
Eye very small, dorsal margin of orbit slightly elevated and slightly convex.Exposed portion of opercle roughly triangular with posterior region slightly elongated; few dermal plates on postopercular area; plates generally contiguous with pterotic-supracleithrum, sometimes with few smaller plates anteriorly leaving large naked area around opercle.Hypertrophied cheek odontodes stout but neither numerous nor very long, with fleshy base sometimes long and thick, posterior odontodes reaching posterior one-half of adpressed opercle.
Oral disk roughly circular; lips covered with minute papillae; lower lip large but not reaching posteriorly to pectoral girdle, its border formed by unequal small flaps.Maxillary barbels, about as large as buccal papilla.Mandibular and premaxillary tooth rows equal in length or latter slightly longer; teeth numerous, bifid, main cusp large and long; lateral cusp minute, pointed, reaching more than one-third length of mesial cusp.
Supraoccipital with margins between surrounding bones and plates except median predorsal plate usually not clearly visible.Odontodes very short on head; central part of supraoccipital slightly granular.Nuchal plate and dorsal-fin spinelet exposed.Five series of lateral plates; mid-dorsal and mid-ventral series ending at level of end of series of platelets located in area occupied by adipose fin in most congeners.Last plate in median series rarely smaller than penultimate Fig. 3. Ancistrus parecis, MCP 35570, holotype, male, 59.5 mm SL; rio Formiga, upper rio Tapajós basin, Campos de Júlio, Mato Grosso, Brazil.plate.Odontodes present on body plates except along dorsal-fin base and on a widely extended area below anal fin; odontodes of males slightly longer on ventral margin of opercle and on pectoral-fin spine.Abdomen entirely devoid of plates.First anal-fin pterygiophore either exposed and forming preanal platelet-like element (holotype) or covered by skin.
Dorsal-fin origin located slightly anterior to pelvic-fin origin; dorsal fin short; tip of fin falling short of median platelets occupying space otherwise occupied by adipose fin.Adipose fin absent, replaced by series of 4 to 6 small median platelets forming low postdorsal ridge.One plate (sometimes none) of dorsal plate series between end of postdorsal ridge and origin of first dorsal procurrent caudal-fin spine (Fig. 4b).Pectoral-fin spine curved and short, extending to anterior onefourth of pelvic-fin spine, and thickened in large specimens.Anal fin short.Caudal fin short, slightly concave.Fin-ray formulae: dorsal i,6 (1) or i,7 (3); pectoral i,6; pelvic i,5; anal i,4; caudal i,14,i.Vertebrae: 28 (2).
Color in alcohol.Ground coloration of body brown or reddish-brown, lower part of caudal peduncle paler.Ill-defined dark-brown and reddish or yellowish areas over body.Small, rounded or elongated lighter spots often present on snout but never very distinct.Ventral surface lighter; lips yellowish; belly light brown (rarely yellowish); when pigmented, chromatophores present on entire surface including central portion, with very ill-defined lighter spots.Fin rays generally dark brown and finely spotted with yellowish to orange, hyaline membranes unpigmented at least on central parts.Caudal fin with tips often yellowish to orange colored (Fig. 3).
Distribution.Ancistrus parecis was collected in small rivers of the upper rio Tapajós basin, in the state of Mato Grosso, Brazil (Fig. 1).
Etymology.The specific name parecis (a noun in apposition) refers to the Chapada dos Parecis, a plateau where the type locality is situated.

Fig. 4 .
Fig. 4. Dorsal view of caudal peduncle in (a) Ancistrus verecundus, MCP 35573, paratype, 54.6 mm SL and (b) Ancistrus parecis, MCP 35570, holotype, 59.5 mm SL.Arrows indicate dermal plates of dorsal series of plates between the end of postdorsal ridge and the origin of the first plate-like procurrent caudal-fin ray.

Table 1 .
Morphometric and meristic data for the holotypes (H) and paratypes of Ancistrus verecundus from upper rio Madeira basin, and Ancistrus parecis from upper rio Tapajós basin.maxillary tooth row slightly wider; teeth bifid, main cusp large; lateral cusp minute, pointed, never reaching more than onethird length of mesial cusp.