New and Noteworthy Venezuelan Glanapterygine Catfishes (Siluriformes, Trichomycteridae), with Discussion of Their Biogeography and Psammophily

2005·0.93 MB·English

by  Scott A. Schaefer

PUBLISHED BY THE AMERICAN MUSEUM OF NATURAL HISTORY
CENTRAL PARK WEST AT 79TH STREET, NEW YORK, NY 10024
Number 3496, 27 pp., 10 figures, 2 tables November 29, 2005
New and Noteworthy Venezuelan Glanapterygine
Catfishes (Siluriformes, Trichomycteridae),
with Discussion of Their Biogeography
and Psammophily
SCOTT A. SCHAEFER,1 FRANCISCO PROVENZANO,2 MARIO DE PINNA,3
AND JONATHAN N. BASKIN4
CONTENTS
Abstract ....................................................................... 2
Introduction .................................................................... 2
Methods ....................................................................... 4
Institutional Abbreviations ..................................................... 5
Comparative Material Examined ................................................ 5
Results ........................................................................ 5
Key to the Species of Pygidianops Myers, 1944 .................................. 5
Pygidianops cuao, new species ................................................. 5
Pygidianops magoi, new species ............................................... 10
Key to the Species of Typhlobelus Myers, 1944 ................................. 14
Typhlobelus guacamaya, new species .......................................... 14
1DivisionofVertebrateZoology (Ichthyology),AmericanMuseumofNaturalHistory([email protected]).
2Instituto de Zoolog´ıa Tropical, Facultad de Ciencias and Curator of Fish Collection, Museo de Biolog´ıa de la
Universidad Central de Venezuela, Apartado de Correos 47058, Caracas 1041-A, Venezuela ([email protected].
ucv.ve).
3Division of Vertebrate Zoology (Ichthyology), American Museum of Natural History; Associate Professor and
Scientific Director, Museu de Zoologia da Universidade de Sa˜o Paulo, Av. Nazare´ 481, Sa˜o Paulo-SP 04263-000,
Brasil([email protected]).
4Biological Sciences Department, California State Polytechnic University Pomona, Pomona, California 91768;
ResearchAssociate,SectionofFishes,NaturalHistoryMuseumofLosAngelesCounty([email protected]).
CopyrightqAmericanMuseumofNaturalHistory2005 ISSN0003-0082
2 AMERICAN MUSEUM NOVITATES NO. 3496
Typhlobelus lundbergi, new species ............................................ 17
Discussion .................................................................... 19
Generic Diagnoses ........................................................... 19
Interspecific Comparisons ..................................................... 20
Biogeography and Psammophily ............................................... 22
Acknowledgments ............................................................. 25
References .................................................................... 25
ABSTRACT
Four new species of the trichomycterid subfamily Glanapteryginae are described from the
R´ıo Orinoco basin of Venezuela. Two new species each in Pygidianops Myers 1944 and
Typhlobelus Myers 1944 represent the first documented occurrence of these genera in Vene-
zuela, and for Pygidianops the first occurrence outside the R´ıo Negro basin. The new species
werecapturedfromsand-bottomhabitatsintwodisparatelocationsintheOrinocoRiverbasin
and display a remarkable suite of reductive features, such as loss of eyes, fins, and pigment,
and reductions or absence of laterosensory canals and odontodes. Pygidianops cuao, n.sp.
from the R´ıo Cuao, a clear-water tributary of the upper Orinoco River, is diagnosed from its
congeners by the presence of diminutive eyes and a triangular skin flap at the corner of the
mouth.Pygidianopsmagoi,n.sp.,knownfromnearthedeltaoftheOrinocoRiver,isdiagnosed
from its congeners by the absence of pectoral and anal fins, presence of four laterosensory
pores, and nine or ten caudal-fin rays. Typhlobelus guacamaya, n.sp. from the R´ıo Cuao is
diagnosedrelativetoitscongenersbythepresenceofthreebranchiostegalrays,posteriornaris
absent, lack of pleural ribs, and is further distinguished from both T. ternetzi and T. macro-
mycterus by the absence of eyes and from T. lundbergiby the presenceofthreelaterosensory
canalpores.Typhlobeluslundbergi,n.sp.fromthelowerOrinocoisdiagnosedbythepresence
of four laterosensory canal pores and further distinguished from T. ternetzi andT.macromyc-
terus by the absence of eyes. We review the characters useful in diagnoses of Pygidianops
and Typhlobelus among trichomycterid catfishes and discuss morphological patterns in the
diversification of the Glanapteryginae. Species of Pygidianops and Typhlobelus are known
only from the rivers draining the Guyana and Brazilian shields, yet within these areas they
occupy all major water types. Such broad ecological range suggests that the geographic dis-
tribution of species of these two genera are not limited by water type. That observation, plus
their common occurrence in the ubiquitous shallow sand-bottom habitats of the larger rivers
of the shield regions of northern South America, indicate that species of Pygidianops and
TyphlobelusmaybeexpectedtooccurthroughouttheentireAmazonandOrinocobasins.The
evolution of habitat preference in glanapterygines seems to follow a trend toward increased
specialization for interstitial environments. The degree of psammophilic adaptation in species
of Pygidianops and Typhlobelus is remarkable, without parallel in siluriforms and perhaps in
any other freshwater fishes. We describe the physical characteristics of the sand and review
the suite of morphological specializations for life in interstitial sand that are shared by these
species, such as loss or reduction of certain structures and presence in these species of paired
metapleural keels along the ventral edges of the abdomen formed by a long ridge of stiffened
integument, underlain by well-differentiated medial infracarinalis muscles, that are superfi-
cially similar to the metapleural folds of sand-dwelling cephalochordates and other interstitial
organisms.
INTRODUCTION phic adaptations known within any single
The siluriform family Trichomycteridae is catfish family assemblage. Apart from the
widely distributed throughout the Neotropics typical free-living, generalized predators of
and includes perhaps the widest rangeoftro- small invertebrates, the rather atypical tro-
2005 SCHAEFER ET AL.: VENEZUELAN CATFISHES 3
phic modes represented amongtrichomycter- of glanapterygines is supported by five syn-
id species include the parasitic hematopha- apomorphiesinvolvingreductionsinthefins,
gous ‘‘candirus’’ of the subfamily Vandeli- caudal skeleton, and laterosensory system
inae and lepidophagous and muciphagous (de Pinna, 1989). Glanapteryx was proposed
species of Stegophilinae (Machado and Sa- by de Pinna (1989) as the sister group to a
zima, 1983), necrophagous species of the clade composed of Pygidianops and Typhlo-
subfamily Pareiodontinae (Goulding, 1979, belus, with Listrura the sister group to those
1980),andtherecentlydiscoveredandpartly three.
algivorous species of the subfamily Copio- The genera Pygidianops and Typhlobelus
dontinae (de Pinna, 1992). The rangeofboth are the most highly modified glanapterygi-
ecological habitats and elevations occupied nes, and species of both genera share ex-
by members of the family rivals the rangeof treme reduction of pigmentation, loss of dor-
trophic specializations represented, and in- sal fin, loss or extreme reduction of pectoral
cludes species restricted to elevations above fins, reduced laterosensory canal, and com-
4000 m in the Andes (Arratia and Menu- plete loss of eyes in some species. Bothgen-
Marque, 1984; Ferna´ndez and Vari, 2000; era are markedly miniaturized, yet retain a
Ferna´ndez and Schaefer, 2003), Andean relatively well-ossified skeleton comparable
lakes, off-shore coastal islands (Ferna´ndez in both bone differentiation and degree of
and Schaefer, 2005), lowland species known calcificationtothatobservedinlargertricho-
only from large rapids (Myers, 1944), leaf- mycterids. Along with Glanapteryxanguilla,
litter puddles, and the bottom of torrential the type species of both genera were collect-
rivers (Arratia, 1998). ed at the same time and place, namely, Feb-
Representatives of the poorly known sub- ruary 1, 1925, at the rocky pools below the
family Glanapteryginae, a group currently Sa˜o Gabriel Rapids on the upper Rio Negro,
comprising four genera and nine species, in- Amazonas State, Brazil. Their smallsizeand
clude someof themostbizarremorphologies occurrence in atypical habitats are probably
and extreme reduction of features thus far most responsible for the fact that glanapter-
known among members of the Siluriformes. ygines are rarely collected and currentlyrep-
The subfamily was described by Myers resented in collections by few specimens.
(1944) to include two new genera and spe- However,recentnewcollectionsindicatethat
cies, Pygidianops eigenmanni and Typhlo- glanapterygines are more widely distributed
belus ternetzi, plus the previously described than previously thought. For example, Nico
Glanapteryx anguilla Myers, 1927, all cap- and de Pinna (1996), following upon the re-
tured from a single locality in the upper Rio port of de Pinna (1989), reported on addi-
NegroofBrazil.Nonewglanapterygineshad tional populations of Glanapteryx in the R´ıo
been discovered for more than four decades, Orinoco basin of Venezuela. Recent collec-
until de Pinna (1988)describedanewgenus, tions made in Guyana by J. Armbruster, M.
Listrura, with two species from southeastern Sabaj, and colleagues have revealed addi-
Brazil, representing the first record of glan- tional populations of Typhlobelus and Pygi-
apterygine occurrence outside the Amazon dianops, perhaps representing additional un-
River basin. Costa and Bockmann (1994) described species.
based their description of Typhlobelus ma- For similar reasons, a more widespread
cromycterus on a single specimen from the distribution for both Pygidianops and Ty-
Rio Tocantins of Brazil. A new species of phlobelus has been suspected for some time,
Glanapteryx, G. niobium, was described by yet unconfirmed. We report herein the exis-
dePinna(1998a)fromtheRioNegroofBra- tence of four new glanapterygine species
zil. Landim and Costa (2002) described Lis- from the R´ıo Orinoco basin of Venezuela,
trura tetraradiata, a glanapterygine with nu- twonewspecieseachinPygidianopsandTy-
merous plesiomorphic features, from coastal phlobelus, from two geographically distant
streams of Rio de Janeiro State, Brazil.Most locations. One new species each of Pygidi-
recently, de Pinna and Wosiacki (2002) re- anops and Typhlobelus was collected by one
ported on still another species of Listrura,L. of us (JNB et al.) during the 1979 trawling
boticario, from southern Brazil. Monophyly expedition of the R/V Eastward in whitewa-
4 AMERICAN MUSEUM NOVITATES NO. 3496
ter of the Orinoco River delta. After a 0.5 m a set of measurements that are relevant in
plankton net, which was being towed behind taxonomic descriptions of those fishes. Most
the boat, inadvertently struck the bottom of measurements involve distances that are too
theriver,specimensofbothspeciesweredis- small to be obtained with calipers and were
covered among the coarse sand and gravel instead taken using an ocular micrometerfit-
that was recovered. An additional new spe- ted to a stereomicroscope. Thus, they are
cies of each genus was collected by three of measured as projections rather than straight-
us (FPR, SAS, JNB) during a joint expedi- line distances. Standard length (SL) was
tion in 2001 to the R´ıo Cuao, a clear water measured with the micrometer for purposes
tributary of the R´ıo Sipapo, itself a western of proportional values, but with digital cali-
Guyana Shield tributary of the upper Ori- pers for absolute values in mm given in lists
noco River of Amazonas State, Venezuela. of material. During measurement, specimens
These collections represent the first docu- were positioned in ethanol under a glass mi-
mented occurrence of Pygidianops and Ty- croscope slide, which served tomaintainori-
phlobelus from Venezuela and, for Pygidi- entation, straighten and compress the speci-
anops, the first occurrence of the genus out- mens onto the viewing plane, and thereby
side the Rio Negro basin. All previously minimize measurement error.
described Typhlobelus species possess di- In addition to standard length, the follow-
minutive eyes, whereas the two new species ing measurements were obtained: caudal pe-
lackeyesentirely.Conversely,thepreviously duncle length—from posterior margin of
described Pygidianops eigenmanni, along anustomiddleofposteriormarginofhypural
with one of the new Orinocoan species, lack plate; body depth—maximum vertical dis-
eyes, while the new species from the R´ıo tance through anterior margin of anus, ex-
Cuao has eyes present, although diminutive. cluding fleshy dorsal-fin fold, when present;
The possibility that these new speciesareju- head length—from rostrum tip to posterior
veniles of other recognized species has been margin opercular flap at pectoral-fin origin;
considered and rejected based on their well- head width—maximum distance perpendic-
ossified skeletons and the apparent presence ular to longitudinal axis through posteriortip
of mature gonads. of opercle; prenasal length—from rostrum
Inthispaper,wediagnoseanddescribethe tipatmidlinetoanteriorbaseofnasalbarbel;
fournewspeciesofPygidianopsandTyphlo- rostrum length—from snout tip to anterior
belusfromtheR´ıoOrinocosystem.Keysare mouth margin; rostrum width—horizontal
provided as an aid to the identification of all maximum through mouth corners; internar-
species of the two genera. We conclude with ial width—between anteriormarginsofnasal
a discussion of the biogeographic implica- barbel bases; preanal length—from rostrum
tions and their psammophilic ecology. tip at midline to base of first anal-fin ray;
preproctal length—from rostrum tip to an-
METHODS terior margin of anus. Data for rostrum
length and prenasal length wereexcludedfor
Due to the minute size of the taxa treated specimens having a damaged or distorted
herein, obtaining morphometric data was rostrum.
problematic and made more difficult by the Because all fin rays in Pygidianops and
absenceofvariousfinsandeyes,therebypre- Typhlobelus species are unbranched and un-
cluding the use of certain traditional land- segmented (except as noted below), counts
mark reference points. The lack of integu- forthecaudalfinincludedthoseraysdirectly
ment pigmentation also makes the visuali- associated with the hypural plate. Anal-fin
zation of superficial traits, such as the nares, ray counts included all rays with a corre-
extremely difficult under opticalmicroscopy. sponding pterygiophore, and the posterior
In view of those particulars inherent to the closely set rays were counted separately.La-
morphology of the species, and in order to terosensory canal pores were countedonwet
provide a standardized future reference for specimens in air; visualization was aided by
obtaining morphometric data fromspeciesof directing a jet of compressed air onto the
PygidianopsandTyphlobelus,weheredefine structures. Vertebral counts and the vertebral
2005 SCHAEFER ET AL.: VENEZUELAN CATFISHES 5
association of the first anal-finpterygiophore M. de Pinna, 10 Nov. 1996. Typhlobelus ter-
were taken fromradiographsandclearedand netzi SU 36558 paratype (25.3 mm SL) Bra-
stainedspecimenpreparationsandincludeall zil, Amazonas, Rio Negro, rock pools below
freevertebra(thoseincorporatedintotheWe- rapids at Sa˜o Gabriel, C. Ternetz, 1 Feb.
berian complex not counted) plus the ural 1925. T. macromycterus MNRJ 12129 ho-
complex counted as a single element. lotype (21.9 mm SL) Brazil, Para´, Rio To-
Osteological preparations (denoted ‘‘c&s’’) cantins near Tucuru´ı, L. C. Alvarenga, Sept.
were made following Taylor and Van Dyke 1984. Typhlobelus sp. INPA 12929 (5) Bra-
(1985). One specimen of each species was zil, Rio Xingu at Arroz Cru, near Senador
critical point dried, gold coated, and exam- Jose´ Porf´ırio, J. Zuanon, 7 Oct. 1996.
ined using a Hitachi S-4700 scanning elec-
tron microscope. Histological preparations RESULTS
were made from 4 mm serial sections that
were imbedded in Paraffin and stained with KEY TO THE SPECIES OF PYGIDIANOPS
Mason’s trichome. Drawings were prepared Myers, 1944
using a camera lucida attached to a stereo-
1A. Anal and pectoral fins absent; caudal fin
microscope. In the listing of material exam-
with nine or ten rays associated with hy-
ined from the R/V Eastward collections,dis-
puralplate;fourlaterosensorypores;low-
tance from the buoy marking the ocean/river
er jaw pointed in ventral view, two man-
mouth are indicated in nautical miles for
dibular rami forming acute angle at mid-
each collections station. Size fractions for line; distance between middle of lower
R´ıoCuaosedimentweredeterminedbypass- jawandanteriormarginofrostrumlarger
ing a wet sample through a series of sieves thanmouthwidth;rostrumlesswidethan
of progressively smaller pore openings, and head width .......... P. magoi, n.sp.
the material collected on each sieve was 1B. Anal and pectoral fins present (the latter as
quantified by volume displacement, de- ashortone-rayedflap);caudalfinwith12
to 14 rays associated with hypural plate;
scribed, and measured using an ocular mi-
six laterosensory pores; lower jaw form-
crometer fitted to a stereomicroscope.
ingcontinuouscurveinventralview;dis-
tance between middle of lower jaw and
INSTITUTIONAL ABBREVIATIONS anterior margin of rostrum smaller than
mouthwidth;rostrumaswideas,orwid-
AMNH American Museum of Natural History,
er than, head width ............... 2
New York
2A. Eyes present; triangular skin flap at mouth
CAS California Academy of Sciences, San
corner; maxillary and rictal barbels ex-
Francisco
tending posteriorly beyond vertical
INPA Instituto Nacional de Pesquisas da
through base of pectoral fin; nasal barbel
Amazoˆnia, Manaus, Brazil
extending posteriorly to posterior half of
MBUCV Museo de Biologia, Universidad Cen-
pectoral fin or longer ... P. cuao, n.sp.
tral de Venezuela, Caracas
2B. Eyes absent; no triangular skin flap at
MNRJ MuseuNacional,RiodeJaneiro,Brazil
mouth corner; maxillary and rictal bar-
MZUSP Museo de Zoologia, Universidade da
bels posteriorly not reaching vertical
Sa˜o Paulo, Sa˜o Paulo, Brazil
through base of pectoral fin; nasal barbel
SU former Stanford University collections,
reaching posteriorly to base of pectoral
now housed at CAS
fin or shorter .....................
.......... P. eigenmanni Myers,1944
COMPARATIVE MATERIAL EXAMINED
Pygidianops eigenmanni SU 36557 para- Pygidianops cuao, new species
types (3:12.3–18.4 mm SL), CAS 11121 Figures 1, 2; Table 1
paratypes(7:10.5–13.6mmSL)Brazil,Ama-
zonas, Rio Negro, rock pools below rapids HOLOTYPE: MBUCV-V-30917 (18.70 mm
at Sa˜o Gabriel, C. Ternetz, 1 Feb. 1925. Py- SL) Venezuela, Estado Amazonas, R´ıo Cuao
gidianops sp. INPA 12427 (5) Brazil, Ama- at Raudal Guacamaya, 8.1 miles upstream
zonas, Igarape´ do Acara´ (tributaryoftheRio from Raudal El Danto, 05807.719N,
Taruma˜, Rio Negro basin), A. Kirovsky and 67831.539W, SAS01–03, F. Provenzano, S.A.
6 AMERICAN MUSEUM NOVITATES NO. 3496
Fig.1. Pygidianopscuao,holotype,MBUCVV-30917,21.06mmSL,Venezuela,EstadoAmazonas,
R´ıo Cuao at Raudal Guacamaya, 8.1 miles upstream from Raudal El Danto. Scale bar is 1 mm.
2
0
0
5
TABLE1 S
Counts and Measurements of Holotype (HT) and Paratypes (PT) of New Venezuelan Pygidianops and Typhlobelus Species C
H
Measurements given as percent head length, unless noted otherwise; mean (median for counts) and standard deviation in parentheses. A
E
F
Pygidianops Typhlobelus E
R
cuao magoi guacamaya lundbergi E
T
HT PT(N518) HT PT(N55) HT PT(N59) HT PT(N54)
A
L
Standardlength(SL) 18.7 17.0 (2.8) 12.6 12.6 (.81) 22.2 22.3 (3.1) 29.0 25.9 (2.6) .:
Headlength(%SL) 16.8 16.1 (1.8) 18.5 17.4 (1.0) 12.2 11.7 (1.0) 11.0 9.7 (0.6) V
Body depth (%SL) 17.5 16.1 (1.4) 14.1 14.0 (2.9) 5.1 5.0 (0.4) 4.6 4.2 (0.7) E
N
Headwidth 63.5 69.0 (4.0) 54.9 56.9 (4.7) 39.3 39.3 (2.7) 44.8 46.2 (3.4) E
Z
Preanallength(%SL) 54.8 58.5 (1.7) — — 70.4 70.1 (2.2) 73.1 70.7 (1.3) U
Preproctallength(%SL) 51.5 56.3 (1.6) 63.8 61.7 (3.0) 69.7 68.5 (1.9) 71.8 68.9 (1.7) E
L
Caudal pedunclelength(%SL) 44.8 44.0 (1.9) — — 29.5 29.4 (0.9) 24.8 30.8 (1.4) A
Rostrumlength 12.7 11.4 (1.7) 17.2 16.4 (3.8) 33.3 35.0 (2.5) 24.5 22.5 (1.8) N
Rostrumwidth 26.3 31.0 (3.7) 18.5 20.7 (2.9) 13.7 15.0 (2.6) 17.2 15.4 (1.8) C
A
Prenasallength 23.2 27.6 (4.3) 24.9 21.2 (2.0) 32.2 34.9 (2.6) 31.3 28.0 (1.3) T
Internarialwidth 26.3 30.4 (5.0) 23.6 23.5 (3.7) 17.4 15.3 (2.9) 18.8 13.7 (4.4) F
I
S
Caudal finrays 13 13 (.24) 9 9.5 (.58) 9 9 (0) 10 9 (0) H
Analfinrays 4 4 (.51) — — 5 5 (0) 5 5 (0) E
S
7
8 AMERICAN MUSEUM NOVITATES NO. 3496
Schaefer, J.N. Baskin, A. Rojas (hereafter DESCRIPTION: General appearance com-
‘‘PSBR’’), 3 March 2001. pact, oblate; head slightly depressed and
PARATYPES (all Venezuela, Estado Ama- body compressed, trunk neither cylindrical
zonas):AMNH232970(23:16.59–24.00mm nor ribbonlike. Dorsal and ventral body pro-
SL), MBUCV-V-29905 (22: 8.13–21.55 mm files gently convex. Dorsal profile of head
SL), MZUSP 82103 (5: 13.4–19.0 mm SL) slightly concave at vertical through opercle,
same dataasholotype;MBUCV-V-29843(1: gently convex across occipital region. Out-
20.00 mm SL) R´ıo Cuao, Can˜o Ceje, 5 min- lineofheadrectangularindorsalview,great-
utesupstreambyboatfromRaudalElDanto, est width (75% HL) at opercle. Anteriorros-
05805.869N, 67831.379W, SAS01–02, PSBR, trum margin blunt, nearly straight between
3 March 2001; AMNH 232978 (11: 12.3– maxillary barbel bases, rounded in lateral
23.15 mm SL), MBUCV-V-29922 (10: profile. Ventrum between pectoral and anal
12.41–20.30 mm SL), MZUSP 82104 (3: fins forming shallow sulcus with margin of
10.6–18.4mmSL)R´ıoCuaoatIsladeCielo, laterally divergent medial infracarinalis
21.3 kilometers upstream from Raudal El (Winterbottom, 1974) fiber bundles (fig. 3).
Danto, 05811.019N, 67831.119W, SAS01–04, Three pairs of barbels; all similar in general
PSBR, 5 March 2001; AMNH 232995 (4: appearance, robust at base. Maxillary barbel
13.95–19.32 mm SL), MBUCV-V-29933 (4: continuous with anterior lip margin; its base
14.46–18.22mmSL)R´ıoCuaoatRaudalPia slightly depressed. Rictal barbel compressed
Poco, 21.5 kilometers upstream from Raudal at base, merging with maxillary barbel base
El Danto, 05810.959N, 67830.819W, SAS01– at mouth corner. Nasal barbel distinctly sep-
05, PSBR, 6 March 2001; MBUCV-V-29977 arate,extendingposteriorlywellbeyondpec-
(3: 8.12–12.15 mm SL) R´ıo Cuao, approxi- toral fin origin. Mouth ventral, upper lip a
mately20minutesbymotorboatdownstream broad fleshy pad, anterior margin of lower
from base camp at SAS01–4, 05810.139N, jawconvex.Smalltriangularflapofskinpro-
67831.769W, SAS01–7, PSBR, 7 March jects from corner of mouth (figs. 1, 2) be-
2001; AMNH 233036 (6: 12.25–19.27 mm tween lower lip margin and rictal barbel
SL), MBUCV-V-29997 (7: 11.05–17.49 mm base.Posterodorsalcornerofbranchialopen-
SL)R´ıoCuaoatRaudalPauj´ı,approximately ing located immediately anterior to pectoral
10 minutes by motorboat downstream from fin base, gill membrane continuing antero-
base camp at SAS01–4, 05808.929N, ventrally, its posterior margin straight to
67832.189W, SAS01–8, PSBR, 8 March slightly concave, not united across isthmus;
2001; MBUCV-V-30105 (4: 8.80–21.65 mm fivebranchiostegalrays.Eyespresent,butre-
SL) R´ıo Cuao, approx. 10 minutes by mo- duced, appearing as compact spherical mass
torboat below Raudal El Danto, 05802.399N, of darkly pigmented cells below slightly
67833.359W, SAS01–13, PSBR, 10 March raised transparent skin surface. Spherical
2001. pigment mass with dorsal indentation filled
DIAGNOSIS: Distinguished from congeners with mass of opaque cells,yieldingrudimen-
by the presence of diminutive eyes (vs. eyes taryeyeballandlensconfiguration.Naresnot
absent), posterior naris absent (vs. nares bi- juxtaposed or connected, but rather wellsep-
laterallypaired),presenceofatriangularskin arated; anterior naris at dorsomesial base of
flap at mouth corner (vs. skin flap absent), nasal barbel, posterior naris larger, located
dorsal and ventral fin fold deep and extend- slightly mesial to and one eye diameter an-
ing forward on the head to a verticalthrough terior to eye, its opening directed laterocau-
tip of pectoral fin (vs. fin fold shallow, ex- dad. Laterosensory system reduced to short,
tending forward on head to point approxi- wide trunk canal segment posterior to supra-
mately two times head length from rostrum cleithrum and dorsal to pectoral fin, canal
tip). Further distinguished from P. magoi by continuing onto head through supracleith-
presence of six laterosensory pores on head rum, pterotic, sphenotic, and frontal to ter-
(vs. four pores), presence of pectoral and minate just posterior to eye. Six pores total
anal fins (vs. fins absent), presence of 12–13 (fig. 2 top, middle), first (anteriormost) im-
caudal fin rays associated with the caudal mediately behind eye and homologous with
plate (vs. 9–10). thesupraorbitalepiphysealpore(‘‘i6’’ofAr-
2005 SCHAEFER ET AL.: VENEZUELAN CATFISHES 9
Fig. 3. Histological cross section through the
caudal region of P. cuao showing dorsal fin fold
and ventrally projecting paired metapleural keels
(arrows). Scale bar is 1 mm.
homologous with pterotic branch (Schaefer
andAquino,2000;‘‘L1’’ofArratiaandHua-
Fig. 2. Pygidianops cuao, paratype, AMNH
quin, 1995), fifth at canal entrance to supra-
232995, 19.2 mm SL, scanning electron micro-
cleithrum and homologous with first lateral-
graphs of head. Scale bar is 1 mm.
line pore, sixth (posteriormost) on trunk at
vertical through middle of pectoral fin and
ratia and Huaquin, 1995), second at frontal/ representingposteriorterminusofshorttrunk
sphenotic junction and homologous with in- canal.
fraorbital canal branch (canal segment ab- Dorsal fin absent, dorsum of body with
sent),thirdatpteroticnearitsanteriormargin thin, semitransparent fin fold (fig. 3) from
and homologous with preoperculomandibu- head to dorsal margin caudal fin; its greatest
lar canal branch (canal segment absent), depth at vertical through anus, contained
fourthatpterotic/supracleithrumjunctionand three times in body depth. Anal fin present,
10 AMERICAN MUSEUM NOVITATES NO. 3496
4–5 (mostly 4) rays, all unsegmented, un- ETYMOLOGY: The specific name is for the
branched; first ray rudimentary, short, about R´ıo Cuao, a clearwater tributary of the R´ıo
0.25 length second ray; first pterygiophore Orinoco and the region of first discovery of
associated with hemal spine of vertebra 17. the species. Treated as a noun in apposition
Ventrum with thin fin fold between base last to the generic name.
anal-fin ray to ventral margin caudal fin; its
greatest depth about 0.5 times depth dorsal Pygidianops magoi, new species
fin fold. Anus and urogenital papilla located Figures 5, 6; Table 1
immediately anterior to first anal-fin ray.
Urogenital papilla length approximately HOLOTYPE: MBUCV-V-31035 (20.0 mm
equal to anus diameter, papilla connected to SL) Venezuela, Estado Delta Amacuro, R´ıo
anal-fin base by median ridge of translucent Orinoco at Puerto Cabrian, 8834.89N,
tissue. Caudal fin with 12–13 raysassociated 62815.99W, R/V Eastward station 36957, mi
with the caudal plate, all unbranched, all but 151, field number T-35-79, 10 ft bottom
thedorsalandventralmostrayswith2–4seg- trawl, capture depth 25 m, 13:55 hrs., John
ments per ray; 4–5 dorsal and 5–7 ventral G. Lundberg et al., 10 Nov. 1979.
procurrent rays; spacing between dorsal pro- PARATYPES (all from Venezuela): AMNH
current rays compacted posteriorly, yielding 233706 (11.71 mm SL), Estado Bol´ıvar, R´ıo
slightly upturned appearance to caudal fin Orinoco between Ciudad Bol´ıvar and Puerto
relative to longitudinal body axis; posterior Ordaz, 8820.169N, 62857.819W, R/V East-
fin-margin rounded. Pectoral fin present, mi- ward station 36901, mi 203, field number T-
nute, its length about 0.3 times head length; 12-79, 10 ft bottom trawl, capture depth 18
one unbranched unsegmented ray, fin mem- m, 16:30 hrs., F. Mago-Leccia et al., 7 Nov.
brane expanded at base, compressed; distal 1979;AMNH233707(12.69mmSL)Estado
tip pointed. Pelvic fin and girdle absent. Delta Amacuro, R´ıo Orinoco just down-
Jaw teeth unicuspid, blunt; 7–9 mandibu- stream from Isla Portuguesa, 88389N,
lar and 6–8 premaxillary teeth per jaw ele- 618499W, field numberT-59-79, mi116.5,10
ment. Odontodes absent. Trunk myomeres ft bottom trawl, capture depth 30–40 m, 15:
39–42 (holotype 42), total vertebrae 41. 07 hrs., J.G. Lundberg et al., 14 Nov. 1979;
COLORATION: Pale tan to grey in life. In AMNH 233708 (11.96 mm SL), MZUSP
ethanol,creamwhiteoverall,withdensecon- 84304 (1c&s: 11.4 mm SL) Estado Bol´ıvar,
centration of dark melanophores on occipital R´ıoOrinoco,8818.39N,62856.19W,R/VEast-
region, extending ventral to posteriormargin ward station 36895, field number P-2-79, mi
swimbladder capsule; deeper lying melano- 200.5, 1 m plankton net, capturedepth26m,
phores along mesethmoidlateralmarginpos- 12:55 hrs., H. Lopez-Rojas et al., 7 Nov.
terior to nasal barbel base and at opercle an- 1979; MBUCV-V-31036 (14.5 mm SL) Es-
terior margin. Trunk with diffuse band of tado Delta Amacuro, Rı´o Orinoco, just
melanophores along dorsal fin-fold base, downstream from Isla Portuguesa, 88389N,
scattered diffuse line along ventral fin fold, 618499W, field numberT-61-79, mi116.5,10
midlateral line with fewsmall,irregularlyar- ft bottom trawl, capture depth 25 m, J.G.
ranged, discrete clusters of melanophores, Lundberg et al., 14 Nov. 1979; MBUCV-V-
ventrum of head and trunk otherwise unpig- 31037 (13.4 mm SL) Estado Bol´ıvar, R´ıo
mented. Orinoco, Isla Isabella, between PuertoOrdaz
DISTRIBUTION: Known only from six col- and Ciudad Bol´ıvar, 8819.79N, 62856.89W,R/
lection localities within the R´ıo Cuao drain- V Eastward station 36924, field number T-
age basin (fig. 4). 18-79, mi 203, 10 ft bottom trawl, capture
fi
Fig. 4. Geographic distribution of the Venezuelan Glanapteryginae. Drainage map of Venezuela
(center);rectanglesdepictregionsofinterestexpandedinAandB.A,lowerR´ıoOrinoco;B,R´ıoCuao.
Symbols designate collection localities; some symbols represent more than one lot. Open symbols des-
ignate holotype; grey star symbol denotes shared type locality for both P. cuao and T. guacamaya.