A New Species of Hisonotus (Siluriformes: Loricariidae: Hypoptopomatinae) from the Laguna dos Patos Basin, Southern Brazil

Abstract

Hisonotus armatus, a new hypoptopomatine species, is described from the Laguna dos Patos basin, Rio Grande do Sul State, southern Brazil. The new species is distinguished from other Hisonotus species by aspects of the morphology of the rostral plate, the arrangement of abdominal plates, and the caudal-fin color pattern. Hisonotus armatus, nova espécie de hipoptopomatíneo, é descrita do sistema da laguna dos Patos, Rio Grande do Sul, sul do Brasil. A nova espécie se diferencia das demais do gênero Hisonotus pela morfologia da placa rostral, pelo arranjo das placas abdominais, e pelo padrão de colorido da nadadeira caudal.

Full text

A New Species of Hisonotus (Siluriformes: Loricariidae:
Hypoptopomatinae) from the Laguna dos Patos Basin,
Southern Brazil
Tiago Pinto Carvalho
1
, Pablo Lehmann A.
1
, Edson H. Lopes Pereira
1
, and
Roberto E. Reis
1
Hisonotus armatus, a new hypoptopomatine species, is described from the Laguna dos Patos basin, Rio Grande do
Sul State, southern Brazil. The new species is distinguished from other Hisonotus species by aspects of the
morphology of the rostral plate, the arrangement of abdominal plates, and the caudal-fin color pattern.
Hisonotus armatus, nova espe´cie de hipoptopomatı´neo, e´ descrita do sistema da laguna dos Patos, Rio Grande do
Sul, sul do Brasil. A nova espe´cie se diferencia das demais do geˆnero Hisonotus pela morfologia da placa rostral,
pelo arranjo das placas abdominais, e pelo padra˜o de colorido da nadadeira caudal.
H
ISONOTUS belongs to the Hypoptopomatinae, a
monophyletic group consisting of 18 genera and
more than 100 species (Schaefer, 2003; Reis and
Carvalho, 2007) within the Loricariidae. As presently
defined, Hisonotus consists of 15 species (Schaefer, 2003;
Casciotta et al., 2006), occurring in the Atlantic coastal
drainages of southern and southeastern Brazil, and the
Parana´–Paraguay basin. Regan (1904) placed Hisonotus,
Parotocinclus, and Microlepidogaster under the synonymy of
Otocinclus. Hisonotus was thereafter retained in synonymy
until resurrected by Schaefer (1998). Currently, the genus is
diagnosed by its reduced or absent snout plates anterior to
the nostril, the rostrum with enlarged odontodes, and the
thickened plates forming the lateral rostral margin (Schae-
fer, 1998). Herein, we describe a new species of Hisonotus,
widely distributed in the Laguna dos Patos basin, in
southern Brazil.
MATERIALS AND METHODS
Measurements were made to the nearest 0.1 mm with digital
calipers under a stereomicroscope on the left side of
specimens following Boeseman (1968:fig. 5), with the
exception of thoracic length, which is the distance of the
origin of pectoral-fin spine to the origin of the pelvic-fin
spine. Additional measurements are: suborbital depth,
defined as the distance between the ventral margin of the
bony orbit and ventrolateral limit of the head, and
mandibular ramus, the longer axis of the dentary bone.
Morphometric data were expressed as percents of standard
length (SL), except subunits of the head which are expressed
as percents of head length. Plate counts and nomenclature
follow the schemes of serial homology proposed by Schaefer
(1997). Vertebral counts included all vertebrae (including
the first five vertebrae incorporated into the Weberian
apparatus), with the compound caudal centrum (PU1 +
U1) counted as one element. Cleared-and-stained specimens
(CS) were prepared according to the method of Taylor and
Van Dyke (1985). Scanning electron micrographs were taken
from dissected alcohol preserved specimens. Species of
Hisonotus referred to by numbers are those first mentioned
in Reis and Carvalho (2007). Institutional abbreviations are
as listed at http://asih.org/codons.pdf, with the addition of
ZVC-P for Facultad de Ciencias, Universidad de la Repu´ blica,
Montevideo, Uruguay.
Hisonotus armatus, new species
Figure 1, Table 1
Hisonotus sp. 5, Reis and Carvalho, 2007:84 [Catalog of fresh
water fishes of Brazil].
Holotype.—MCP 41323, 44.4 mm SL, female, Brazil, Rio Grande
do Sul,PedroOso´rio, Arroio Arambare´, about 5 km south of Vila
Bası´lio, on road to Pedro Oso´rio, 31u549340S, 53u019390W, 22
April 2005, R. E. Reis, P. Lehmann, and E. H. L. Pereira.
Paratypes.—All from Brazil, Rio Grande do Sul, Sa˜o Gonc¸alo
drainage: MCP 37682, 13 + 4 CS, 33.9–44.2 mm SL; ANSP
187116, 5, 33.7–42.5 mm SL; MZUSP 93884, 5, 37.7–
45.1 mm SL, all collected with the holotype. MCP 40787,
20, 32.5–45.6 mm SL, Arroio Mata Olho, on road between
Pedro Oso´ rio and Bası´lio, 31u549560S, 53u009160W, 15 Nov.
2003, R. E. Reis, P. Lehmann, M. C. Abreu, and C. S. Alho.
MCP 34776, 31, 27.6–43.9 mm SL, Arroio Arambare´, on road
from Pedro Oso´ rio to Herval, 31u589370 S, 53u069150W, 15
Nov. 2003, R. E. Reis, P. Lehmann, M. C. Abreu, and C. S.
Alho. MCP 25138, 9 + 3 CS, 27.9–45.9 mm SL, Arroio Santa
Fe´, on road between Pinheiro Machado and Piratini,
31u309120S, 53u139560W, 21 Nov. 1999, C. A. Lucena, Z. M.
Lucena, E. H. L. Pereira, and V. A. Bertaco.
Non-type specimens.—All from Brazil, Rio Grande do Sul, Sa˜o
Gonc¸alo drainage: MCN 12617, 3, 37.1–37.3 mm SL,
Pelotas, Arroio Pelotas, on road BR116, 31u379550S,
52u199390W; MCP 25140, 4, 37.6–46.7 mm SL, Pedro Oso´rio,
Arroio Mata Olho, on road between Pedro Oso´ rio and
Bası´lio, 31u549560S, 53u009170W; MCP 25147, 2, 30.1–
36.3 mm SL, Piratini, Arroio Piratinizinho, on secondary
1
Laborato´rio de Ictiologia, Pontifı´cia Universidade Cato´lica do Rio Grande do Sul, Av. Ipiranga 6681, Caixa Postal 1429, 90619-900 Porto
Alegre, RS, Brazil; E-mail: (TPC) tiagobio2002@yahoo.com.br. Send reprint requests to TPC.
Submitted: 6 June 2007. Accepted: 5 November 2007. Associate Editor: C. J. Ferraris.
F 2008 by the American Society of Ichthyologists and Herpetologists
DOI: 10.1643/CI-07-130
Copeia 2008, No. 3, 510–516

road off BR293, 31u439020S, 52u599340W; MCP 25154, 14 + 1
CS, 28.0–45.4 mm SL, Piratini, Arroio Piratinizinho, on
secondary road off BR293, 31u439020S, 52u599340W; MCP
25158, 8, 34.4–45.2 mm SL, Piratini, Arroio Piratini Menor,
about 500 m from road between Piratini and Pelotas,
31u309030S, 53u059350W; MCP 25159, 24, 28.9–42.1 mm
SL, Piratini, Rio Piratini, on road BR293, 31u439110S,
52u549000W; MCP 34777, 1, 28.5 mm SL, Herval, Arroio
Arambare´, on road from Pedro Oso´rio to Herval, 31u589370S,
53u069150W; MCP 34780, 4, 36.6–40.5 mm SL, Pedras Altas,
headwaters of Arroio Alegria between Pedras Altas and
Pinheiro Machado, 31u409410S, 53u329120W; MCP 37685,
13, 27.7–44.2 mm SL, Pedro Oso´ rio, stream tributary to
Arroio Arambare´ near Carvalho de Freitas, about 35 km from
Pedro Oso´ rio, on railroad bridge, 31u519510S, 52u499240W.
Rio Jaguara˜o drainage: MCP 11307, 2, 16.9–39.2 mm SL,
Jaguara˜o, mouth of Rio Telho on Rio Jaguara˜o, approx.
32u319S, 53u279W; MCP 27184, 5, 14.2–36.3 mm SL, Can-
diota, Arroio Quebra Jugo no passo dos Pinheiros,
31u329590S, 53u469170W; UFRGS 4224, 3, 32.3–38.2 mm SL,
Candiota, downstream of Arroio Candiota dam, approx.
31u329S, 53u409W. Rio Camaqua˜ drainage: MCN 11179, 1,
34.2 mm SL, Cac¸apava do Sul, Arroio Seival at dam,
30u439040S, 53u439420W; MCP 11337, 5, 25.9–38.7 mm SL,
Encruzilhada do Sul, Arroio dos Ladro˜es, 30u419S, 52u209W;
MCP 25869, 1, 43.3 mm SL, Bage´, Arroio Camaqua˜ Chico,
on road between Bage´ and Lavras do Sul, 30u549270S,
53u499130W; MCP 40647, 2, 22.7–27.3 mm SL, Bage´, Arroio
do Tigre, on road between Bage´andLavrasdoSul,
31u049470S, 53u549030W; MCP 40748, 1, 33.0 mm SL, Bage´,
Arroio das Traı´ras, on road BR153, 31u059290S, 53u439330W;
MCP 40751, 1, 41.5 mm SL, Lavras do Sul, Arroio Manti-
queira, on road between Bage´ and Lavras do Sul, 30u549220S,
53u589020W; MCP 40764, 1, 38.6 mm SL, Lavras do Sul,
Arroio da Cria, on road between Bage´ and Lavras do Sul,
30u579190S, 53u579220W; MCP 41306, 1, 36.6 mm SL,
Fig. 1. Hisonotus armatus, holotype, MCP 41323, 44.4 mm SL, female, Brazil, Rio Grande do Sul, Pedro Oso´rio, Arroio Arambare´, about 5 km south
of Vila Bası´lio, on road to Pedro Oso´rio.
Carvalho et al.—New species of Hisonotus 511

Camaqua˜, Arroio Duro, on road from Vila Aurora to Dom
Feliciano, 30u459 340S, 51u519570W; UFRGS 8222, 5, 32.2–
39.8 mm SL, Amaral Ferrador, creek on Fazenda Ferraria;
UFRGS 8240, 1, 33.3 mm SL, Canguc¸u, Rio Camaqua˜on
bridge of road RS471; UFRGS 8975, 3, 14.7–35.3 mm SL,
Encruzilhada do Sul, Arroio Abranjo, 30u539580S,
52u329180W. Lago Guaı´ba drainage: MCN 16246, 3, 31.9–
43.9 mm SL, Porto Alegre, Parque Estadual Delta do Jacuı´,
Saco da Po´lvora, approx. 30u019S, 51u149W; MAPA 1735, 14,
21.3–38.9 mm SL, Barra do Ribeiro, ac¸ude dos Garcia, on
road BR116, 30u239140S, 51u269100W; MCP 10450, 2, 41.7–
49.9 mm SL, Porto Alegre, Lago Guaı´ba at Ilha Maua´,
approx. 30u010S, 51u140W; MCP 16010, 10, 14.8–42.3 mm
SL, Viama˜o, Lago Guaı´ba at Praia de Itapua˜, near mouth of
Riacho Itapua˜, 30u15900S, 51u029200W, UFRGS 6718, 1,
33.9 mm SL, Viama˜o, Lago Guaı´ba at Praia das Pombas,
30u209440S, 51u019320W; UFRGS 8460, 1, 39.5 mm SL,
Eldorado do Sul, Estac¸a˜o Agronoˆmica da UFRGS. Rio Jacuı´
drainage: MAPA 1737, 10, 21.9–38.0 mm SL, Gravataı´,
Arroio Passo dos Ferreiros; MAPA 1749, 1, 38.8 mm SL,
Nova Petro´ polis, Arroio Macaquinhos, Pinhal Alto, approx.
29u259S, 51u029W; MAPA 2391, 3, 35.9–44.1 mm SL, Santo
Antonio da Patrulha, Rio dos Sinos, bridge at Nossa Senhora
de Mont Serrat, approx. 29u459S, 50u249W; MCN 6660, 2,
24.0–37.5 mm SL, Treˆs Coroas, Arroio Quilombo, approx.
29u279S, 50u499W; MCN 16124, 4, 33.2–40.1 mm SL, Pinhal
Grande, Rio Ferreira, 29u169330S, 53u149420W; MCP 9294, 2,
23.4–34.0 mm SL, Cachoeira do Sul, Arroio Paraı´so, Rinca˜o
da Porta, approx. 29u419S, 53u090W; MCP 14640, 1, 23.7 mm
SL, Caraa´, Rio Caraa´ near Rio dos Sinos, 29u479400S,
50u269010W; MCP 17166, 2, 27.1–27.9 mm SL, Porto Alegre,
Rio Jacuı´ at Saco da Alemoa, approx. 30u009S, 51u149W; MCP
17500, 1, 45.3 mm SL, Venaˆncio Aires, Arroio at Linha
Brasil, approx. 29u339S, 52u179W; MCP 18632, 13, 26.1–
38.0 mm SL, Candela´ria, Rio Pardo, on road from Santa Cruz
do Sul to Candela´ria, 29u409360S, 52u469170W; MCP 25262,
5, 29.1–38.1 mm SL, Agudo, Lageado da Gringa between
Linha da Ressaca and mouth of Rio Jacuizinho, 29u239080S,
53u129530W; MCP 25458, 7 + 3 CS, 16.2–42.3 mm SL,
Agudo, Arroio Corupa´, on road between Agudo and Dona
Francisca Dam, 29u339540S, 53u179090W; MCP 25721, 5,
27.3–41.4 mm SL, Ibarama, Arroio da Gringa, about 12 km
north from UHE Dona Francisca, 29u239160S, 53u139230W;
MCP 25722, 3, 25.3–40.2 mm SL, Ibarama, lageado do
Gringo about 2 km from UHE Dona Francisca, 29u269490S,
53u159360W; MCP 26052, 1, 35.0 mm SL, Lindolfo Collor,
Arroio Feitoria, 29u349540S, 51u149030W; MCP 26528, 1,
28.7 mm SL, Santa Cruz do Sul, Rio Pardinho, downstream
Corsan dam, approx. 29u409S, 52u289W; MCP 26542, 3,
29.6–35.6 mm SL, Agudo, Rio Jacuı´ downstream from Dona
Francisca dam, approx. 29u319S, 53u169W; MCP 33557, 1,
34.7 mm SL, Santa Ba´rbara, Rio das Antas, near mouth of Rio
Carreiro, 29u059290S, 51u429420W; MCP 38901, 6, 22.2–
40.8 mm SL, Bento Gonc¸alves, Rio das Antas, 29u019590S,
Table 1. Morphometrics and Meristics of Hisonotus armatus. Values are given as percents of standard length or head length. SD 5 Standard deviation, n
5 number of specimens, H 5 holotype.
Types
H n Low High Mean SD
Standard length (mm) 40 29.6 46.0 39.1
Percent of standard length
Head length 34.4 40 31.7 38.2 34.2 1.2
Predorsal length 47.4 40 44.7 51.3 46.8 1.3
Dorsal-fin spine length 26.8 40 22.5 27.7 25.1 1.4
Anal-fin spine length 16.9 40 13.7 17.9 16.0 1.0
Pectoral-fin spine length 27.2 40 21.5 28.1 26.0 1.4
Ventral-fin spine length 17.0 40 15.1 21.4 18.0 1.6
Cleitral width 25.0 40 21.9 25.4 23.7 0.9
Thoracic length 16.9 40 15.3 18.5 16.7 0.8
Abdominal length 21.9 40 18.8 22.4 20.8 0.9
Body depth at dorsal-fin origin 19.8 40 16.5 20.9 18.6 1.0
Post anal fin peduncle length 31.9 40 30.3 35.0 33.0 1.2
Depth of caudal peduncle 12.0 40 9.9 12.7 11.0 0.6
Percent of head length
Snout length 50.2 40 47.9 53.3 50.3 1.2
Orbital diameter 16.7 40 14.8 18.4 16.6 0.8
Interorbital width 40.5 40 37.8 46.5 42.3 1.9
Head depth 49.9 40 45.2 53.8 49.3 2.2
Suborbital depth 18.6 40 16.4 21.6 19.2 1.0
Mandibular ramus 8.6 40 7.0 10.5 8.5 0.8
Meristics
Left premaxillary teeth 15 39 14 20 17.6 1.6
Right premaxillary teeth 17 39 15 22 17.7 1.6
Left dentary teeth 16 40 12 19 15.0 1.4
Right dentary teeth 15 40 12 19 15.1 1.6
Left median series lateral scutes 24 40 24 25 24.4 0.5
Right median series lateral scutes 24 40 23 25 24.3 0.6
512 Copeia 2008, No. 3

51u279130W; MCP 40512, 6, 22.1–40.9 mm SL, Santa Maria
do Herval, Rio Cadeia on Farroupilha bridge, 29u299430S,
51u029500W; UFRGS 2350, 1, 35.2 mm SL, Arroio dos Ratos,
Arroio dos Ratos at bathing spot, approx. 30u039S, 51u379W;
UFRGS 8762, 3, 29.8–36.2 mm SL, Sa˜o Sepe, creek on
Fazenda Sa˜o Sepe, 30u149390S, 53u419200W; UFRGS 8768, 3,
31.6–35.4 mm SL, Rio Pardo, creek at Fazenda Velha; UFRGS
8805, 5, 38.5–43.1 mm SL, Lageado, mouth of Arroio
Pinheirinho on Rio Forqueta, 29u199210S, 52u149030W;
Other drainages in Laguna dos Patos basin: MAPA 1747, 5,
25.8–39.9 mm SL, Camaqua˜, Arroio Velhaco, on road BR116
between Tapes and Camaqua˜, approx. 30u459S, 51u389W.
Diagnosis.—Hisonotus armatus differs from all congeners
except Hisonotus notatus and H. leucofrenatus in having the
anterior margin of the snout completely covered by
odontodes (Fig. 2A, C), vs. anterior margin of the snout
with a narrow or wide odontode-free band (Fig. 2B, D); and
in having large plates in the abdominal median series,
usually comprising one series of plates between the lateral
abdominal plates (Fig. 3), vs. abdominal median series of
plates small, with several plate series irregularly arranged
between the lateral abdominal ones. The new species differs
from H. notatus and H. leucofrenatus in the presence on the
caudal fin of a series of light hyaline spots, forming a vertical
light bar, vs. a rounded hyaline blotch or no hyaline area in
the midventral portion of caudal fin.
Description.—Morphometrics and meristics given in Table 1.
Adult size moderate to large for members of this genus
(maximum 49.9 mm SL). Body robust, without conspicuous
keels, caudal peduncle round in cross section. Dorsal profile
slightly convex from snout tip to supraoccipital bone,
slightly concave posterior to rostral plate, almost straight
from supraoccipital to anterior margin of nuchal plate,
ascending from that point to dorsal-fin origin; straight and
descending at dorsal-fin base. Profile almost straight from
last dorsal-fin ray to caudal-fin origin. Greatest body depth
at dorsal-fin origin. Least body depth at posterior end of
caudal peduncle. Head and snout broad, snout rounded
anteriorly in dorsal view, body progressively narrowing
posterior of cleithrum. Snout region anteriorly of nares
concave, interorbital region slightly convex to almost
straight. Upper margin of orbit not elevated. Eye dorsolat-
erally positioned. Iris diverticulum present, large, its length
more than half of pupil diameter.
Pectoral fin with six branched rays, posterior fin margin
slightly rounded; when depressed tip extending beyond
middle of pelvic fin. Posterior margin of pectoral-fin spine
smooth. Pectoral-fin axillary slit present, located below
posterior bony margin of cleithral process. Pelvic fin
moderately short, with five branched rays. Tip of depressed
fin not reaching anal-fin origin in females, but extending
beyond that point in males. Adult males with fleshy flap
along dorsal margin of first thickened pelvic-fin ray. Flap
Fig. 2. Scanning electron microscope images of anterior tip of snout. Hisonotus armatus, MCP 37682, 40.1 mm SL (A, C), showing the snout
completely covered by odontodes; and Hisonotus laevior, MAPA 1755, 40.9 mm SL (B, D), showing a stripe devoid of odontodes.
Carvalho et al.—New species of Hisonotus 513

widest basally and progressively narrowing distally. Dorsal
fin with seven branched rays. Dorsal-fin origin located at
vertical through pelvic-fin origin. Dorsal-fin spinelet
present. Anal fin with five branched rays. First anal-fin
pterygiophore exposed anterior to anal fin. Adipose fin
absent.
Body almost entirely covered by plates except for region
overlying opening of swim bladder capsule, area between
pectoral girdle and lower lip, region around anus, and area
around bases of paired fins. Rostral plate with posterior
notch articulating with mesethmoid. Snout plates anterior
to nostril reduced. Three rows of predorsal plates, including
nuchal plate. Lateral median-plate series formed by 23–25
plates. Lateral line incomplete, with small gap without pores
along middle length of body. Abdominal plates arranged in
three rows anteriorly and irregularly arranged between
pelvic-fin insertions. Lateral abdominal plates slightly larger
and forming regular series. Median abdominal series usually
formed by one plate row, posterior median abdominal plates
sometimes smaller and greater in number (Fig. 3). Coracoid
and cleithrum exposed and covered by odontodes, except
for median region of cleithrum and area surrounding
arrector fossa.
Head without crests in adults. Odontodes on posterior
supraoccipital tip uniform in size, and not enlarged in
adults. Somewhat prominent crest preceded by anterior pair
of crests in small juveniles. Compound pterotic with small-
to-median size perforations along its anteroventral margin.
Head, fin spines, and body plates covered with odontodes,
largest odontodes found on anterior surface of all fin spines.
Odontodes on head and trunk of uniform size and
distribution, except for enlarged odontodes on ventral and
dorsal margins of rostral plates. Plates forming lateral rostral
margin thickened. Lips roundish and papillose.
Premaxillary and dentary teeth slender proximally and
flattened distally; teeth bifid, with medial cusp large and
rounded, lateral cusp minute and pointed. Accessory patch
of teeth absent on dentary and premaxilla.
Posterior margin of caudal-fin skeleton usually with slight
median notch. Notch in one specimen extends anteriorly,
almost reaching half centrum of last vertebrae. Total
vertebrae 29 (5 CS).
Color in alcohol.—Ground color of dorsolateral surface of
head and body light to dark brown. Midlateral region of
body dark gray and ventral region largely unpigmented.
General color pattern of dorsal surface of body composed of
dark blotches contrasting with somewhat reticular light
areas. Ventrolateral portion of head more lightly pigmented
with scattered dark blotches. Ventral portion of head and
body pale yellowish with scattered chromatophores. Chro-
matophores more prominent on posterior region of lips and
region surrounding base of pectoral and anal fins. All fins
mostly hyaline, with chromatophores forming transverse
dark bands; bands most conspicuous on unbranched rays.
Dorsal fin with about seven narrow dark bands. Caudal fin
darkly pigmented ventrally, unbranched rays with striped
pattern. Two dorsal-most branched rays almost hyaline,
except for transversal dark bands, one hyaline transverse
band formed by round light spots crossing caudal fin. Some
specimens with anterior portion of caudal fin lighter and
forming second transverse light band with caudal hyaline
areas larger. Hyaline vertical band on caudal fin inconspic-
uous or even absent in juveniles.
Sexual dimorphism.—The sexual dimorphism is characterized
mainly by the urogenital papilla, positioned just after the
anal opening in males and absent in females. Adult males
also possess a fleshy flap along the dorsal margin of first
thickened pelvic-fin ray that is absent in females. In juvenile
males the flap is smaller or absent. Males have a longer
pelvic-fin spine that extends up to the anal-fin origin, with
the spine never reaching that point in females.
Distribution and habitat.—Hisonotus armatus is widely dis-
tributed in the Laguna dos Patos system from the southern
most Rio Jaguara˜o drainage, to the Rio Jacuı´ and Rio Taquari
drainages (Fig. 4). The new species is unknown from the
headwaters of the Rio Jacuı´ and Rio Taquari drainages. This
species inhabits slow to median flowing watercourses, with
clear to brown waters over sandy bottom and is found in
marginal or submerged aquatic vegetation. Hisonotus arma-
tus is sympatric throughout its distribution with H. laevior
(see Discussion for diagnostic features). It was also collected
together with H. nigricauda in some localities of the Lago
Guaı´ba drainage, with Hisonotus sp. 4 in the Rio Jacuı´ and
Taquari drainages, and with Hisonotus sp. 6 in the upper
reaches of the Rio Camaqua˜ drainage.
Etymology.—The specific epithet, armatus, is from Latin,
arma, weapon + atus, meaning armed, alluding to the
complete covering of odontodes on the anterior tip of the
snout.
DISCUSSION
The most distinctive feature of Hisonotus armatus is the
snout completely covered with odontodes, without an
anterior odontode-free band, which easily distinguishes this
new species from all other Hisonotus species in the Laguna
dos Patos basin (a narrow naked band in H. nigricauda,
sometimes absent in smaller specimens). The new species
shares this and a few other features with the congeners
Hisonotus notatus (type-species) and Hisonotus leucofrenatus,
both species distributed in the southeastern Brazilian coastal
Fig. 3. Arrangement of abdominal plates in Hisonotus armatus, female,
MCP 25138, 42.5 mm SL. Anterior toward top. Scale bar represents
2 mm.
514 Copeia 2008, No. 3

drainages. These three species possess the anterior margin of
the snout fully covered with odontodes, a similar pattern of
abdominal plates, 23–25 median lateral plates, three
predorsal plate rows, and absence of a raised tuft of
odontodes on the supraoccipital.
Four species of Hisonotus were previously described from
the Laguna dos Patos basin: Hisonotus nigricauda, H. laevior,
H. leptochilus, and H. taimensis. The presence of H. armatus,
plus five additional unnamed species listed in Reis and
Carvalho (2007), is indicative of a successful group in the
region as well as species richness and endemism in the
Laguna dos Patos basin. Other loricariid genera with a large
number of species in the basin are Eurycheilichthys, with
eight species, seven of which are undescribed, and Rinelor-
icaria, with six species.
MATERIAL EXAMINED
Hisonotus candombe: ZVC-P 5595, holotype, Uruguay, De-
partamento Salto, Rio Uruguay basin, arroyo Palomas.
Hisonotus charrua: ZVC-P 5639, holotype, Uruguay, Departa-
mento Tacuarembo´ , Cana˜da de los Pena. MCP 40256, 4 + 1
CS, same type-locality.
Hisonotus francirochai: MCP 41341, 4, Brazil, Sa˜o Paulo,
Araras, stream tributary of Rio Mogi–Guac¸u (Rio Grande
drainage).
Hisonotus insperatus: MZUSP 78957, holotype, Brazil, Sa˜o
Paulo, Botucatu, Rio Capivara (Rio Tieteˆ drainage).
Hisonotus laevior: ANSP 21563, holotype, Brazil, Rio Grande
do Sul, Rio Jacuı´. MAPA 1755, 24 + 3 CS, Brazil, Rio Grande
do Sul, Sa˜o Sebastia˜o do Caı´, small creek in Rio Branco.
Hisonotus leptochilus: ANSP 21564, holotype, Brazil, Rio
Grande do Sul, Rio Jacuı´.
Hisonotus leucofrenatus: MZUSP 36565, 20, Brazil, Sa˜o Paulo,
Eldorado, small creek on the road Eldorado to Sete Barras
(Rio Ribeira de Iguape drainage).
Hisonotus maculipinnis: BMNH 1909.4.2.19–22, syntypes of
Otocinclus maculipinnis, La Plata.
Hisonotus nigricauda: BMNH 1891.3.16.53–62, syntypes of
Otocinclus nigricauda, Brazil, Rio Grande do Sul, Rio Cama-
qua˜. MCP 17416, 20 + 3 CS, Brazil, Rio Grande do Sul, marsh
at the side of Rio Camaqua˜ on Pacheca.
Hisonotus notatus: BMNH 1904.1.28.13–16, syntypes, Brazil,
Rio de Janeiro, Rio Grande (Arroio Fundo) on Fazenda Santa
Cruz. MCP 18098, 204 + 4 CS, Brazil, Espı´rito Santo, Rio Sa˜o
Jose´ dos Torres, on road BR 101.
Hisonotus paulinus: BMNH 1907.7.6.9, holotype of Otocinclus
paulinus, Brazil, Sa˜o Paulo, Rio Piracicaba.
Hisonotus ringueleti: ILPLA 886, holotype, Uruguay, Rivera,
creek at km 18 of route joining Santana do Livramento to
Rivera (Rio Uruguay basin).
Hisonotus taimensis: MCN 4835–4844, paratypes of Micro-
lepidogaster taimensis, Brazil, Rio Grande do Sul, Santa Vito´ ria
do Palmar, new channel of Arroio Taim, Estac¸a˜o Ecolo´ gica
do Taim.
Hisonotus sp. 1: MCP 40942, 24, Brazil, Rio Grande Sul, Nova
Prata, rio da Prata at Passo do Despraiado.
Hisonotus sp. 2: MCP 40945, 8 + 2 CS, Brazil, Rio Grande
Sul, Serafina Correˆa, rio Carreiro downstream Carreiro
bathing spot.
Hisonotus sp. 3: MCP 22701, 27 + 3 CS, Brazil, Rio Grande
Sul, Cruz Alta, rio Passo Novo, on road from Cruz Alta to
Ibiruba´.
Hisonotus sp. 4: UFRGS 8812, 14, Brazil, Rio Grande do Sul,
Lageado, mouth of Arroio Pinheirinho on Rio Forqueta.
Hisonotus sp. 6: MCP 40748, 2, Brazil, Rio Grande do Sul,
Bage´, Arroio da Traı´ras, on road BR 153.
ACKNOWLEDGMENTS
We thank the following people for their help and support
while visiting their institutions and for the loan of
specimens: M. Sabaj and J. Lundberg (ANSP), J. Maclaine
and R. Britz (BMNH), A. Miquelarena (ILPLA), F. Meyer
(MAPA), M. Azevedo (MCN), M. Azpelicueta (MLP), O.
Oyakawa (MZUSP), J. Ferrer and L. Malabarba (UFRGS). We
thank J. Wingert and M. Lucena for support on the MCP
collection. Thanks to the Centro de Microscopia e Micro-
ana´lises–CEMM, PUCRS for the SEM preparations. This
paper was financially supported by the ‘‘All Catfishes Species
Inventory’’ Project (NSF DEB 0315963) that provided
funding to visit museum collections and field work. Thanks
are also due to the Conselho Nacional de Desenvolvimento
Cientı´fico e Tecnolo´ gico–CNPq, for a fellowship to TPC
(process #132879/2006-9). EHLP is partially financed by a
doctoral fellowship from CAPES. RER is partially supported
by CNPq (process #301748/2004-7).
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