Rineloricaria osvaldoi (Siluriformes: Loricariidae): a new species of armored catfish from rio Vermelho, Araguaia basin, Brazil

A new species of Rineloricaria Bleeker from the rio Vermelho, Araguaia basin, Goias, Brazil is described. Rineloricaria osvaldoi, new species, can be distinguished from its congeners by the combination of the following characters: surface of thoracic area trapezoidal with greatest width between pectoral fins, up to 13 premaxillary teeth, largest body width at the section of the canal plate, anterior profile of the head of mature males semicircular in dorsal view. Although eight genera of Loricariinae are known from the rio Araguaia basin, R. lanceolata was only species of Rineloricaria previously reported from that basin. Therefore, the discovery of the R. osvaldoi increases the scenery of diversity of Loricariinae within this drainage basin.


Introduction
The genus Rineloricaria Bleeker is one of the most species-rich genera of the Loricariinae (see Ferraris, 2003) and taxonomically the most problematic one (Reis & Cardoso, 2001;Rodriguez & Miquelarena, 2005).The genus comprises 59 valid species (Ferraris, 2003;Knaack, 2003;Ghazzi, 2008;Rodriguez & Reis, 2008), distributed from Panama, in Central America to Northeast Argentina.Rineloricaria species are found in a large variety of habitats, including large rivers, streams, and lagoons, associated with bottoms consisting of sand or rocks, sometimes found in marginal vegetation.They are also found to tolerate environments with a wide temperature gradient (Reis & Cardoso, 2001).
Although there is no unique apomorphic character that can be used to diagnose the genus, Rineloricaria is diagnosed by the combination of the following characteristics: postorbital notch; short rounded papillae on the inferior lip of the mouth; seven to 15 teeth on each premaxilla; dentary teeth strong, deeply bicuspidate, and larger than the premaxillary teeth; dark-brown bars or blotches on dorsal region; and a conspicuous polygonal preanal plate, which usually contacts three other large trapezoidal plates.In addition, features associated with sexual dimorphism are useful characters to diagnose mature males of some species of the genus.Dimorphic characters usually consist in numerous hypertrophied odontodes along the sides of the head and the dorsal surface of the unbranched pectoral-fin rays, which are generally thick, short, and curved in males (vs.thin, elongated and almost straight in females and immature males).Males of some species of Rineloricaria possess well-developed odontodes over all of the predorsal area, or sometimes restricted to the posterior edge of parieto-supraocciptal, as in R. formosa (Isbrücker & Nijssen, 1979).
Although the Araguaia basin has a high diversity of fishes, specimens of Rineloricaria from this basin are poorly represented in ichthyological collections.This region has been relatively well sampled through last decades, especially when compared with other large tributaries of the Amazon basin.For a long time only R. lanceolata was recorded from the rio Araguaia basin (pers.obs., Fichberg) and R. hasemani recorded from the rio Tocantins (Ferraris, 2003(Ferraris, , 2007)).In 1966 the "Expedição do Departamento de Zoologia", collected samples from rio Vermelho, a tributary to the rio Araguaia that contained five specimens of an undescribed species of Rineloricaria.
In 2005 an expedition to Central Brazil collected several species of the Loricariinae including Farlowella sp., Hemiodontichthys acipenserinus (Kner,1853), Loricaria sp., Loricariichthys sp., Sturisoma sp., Rineloricaria lanceolata (Günther, 1868), and additional specimens of the Rineloricaria species collected in 1966.Other species of the Loricariidae were recorded to this expedition and represented approximately 25% of total fishes collected.From the results of these expeditions, it appears that the Loricariinae are reasonably diverse in the rio Araguaia basin and that the low diversity of Rineloricaria is accurate, rather than a sampling problem.The aim of this paper is to describe a new species of Rineloricaria from rio Vermelho.

Material and Methods
Measurements followed Boeseman (1968), Reis &Cardoso (2001), andRodriguez &Miquelarena (2005) except the head width, which was measured between the canal plate.All measurements were taken point-to-point with a dial caliper under a binocular stereomicroscope.All measurements and counts of bilateral structures were obtained from the left side of the specimens, whenever possible.The body measurements are expressed as proportions of standard length (SL), except for subunits of the head, which are expressed as proportions of head length (HL).Plate counts and nomenclature follow schemes of serial homology proposed by Schaefer (1997).Opercular series nomenclature follows Schaefer (1988).Cranial osteology nomenclature follows Aquino & Schaefer (2002).Orbital diameter on Table 1 includes postorbital notch.The meristic data in the description are expressed in range of values and followed by the mode, between parentheses.

Rineloricaria osvaldoi, new species
Figs. Head short.In dorsal view, head rounded to triangular in females and immature males with tip of snout and distal margin of opercle rounded (Fig. 3); head margin of mature males strongly rounded, shaped as semicircle (Figs.3a-b).Snout with very small, elliptical, naked area, not reaching most anterior pore of infraorbital ramus of sensory canal.
Predorsal area weakly keeled with small odontodes covering plates; posterior margin of compound-pterotic with dark-brown spots around first pores of lateral-line canal.Eyes elliptical with large, deep postorbital notch.
Mouth opening large.Upper lip very short and separated from naked area of snout by extremely thin row of plates (sometimes absent) covered by tiny odontodes; margin of upper lip adorned with rounded papillae.Two or three rows of papillae between anteroventral border of upper lip and anterior border of premaxillary ramus; lower lip covered by irregularly sized papillae well organized and arranged concentrically around oral cavity; edge of lower lip fringed, triangular in shape.Short maxillary barbel adorned with very small papillae; teeth acute and strongly bicuspidate; dentary teeth larger than those of premaxilla; 5-13 (8) teeth on premaxilla and 5-13 (7) on dentary; accessory cusp almost same size as principal cusp.
Body covered by 26-29 (27) plates on median series, coalescent plates on 16-19 (17) and, 6-7 (6) lateral abdominal plates.Five longitudinal rows of plates at dorsal-fin origin.Lateral plates weakly keeled with odontodes along lateral line pores slightly better developed than those on rest of body.
Ventral region completely covered by plates, from cleithrum to caudal peduncle.Ventral plates well organized in three sections.Anterior section consisting of small quadrangular plates on pectoral girdle area, middle section includes large, trapezoidal plates between pectoral and pelvic girdles, and posterior section represented by preanal shield formed by three large plates surrounding polygonal preanal plate.Dorsal-fin rays i,7, pectoral-fin rays i,6, pelvic-fin rays i,5, anal-fin rays i,5, caudal-fin rays i,10,i; adpressed pectoral fin in females and immature males surpassing pelvic fin by approximately 15% of length of first unbranched ray of pelvic fin.Pelvic fin reaching insertion of anal fin.Caudal fin truncate, with short, thin filament on dorsal caudal-fin ray.Lower caudalfin ray without filament.Sexual dimorphism.Head margin of mature males rounded, with abundant hypertrophied odontodes extending from postrostral plates to opercle, along margin of head (see Fig. 3a); pectoral-fin unbranched ray thick, curved and shorter than in females; unbranched pectoral-fin ray and first four branched rays covered dorsally by numerous, well developed odontodes.
Geographic distribution.Rineloricaria osvaldoi is only known from the rio Vermelho and it tributary, the rio Bugre, in the rio Araguaia basin, Brazil (Figs. 4-5).
Ecological notes.The specimens were collected in clear water over a sand bottom with some rocks, at the altitude of approximately 496 meters above sea level.Both expeditions  were carried out in dry season when the waters were low.
Etmology.The name of the new species is given in honor of Dr. Osvaldo Takeshi Oyakawa, the collection manager of the fish collection of the Museu de Zoologia da Universidade de São Paulo and also a specialist of the Loricariinae, particularly of the genus Harttia.

Discussion
Species of Rineloricaria are known from Panamá to Argentina.Although the group is widespread throughout the Neotropical region, only a few species are known to occur in some basins, such as Araguaia-Tocantins and São Francisco rivers, in contrast to South and Southeastern Brazilian drainages, in which many species of Rineloricaria are known (see Ferraris, 2003;Rodriguez & Miquelarena, 2005;Ghazzi, 2008, andRodriguez &Reis, 2008).Only two other species are known from the rio Araguaia-Tocantins system, R. lanceolata and R. hasemani.Rineloricaria lanceolata is widespread in the Amazon and Paraguay basins (Ferraris, 2003(Ferraris, , 2007)), while R. hasemani is apparently restricted to the lower Amazon basin, in forest streams near Belém and the rio Tocantins (Ferraris, 2003;2007).
Rineloricaria osvaldoi is easily distinguished from R. lanceolata and R. hasemani by having a broader body (cleithral width 18.4-23.3% of SL vs. 14.1-14.6% in R. lanceolata and 15.7% in R. hasemani, which only the holotype measurement is available) and on a more rounded head margin in mature males (vs.triangular).In addition, R. hasemani has five transverse bars on the dorsum (Isbrücker, 1973), that are more conspicuous than in R. osvaldoi, in which the bars are lighter and sometimes inconspicuous.Rineloricaria lanceolata has a very conspicuous color pattern consisting of six black transverse bars on the dorsum, and fins well pigmented with a pale spot at the base of each and most noticeable on the pectoral fin (Isbrücker & Nijssen, 1979).
Mature males of Rineloricaria osvaldoi have the same pattern of secondary sexual dimorphic features seen frequently in Rineloricaria species, a pattern that consists of development of odontodes on the pre-dorsal area and a thickened pectoral-fin unbranched ray.Nevertheless, the overall rounded shape of the head margin in dorsal view due, in part, to the great development of odontodes and associated tissue on the sides of the head, is unique.In most species, the males of Rineloricaria have enlarged lateral sides of the head, but never as seen in R. osvaldoi.A similar pattern was only observed in R. latirostris, a species distributed in the upper rio Paraná basin (Langeani & Araujo, 1994).However, R. osvaldoi can be distinguished from R. latirostris by having eight to 13 premaxillary teeth (vs.five to 10 in R. latirostris); the ventral surface of the body always completely covered by plates (vs.not always completely covered in R. latirostris); and the unbranched pectoral-fin ray in mature males thicker, shorter and more curved in R. latirostris than in R. osvaldoi.In addition, R. latirostris has six dark-brown transverse bars on the dorsum of the body (vs.five or sometimes inconspicuous in R. osvaldoi); a thicker and more elongate caudal filament than in R. osvaldoi; and, the greatest body width is in the region of the cleithrum in R. latirostris (Fig. 6), whereas it is at the canal plate region in R. osvaldoi.Taxonomic comments.Rineloricaria was described in 1862 by Bleeker to accommodate Loricaria lima (Kner, 1853), from an unknown type locality.In the same publication, Bleeker created Hemiloricaria to accommodate the new species H. caracasensis.In 1980, Isbrücker published a catalogue of the Loricariidae in which he treated Hemiloricaria as a synonym of Rineloricaria.Later, Isbrücker (2001) named two other genera, Fochiiichthys and Leliella, to accommodate three species previously included within Rineloricaria: Leliella heteroptera, Fonchiiichthys rupestris, and F. uracantus.Hemiloricaria was revalidated in that paper and 24 species were included into this genus while 18 species remained in Rineloricaria.In 2003, Ferraris (2003) included all species from Isbrücker (2001) as synonyms of Rineloricaria, at that time with 47 valid species.In 2007, Ferraris split again Rineloricaria into three genera, revalidating Hemiloricaria and Fochiiichthys, but not Leliella.Explanations for those taxonomic rearrangements were not given to support those decisions.Later, Rodriguez & Reis (2008) suggested an explanation to consider both Hemiloricaria and Rineloricaria valid, based mainly in some external morphological characters and the distribution of the included species.In summary, Hemiloricaria corresponds to the more widely distributed genus, found throughout South America, except in upper Paraná basin and Atlantic coastal drainages.In addition, Hemiloricaria has a narrow body, unbranched caudal-fin rays and sometimes rays of the dorsal and ventral-fins prolonged as a filament, and the abdominal area completely plated.It is usually darker than Rineloricaria, with dark blotches over the body, and the sexually dimorphic characters normally consist of "hypertrophied odontodes over the top of the head, from the interorbital region to the predorsal area", and on the cheeks.On the other hand, according to these authors, Rineloricaria is distributed only along rio Paraná basin and Atlantic costal drainages from Uruguay to Northeast of Brazil.The genus is characterized by a wide body, unbranched caudal-fin rays without a filament (except R. catamarcensis, R. kronei, R. pentamaculata, and R. strigilata, which usually have a short filament), the abdominal region with a variable plate cover, light-brown as background color, with five saddle bars over the body and hypertrophied odontodes in males restricted to lateral sides of the head and pectoral fin.This classification seems to contribute to the understanding of the taxonomy of the group, especially in eastern basins.However, it appears not to be helpful to Amazonian species that have greater morphological and color diversity.The species herein described has some characters of Hemiloricaria, such as the abdominal region fully plated, and the upper caudal-fin ray prolonged as a filament.In addi-tion, it resides in the geographic distribution area of Hemiloricaria.Nevertheless, R. osvaldoi would belong in the Rineloricaria group by the presence of following morphological characters: wide body, dimorphic features and color pattern.Based on the information mentioned above, we decided to place the new species in Rineloricaria sensu Isbrücker (1980) that treated all species as Rineloricaria, until the relationship into the group can be tested through systematic analysis in order to support more stable taxonomic decisions.