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Systematics and Biodiversity 3(4): 407–432 Issued 24 November 2005
doi:10.1017/S1477200005001726 Printed in the United Kingdom C
The Natural History Museum
Phylogenetic systematics and historical biogeography
of the Neotropical electric fish Sternopygus (Teleostei:
Gymnotiformes)
Kevin G. Hulen1,2, William G. R. Crampton1&JamesS.Albert
1,2∗
1Department of Biology, University of Louisiana at Lafayette, Lafayette, LA 70504-2451, USA
2Department of Zoology, University of Florida, Gainesville, Florida, 32611 USA
submitted January 2004
accepted November 2004
*Corresponding author. Email: jxa4003@louisiana.edu
Contents
Abstract 407
Introduction 408
History of the classification 408
Nomenclature 410
Materials and methods 412
Data acquisition 412
Phylogenetic methods 415
Results 415
Descriptive morphology 415
Pigmentation 415
Body proportions 416
Neurocranium 418
Oral jaws 419
Suspensorium 420
Pectoral girdle 420
Axial skeleton 420
Interrelationships of Sternopygus 421
Key to the adults of Sternopygus species 424
Discussion 424
Historical biogeography 424
Historical ecology 425
Continuous traits as phylogenetic characters 426
Acknowledgements 426
References 426
Appendices 428
Abstract Interrelationships among 10 extant species of the Neotropical electric fish Sternopygus are inferred from
phylogenetic analysis of 66 morphological characters, including features of pigmentation, body proportions, meristics
and osteology. A total of 287 lots containing 677 specimens were examined. The important findings of this study are:
(1) S. branco is the most basal species unique among congeners in being restricted to whitewater rivers in the Central
Amazon Basin, (2) S. sp. ‘cau’ from the Rio Caura of Venezuela is the sister taxon to (S. obtusirostris +S. astrabes),
(3) S. castroi is a junior synonym of S. astrabes,(4)S. macrurus is the sister taxon to (S. arenatus +S. xingu +
S. aequilabiatus species group) and (5) S. arenatus is the sister taxon to (S. xingu +S. aequilabiatus species group). A key
to the adults of Sternopygus species is provided. Several features of S. astrabes previously thought to be plesiomorphic
are now considered derived, including: short body cavity, paedomorphic cranial osteology, and the habitat restriction
to terra firme streams. Sternopygus species assemblages in the Pacific (trans-Andean) and Atlantic (cis-Andean) slopes of
northwestern South America are not monophyletic and do not result exclusively from local or regional radiations. The clade
407
408 Kevin G. Hulen et al.
composed of S.macrurus, S. arenatus, S. xingu and the S. aequilabiatus species group is inferred to predate the Middle
Miocene uplift of the Eastern Cordillera (c. 11.8–12.2 Ma). As currently recognized S. macrurus is the most widely distributed
and most eurytopic gymnotiform species, inhabiting all hydrogeographical regions of tropical South America and most
lowland aquatic habitats. Other Sternopygus species have much more restricted geographic and ecological distributions.
Perceptions of phylogenetic patterns in Sternopygus are shown to be highly sensitive to taxon sampling.
Key words biodiversity, classification, comparative osteology, evolution, South America, ontogeny
Introduction
Neotropical electric fishes (Gymnotiformes) are a diverse
group of ostariophysan fishes found throughout Neotrop-
ical freshwaters and are represented by at least 131 spe-
cies belonging to 31 genera (Albert, 2001, 2003; Albert &
Crampton, 2003; Crampton & Albert, 2005). Gymnotiformes
are readily distinguished from other Neotropical fishes by their
‘eel-like’ culteriform body shape, highly elongate anal fin with
more than 100 rays (Albert, 2001), absence of dorsal and pel-
vic fins, reduced eyes and central visual pathways, and the
ability to generate and detect electric fields used in com-
munication and navigation (Ellis, 1913; Fink & Fink, 1981;
Albert, 2001). Gymnotiformes provide unique materials for
studies of the evolution of specialized sensory systems and
the diversification of animals species in tropical ecosystems
(Crampton, 1998; Albert 2001, 2002; Crampton & Albert,
2005). Gymnotiformes possess a combined electrogenic-
electroreceptive system which is employed for both active elec-
trolocation, and electrocommunication. Active electrorecep-
tion allows gymnotiforms to communicate, navigate, forage
and orient themselves relative to the substrate at night and in
dark, sediment-laden waters, and contributes to their ecological
success in Neotropical aquatic ecosystems. The derived and
highly specialized features of electrosensory and electrogenic
structures notwithstanding, patterns of diversity in gymnoti-
form fishes are similar to those of many diverse tropical taxa
(Albert et al., 2005b). For example, most gymnotiform clades
are thought to be ancient and many genera are distributed
in polyphyletic regional species assemblages (Albert et al.,
2005a).
The family Sternopygidae is represented by five gen-
era: Sternopygus (M¨
uller & Troschel, 1849), Eigenmannia
(Jordan & Evermann, 1896), Rhabdolichops (Eigenmann &
Allen, 1942), Archolaemus (Korringa, 1970), and Distocyclus
(Mago-Leccia, 1978). Within gymnotiform fishes, sternopy-
gids share the following unique combination of characters:
(1) multiple rows of small, villiform (brush-like) teeth on dent-
ary, (2) relatively large eyes (diameter equal to or greater than
distance between nares), (3) large bag-like infraorbital bones
with expanded bony arches, (4) anterior nares located outside
gape, (5) anal-fin origin at isthmus, (6) absence of urogen-
ital papilla, (7) no caudal fin or dorsal organ (Albert, 2001),
and (8) a weak (less than one volt) tone-type electric organ
discharge, characterized by a monophasic hyperpolarization
from a negative baseline (Crampton, 1998).
The genus Sternopygus is distributed throughout the
humid Neotropics, from Panama and the Pacific Slope of
Colombia to the Paraguay–Paran´
a Basin of Paraguay (Table 1;
Fig. 1). Sternopygus species attain medium to large body sizes
(18–140 cm max. total length), with a straight to rounded, or
strongly concave snout (Fig. 2). Sternopygus is monophyletic
and is unambiguously diagnosed by the following unique
combination of characters (modified from Albert, 2001):
(1) large gape (Mago-Leccia, 1978); (2) large branchial open-
ing (Mago-Leccia, 1978); (3) long, evenly curved maxilla;
(4) anterior process of maxilla extends as a narrow hook-like
process (Lundberg & Mago-Leccia, 1986); (5) dorsal portion
of ventral ethmoid elongate (Albert & Fink, 1996); (6) post-
temporal fossa present between pterotic and epioccipital bones
(Lundberg & Mago-Leccia, 1986); (7) gill rakers composed of
three bony elements, the middle one with 3–10 small teeth
(Mago-Leccia, 1978); (8) gill rakers not attached to branchial
arches (Albert & Fink, 1996); (9) gap between parapophyses
of second vertebra; (10) unossified post cleithrum (Albert &
Fink, 1996); (11) long body cavity, with 18–30 precaudal ver-
tebrae (Albert & Fink, 1996); (12) long anal fin with more
than 220 rays (Albert & Fink, 1996), (13) unbranched anal-
fin rays (Fink & Fink, 1981), (14) developmental origin of
adult electric organ from both hypaxial and epaxial muscles
(Unguez & Zakon, 1998; Albert, 2001), (15) absence of jam-
ming avoidance response (Heiligenberg, 1991; Albert, 2001),
(16) presence of a ‘medial cephalic fold’ (Triques, 2000), a
ridge of ectodermal tissue extending from the ventral limit
of the opercular opening anteromedially to the branchial
isthmus.
History of the classification
The genus Sternopygus wasestablishedbyM
¨
uller & Troschel
(1849) to place species of ‘Gymnotini’ with ‘hackle-shaped
(long and slender) teeth’, ‘head laterally compressed’, and
‘anterior nostrils on the upper side of the head’. Eigenmann &
Ward (1905) later regarded Sternopygus as a junior synonym
of Gymnotus, based on several characters now regarded to be
of ambiguous polarity. Sternopygus was reinstated by Ellis
(1913) to place Gymnotiformes with a free orbital margin (i.e.
eye not subdermal).
The locality of the type species S.macrurus (Bloch &
Schneider, 1801) is unknown, although the syntypes were
probably described from materials obtained from the Dutch
colonies, in either Recife (Brazil) or Surinam (L¨
onnberg, 1896;
Wheeler, 1991). As currently recognized S. macrurus is the
most widely distributed gymnotiform species, occurring west
of the Andes from the Pacific slope and Magdalena Basins
Phylogenetic systematics Sternopygus 409
Species MA PS NW GO WA EA NE SE PA
S. aequilabiatus X
S. arenatus X
S. astrabes XYY
S. branco XY
S. dariensis XYY
S. macrurus YYYYYYYY
S. obtusirostris XY
S. pejeraton X
S. sp. ‘cau’ Y
S. xingu X
Total 1 3 4 3 4 5 1 1 1
Table 1 Geographic distributions of nine Sternopygus species. Hydrogeographic regions modified from
Albert (2001). X, region of type locality; Y, specimens from other region(s); Abbreviations:
EA, Amazon Basin east of Purus Arch and tributaries below fall-line of Guyana Shield
(2 985 000 km2); GO, Guyanas–Orinoco Basin, incl. island of Trinidad and Upper Negro
drainages above fall line (1 843 000 km2); MA, Atlanticand Pacific slopes of Middle America
from the Motagua to Tuyra Basins (393 000 km2); NE, coastal drainages of northeast Brazil
incl.Parna´ıba, Piaui, S˜ao Francisco and Jequitinhonha Basins (1 357 000 km2);NW,
Northwestern South America incl. Atrato, Magdalena and Maracaibo Basins, and north slope of
Venezuela (471 000 km2); PA,Paraguay–Paran ´a Basin including Dulce-Sal´ı and Salado Basins
of Argentina (3 185 000 km2); PS, Pacific slopes of Colombia and Ecuador, from Baud´oto
Guayaquil Basins (200 000 km2); SE, coastal drainages of southeast Brazil and Uruguay from
Doc´e to Lagoa Mirim Basins (628 000 km2); WA, Amazon Basin west of Purus Arch, below c.
500 m elevation (3 556 000 km2). Distribution data from Appendix 1.
Albert
Albert & Fink
Species (1996) (2001) (2003) This paper
S. aequilabiatus XXXX
S. arenatus XX X
S. astrabes XXXX
S. branco X
S. castroi XX
S. dariensis XX
S. macrurus XXXX
S. obtusirostris XX
S. pejeraton XX
S. xingu XXXX
Table 2 Summary of Sternopygus species recognized in recent literature reports.
of Colombia, throughout the Amazon-Orinoco Basins, in the
arid northeast of Cear´
a (Brazil), the Atlantic coast of southeast
Brazil and the Paraguay-Paran´
a Basin of Paraguay (Table 1,
Fig. 1a). The family name Sternopygidae was coined by Cope
(1871) to place the taxa recognized as all Gymnotiformes.
Mago-Leccia (1978) was the first to use the name Sternopy-
gidae in its modern sense.
Albert & Fink (1996) proposed the only previous hypo-
thesis of phylogenetic interrelationships among Sternopygus
(Table 2) recognizing four species: (1) Sternopygus astrabes
(Mago-Leccia, 1994) from terra firme streams and rivers of
Venezuela and Brazil (Table 1, Fig. 1b), as the most basal
taxon; (2) S. macrurus as sister taxon to remaining Sterno-
pygus species; (3) Sternopygus xingu (Albert & Fink, 1996)
from the Rio Tocantins and Xingu Basins of Brazil (Table 1,
Fig. 1b); and (4) Sternopygus aequilabiatus (Humboldt &
Bonpland, 1811) from the Magdalena Basin (Table 1, Fig. 1b).
Sternopygus arenatus (Eydoux & Souleyet, 1841) from the Rio
Guyaquil and Esmeraldas Basins of Ecuador (Table 1, Fig. 1b),
S. dariensis (Meek & Hildebrand, 1916) from Panama and the
Pacific slope of Colombia (Table 1, Fig. 1b), and S. pejeraton
(Schultz, 1949) from the Maracaibo basin of Venezuela and
Colombia (Table 1, Fig. 1b) were considered junior synonyms
of S. aequilabiatus.Sternopygus obtusirostris (Steindachner,
1881) from the Central Amazon, Brazil (Table 1, Fig. 1b) was
synonymized with S. macrurus. Albert (2001) recognized six
species of Sternopygus (Table 2), maintained the synonymy of
S. macrurus and S. obtusirostris, and regarded S. dariensis,
410 Kevin G. Hulen et al.
Figure 1 Map of South America showing the distribution of Sternopygus constructed from 168 museum lots containing 298 specimens.
(a) S. macrurus (closed triangles). (b) S. branco (closed circles, a =type locality), S. obtusirostris (open squares, b =type locality),
S. astrabes (closed diamonds, c =type locality), S. sp. ‘cau’ (open diamonds, d), S. xingu (closed squares, e =type locality),
S. arenatus (stars, f =type locality), S. dariensis (inverted open triangles, g =type locality), S. pejeraton (open triangles, h =type
locality), S. aequilabiatus (inverted closed triangles, i =type locality).
S. pejeraton and S. aequilabiatus as members of the
S. aequilabiatus species group. Albert (2003) recognized nine
species of Sternopygus (Table 2).
Nomenclature
We recognize nine valid species of Sternopygus (Table 2),
which includes S. branco (Crampton et al., 2004), a new spe-
cies described from the Amazon River between its confluences
with the Rios Japur´
a and Negro and the lower 100 km of the
Rio Negro (Fig. 1b, Table 1). The taxonomic status of
S. aequilabiatus,S.dariensis and S.pejeraton are not fully
understood (Mago-Leccia, 1994; Albert & Fink, 1996; Albert,
2001), so are still referred to as the S. aequilabiatus species
group.
Examination of four specimens in the type series of
S. castroi (Triques, 2000) from the Rio Negro tributary of
the Amazon basin shows they are indistinguishable from
S. astrabes. Triques (2000) diagnosed S. castroi by the
Phylogenetic systematics Sternopygus 411
Figure 2 Shape differences in nine adult Sternopygus species. (a) S. branco (MCP 32451), (b) S. sp. ‘cau’ (AMNH 58643), (c) S. obtusirostris
(MCP 32262), (d) S. astrabes (MCP 32235), (e) S. macrurus (ANSP 172171), (f) S. arenatus (MCZ 48804), (g) S. xingu (INPA 6425),
(h) S. dariensis (UF 15451), (i) S. pejeraton (UMMZ 157671). Scale bars equal 10 mm.
simultaneous absence of an intraopercular fold and presence
of a humeral spot. In the specimens examined for the present
study neither of these features were determined to be diagnostic
of S. castroi. Like many features of soft surface anatomy, the
intraopercular fold is highly variable in appearance within and
among Sternopygus species depending on preservation quality
and body size. The type specimens of S. castroi do possess
a slightly darkened humeral region, but such a distorted pat-
tern of enhanced pigmentation in the humeral region is also
observed in specimens of S. astrabes and S. pejeraton.The
appearance of this slightly darkened patch is distinct from the
dark humeral spot defined in character 4 as a well-defined black
patch with sharp margins, which is observed in S. sp. ‘cau’,
S. macrurus,andS. xingu. In addition, the type specimens of
S. castroi possess the principal diagnostic feature of S. astrabes
(Mago-Leccia, 1994): two broad dark wide vertical bands in
adults (visible in Triques, 2000, Fig. 1). The available meristic
data (i.e. anal and pectoral fin rays) from the type specimens
of S. castroi are well within the range observed in popula-
tions of S. astrabes from throughout the Guyanas and Amazon
basin.
In addition to the nine valid Sternopygus species we
recognize S. sp. ‘cau’ as an undescribed species. Two
paratype specimens of S. astrabes from the Rio Caura
in the Venezuelan state of Bolivar were discovered to
have different morphometric and meristic values than those
from other populations, including the holotype from near
Porto Ayacucho in the Venezuelan state of Amazonas.
The specimens from the Rio Caura have a larger adult
body size (mean 215 vs. 121 mm) and a non-overlapping
higher range in pre-caudal vertebrae (mode 24 vs. 19).
A formal description of this species will be presented
elsewhere.
Sternopygus species recognized in this phylogenetic re-
view are listed below. Square brackets contain modern or
corrected spellings for river or place names.
412 Kevin G. Hulen et al.
Figure 3 Allometric growth of relative head length (HL%) in three species of Sternopygus illustrating method of estimating size of maturity.
Plot of length to end of anal fin (LEA) and head length as a percentage of LEA (HL%) for three Sternopygus species: (a) S. macrurus
(closed triangles) and S. obtusirostris (open squares). (a, b) S. astrabes (closed diamonds). Dashed lines represent point where
specimens are at or near asymptotic value of HL% are considered to have attained adult size.
1. Sternopygus macrurus (Bloch & Schneider, 1801)
Gymnotus macrurus Bloch & Schneider, 1801: 522
(Brazil).
Sternopygus marcgravii Reinhardt, 1852: 146 (Rio das
Velhas, Brazil).
Carapus sanguinolentus Castelnau, 1855: 85, 94, Pl. 46,
fig. 1. (R´
ıo Urubamba, Upper R´
ıo Ucayali, Peru).
Hildatia brasiliensis Fern´
andez-Y´
epez, 1968: no pa-
gination, fig. (unlabelled) (Sarapo, Piauhy [Piaui],
Brazil).
2. Sternopygus aequilabiatus (Humboldt & Bonpland, 1811)
Gymnotus aequilabiatus Humboldt, in Humboldt &
Bonpland, 1811: 79, P. 10, fig. 1 (R´
ıo Magdalena,
Colombia).
3. Sternopygus arenatus Eydoux & Souleyet, 1841: 143,
Pl. 8, fig. 2 (R´
ıo Guayaquil, Ecuador).
4. Sternopygus obtusirostris Steindachner, 1881: 143, Pl. 2,
fig. 3 (Rio Amazonas [Solim˜
oes] at Teff´
e[Tef
´
e], Lago
Alexo [Aleixo] and Manacapouru [Manacapuru], Rio
Puty [Poti], Rio Madeira, all from Thayer Expedition).
5. Sternopygus dariensis Meek & Hildebrand, 1916: 309,
Pl. 26, fig. 21 (Marrigante, R´
ıo Tuyra, Panama).
6. Sternopygus pejeraton Schultz, 1949: 60–61, Pl. 1A (R´
ıo
Ap´
on, Maracaibo basin, Venezuela).
7. Sternopygus astrabes Mago-Leccia, 1994: 79–80, Pl. 87
(Ca˜
no Pozo Azul, Agua Linda, 23 km NE. Puerto Ay-
acucho, tributary of R´
ıo Orinoco, Amazonas, Venezuela).
Sternopygus castroi Triques, 2000: 19–26, figs 1–2
(Igarap´
e Jarad´
a, Rio Cueiras, tributary of Rio Negro,
Brazil).
8. Sternopygus xingu Albert & Fink, 1996: 85–102, figs 7–9
(Rio Batovi, Mato Grosso do Sul, Brazil).
9. Sternopygus branco Crampton, Hulen & Albert, 2004
(Amazon River between its confluences with the Rio
Japur´
a and Rio Negro, Lower Rio Negro, Brazil).
10. Sternopygus sp. ‘cau’, undescribed (Rio Caura, Bolivar,
Venezuela).
Materials and methods
Data acquisition
A total of 287 lots containing 677 specimens were examined
(Appendix 1). Due to growth allometry, morphometric data are
reported as mean adult values. Adult morphology was determ-
ined from plots of head length as a percentage of length to the
end of anal fin (Fig. 3), and from examination of neurocranial
shape from radiographs (Figs 4, 5). Sexual maturity and sex in
Sternopygus can only be assessed through dissection of gon-
ads. In mature specimens, testes are pinkish-white and ovaries
are packed with yellow eggs. Immature specimens cannot be
sexed reliably. Sexual dimorphism of morphology has not been
observed in Sternopygus.
Phylogenetic systematics Sternopygus 413
Figure 4 Tracings of adult neurocranial outlines for nine
sternopygids, superimposed in lateral view. (a) S. branco
(n=9), (b) S. obtusirostris (n=10), (c) S. astrabes
(n=13), (d) S. macrurus (n=11), (e) S. arenatus (n=4),
(f) S. xingu (n=3), (g) S. aequilabiatus (n=12), (h) S. sp.
‘cau’ (n=2), (i) A. blax (n=4), (j) D. conirostris (n=3).
Figure 5 Tracings of juvenile neurocranial outlines for nine
sternopygids, superimposed in lateral view. (a) S. branco
(n=2), (b) S. obtusirostris (n=4), (c) S. astrabes (n=9),
(d) S. macrurus (n=10), (e) S. arenatus (n=2),
(f) S. aequilabiatus (n=3), (g) A. blax (n=2),
(h) D. conirostris (n=2).
Morphometric techniques used to measure body propor-
tions were adapted from Albert & Fink (1996). Digital cal-
ipers were used to measure point-to-point linear distances from
standard landmarks to the nearest 0.1 mm (Fig. 6). Small spe-
cimens were measured using an ocular micrometer and an
Olympus SZX12 dissecting microscope. Measurement accur-
acy and precision were estimated by comparing the standard
deviation of ten repeated measures of each morphometric vari-
able. All unilateral measurements were taken on the left side
of the fish. Measurements of body size include: (1) length to
the end of the anal fin (LEA), measured from the tip of snout
(anterior margin of upper jaw at mid-axis of body) to end of
anal fin (where membrane posterior to last ray contacts the
ventral surface of body); (2) anal-fin length (AFL), from ori-
gin of anal fin to posterior end of anal fin; (3) caudal appendage
(CA), measured as the distance from the last anal-fin ray to
the distal end of the caudal filament, which is often damaged
and not fully regenerated, so was selectively excluded from
the analysis; (4) body depth (BD), vertical distance from ori-
gin of anal fin to dorsal body border; (5) body width (BW),
maximum body width at origin of anal fin; (6) head length
(HL), measured from posterior margin of the bony opercle to
tip of snout (anterior margin of upper jaw at mid-axis of body);
(7) postorbital head length (PO), from posterior margin of the
bony opercle to posterior margin of eye (at edge of the free
orbital margin); (8) preorbital head length (PR), from anterior
margin of eye (at edge of the free orbital margin) to tip of snout
(anterior margin of upper jaw at mid-axis of body); (9) eye dia-
meter (ED), horizontal distance between anterior and posterior
margin of eye (at edge of free orbital margin); (10) interorbital
length (IO), between dorsomedial margins of eyes (at edge of
free orbital margin); (11) inter-narial distance (NN), from pos-
terior margin of the anterior nares to the anterior margin of the
posterior nares; (12) mouth width (MW), horizontal distance
of gape at rictus; (13) branchial opening (BO), from postero-
dorsal to anteroventral extent of fold along anterior margin;
(14) head depth (HD), vertical distance at nape to ventral body
border with lateral line held horizontal; (15) head width (HW),
width at nape; (16) preanal distance (PA), from origin of anal
fin to posterior margin of anus; (17) pectoral-fin length (P1),
from dorsal border of fin base where it contacts cleithrum to
tip of the longest ray.
Neurocranium measurements were obtained from 71 ra-
diographs of adult sternopygids. Adults were distinguished
from juveniles based on the convexity of the parasphenoid
and frontal bone, with adults achieving straighter margins
(Figs 4, 5). Radiographs were developed on Kodak diagnostic
film (Ektascan EM-1) and analysed with the aid of an Olym-
pus SZX12 dissecting microscope. Distinct landmarks iden-
tified along margins of bones were digitized using tpsDig
1.37 (Rohlf, 2003) and the distances between them calculated.
Neurocranium measurements include: neurocranium length
(NL), from ventro-posterior margin of basioccipital to anterior
margin of mesethmoid; neurocranium depth (ND), from dorso-
posterior margin of supraoccipital to ventro-posterior margin
of basioccipital; and basioccipital length (BaL), from ventro-
posterior margin to ventro-anterior margin of basioccipital.
Meristic protocols follow Albert & Fink (1996). Skeletal
counts obtained from 146 radiographs include: precaudal ver-
tebrae (PCV), which include those of the Weberian appar-
atus and are a good measure of body cavity length (Albert,
2001); and anal-fin rays (AFR). Additional meristics include:
pectoral-fin rays (P1R); lateral line scales (LLS), from pos-
terior edge of opercle to end of tail; scales above lateral line
(SAL), from a point three times head length back from the tip
of the snout at the lateral line to dorsomedial margin; scales
below lateral line (SBL), from same point as SAL to base of
anal-fin pterygiophores, (7) scales over pterygiophores (SOP),
from same point as SAL at base of anal-fin pterygiophores to
anal fin ventral border.
414 Kevin G. Hulen et al.
Figure 6 Measurements used for morphometric analysis of Sternopygus. Body proportions shown for S. macrurus (ANSP 172171). (a) Body,
lateral view, (b) Head, lateral view, (c) Head, dorsal view, (d) Head, ventral view. Scale bars equal 10 mm.
Figure 7 Articulated suspensorium and pectoral girdle of S. macrurus (MCP 32254), in lateral view. Cartilage represented by gray shading.
(a) Suspensorium, (b) Pectoral girdle. Abbreviations: Max, maxilla; Den, dentary; Ang, anguloarticular; Ret, retroarticular; Mes,
mesopterygoid; Met, metapterygoid; Sym, symplectic; Hyo, hyomandibula; Int, interopercle; Pre, preopercle; Sub, subopercle; Ope,
opercle; Pos, posttemporal; Sup, supracleithrum; Cle, cleithrum; Cor, coracoid; Sca, scapula; FPr, first pectoral ray; PrR, proximal
radials. Scale bar equals 10 mm.
Osteological data were obtained from 33 cleared and
stained specimens representing 19 lots of sternopygid spe-
cies. One large and small mature specimen of each species
was cleared and stained using the enzyme technique of Taylor
& Van Dyke (1985) with reagent concentrations and reaction
times adjusted for each specimen. The neurocranium, sus-
pensorium, and pectoral girdle were removed from all speci-
mens using standard methods for small teleosts (Weitzman,
1974; Albert, 2001). Bone nomenclature follows Fink & Fink
(1981) for the skeletal system (Fig. 7) and Patterson (1975) for
bony elements of the skull (Fig. 8). Additionally, eight adult
specimens of a single population of S. macrurus from the state
of Apure, Venezuela (LEA 203–298 mm) were cleared and
stained for information on population-level osteological vari-
ation. The morphology used in coding osteological characters
was not noticeably different in these specimens. Specimens
of S. pejeraton and S. aequilabiatus were not available for
osteological examination. For osteological descriptions the
S. aequilabiatus group is represented by S. dariensis.Out-
lines of articulated and disarticulated bones were sketched
with the aid of an Olympus SZX12 dissecting micro-
scope equipped with a camera lucida. Sketches were then
Phylogenetic systematics Sternopygus 415
Figure 8 Neurocranium of S. macrurus (MCP 32254), in lateral view. Foraminae and other non-ossified areas represented by gray shading.
Abbreviations: F. V2–3, foramen of some trigeminal and lateral line nerve rami; F. VII +LL, foramen of facial nerve and lateral line
nerves; F. IX +X, foramen of glossopharyngeal and vagus nerves; SOC, supraorbital canal; MEt, mesethmoid; VEt, ventral ethmoid;
LEt, lateral ethmoid; Vom, vomer; Fro, frontal; PaS, parasphenoid; OrS, orbitosphenoid; PtS, pterosphenoid; SpO, sphenotic;
PrO, prootic; PtO, pterotic; Par, parietal; ExS, extrascapular; EpO, epioccipital; SuO, supraoccipital; ExO, exoccipital; BaO,
basioccipital. Scale bar equals 5 mm.
traced into FLASH MX (Macromedia) to create line art
figures.
Phylogenetic methods
In selecting and coding characters we were guided by the
philosophy that phylogenetic congruence among all obser-
vations is the most reliable method to assess homology
(Patterson, 1982; Eernisse & Kluge, 1993). Outgroup taxa
were selected based on the results of previous research
(Albert, 2001). These include at least one species from each of
the four non-Sternopygus sternopygid genera, and a non-adult
member of a phylogenetically basal species (Parapteronotus
hasemani) from the sister family Apteronotidae. Due to the
derived snout shape of P. hasemani, morphometric measure-
ments of an apteronotid species are reported for ‘Apteronotus
bonaparti’. MacClade 4.03 (Maddison & Maddison, 2000)
was used to construct a matrix containing 66 characters, which
include previously published characters (Albert & Fink, 1996;
Albert, 2001) and new observations. Pigmentation characters
apply to juveniles as well as adults in species paedomorphic
for those characters. Osteological and morphometric charac-
ters apply to morphologically (as opposed to reproductively)
mature specimens. Morphometric and meristic traits were ex-
amined as both continuous and discrete (coded) data.
Relative mean, median or modal adult trait values were
coded into multiple alternative character states and the cod-
ing scheme was selected that exhibited maximum congruence
with the distributions of other characters in the data matrix
(Westneat, 1993; Wiens, 2000). The alternative coding sche-
mes differ in the number of states and range cutoffs. Tree
statistics calculated from character states optimized unam-
biguously on a strict consensus topology of all the data, and
interpreting character state changes on ‘hard’ polytomies (mul-
tiple speciation events). Congruence was assessed by values
of the ‘rescaled consistency index’, which is not influenced by
symplesiomorphies or autapomorphies (Farris, 1989). All
characters were coded as unordered except: the multi-state
morphometric characters (char. 6, 7, 12, 30, 55), ratio of
opercle dorsal margin (char. 46), rib count (char. 60), number
of postcleithrae (char. 61) and body cavity length (char. 62).
The following options were employed in maximum parsi-
mony (MP) analyses using PAUP 4.0b10 (Swofford, 2003).
Heuristic searches were used with options set to save all min-
imum length trees. Tree-bisection-reconnection (TBR) branch
swapping was performed with and without the steepest des-
cent option. Bremer decay values (Bremer, 1994) were calcu-
lated using TreeRot (Sorenson, 1999) to generate constraint
files for PAUP. Three support indices (sensu Wilkinson et al.,
2003) are reported for each internal node including branch
lengths as character state changes (steps) of unambiguous op-
timization. Diagnoses were generated using the export branch-
list option in the MacClade software with all characters op-
timized unambiguously on the single most parsimonious tree
topology.
Results
Descriptive morphology
Characters of pigmentation are listed first, followed by those
of body proportions, neurocranium, oral jaws, suspensorium,
pectoral girdle, and axial skeleton. Figures 2–6 and Tables 3–5
display body proportions and counts, and Figures 7–16 dis-
play osteology, used in coding characters for the phylogenetic
analysis.
Pigmentation
1. Body colour. 0: dark, with saddles or pale lateral stripe.
1: uniformly pale, no saddles or pale lateral stripe.
2. Pale lateral stripe. 0: absent from ontogeny. 1: present in
juveniles. 2: present in juveniles and adults.
3. Dark saddles. 0: absent. 1: present in juveniles.
4. Dark humeral region. 0: no dark pigments. 1: well defined
black patch, sharp margins.
416 Kevin G. Hulen et al.
LEA AFL CA %
Species n range mean n range mean n range mean
A. blax 4 170–373 231 4 140–304 188 3 27.2–35.3 30.8
A. bonaparti 6 152–300 216 6 129–264 190 4 8.0–15.2 11.3
D. conirostris 5 150–224 197 4 139–195 173 3 31.4–44.7 37.5
S. aequilabiatus 16 160–390 228 16 134–335 189 12 11.0–29.0 17.8
S. arenatus 6 195–455 329 6 153–380 261 4 10.9–23.1 17.1
S. astrabes 22 81–177 121 22 64–148 102 16 23.4–43.2 34.0
S. branco 13 171–353 265 13 141–309 231 13 24.4–41.3 32.9
S. macrurus 76 140–455 265 66 114–405 224 47 10.6–28.7 18.5
S. obtusirostris 16 167–520 291 16 120–465 252 10 9.0–25.1 15.7
S.sp. ‘cau’ 2 200–230 215 2 171–202 187 2 14.3–33.5 23.9
S. xingu 5 162–446 283 5 134–371 236 3 13.3–27.2 21.0
Total 171 160 117
BD % BW % HL %
Species n range mean n range mean n range mean
A. blax 4 10.3–12.2 11.2 4 5.0–7.3 6.3 4 14.5–16.7 15.5
A. bonaparti 6 10.1–12.3 10.9 6 4.4–5.4 5.0 6 12.6–14.7 13.9
D. conirostris 4 9.8–11.9 10.8 4 4.2–5.4 4.9 4 11.6–12.3 11.9
S. aequilabiatus 16 10.5–13.8 12.1 16 5.3–6.3 5.9 16 13.4–16.1 15.1
S. arenatus 2 12.4–13.3 12.9 2 5.8–5.9 5.9 6 13.2–16.8 14.6
S. astrabes 22 10.4–12.4 11.5 22 4.6–6.6 5.5 22 11.7–14.7 13.3
S. branco 13 8.3–10.9 9.3 13 4.2–6.4 4.5 13 11.4–14.3 12.6
S. macrurus 66 10.3–15.2 12.8 66 4.8–8.3 6.1 66 12.5–16.8 14.3
S. obtusirostris 16 9.5–12.2 10.6 16 3.9–6.0 4.7 16 10.4–12.7 11.7
S.sp. ‘cau’ 2 9.4–9.8 9.6 2 4.4–4.8 4.6 2 10.3–11.3 10.8
S. xingu 5 13.4–16.1 14.4 5 6.2–8.2 6.8 5 16.2–19.6 17.2
Total 156 156 160
HL PO % PR %
Species n range mean n range mean n range mean
A. blax 4 26.6–62.2 36.4 4 39.4–42.1 40.6 4 44.9–48.2 47.0
A. bonaparti 6 22.3–42.3 29.9 6 54.9–60.5 57.9 6 36.3–39.5 37.9
D. conirostris 4 17.4–26.5 23.2 4 56.8–58.6 57.3 4 32.8–36.2 33.7
S. aequilabiatus 16 23.5–55.8 34.2 16 55.9–60.0 58.7 16 30.6–36.0 33.1
S. arenatus 6 32.7–62.2 47.5 6 56.3–59.1 57.6 6 32.7–37.5 35.2
S. astrabes 22 11.2–23.4 16.0 22 48.2–59.5 54.2 22 28.9–35.5 32.7
S. branco 13 24.4–41.3 32.9 13 50.8–54.9 53.0 13 36.1–40.6 38.4
S. macrurus 66 18.2–63.0 37.8 66 51.6–60.8 56.5 66 30.8–39.3 36.1
S. obtusirostris 16 20.1–54.2 33.6 16 53.4–61.2 57.3 16 31.0–35.9 34.0
S.sp. ‘cau’ 2 22.5–23.8 23.2 2 52.9–53.8 53.3 2 35.1–35.3 35.2
S. xingu 5 26.3–75.6 49.3 5 54.7–59.3 56.7 5 31.9–33.9 33.0
Total 160 160 160
Table 3 Morphometrics for 10 sternopygid and one apteronotid species. Abbreviations are referenced in Materials and methods. All
measurements expressed as a per cent of head length, except HL%, BD %, BW % and CA %, which are reported as a per cent of LEA.
Body proportions
5. Body depth. 0: slender, mean BD 9–11% LEA. 1: deep,
mean BD 12–15% LEA.
6. Head length. 0: short, mean HL 10–13% LEA. 1: long,
mean HL 14–15% LEA. 2: very long, mean 16–17%
LEA.
7. Head depth. 0: deep, mean HD 76–78% HL. 1: moderate,
mean HD 69–75% HL. 2: slender, mean 60–67% HL.
8. Head width. 0: narrow, mean HW 37–41% HL. 1: wide,
mean HW 42–47% HL.
9. Preorbital length. 0: snout long, mean PR 36–47% HL.
1: snout short, mean PR 30–35% HL.
Phylogenetic systematics Sternopygus 417
ED % IO % NN %
Species n range mean n range mean n range mean
A. blax 4 13.9–16.8 15.6 4 15.3–18.5 16.7 4 8.6–11.3 10.2
A. bonaparti 6 6.6–10.8 8.0 6 15.1–18.7 17.3 6 11.9–14.7 13.0
D. conirostris 4 9.1–12.1 10.2 4 21.1–23.8 22.1 4 3.4–4.0 3.7
S. aequilabiatus 16 6.8–9.8 8.6 16 14.4–21.7 17.5 16 10.2–14.4 12.2
S. arenatus 2 7.4–9.8 8.6 2 22.4–33.0 27.7 2 22.0–22.9 22.5
S. astrabes 22 13.8–19.5 15.5 22 23.8–30.4 26.1 17 14.5–19.8 17.3
S. branco 13 9.8–13.5 10.7 13 22.2–25.7 24.2 13 14.9–17.4 16.0
S. macrurus 66 7.5–14.6 10.3 66 17.6–31.7 25.5 66 8.3–17.9 13.9
S. obtusirostris 16 10.1–13.5 11.9 16 22.7–28.3 24.9 16 13.5–20.0 16.9
S. sp. ‘cau’ 2 12.0–12.2 12.1 2 24.8–24.9 24.8 2 14.3–18.7 16.5
S. xingu 5 6.7–12.2 9.4 5 16.7–22.4 19.2 5 11.4–15.6 13.3
Total 156 156 151
MW % BO % HD %
Species n range mean n range mean n range mean
A. blax 4 8.6–12.4 10.8 4 17.1–30.9 22.5 4 56.3–62.0 59.8
A. bonaparti 6 13.1–21.3 16.5 6 19.7–24.0 21.7 6 73.1–79.4 75.5
D. conirostris 4 14.7–17.2 16.5 4 22.4–37.7 30.4 4 74.3–83.1 78.0
S. aequilabiatus 16 11.1–16.8 13.2 16 20.0–27.8 23.8 16 59.5–67.7 62.0
S. arenatus 2 11.0–13.8 12.4 2 15.7–16.5 16.1 2 68.8–73.4 71.1
S. astrabes 22 12.8–20.9 15.5 22 28.9–48.0 37.1 22 66.4–77.4 72.3
S. branco 13 12.3–13.9 12.9 13 25.9–31.1 28.2 13 57.8–68.4 64.7
S. macrurus 66 13.4–21.4 16.8 66 25.4–50.0 31.3 66 64.8–80.2 71.3
S. obtusirostris 16 14.4–17.6 15.8 16 25.4–45.3 36.9 16 68.6–79.5 73.8
S.sp. ‘cau’ 2 13.3–13.9 13.6 2 28.0–36.6 32.3 2 68.4–70.2 69.3
S. xingu 5 17.1–19.8 18.5 5 35.2–51.4 42.1 5 65.3–75.7 69.1
Total 156 156 156
HW % PA % P1 %
Species n range mean n range mean n range mean
A. blax 4 37.8–44.7 40.1 4 37.2–57.9 51.4 4 66.7–79.9 71.7
A. bonaparti 6 34.4–39.5 37.3 6 9.6–33.6 22.7 6 91.9–107.4 100.7
D. conirostris 4 42.7–45.4 43.9 4 29.3–59.8 48.4 4 78.9–87.7 83.1
S. aequilabiatus 16 35.9–44.6 38.8 16 40.1–56.3 47.0 16 43.7–53.3 48.8
S. arenatus 2 42.8–47.1 44.9 2 61.6–67.0 64.3 6 40.0–56.0 45.0
S. astrabes 22 37.5–51.9 46.4 22 14.3–52.6 39.4 22 43.6–67.8 58.0
S. branco 13 36.1–43.4 39.8 13 30.3–38.2 33.8 13 50.0–57.2 53.2
S. macrurus 66 33.5–59.4 46.7 66 32.7–65.1 47.6 64 37.8–64.7 48.6
S. obtusirostris 16 36.7–50.7 42.9 16 29.0–50.9 37.1 16 45.8–60.5 52.3
S. sp. ‘cau’ 2 44.9–45.0 44.9 2 36.9–41.2 39.0 2 52.4–57.1 54.8
S. xingu 5 38.8–47.3 43.4 5 32.7–42.4 36.6 5 36.8–43.0 39.7
Total 156 156 158
Table 3 Continued.
10. Snout profile dorsal margin. 0: straight or slightly
convex (Fig. 2a–e, 4). 1: strongly concave
(Fig. 2f–i).
11. Interorbital distance. 0: narrow, mean IO 17–24% HL.
1: wide, mean IO 25–28% HL.
12. Internarial distance. 0: short, mean NN 4–13% HL.
1: moderate, mean NN 14–18% HL. 2: long, mean 18–
23% HL.
13. Mouth width. 0: narrow; mean MW 11–14% HL.
1: broad; mean MW 16–19% HL.
14. Gape. 0: larger or equal to eye diameter. 1: smaller than
eye.
15. Eye diameter. 0: small, mean ED 8–11% HL. 1: large,
mean ED 12–16% HL.
16. Orbital margin. 0: covered by epidermis (Fig. 2i). 1: free
(Fig. 2a–h).
418 Kevin G. Hulen et al.
Figure 9 Neurocrania of seven sternopygids, in lateral view. Shading as in Figure 8. (a) S. branco (MCP 32245), (b) S. obtusirostris
(MCP T-032), (c) S. astrabes (MCP 32235), (d) S. xingu (USNM 218830; adapted from Albert & Fink, 1996; Fig. 4.), (e) S. aequilabiatus
(NRM 27746), (f) A. blax (INPA 18451), (g) D. conirostris (WGRC 21.020999). Scale bars equal 5 mm.
NL ND % BaL %
Species n range mean range mean range mean
A. blax 4 16.2–16.5 16.3 25.8–29.2 27.6 12.7–18.4 16.3
D. conirostris 3 16.5–16.6 16.6 27.6–29.9 28.6 19.4–23.8 21.6
S. aequilabiatus 12 16.0–16.8 16.5 29.9–35.1 32.8 12.7–18.9 15.6
S. arenatus 4 16.1–16.6 16.4 31.6–38.0 35.5 10.8–22.8 17.9
S. astrabes 13 16.0–16.8 16.6 33.5–39.1 35.7 16.3–23.6 19.5
S. branco 9 16.2–16.6 16.4 31.7–34.1 33.0 14.2–18.7 16.2
S. macrurus 11 16.3–16.9 16.5 32.4–38.3 36.4 13.9–18.2 15.8
S. obtusirostris 10 16.0–16.8 16.4 35.5–39.1 37.2 16.2–24.0 19.1
S. sp. ‘cau’ 2 16.3–16.7 16.5 36.0–36.2 36.1 18.4–19.9 19.1
S. xingu 3 16.3–16.6 16.5 28.9–34.2 31.9 16.3–18.7 17.2
Total 71
Table 4 Neurocranium measurements for 10 sternopygid species. Abbreviations are referenced in Materials and
methods. Neurocranium depth and basioccipital length are expressed as a per cent of neurocranium length.
17. Infraorbitals 3–4. 0: tube shaped. 1: enlarged, bony.
18. Infraorbital canals. 0: small and tubular. 1: large, open
cylinders.
19. Branchial opening. 0: wide, mean BO 31–40% HL.
1: narrow, mean BO 16–30% HL.
Neurocranium
20. Ethmoid region. 0: well ossified (Fig. 8, 9a–e, 9g). 1: less
ossified (Fig. 9f).
21. Ventral ethmoid. 0: short (Fig. 9f, g). 1: long (Fig. 8, 9a–e).
22. Mesethmoid. 0: gracile in lateral aspect (Fig. 9f, g).
1: robust (Fig. 8, 9a–e).
23. Lateral ethmoid cartilage. 0: remote from maxilla. 1: con-
tacting maxilla.
24. Lateral ethmoid ossification. 0: independent ossification
(Fig. 8, 9a–e). 1: co-ossified with frontal (Fig. 9f, g).
25. Lateral ethmoid anterior process. 0: short, not extending
to dorsal margin of vomer (Fig. 9f). 1: long, extending
laterally to dorsal margin of vomer (Fig. 8, 9a–e, 9g).
26. Vomer. 0: short, broad, length less than five times width
at midlength. 1: long, narrow, length more than five times
width.
27. Antorbital process of frontal. 0: absent. 1: present (Fig. 8,
9a–g).
Phylogenetic systematics Sternopygus 419
PCV P1R AFR LLS SAL SBL SOP
Species n range med. n range med. n range med. n range med. n range med. n range med. n range med.
A. blax 6 14–15 15 8 17–19 19 3 175–210 204 4 116–156 137 4 10–15 14 4 5–9 7 4 8–15 11
A. bonapartii NA NA–NA NA 6 16–18 17 NA NA–NA NA NA NA–NA NA 5 6–7 6 5 12–14 13 5 4–6 4
D. conirostris 5 14–14 14 5 16–18 17 NA NA–NA NA NA NA–NA NA 5 11–17 14 5 20–22 22 5 9–12 10
S. aequilabiatus 16 23–25 24 20 14–17 17 16 228–310 284 18 200–305 236 18 12–24 17 18 7–13 9 18 10–16 13
S. arenatus 6 21–24 21 9 15–17 15 1 215–215 215 5 179–245 221 6 15–16 16 6 7–9 8 6 15–16 16
S. astrabes 29 18–19 19 23 15–17 16 19 170–298 200 17 185–235 224 19 11–18 15 19 9–14 12 19 10–16 14
S. branco 12 25–27 26 13 12–15 13 12 250–340 309 10 280–340 299 10 17–26 19 10 13–17 16 10 13–20 17
S. macrurus 52 24–28 26 95 13–17 15 44 195–300 256 45 115–340 222 55 12–22 16 55 5–20 9 55 9–17 13
S. obtusirostris 14 22–26 25 20 15–17 15 14 195–312 285 18 190–280 240 18 15–21 18 18 7–13 11 18 14–19 17
S. sp. ‘cau’ 2 24–24 24 2 15–15 15 2 288–295 292 2 285–316 301 2 17–19 18 2 10–10 10 2 14–16 15
S. xingu 4 28–29 29 6 12–15 12 4 292–321 312 3 155–205 192 3 14–16 15 3 6–8 7 3 14–19 18
Total 146 207 115 122 145 145 145
Table 5 Meristics for 10 sternopygid and one apteronotid species. Abbreviations are referenced in Materials and methods.
Figure 10 Dorsal (left) and ventral (right) views of the premaxilla for
seven Sternopygus species. (a) S. branco (MCP 32243),
(b) S. obtusirostris (MCP 32262), (c) S. astrabes
(MCP 32235), (d) S. macrurus (MCP 32256),
(e) S. arenatus (MCZ 58604), (f) S. xingu (UMMZ 228961),
(g) S. aequilabiatus (NRM 27746). Scale bars equal 1 mm.
Figure 11 Maxilla for nine sternopygids, in lateral view. (a) S. branco
(MCP 32243), (b) S. obtusirostris (MCP 32262),
(c) S. astrabes (MCP 32235), (d) S. macrurus (MCP 32256),
(e) S. arenatus (MCZ 58604), (f) S. xingu (UMMZ 228961),
(g) S. aequilabiatus (NRM 27746), (h) A. blax
(INPA 18451), (i) D. conirostris (WGRC 27.020299). Scale
bars equal 1 mm.
28. Frontal margin. 0: convex dorsal to lateral ethmoid (Fig. 8,
9a–c). 1: straight dorsal to lateral ethmoid (Fig. 9d–g).
29. Sphenotic spine. 0: absent (Fig. 8, 9a–e). 1: present
(Fig. 9f, g).
30. Neurocranium depth. 0: deep, mean ND 35–50% NL.
1: moderate, mean ND 30–35% NL. 2: slender, mean ND
25–30% NL.
31. Parasphenoid shape anterior portion. 0: ventral margin
straight in adults. 1: ventral margin convexity retained in
adults.
32. Parasphenoid width at prootic foramen. 0: narrower than
PaS at PtS-OrS junction. 1: as wide or broader than PaS
at PtS-OrS junction.
33. Basioccipital length. 0: Short, mean BaL 15–18% NL.
1: Long, mean BaL 18.1–22% HL.
Oral jaws
34. Premaxillary teeth. 0: conical, arranged in 1–2 regular
rows. 1: villiform, arranged in multiple irregular rows
(Fig. 10a–g).
35. Premaxilla shape. 0: robust, rectangular in dorsal view
(Fig. 10f). 1: gracile, triangular in dorsal view (Fig. 10a–
e, g).
36. Maxilla width. 0: midlength as wide as broadest area
near palatine articulation (Fig. 11a–e, h). 1: midlength
420 Kevin G. Hulen et al.
Figure 12 Dentary, anguloarticular, and retroarticular for nine sternopygids, in lateral view. (a) S. branco (MCP 32243), (b) S. obtusirostris
(MCP 32262), (c) S. astrabes (MCP 32235), (d) S. macrurus (MCP 32256), (e) S. arenatus (MCZ 58604), (f) S. xingu (UMMZ 228961),
(g) S. aequilabiatus (NRM 27746), (h) A. blax (INPA 18451), (i) D. conirostris (WGRC 27.020299). Scale bars equal 1 mm.
half width of area near palatine articulation (Fig. 11f,
g, i).
37. Meckel’s cartilage ossification. 0: cartilaginous in adults.
1: dorsal margin ossified completely in adults.
38. Dentary teeth. 0: present (Fig. 12a–h). 1: absent (Fig. 12i).
39. Retroarticular anterior process. 0: absent (Fig. 12a–c).
1: present (Fig. 12d–i).
40. Anguloarticular ascending process. 0: elongate, extends
to or beyond dorsal margin of anguloarticular (Fig. 12a–
g). 1: truncate, does not extend beyond dorsal margin of
anguloarticular (Fig. 12h, i).
Suspensorium
41. Mesopterygoid process. 0: thin, not contacting neurocra-
nium (Fig. 13i). 1: robust strut; contacting neurocranium
(Fig. 13a–h).
42. Mesopterygoid dentition. 0: absent. 1: present.
43. Hyomandibular trigeminal nerve. 0: preopercular-
mandibular ramus of trigeminal nerve emerging from
descending limb of hyomandibula (Fig. 14h, i).
1: preopercular-mandibular ramus emerging from anterior
shelf of hyomandibula (Fig. 14a–g).
44. Hyomandibular lateral ridge. 0: long, extending close
to ventral margin of hyomandibula (Fig. 14a, b, d–i).
1: short, remote from ventral margin of hyomandibula
(Fig. 14c).
45. Opercle posterior margin. 0: convex, evenly rounded (Fig.
15d, e, h, i). 1: straight, incompletely ossified (Fig. 15a–c,
f, g).
46. Opercle, dorsal margin. 0: long, 76–90% distance of
anterio-ventral margin (Fig. 15e–i). 1: moderate, 70–
75% distance of anterio-ventral margin (Fig. 15a, d). 2:
short, 67–79% distance of anterio-ventral margin (Fig.
15b, c).
47. Interopercle ventral margin. 0: entire (Fig. 15a–c, e–i).
1: convex (15d).
48. Gill rakers. 0: simple, attached to gill arches. 1: complex
(see text), separated by unmineralized tissue.
Pectoral girdle
49. Scapula foramen. 0: scapula small, foramen as notch in
coracoid (Fig. 16a–g). 1: scapula large, with large foramen
included (Fig. 16h, i).
50. Supracleithrum. 0: long and slender (Fig. 16b–h). 1: short
and robust (Fig. 16a, i).
51. Posttemporal. 0: fused with supracleithrum (Fig. 16h, i).
1: not fused with supracleithrum (Fig. 16a–g).
52. Posttemporal length. 0: short, less than 50% length dor-
soposterior margin of cleithrum (Fig. 16a–f, h, i). 1: long,
greater than 75% length dorsoposterior margin of clei-
thrum (Fig. 16g).
53. Posttemporal and supracleithral canal bones. 0: small,
canal and non-canal portions equal width (Fig. 16a, c–g).
1: expanded, canal portions wider than non-canal
(Fig. 16b, h, i).
54. Pectoral distal radials. 0: 1–4 independent (Fig. 16a–c).
1: 3 +4 fused (Fig. 16d–i).
55. Pectoral fin. 0: long, mean P1 61–101% HL. 1: short,
mean P1 51–60% HL. 2: very short, mean P1 40–50%
HL.
56. Pectoral fin rays. 0: many, mode 17–19. 1: few, mode
13–16.
Axial skeleton
57. Intermuscular bones. 0: slightly branched. 1: highly
branched.
58. Dorsal myorhabdoid bones. 0: loosely packed and lightly
ossified. 1: densely packed and heavily ossified.
Phylogenetic systematics Sternopygus 421
Figure 13 Quadrate, mesopterygoid, and metapterygoid for nine
sternopygids, in lateral view. (a) S. branco (MCP 32243),
(b) S. obtusirostris (MCP 32262), (c) S. astrabes (MCP
32235), (d) S. macrurus (MCP 32256), (e) S. arenatus
(MCZ 58604), (f) S. xingu (UMMZ 228961),
(g) S. aequilabiatus (NRM 27746), (h) A. blax (INPA
18451), (i) D. conirostris (WGRC 27.020299). Scale bars
equal 5 mm.
59. Rib length. 0: 70–75% depth of body cavity. 1: 80–100%
depth of body cavity.
60. Rib count. 0: mode 13–20. 1: mode 8–12. 2: mode 6–7.
61. Postcleithrae. 0: three. 1: one or two. 2: zero.
62. Body cavity. 0: moderately long, mode PCV 18–19.
1: long, mode PCV 21–29. 2: short, mode PCV 11–15.
63. Anterior vertebrae. 0: compressed. 1: not compressed (see
text).
64. Anal-fin rays. 0: few, median AFR 200–240. 1: many,
median AFR 250–320.
65. Anal-fin ray structure. 0: all or most rays branched about
half way from base to tip. 1: all rays entirely unbranched
from base to tip.
66. Caudal rod. 0: regenerates as unossified cartilage. 1: re-
generates as ossified bar.
Figure 14 Hyomandibula for nine sternopygids, in lateral view.
(a) S. branco (MCP 32243), (b) S. obtusirostris
(MCP 32262), (c) S. astrabes (MCP 32235), (d) S. macrurus
(MCP 32256), (e) S. arenatus (MCZ 58604), (f) S. xingu
(UMMZ 228961), (g) S. aequilabiatus (NRM 27746),
(h) A. blax (INPA 18451), (i) D. conirostris
(WGRC 27.020299). Scale bars equal 1 mm.
Interrelationships of Sternopygus
Interrelationships of Sternopygus inferred in this study are de-
picted in Fig. 17, with Branch Lengths (BL) and Bremer Decay
Indices (BDI) for all nodes provided in Table 7. Diagnoses for
seven clades are provided in Appendix 2.
Sternopygus is diagnosed in having: gape larger and
sometimes equal to eye diameter (char. 14); enlarged bony in-
fraorbitals 3–4 (char. 17); robust mesethmoid (char. 22); long
ventral ethmoid (char. 21); lateral ethmoid cartilage contacting
maxilla (char. 23); anterior process of lateral ethmoid long, ex-
tending laterally to and sometimes beyond the dorsal margin
of the vomer (char. 25); neurocranium depth moderate, mean
30.1–34.9% NL (char. 30); triangular premaxilla (char. 35);
dorsal margin of Meckels cartilage completely ossified to an-
guloarticular (char. 37); robust mesopterygoid process contact-
ing the neurocranium (char. 41); preopercular-mandibular ra-
mus of trigeminal nerve emerging anterior to the hyomandibu-
lar shelf (char. 43); length of opercle dorsal margin moder-
ate, as measured point-to-point, 70–75% distance of anterio-
ventral margin (char. 46); gill rakers separated from gill arches
by unmineralized tissue, not attached to ceratobranchials and
epibranchials of all four branchial arches, hypobranchials of
first and second arches, and the pharyngobranchials of fourth
arch (char. 48). Each raker formed from three separate ossific-
ations, two large elongate lateral ossifications, and a smaller
(ovoid) central ossification; posttemporal and supracleithrum
not fused (char. 51); pectoral fin length short, mean 51–60%
422 Kevin G. Hulen et al.
Figure 15 Opercular series for nine sternopygids, in lateral view. (a) S. branco (MCP 32243), (b) S. obtusirostris (MCP 32262), (c) S. astrabes
(MCP 32235), (d) S. macrurus (MCP 32256), (e) S. arenatus (MCZ 58604), (f) S. xingu (UMMZ 228961), (g) S. aequilabiatus
(NRM 27746), (h) A. blax (INPA 18451), (i) D. conirostris (WGRC 27.020299). Scale bars equal 5 mm.
HL (char. 55); few pectoral fin rays, mode 13–16 (char. 56);
anterior vertebrae not compressed (char. 63); anal-fin rays un-
branched from base to tip (char. 65) (Clade A: Appendix 2;
Fig. 17).
Sternopygus branco, sister taxon to all other species of
Sternopygus (Appendix 2; Fig. 17), is distinct in having: a
uniformly pale body with no dark saddles or pale lateral stripe
(char. 1); a slender head, mean HD 60–67% HL (char. 7); a
short and robust supracleithrum (char. 50).
Sternopygus sp. ‘cau’ is sister taxon to clade containing S.
astrabes and S. obtusirostris (Appendix 2; Fig. 17) and an un-
described species identified by the presence of a well defined
dark humeral spot with sharp margins (char. 4). Sternopy-
gus sp. ‘cau’ shares with S. astrabes and S. obtusirostris the
presence of dark saddles as juveniles (char. 3), and a large eye,
mean ED 12–16% HL (char. 15).
Sternopygus obtusirostris and S. astrabes are sister taxa
(Clade D: Appendix 2; Fig. 17) sharing the following charac-
ters: short head, mean HL 10–13% LEA (char. 6); moderate
head depth, mean HD 69–75% HL (char. 7); internarial dis-
tance long, mean NN 19–23% HL (char. 12); broad mouth,
mean MW 16–19% HL (Char. 13); short pectoral fin, mean
P1 51–60% HL (char. 55). Sternopygus obtusirostris is distin-
guished from S. astrabes by not having a pale lateral stripe as a
juvenile (char. 2). Sternopygus astrabes is distinguished from
other species of Sternopygus in having a moderately long body
cavity, mode PCV 18–19 (char. 62); short hyomandibular lat-
eral ridge not descending to ventral margin of hyomandibula
(char. 44); many anal-fin rays, median AFR 250–320
(char. 64).
Sternopygus macrurus is the sister taxon to the clade
containing the remaining species of Sternopygus (Appendix
2; Fig. 17) sharing with them the following characters: deep
body, mean BD 12–15% LEA (char. 5); long head, mean HL
14–15% LEA (char. 6); pectoral distal radials 3 and 4 fused
(char. 54); very short pectoral fin, mean P1 40–50% HL (char.
Phylogenetic systematics Sternopygus 423
Figure 16 Pectoral girdle for nine sternopygids, in lateral view. (a) S. branco (MCP 32243), (b) S. obtusirostris (MCP 32262), (c) S. astrabes
(MCP 32235), (d) S. macrurus (MCP 32256), (e) S. arenatus (MCZ 58604), (f) S. xingu (UMMZ 228961), (g) S. aequilabiatus
(NRM 27746), (h) A. blax (INPA 18451), (i) D. conirostris (WGRC 27.020299). Scale bars equal 5 mm.
1–10 11–20 21–30 31–40 41–50 51–60 61–66
Parapteronotus hasemani 0000000000 0101000010 0000000002 00100000 ?0 0000000000 0000000000 000100
Archolaemus blax 0000012000 0111110110 0001011112 1001000001 1100000010 0010001011 120001
Distocyclus conirostris 1000000111 0001000111 0000101112 0011010101 1000000011 0011001012 120101
Eigenmannia virescens 0000 ?00110 ???1000111 0000001010 0011000000 01?0010010 0011??1012 120001
Rhabdolichops 0000000110 ???1001111 0000001010 0011000001 1110110010 0001 ?11112 120101
electrogrammus
Sternopygus branco 1000002000 0100011110 1110101001 0001101010 1110110101 1010110000 211111
Sternopygus sp. ‘cau’ 0211001110 110011 ??0? ???????0?0??1??????? ?????????? ????11 ??00 ?11111
Sternopygus obtusirostris 0010001110 1210111100 1110101000 1011101010 1110120100 1000110000 211111
Sternopygus astrabes 0210001110 1210111100 1110101000 1011101010 1111120100 1000110000 201011
Sternopygus macrurus 0201111100 1110011100 1110101000 0001101000 1110011100 1001210000 211111
Sternopygus arenatus 0200111110 1200011110 1110111100 0001101000 1110000100 1001210000 211011
Sternopygus xingu 0201121111 0110011100 1111111101 0101011000 1110100100 1001210000 211111
Sternopygus aequilabiatus 0200112011 0100011110 1110111101 0101111000 1110100100 1101210000 211111
Eigenmannia virescens also coded from Eigenmannia sp., MBUCV 7509 (Mago-Leccia, 1978, Figs 10–18).
Parapteronotus hasemani coded from mature females and non-mature males. Parapteronotus hasemani: head length (HL%), A. bonaparti =0; head width
(HW%) juveniles and adults =0; also A. bonaparti juveniles and adults; gape juveniles and adults =0; also A. bonaparti juveniles and adults; vomer with
no ascending process; basioccipital length (BaL) juveniles =0; also A. bonaparti juveniles and adults. Rhabdolichops electrogrammus: head length (HL%),
R. sp. ‘nig’ =0; opercle ratio of long axes, R. sp. ‘nig’. Sternopygus macrurus also coded from MBUCV 7515 (Mago-Leccia, 1978, Figs 24–28). Sternopygus
xingu, hyomandibular lateral ridge UMMZ 228961, c. 250 mm.
Table 6 Matrix of 66 characters coded for seven Sternopygus species, and five outgroup taxa including four sternopygids and one
apteronotid. Missing data indicated by ‘?.’ Character descriptions are referenced in Descriptive morphology.
424 Kevin G. Hulen et al.
Figure 17 Interrelationships of Sternopygus species inferred from
maximum parsimony analysis of 66 characters coded from
features or pigmentation, body proportions, meristics and
osteology. Terminal taxa include eight species of
Sternopygus, four other sternopygid species and one
apteronotid species. The topology is a single most
parsimonious tree, with 127 steps, from data in Table 2
(CI =0.58, RI =0.70, RC =0.41). Letters adjacent to
nodes represent clades listed in Appendix 2.
Clade Name BL BDI
ASternopygus 17 15
B unnamed clade 4 2
C unnamed clade 2 2
DS. obtusirostris group 2 2
E unnamed clade 4 3
F unnamed clade 3 2
GS. aequilabiatus group 5 4
Table 7 Clade names and support indices for Sternopygus species.
Clade names from Fig. 17. The topology is a single most
parsimonious tree, with 127 steps, from data in Table 2
(CI = 0.58, RI = 0.70, RC = 0.41). Steps calculated for
polytomies assuming hard-polytomy option. BL, Branch
length; BDI, Bremer Decay Index.
55). Sternopygus macrurus is distinguished in having: a well-
defined dark humeral spot with sharp margins (char. 4); broad
mouth, MW 16–19% HL (char. 13); ventral margin of intero-
percle convex (char. 47).
Sternopygus arenatus is the sister taxon to the clade con-
taining S. xingu and the S. aequilabiatus species group (Ap-
pendix 2; Fig. 17), sharing with them the following characters:
long narrow vomer, length more than five times width (char.
26); frontal margin straight at the point dorsal to lateral ethmoid
(char. 28); dorsal margin of opercle long, 76–90% distance of
anterio-ventral margin (char. 46). Sternopygus arenatus is dis-
tinguished in having a long internarial distance, mean NN
18.1–23% HL (char. 12) and few anal-fin rays, median AFR
200–240 (char. 64).
Sternopygus xingu and the S. aequilabiatus species group
are sister taxa (Clade G: Appendix 2; Fig. 17), sharing the fol-
lowing characters: dorsal margin of the snout profile strongly
concave (char. 10); narrow interorbital distance, IO 17–24%
HL (char. 11); moderate neurocranium depth, ND 30–35%
NL (char. 30); width of parasphenoid at a vertical with the an-
terior margin of the prootic foramen as broad or broader than
width of parasphenoid at vertical with the pterosphenoid –
orbitosphenoid junction (char. 32); width of maxilla at its
midlength narrow, less than or equal to half the width of
the maxillary at area near palatine articulation (char. 36).
Sternopygus xingu is distinguished in having: a well-defined
dark humeral spot with sharp margins (char. 4); very long
head, HL 16–17% LEA (char. 6); broad mouth, MW 16–
19% HL (char. 13); lateral ethmoid co-ossified with frontal
(char. 24); premaxilla rectangular and robust from dorsal view
(char. 35).
The S. aequilabiatus species group is characterized in
having: a slender head, HD 60–70% HL (char. 7); narrow head,
HW 37–41% HL (char. 8); and long post-temporal, greater than
75% dorso-posterior margin of cleithrum (char. 52).
Key to the adults of Sternopygus
species
1a. Dorsal margin of snout profile straight or convex ......2
1b. Dorsal margin of snout profile strongly concave .......6
2a. Body uniformly coloured with pigmentation; pale lateral
stripe along the base of the anal fin pterygiophores; head
depth (HD) 69–79% head length (HL)................3
2b. Body colour uniformly pale with no pigmentation or pale
lateral stripe; HD 58–68% HL ............... S. branco
3a. Eye diameter large, 12–16% HL; pectoral fin length (P1)
50–60% HL ....................................... 4
3b. Eye diameter small, 7–15% HL; P1 40–50% HL ...... 5
4a. Two to four dark vertical saddles on body of adults and
juveniles; caudal appendage (CA) 23–43% length to end
of anal fin (LEA); HL 12–15% LEA ........ S. astrabes
4b. Dark vertical bands absent in adults only (LEA >
140 mm); CA 12–25% LEA; HL 10–13% LEA ........
......................................S. obtusirostris
5a. Distinct dark humeral spot; dorsal margin of snout profile
slightly convex; branchial opening large (BO) 25–50%
HL ..................................... S. macrurus
5b. Dark humeral spot absent; dorsal margin of snout profile
straight; BO small, 16–17% HL ............ S. arenatus
6a. Distinct dark humeral spot; P1 37–43% HL; HL 17–20%
LEA; BO 35–51% HL ........................S. xingu
6b. Dark humeral spot absent or very diffuse; P1 44–53% HL;
HL 13–16% LEA; BO 20–28% HL ...................
........................S. aequilabiatus species group
Discussion
Historical biogeography
Miocene tectonism in the northeastern Andes resulted in the
formation of the modern watersheds of northwestern South
Phylogenetic systematics Sternopygus 425
S. branco
S. sp. cau''
S. astrabes
S. obtusirostris
S. macrurus
S. arenatus
S. xingu
S. aequilabiatus group
polytopic
trans-andean
cis-andean g
f
e
b
ad
c
Figure 18 Historical biogeography of Sternopygus. ‘Polytopic’ indicates geographic distribution in both cis- and trans-Andean watersheds.
This topology is consistent with a minimum divergence of Clade E before the most recent uplift of the Andean Eastern Cordillera
c.12Ma.
America, including the Western Amazon, Orinoco, Maracaibo
and Magdalena Basins (Hoorn et al., 1995). Also during
the Middle Miocene the Choco Block underlying the mod-
ern San Juan and Atrato Basins was accreted to the north-
west corner of South America (Duque-Caro, 1990). Before
the Middle Miocene most of the area of the modern Western
Amazon drained northward to a delta located in the area of
the modern Maracaibo Basin, and lowland Amazonian ichthy-
ofaunas were present throughout much of northwestern South
America (Lundberg, 1997; Lundberg, 1998; Lundberg et al.,
1998).
With the uplift of the Eastern Cordillera (c. 11.8–12.2 Ma)
the Amazon-Orinoco, Maracaibo, Magdalena and Atrato-
Pacific Slope regions became isolated (Hoorn et al., 1995).
According to a simple vicariance model this event would have
separated the two (or three) cis-trans Andean sister-taxa pairs
depicted in Fig. 18: S. macrurus (populations in the Choco and
Amazon), Clade F (S. arenatus and Clade G) and/or Clade G
(S. xingu and S. aequilabiatus group). Under this model, the
origin of Clade E (Fig. 18) may therefore be inferred to predate
c. 12 Ma. Such pre-Pleistocene origins of multiple Sternopygus
taxa with cis-trans Andean distributions resemble other groups
of Neotropical fishes for which species-level phylogenies have
been proposed (Vari, 1988; Vari & Weitzman, 1990; Vari, 1995;
Bermingham & Martin, 1998; Martin & Bermingham, 2000;
Albert & Crampton, unpubl. obs.).
As currently recognized, S. macrurus is the most widely
distributed gymnotiform species, and is known from all nine
hydrogeographical regions of tropical South America (Table 1,
Fig. 1a). These include habitats and regions as disparate as the
Pacific slope of the Andes, the arid northeast of Brazil and the
Pampas of Argentina. Although populations from several of
these hydrogeographical regions do possess differences in the
mean or modal value of morphometric and meristic features, no
unambiguous diagnostic features were recovered. The conclu-
sion that populations from throughout the continent represent
a single morphospecies is based on examination of 177 lots
containing 406 specimens (Appendix 1).
From comparisons with results of other studies on geo-
graphically widespread morphospecies of Neotropical fishes
we expect this continental distribution will not be confirmed
with other non-traditional datasets. Future work using molecu-
lar sequences, microsatellite DNA, and chromosome morpho-
logy will be used to test the hypothesis that all populations of
S. macrurus currently recognized represent a single evolution-
ary lineage (Lovejoy & de Ara´
ujo, 2000).
Historical ecology
Sternopygus macrurus is the most eurytopic species of the
genus, being found in most lowland aquatic habitats, including
high conductivity whitewater river channels and floodplains
(v´
arzea) and low conductivity non-floodplain (terra firme)
black and clearwater rivers and streams. All other Sternopygus
species have much more restricted geographic and ecological
distributions (Fig. 1b).
Sternopygus branco is unique among its congeners in
being entirely restricted to whitewater rivers in the Central
Amazon Basin. The capacity to inhabit large and deep (up
to 25 m) Amazonian river channels is a derived feature of
the Sinusoidea, a clade of gymnotiform fishes represented by
two families with a high frequency wave-type EOD, Apter-
notidae and Sternopygidae (Albert, 2001). Habitat utilization
of Amazonian river channels is associated with a suite of beha-
vioural, physiological and morphological traits. Many of these
traits are observed in S. branco including reduced pigmentation
and a streamlined body and head morphology (Albert, 2001).
The utilization of Amazonian river channels in S. branco is
inferred to be plesiomorphic.
In a combined morphological and molecular analysis of
all gymnotiform fishes (Albert, 2001) S. astrabes was inferred
to retain the most plesiomorphic set of character states among
extant taxa, including (among other characters): small adult
body size (Fig. 2, 3); relatively short body cavity with 18–19
precaudal vertebrae (Table 4); paedomorphic features of cra-
nial osteology (Figs 6, 15, 16). Here we recognize that the
426 Kevin G. Hulen et al.
position of S. obtusirostris and S. sp. ‘cau’ as members of a
clade including S. astrabes, indicate the polarity of small body
size, short body cavity length, and short anal fin length is de-
rived. Similarly, the unique restriction of S. astrabes among
its congeners to terra firme streams is inferred to be derived.
This fundamental change in our perception of the evolution
in Sternopygus highlights the sensitivity of both phylogen-
etic systematics and character-state reconstruction to taxon
sampling.
Continuous traits as phylogenetic characters
There are many approaches to abstracting aspects of mor-
phological diversity into hypotheses of character-state change.
Empirical and theoretical challenges associated with coding
continuously varying traits into discrete phylogenetic char-
acters have been discussed extensively (e.g., Hormiga et al.,
2000; Weins, 2000). Here we tested the sensitivity of the tree
topology to the presence of morphometric characters by ex-
cluding from the analysis those characters pertaining to body
proportions (8 of 66 characters), and by employing multiple
coding schemes to investigate the polarity and integrity of
the characters. Excluding these characters resulted in a single
most parsimonious tree topology, which differed from the total
evidence analysis in one regard: S. branco is the sister to the
clade [S. obtusirostris +S. sp. ‘cau’ + S.astrabes], and is
not the sister to all other congeners. This result emphasizes
the importance of the observation that S. branco retains the
plesiomorphic slender body shape of outgroup taxa.
Acknowledgements
We acknowledge the following people for access to specimens, in-
formation and ideas; B. Brown, X. Freilich, S. Schaefer (AMNH);
J. Lundberg, M. Sabaj (ANSP); J. Armbruster (AUM); O. Crimmen,
D. Siebert (BMNH); D. Catania, W. Eschmeyer (CAS); L. Page,
R. Robins (FLMNH); B. Chernoff, M. Rogers (FMNH); L. Rapp
Y Daniel (INPA); A. Machado-Allison, F. Provenzano, R. Royero
(MBUCV); R. Reis (MCP); K. Hartel (MCZ); P. Buckup, R. Campos-
da-Paz (MNRJ); H. Britski, M. de Pinna, J. Lima De Figueiredo, O.
Oyakawa, (MZUSP); E. Ahlander, S. Kullander, A. Silvergrip (NRM);
W. Fink, D. Nelson (UMMZ); S. Jewett, L. Parenti, R. Vari (USNM).
We appreciate additional exchanges of data and ideas with E. Ber-
mingham, N. Lovejoy, D. Stewart and M. Triques. Special thanks to
S. Wolgemuth for assisting with translation from German. We ac-
knowledge the Neodat project (NSF /AID DEB grant 90–24797) for
collection information. Aspects of this research were supported by
grants to WGRC from the Fisheries Society (UK), CNPq (Brazil),
and to JSA from the U.S. National Science Foundation (NSF-DEB
0215388, 0317278, 0138633).
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Appendix 1: material
Materials examined from 287 lots containing 677 specimens of
sternopygid species. Data are arranged alphabetically by spe-
cies, country, state, then by museum acronym and catalogue
number, followed in parentheses by number of specimens, size
(mean or range) in millimeters total length, but sometimes us-
ing length to the end of anal-fin (LEA) when caudal appendage
of specimen was damaged, type-status (HT, holotype; PT, para-
type), specimen status (C&S, cleared and stained), summary
of locality, latitude, longitude, and date of capture when avail-
able. Institutional abbreviations follow (Leviton et al., 1985)
with the addition of INPA (Instituto Nacional de Pesquisas da
Amazˆ
onia, Manaus). Specimens of S. macrurus are arranged
by region alphabetically (region abbreviations described in
Tabl e 1 ) .
Outgroup specimens
Apteronotus sp.–Brazil: Amazonas: MCP uncat., WGRC
03.180199 (1, 205), Rio Japur´
a-Solim˜
oes confluence,
3◦0644S, 64◦4732W, 18.I.1999. MCP uncat., WGRC
06.130199 (1, 152), Rio Japur´
a-Solim˜
oes confluence,
3◦0644S, 64◦4732W, 13.I.1999. MCP uncat., WGRC
15.110100 (1, 300), Rio Japur´
a-Solim˜
oes confluence,
3◦0644S, 64◦4732W, 11.I.2000. MCP uncat., WGRC
26.260199 (1, 230), Rio Japur´
a-Solim˜
oes confluence,
3◦0644S, 64◦4732W, 26.I.1999. MCP uncat., WGRC
38.231099 (1, 249), Rio Tef´
e, 3◦4719S, 64◦5955W,
23.X.1999. MCP uncat., WGRC 74.041299 (1, 160),
Rio Japur´
a-Solim˜
oes confluence, 3◦0708S, 64◦4718W,
04.XII.1999.
Archolaemus blax.–Brazil: Amazonas: INPA 18451 (7,
90–202, 2 C&S), Tucurui, Rio Tocantins, 04◦25S, 49◦32W,
22.X.1984. Par´
a: INPA 5064 (1, 373), Rio Trombetas, Rio Ca-
chorro, 01◦05S, 57◦02W, 15.IV.1985.
Distocyclus conirostris.– Brazil: Amazonas: MCP un-
cat., WGRC 03.030299 (1, 216), Rio Japur´
a-Solim˜
oes con-
fluence, 03◦0708S, 64◦4718W, 03.II.1999. MCP un-
cat., WGRC 06.140199 (1, 224), Rio Japur´
a-Solim˜
oes con-
fluence, 03◦0644S, 64◦4732W, 14.I.1999. MCP uncat.,
WGRC 06.260199 (1, 143), Rio Japur´
a-Solim˜
oes conflu-
ence, 03◦0644S, 64◦4732W, 26.I.1999. MCP uncat.,
WGRC 10.030299 (1, 185), Rio Japur´
a-Solim˜
oes confluence,
03◦0708S, 64◦4718W, 03.II.1999. MCP uncat., WGRC
21.020999 (1, 150, C&S), Rio Japur´
a-Solim˜
oes confluence,
03◦0644S, 64◦4732W, 02.II.1999. MCP uncat., WGRC
27.020299 (1, 212, C&S), Rio Japur´
a-Solim˜
oes confluence,
03◦0644S, 64◦4732W, 02.II.1999.
Ingroup specimens
Sternopygus arenatus.– Ecuador: Esmeraldas: MCZ 54969
(4, 56–145), Rio Cayapas, 0◦44N, 78◦55W, 29.VI.1977.
MCZ 58604 (1, 248, C&S), Rio Cayapas, 01◦44N, 77◦55W,
29.VI.1977. Guayas: NRM 28178 (2, 490–595), Guaya-
quil, 26.XI.1934. UMMZ 205390 (4, 195–455), Guayaquil,
02◦10S, 79◦54W. Los Rios: MCZ 48804 (1, 390), Quevedo,
1◦S, 79◦27W, 04.XI.1971.
Sternopygus astrabes.– Brazil: Amazonas: BMNH
1998.3.11.15a (1, 195), Rio Tef´
e, Lago Tef´
e, 03◦2008S,
64◦4210W, 27.VII.1996. INPA 09980 (2, 102–131), Rio
Demini, 00◦2318S, 62◦5155W, 29.X.2000. INPA 9980
(1, 135), Lago Aman˜
a, 2◦3847S, 64◦3919W, 5.I.1995.
INPA 9981 (1, 166), Lago Aman˜
a, 2◦3847S, 64◦3919W,
5.I.1995. MCP 32230 (1, 107), Rio Tef´
e, Tef´
e, 03◦2428S,
64◦4410W, 30.XII.1998. MCP 32231 (2, 50–55), Rio Tef´
e,
Tef ´
e, 03◦2428S, 64◦4410W, 24.VIII.1999. MCP 32232
(1, 63, C&S), Rio Tef´
e, Tef´
e, 03◦2428S, 64◦4410W,
21.IX.1999. MCP 32233 (1, 81, C&S), Rio Tef´
e, Tef´
e,
03◦2428S, 64◦4416W, 17.III.2000. MCP 32234 (1, 81),
Rio Tef´
e, Tef´
e, 03◦2428S, 64◦4410W, 10.X.2000. MCP
32235 (10, 104–143, 2 C&S), Rio Demini, 00◦2318S,
62◦5155W, 29.X.2000. MCP 32236 (4, 75–91), Rio Tef´
e,
Tef ´
e, 03◦2428S, 64◦4410W, 16.X.2002. MCP 32237
(1, 97), Rio Solim˜
oes, Alvar˜
aes, 03◦1605S, 64◦4742W,
27.XI.2002. MCP 32238 (1, 70), Rio Tef´
e, Tef´
e, 03◦2428S,
64◦4410W, 24.I.2003. MCP 32239 (2, 74–75), Rio Tef´
e,
Tef ´
e, 03◦2428S, 64◦4410W, 20.II.2003. MCP 32240 (2,
78–95), Rio Tef´
e, Tef´
e, 03◦2428S, 64◦4410W, 26.II.2003.
MZUSP 47987 (1, 130, S. castroi HT), Rio Cuieras,
Igarap´
e Jarad´
a, 02◦70S, 60◦40W, 30.I.1977. MZUSP 48911
(1, 117, S. castroi PT), Rio Cuieras, Igarap´
e Jarad´
a, 02◦40S,
60◦20W, 01.II.1977. MZUSP 48912 (1, 178, HT), Igarape
Jarad´
a, Rio Cuieiras, 1.II.1977. MZUSP 49788 (1, 142,
PT), Igarape Jarad´
a, Rio Cuieiras, 1.II.1977. Venezuela:
Amazonas: ANSP 162128 (1, 75, PT), Rio Orinoco, nr. Isla
Temblador, 03◦04N, 66◦28W, 10.III.1987. ANSP 162663
(4, 70–177), Rio Autana, Raudal Peresa, 04◦46N, 67◦19W,
13.XI.1985. MBUCV 13896 (6, PT), Rio Orinoco, 30.III.1983.
MBUCV 14182 (1, 196, HT), Rio Orinoco, 30.III.1983.
Sternopygus branco.– Brazil: Amazonas: INPA 12370
(1, 171), Rio Negro, Lago do Prato, 02◦3736S, 60◦57W,
18.IX.1991. INPA 15786 (1, 492, PT), Rio Japur´
a, Paran´
a
Maiana, 03◦0644S, 64◦4732W, 28.I.1999. INPA 18236
(1, 265, PT), Rio Solim˜
oes-Japur´
a confluence, 03◦0908S,
64◦4704W, 24.II.2000. MCP 32241 (1, 353, PT),
Rio Solim˜
oes-Japur´
a confluence, 03◦0908S, 64◦4704W,
08.II.1999. MCP 32242 (3, 180–211, PT, 2 C&S),
Rio Solim˜
oes-Japur´
a confluence, 03◦0708S, 64◦4718W,
07.XII.1999. MCP 32243 (1, 252, PT, C&S), Rio Japur´
a,
Paran ´
a Maiana, 03◦0450S, 64◦4718W, 12.I.2000. MCP
32244 (1, 253, PT), Rio Japur´
a, Paran´
a Maiana, 03◦0644S,
64◦4732W, 22.II.2000. MCP 32245 (2, 246–251, PT,
1 C&S), Rio Solim ˜
oes-Japur´
a confluence, 03◦0908S,
64◦4704W, 24.II.2000. MCP 32246 (3, 319–345, PT),
Rio Solim˜
oes-Japur´
a confluence, 03◦0908S, 64◦4704W,
07.II.2001. MCP 32451 (1, 333, HT), Rio Solim˜
oes-Japur´
a
confluence, 03◦0908S, 64◦4704W, 07.II.2001. MZUSP
56187 (1, 421), Rio Negro, Manaus, 03◦0S, 60◦24W,
13.XII.1993.
Sternopygus dariensis.– Colombia: Antioquia: NRM
27742 (1, 326), Rio Atrato, Buchad´
o, 06◦25N, 77◦46W,
28.I.1989. NRM 27745 (1, 390), Rio Atrato, Buchad´
o,
06◦25N, 74◦46W, 27.I.1989. Choc´
o: FSUC uncat. (2, 145–
252), upper Rio Nercua, Rio Truando, 28.VIII.1967. FSUC
uncat. (11, 103–320), near Teresita, Rio Solando, 08.II.1968.
Phylogenetic systematics Sternopygus 429
NRM 10697 (1, 170), Rio Saija, 1939. NRM 10698 (3),
Rio San Juan, 1939. NRM 27746 (6, 210–291, 2 C&S),
Rio Baud´
o, Boca de Pep´
e, 05◦04N, 77◦03W, 22.II.1989.
Panama: Cocle: UF 27523 (5, 93–245), nr. El Valle, 08◦31N,
80◦33W, 24.IV.1965. Darien: CAS 14037 (1), Rio Tuyra, Mar-
rigante, III.1912. FMNH 8829 (1, PT), Rio Tuyra, Marrig-
ante, 08.III.1912. FMNH 8949 (1, HT), Rio Tuyra, Marrig-
ante, 08.III.1912. UF 15451 (2, 348–355), Rio Pirri, El Real,
08◦0759N, 77◦4359W, VI.1967. Colon: USNM 329425 (2,
180–185), Rio Mebrillo, 22.III.1967. Herrera: UF 12978 (2,
226–242), nr. Chepo, 07◦4359N, 80◦4869W, 29.IV.1965.
Sternopygus macrurus (EA). – Brazil:Goi
´
as: MCP
18204 (1, 361), Rio Araguia, nr. L´
uis Alves, 13◦14S, 50◦35W.
MNRJ 12189 (2, 33–126), Rio Maranh˜
ao, Rio da Mula,
14◦16S, 49◦04W, 10.VII.1985. MNRJ 12190 (2, 116–117),
Rio Tocantins, Serra da Mesa, 14◦50S, 48◦19W, 20.X.1985.
MNRJ 12191 (10, 115–310), Rio Tocantins, C´
orrego Bar-
riguda, 14◦05S, 48◦20W, 15.X.1985. MNRJ 12208 (2, 76–
168), Rio Tocantins, C´
orrego Lajeado, 13◦31S, 49◦10W,
29.V.1987. MNRJ 12209 (4, 104–113), Rio Tocantins, C´
orrego
Lajeado, 13◦39S, 48◦09W, 06.I.1987. Par´
a: INPA 4843
(12, 114–220), Rio Tocantins, Tucuru´
ı, 04◦25S, 49◦32W,
01.XII.1984. INPA 5739 (1, 162), Rio Trombetas, Rio
Cachorro, 00◦58S, 57◦0259W, 08.XII.1988. INPA 6409
(1, 256), Rio Tocantins, Breu Branco, 04◦0159S, 49◦40W,
14.XI.1981. INPA 6410 (1, 382), Rio Tocantins, Igarap´
e
Jatobal, 08◦56S, 49◦46W, 31.X.1980. INPA 6411 (2, 234–
317), Rio Tocantins, Breu Branco, 04◦0404S, 49◦3808W,
13.VII.1982. INPA 6414 (2, 118–220), Rio Tocantins, Igarap´
e
Jatobal, 08◦56S, 49◦46W, 08.VII.1982. INPA 6416 (1, 425),
Rio Tocantins, Tucuru´
ı, 03◦42S, 49◦42W, 26.X.1980. INPA
6431 (3, 366–495), Rio Tocantins, Tucuru´
ı, 03◦42S, 49◦42W,
31.XXXI.1985. INPA 9092 (2, 225–271), Rio Tocantins,
Laguinho, 08◦56S, 49◦46W, 11.XI.1981. INPA uncat. (6,
236–433), Rio Jarim, Cachoeira Santo Antonio, 01◦09S,
51◦54W, 9–18.VI.1987. INPA uncat. (6, 236–433), Rio Jarim,
Cachoeira Santo Antonio, 01◦09S, 51◦54W, 9–18.VI.1987.
MCZ 9409 (1, 320), Ilha do Maraj´
o, Lago Arari, 00◦20S,
49◦10W, 01.III.1866. MCZ 9412 (2, 234–455), Rio Par´
a, nr.
Bel´
em, 01◦27S, 48◦29W, 10.VIII.1865. MCZ 9442 (2, 385–
390), Rio Par´
a, nr. Bel´
em, 01◦27S, 48◦29W, 10.VIII.1865.
MCZ 9453 (1, 212), Lago Aleixo, Rio Negro, 27.XI.1865.
MCZ 9456 (5, 310–368), Rio Par´
a, nr. Bel´
em, 01◦27S,
48◦29W, 10.VIII.1865. MCZ 9829 (2, 185–448), Rio Xingu,
Porto de Moz, 01◦45S, 52◦10W, IX.1865. MCZ 25708 (1,
300), Rio Xingu, Porto de Moz, 01◦45S, 52◦10W, IX.1865.
MCZ 45193 (6, 119–286), Ilha do Maraj´
o, Cachoeira do
Arari, 01◦11S, 48◦45W, VII.1965. MCZ 60047 (1, 140),
Rio Xingu, Porto de Moz, 01◦45S, 52◦10W, 23.VIII.1865.
UMMZ 203393 (1, 355), Rio Tocantins, Bel´
em, 19.VII.1935.
Mato Grosso: INPA 11578 (1, 112), Rio Aripuan˜
a, Dard-
anelos, 09◦10S, 60◦38W, 09.XI.1976. MZUSP 25136 (1),
Ilha de Taiam˜
a (Sema), Rio Paraguay, 8.VIII.1980. MZUSP
27740 (1), Rio Taquari, Coxim. MZUSP 28568 (1), Rio
Taquari, junto `
a cidade de Coxim, X.1983. MZUSP 36339
(2), Lad´
aRioCorumb
´
a, Mato Grosso, IX.1985. MZUSP
44418 (3), C´
aceres, Rio Paraguay, 11–12.VIII.1991. MZUSP
45345 (2), riacho Monjolinho, Rio Preto, S˜
ao Francisco,
24.X.1992. USNM 326121 (3, 133–368), Waura, Rio Batovi,
Rio Xingu,VIII.1964. USNM uncat. (6, 125–215), Waura, Rio
Batovi, Rio Xingu, VIII.1964. USNM uncat. (2, 161–164),
Waura, Rio Batovi, Rio Xingu, VIII.1964. Tocantins: INPA
4536 (1, 166), Rio Tocantins, Itupiranga, 05◦09S, 49◦20W,
06.VII.1980. INPA 4825 (1, 460), Rio Tocantins, Lago Grande,
05◦09S, 49◦20W, 21.XI.1981. INPA 6415 (1, 193), Rio
Tocantins, Itupiranga, 05◦09S, 49◦20W, 29.VII.1982.
Sternopygus macrurus (GO). – Brazil: Roraima: INPA
1156 (1, 76), Rio Branco, Boa Vista, 02◦49N, 60◦40W. INPA
2046 (8, 129–525), Rio Uraricoera, Ilha Marac´
a, 03◦02N,
60◦30W, 12.III.1988. INPA 2060 (1, 221), Rio Uraricoera,
Ilha Marac´
a, 03◦02N, 602◦30W, 13.III.1988. INPA 2062 (10,
70–395), Rio Uraricoera, Ilha Marac´
a, 03◦02N, 60◦30W,
14.III.1988. INPA 4540 (1, 159), Rio Mucaja´
ı, Cachoeira
Pared ˜
ao, 02◦25N, 60◦52W, 18.II.1987. INPA 4874 (1, 132),
Rio Uraricoera, Ilha Marac´
a, 03◦02N, 60◦30W, 11.III.1988.
INPA 6412 (2, 262–361), Rio Mucaja´
ı, Cachoeira Pared˜
ao,
02◦25N, 60◦52W, 03.X.1986. INPA 6419 (1, 317), Rio Mu-
caja´
ı, Cachoeira Pared˜
ao, 02◦25N, 60◦52W, 19.II.1987. INPA
7417 (1, 113), Rio Branco, Igarap´
e Juruaquim, 03◦22N,
60◦19W, 27.III.1992. Guyana: Essequibo: UMMZ 13054
(1, 308), Botami Gardens, Georgetown. UMMZ 215184 (1,
180), Mahida Creek, Potaro River, 20.VIII.1971. UMMZ
215834 (2, 138–461), tidal canal at Anna Regina, 07◦16N,
58◦30W, 27.VIII.1971. UMMZ 215916 (1, 384), Barana
River at Kokerite Village, 01.IX.1971. USNM 209204 (1,
160), Crusa Creek, Rupununi District, 15.V.1970. Suriname:
Marowijne: UF 16268 (1, 161), Marowijne River, 05◦30N,
54◦03W, VII.1967. Venezuela: Apure: FMNH 100719 (1,
175), Rio Anarco near Rio Suripa, Rio Apure, 01.I.1991.
FMNH 100725 (5), Ca˜
no Socopo, Rio Suripa, Rio Apure,
07.I.1991. FMNH 100726 (1, 197), Ca˜
no Socopo, Rio Suripa,
Rio Apure, 12.I.1991. MCNG 3733 (10, 177–398, 8 C&S),
Rio Apure, Munoz, 07◦2830N, 69◦3050W, 19.III.1981.
UF 80888 (2, 164–195), Rio Apure, Munoz, 07◦2520N,
69◦3540W, 13.II.1979. Portuguesa: UF 80862 (2, 176–180),
Laguna Chiriguare, 08◦48N, 68◦30W, 03.IV.1984. UMMZ
212346 (1, 36), Guarico, Rio Apure, 21.VIII.1981. USNM
194179 (1, 306), Rio Las Palmas, Barinas, 15.VI.1958.
Sternopygus macrurus (NE). – Brazil:Bahia:MCP
16730 (1, 338), Rio Tato, nr. Barra de Cocos, 14◦1422S,
44◦3142W, 16.VII.1993. MZUSP 2644 (1), Rio S˜
ao
Francisco, 1908. UMMZ 216316 (1, 275), Barreiras, mouth
of Rio Grande, 28.III.1942. Minas Gerais: ANSP 172171
(2, 54–235), Rio Verde Grande, nr. Janauba, 16◦3901S,
43◦4249W, 20.VII.1993. MZUSP 39474 (3), Rio S˜
ao
Francisco, Barra do Rio Formoso, 8–10.II.1988. MZUSP
39640 (1), Rio Abaet´
e, Tiros, 18.III.1988. MZUSP 39951
(1), ´
Agua Vermelha, Rio Grande, 27.VI.1978. MZUSP
47447 (1), Rio Verde, entre Francisco S´
a e Montes Claros,
23.VII.1994. MZUSP 24652 (1), Pedra Ponte, Trˆ
es Marias,
23.VIII.1978. USNM 44967 (1, 354), Rio das Velhas, S˜
ao
Francisco,15.II.1895. Cear´
a: MCZ 9418 (1, 420), Ceara,
nr. Fortaleza, 03◦45S, 38◦30W, 05.VIII.1865. Piaui: AUM
20601 (1), Rio Parnaiba, Rio Gurgueia, 06◦14S, 42◦37W,
5.IX.1971. AUM 20630 (1), Rio Parnaiba, Rio Esfolado,
07◦24S, 43◦38W, 5.IX.1971. AUM 20757 (9), Rio Parnaiba,
430 Kevin G. Hulen et al.
Santa Filomena, 09◦08S, 45◦55W, 8.IX.1971. MCZ 9450
(3, 263–370), Rio Parnaiba, Rio Puty, 05◦05S, 42◦49W,
XII.1865. MCZ 46859 (1, 143), Rio Parnaiba, Lagoa Seca,
03◦11S, 41◦50W, 29.VIII.1968. Rondˆ
onia: INPA uncat (polo.
1206) (2, 175–390), Rio Machado, Nazar´
e, 10◦05S, 62◦18W,
21.III.1987. INPA uncat (polo. 1353) (4, 119–205), Rio Jamari,
UHE Samuel, 08◦45S, 63◦28W, 07.VI.1988. INPA uncat
(polo. 146) (6, 164–330), Rio Machado, Rio Urup´
a, 10◦52S,
61◦58W, 04.VI.1984. INPA uncat (polo. 204) (1, 420), Rio
Guapor´
e, Surpresa, 11◦54S, 64◦59W, 16.VI.1984. INPA un-
cat (polo. 610) (1, 155), Rio Machado, Nazar´
e, 10◦05S,
62◦18W, 09.XI.1983. INPA uncat (polo. 629) (4, 170–290),
Rio Machado, Jiparan´
a, 08◦03S, 62◦52W, 16.VI.1984. INPA
uncat (polo. 709) (2, 137–150), Rio Marmor´
e, Guajar´
a-
Mirim, 10◦48S, 65◦22W, 26.XI.1983. INPA uncat (polo. 754)
(15, 135–155), Rio Machado, Rio Urup´
a, 10◦52S, 61◦58W,
05.VI.1984. INPA uncat (polo. 867) (1, 142), Rio Jamari,
UHE Samuel, 08◦45S, 63◦28W, 04.IX.1985. INPA uncat
(polo. 949) (8, 131–286), Rio Jamari, UHE Samuel, 08◦45S,
63◦28W, 10.IX.1985. Sergipe: MZUSP 24476 (1), Rio S˜
ao
Francisco, Propri´
a, 18.XII.1975.
Sternopygus macrurus (NW). – Colombia: Magdalena:
UF 17210 (1, 192), Rio Magdalena, Cartagena, 11◦01N,
74◦15W, 18.VIII.1969.
Sternopygus macrurus (PA). – Paraguay: Canendiyu:
UMMZ 206424 (1, 144), Rio Paraguay, 24◦0212S, 54◦19W,
13.VII.1979. Concepcion: NRM 23196 (1, 140), Rio Paraguay,
Concepcion, 23◦48S, 56◦17W, 18.VIII.1993. UMMZ 206765
(1, 450), Rio Aquidaban, Parque Cerro Cora, 22◦3812S,
56◦03W, 25.VII.1979. UMMZ 206794 (1, 115), Rio Apa,
nr. Bella Vista, 22◦0630S, 56◦30W, 27.VII.1979. UMMZ
208004 (1, 80), Rio Paraguay, Concepcion, 23◦1518S,
56◦30W, 11.IX.1979.
Sternopygus macrurus (PS). – Colombia: Choc ´
o: NRM
27740 (4, 180–251), Rio Baud´
o, Boca de Pep´
e, 05◦04N,
77◦03W, 22.II.1989. UMMZ 179240 (1, 312) Rio Meta, 1936.
Sternopygus macrurus (SE). – Brazil: Rio de Janeiro:
MCZ 45096 (1, 201), Rio Paraiba do Sul, nr. Rio de Janeiro,
22◦53S, 43◦17W, II.1872.
Sternopygus macrurus (WA). – Argentina: La Plata:
ANSP 78191 (1), R´
ıo de la Plata, 34◦55S, 57◦57Wap-
prox 1870s. Santiago del Estero. USNM 246086 (1), R´
ıo
Dulce, 27◦47S, 64◦16W, 12.VI.1933. Bolivia: Beni: AMNH
39822 (1), R´
ıo Mamor´
e, Costa Marquez, 12◦33S, 64◦12W,
9.X.1964. AMNH 40159 (1), R´
ıo Mamor´
e, Guayaramerin,
10◦51S, 65◦21W, 20.X.1964. UMMZ 204744 (19, 124–
427), R´
ıo Mamor´
e, R´
ıo Itenez, 12◦31S, 64◦19W, 30.IX.1964.
UMMZ 204800 (2, 320–322), R´
ıo Mamor´
e, R´
ıo Baures,
12◦34S, 64◦19W, 3.X.1964. UMMZ 204888 (11, 145–411),
Rio Itenez, Rio Baures, 07.X.1964. USNM 305511 (1),
R´
ıo Mamor´
e, R´
ıo Matos, 14◦55S, 66◦17W, 28.VIII.1987.
Pando: FMNH 106700 (1), R´
ıo Mamor´
e, Cobija, 11◦26S,
69◦01W, 4.IX.1996. Santa Cruz Dept: UF 82344 (1), R´
ıo
Mamor´
e, R´
ıo Jorge, 17◦31S, 63◦15W, 10.VIII.1986. Brazil:
Amazonas: BMNH 1998.3.11.02 (1, 212), Rio Solim˜
oes,
nr. Alvar˜
aes, 03◦0617S, 64◦5507W, 29.VIII.2003. BMNH
1998.3.11.03 (1, 145), Rio Solim ˜
oes, nr. Alvar˜
aes, 03◦0617S,
64◦5507W, 29.VIII.2003. BMNH 1998.3.11.04 (1, 150),
Rio Solim˜
oes, nr. Alvar˜
aes, 03◦0617S, 64◦5507W,
29.VIII.2003. BMNH 1998.3.11.05 (1, 157), Rio Solim˜
oes,
nr. Alvar˜
aes, 03◦0617S, 64◦5507W, 29.VIII.2003. BMNH
1998.3.11.06 (1, 161), Rio Solim˜
oes–Japur´
a Confluence,
02◦5446S, 64◦5426W, 16.IX.1993. BMNH 1998.3.11.07
(1, 163), Rio Solim˜
oes, nr. Tef´
e, 03◦1605S, 64◦4121W,
05.IX.1993. BMNH 1998.3.11.10 (1, 257), Lago Tef´
e,
03◦2008S, 64◦4210W, 27.VII.1996. BMNH 1998.3.11.11
(1, 210), Lago Tef´
e, 03◦2008S, 64◦4210W, 27.VII.1996.
BMNH 1998.3.11.12 (1, 187), Lago Tef´
e, 03◦2008S,
64◦4210W, 27.VII.1996. BMNH 1998.3.11.13 (1, 43), Rio
Tef ´
e, Igarap´
e Curupira, 03◦2601S, 64◦4347W, 04.II.1995.
INPA 15783 (1, 418), Lago Aman˜
a, 02◦2854S, 64◦4248W,
30.XI.1998. INPA 15802 (2, 286–305), Rio Solim˜
oes–
Japur´
a Confluence, 03◦0708S, 64◦4718W, 15.X.1999.
INPA 17143 (2, 207–242), Rio Purus, Lago Jar´
ı, 04◦5451S,
62◦2126W, 08.VI.2001. INPA 17305 (1, 190), Rio Purus,
Sacado de Santa Luzia, 04◦4218S, 62◦2226W, 04.VI.2001.
INPA 18165 (1, 204), Rio Solim˜
oes-Japur´
a Confluence,
03◦0908S, 64◦4704W, 08.XII.1999. INPA 18166 (3, 172–
221), Rio Japur´
a, Paran´
a Maiana, 03◦0450S, 64◦4718W,
15.X.1999. INPA 18188 (3, 232–283), Lago Tef´
e, 03◦3435S,
64◦5919W, 22.VI.1999. INPA 18190 (4, 360–492), Rio
Japur´
a, Paran´
a Maiana, 03◦0450S, 64◦4718W, 13.I.1999.
INPA 18233 (1, 252), Rio Tef´
e, 03◦4649S, 64◦5929W,
01.VI.2000. INPA 18234 (1, 168), Rio Solim˜
oes-Japur´
a
Confluence, 03◦0908S, 64◦4704W, 08.XII.1999. INPA
18235 (1, 220), Rio Solim˜
oes-Japur´
a Confluence, 03◦0908S,
64◦4704W, 24.II.2000. INPA 18238 (1, 88), Lago Cai-
amb´
e, 03◦3534S, 64◦2637W, 28.XII.1998. INPA 18316 (1,
345), Rio Japur´
a, Paran´
a Maiana, 03◦0644S, 64◦4732W,
05.XII.1999. INPA 18317 (1, 48), Rio Tef´
e, Igarap´
e Curupira,
03◦2601S, 64◦4347W, 07.II.2000. INPA 4736 (3, 94–
147), Rio Solim˜
oes, Lago Janauac´
a, 03◦2528S, 60◦1653W,
17.III.1978. INPA 4809 (2, 212–357), Rio Solim˜
oes, Lago
Janauac´
a, 03◦2528S, 60◦1653W, 07.IV.1978. INPA 4824
(1, 450), Rio Solim˜
oes, Ilha do Careiro, 03◦12S, 59◦45W,
02.XII.1985. INPA 4837 (1, 310), Rio Uatam˜
a, Balbina,
01◦53S, 59◦28W, 24.X.1987. INPA 4841 (1, 325), Rio
Solim˜
oes, Ilha do Careiro, 03◦12S, 59◦45W, 18.XI.1985.
INPA 4869 (6, 33–130), Rio Solim˜
oes, Lago Janauac´
a,
03◦2528S, 60◦1553W, 25.II.1978. INPA 6428 (1, 165),
Rio Solim˜
oes, Aramac´
a, 04◦20S, 69◦55W. INPA 6429 (2,
305–383), Rio Japur´
a, 30.IX.1976. INPA 6432 (3, 377–
489), Rio Solim˜
oes, Ilha do Careiro, 03◦12S, 59◦45W,
26.II.1986. INPA 6433 (1, 443), Rio Solim˜
oes, Ilha do
Careiro, 03◦12S, 59◦45W, 31.III.1987. INPA 9933 (1,
287), Rio Ja´
u, Miracutucu, 01◦54S, 61◦26W, 29.X.1994.
Par´
a: INPA uncat. (6, 236–433), Rio Jarim, Cachoeira
Santo Antonio, 01◦09S, 51◦54W, 9–18.VI.1987. INPA
uncat. (6, 236–433), Rio Jarim, Cachoeira Santo Ant-
onio, 01◦09S, 51◦54W, 9–18.VI.1987. MCP 32247 (1,
101), Rio Solim˜
oes, nr. Alvar˜
aes, 03◦0618S, 64◦5507W,
29.VIII.2003. MCP 32248 (2, 145–147), Rio Japur´
a, Nova
Colˆ
ombia, 02◦5447S, 64◦5426W, 16.IX.1993. MCP
32249 (8, 42–75), Lago Caiamb´
e, 03◦3534S, 64◦2637W,
28.XII.1998. MCP 32250 (1, 157), Rio Solim˜
oes–Japur´
a Con-
fluence, 03◦0708S, 64◦4718W, 19.I.1999. MCP 32251
Phylogenetic systematics Sternopygus 431
(3, 39–122), Rio Solim˜
oes–Japur´
a Confluence, 03◦0644S,
64◦4732W, 26.I.1999. MCP 32252 (1, 157), Lago Tef´
e,
03◦3435S, 64◦5919W, 22.VI.1999. MCP 32253 (4, 184–
303), Lago Tef´
e, 03◦3435S, 64◦5919W, 22.VI.1999. MCP
32254 (3, 132–310, C&S), Rio Tef´
e, 03◦4649S, 64◦5929W,
13.VII.1999. MCP 32255 (1, 85), Rio Tef´
e, Igarap´
e Repar-
timento, 03◦2428S, 64◦4410W, 29.VII.1999. MCP 32256
(1, 173, C&S), Rio Tef´
e, 03◦4719S, 64◦5955W, 22.X.1999.
MCP 32257 (1, 88), Rio Tef´
e, Tef´
e, 03◦2428S, 64◦4410W,
22.XII.1999. MCP 32258 (1, 264), Rio Solim˜
oes-Japur´
a
Confluence, 03◦0908S, 64◦4704W, 07.II.2001. MCP un-
cat. (1, 159), Rio Solim˜
oes, Tef´
e, 03◦46S, 73◦15W. NRM
14073 (1, 505), Joapoary, 30.XI.1924. Ecuador: Napo:
FMNH 103297 (1, 230), Rio Payamino, 00◦26S, 77◦212W,
20.IX.1981. FMNH 103299 (3, 115–257), Rio Sardinas,
00◦06S, 77◦1230W, 29.IX.1981. FMNH 103300 (2, 178–
320), Rio Napo, 00◦2324S, 76◦3706W, 04.X.1981. Peru:
Cajamarca: ROM 5228 (1, 163), R´
ıo Tabaconas, 05◦23S,
78◦45W, 7.VII.1986. Loreto: UF 116550 (1, 415), Rio
Nanay, Mixana, 03◦5246S, 73◦2933W, 26.III.2001. UF
117121 (2, 400–401), Rio Nanay, Mixana, 03◦5246S,
73◦2933W, 26.III.2001. UF 122829 (1, 162), nr. Iquitos,
03◦46S, 73◦15W, 20–28.V.2002. UF 122830 (1, 167), nr.
Iquitos, 03◦46S, 73◦15W, 20–28.V.2002. UF 122831 (1,
137), nr. Iquitos, 03◦46S, 73◦15W, 20–28.V.2002. UF 122832
(1, 88), nr. Iquitos, 03◦46S, 73◦15W, 20–28.V.2002. UF
122835 (1, 122), nr. Iquitos, 03◦46S, 73◦15W, 20–28.V.2002.
UF 122838 (1, 113), nr. Iquitos, 03◦46S, 73◦15W, 20–
28.V.2002. UMMZ 187220 (1, 185 SL), R´
ıo Purus, R´
ıo Cur-
anja, 10◦08S, 71◦13W, VII.1966. UMMZ 228964 (2, 270–
285), Buen Suceso, Rio Javari, 15.V.1993. UMMZ 228965 (1,
224), Santa Ana, Rio Tahwayo, 6.V.1993. USNM 86835 (1,
176), Rio Pichis, 1920. Madre de Dios: USNM 263888 (1), R´
ıo
Madre de Dios, Tambopata, 12◦49S, 69◦16W, 20.VIII.1983.
Ucayali: ROM 55540 (1, 167), R´
ıo Ucayali, Pucallpa, 08◦23S,
74◦32W, 1988.
Sternopygus obtusirostris.– Brazil: Amazonas: BMNH
1998.3.11.14 (1, 195), Rio Tef´
e, Lago Tef´
e, 03◦2008S,
64◦4210W, 27.VII.1996. BMNH 1998.3.11.15 (1, 180),
Rio Tef´
e, Lago Tef´
e, 03◦2008S, 64◦4210W, 27.VII.1996.
BMNH 1998.3.11.16 (1, 200), Rio Tef´
e, Lago Tef´
e,
03◦3435S, 64◦5919W, 10.VIII.1996. BMNH 1998.3.11.17
(1, 180), Rio Tef´
e, Lago Tef´
e, 03◦3435S, 64◦5919W,
10.VIII.1996. INPA 15787 (1, 180), Rio Tef´
e, Lago Tef´
e,
03◦2008S, 64◦4210W, 05.V.1996. INPA 15797 (2, 437–
523), Rio Tef´
e, Lago Tef´
e, 03◦3435S, 64◦5919W,
28.VIII.1999. INPA 16579 (2, 167–183), Rio Jauaperi, Igarap´
e
Cambeua, 01◦2559S, 61◦35W, 01.XII.2000. INPA 18155
(2, 215–398), Rio Tef´
e, 03◦4719S, 64◦9155W, 23.X.1999.
INPA 18232 (1, 422), Lago Aman˜
a, 02◦3946S, 64◦3909W,
01.V.1994. INPA 18237 (1, 174), Lago Aman˜
a, 02◦3231S,
64◦4130W, 24.XI.1998. INPA 6430 (1, 520), Rio Solim˜
oes,
Ilha do Careiro, 03◦12S, 59◦45W, 31.III.1987. INPA 9072 (1,
356), Rio Negro, Anavilhanas, 02◦42S, 60◦45W, 06.III.1976.
MCP 32259 (1, 121), Rio Tef´
e, Lago Tef´
e, 03◦2008S,
64◦4210W, 04.V.1996. MCP 32260 (1, 118), Rio Tef´
e,
Lago Tef´
e, 03◦2008S, 64◦4210W, 05.V.1996. MCP 32261
(1, 142), Rio Tef´
e, Ilha Martelo, 03◦4649S, 64◦5929W,
26.VII.1999. MCP 32262 (6, 288–431, 1 C&S), Rio Tef´
e,
03◦47S, 64◦5955W, 25.X.1999. MCP 32263 (1, 125), Rio
Tef ´
e, Ilha Martelo, 03◦4649S, 64◦5929W, 14.VI.2000.
MCP 32264 (1, 123), Rio Tef´
e, Lago Tef´
e, Igarap´
e Repar-
timento, 03◦2428S, 64◦1710W, 02.II.2003. MCP T-032 (1,
180, C&S), Rio Tef´
e, Toco Preto, 03◦4719S, 64◦5955W,
24.X.1999. MCZ 9411 (1, 175), Rio Amazonas, nr. Parintins,
02◦40S, 56◦45W, 30.VIII.1865. MCZ 9413 (1, 208, ST),
Rio Tef´
e, Lago Tef´
e, 03◦2419S, 64◦45W, X.1865. MCZ
9425 (1, 295, ST), Rio Ma´
ues, Ma´
ues, 03◦22S, 57◦38W,
15.XII.1865. MCZ 9453 (1, 206, ST), Rio Negro, Lago Aleixo,
03◦05S, 59◦53W, 06.XII.1865. MZUSP 6100 (1, 524), Rio
Puraquequara, 03◦0259S, 59◦46W, 17.IV.1967. Par´
a: MCZ
2768 (1, 175), Rio Amazonas, ´
Obidos, 01◦52S, 55◦30W,
XII.1865.
Sternopygus pejeraton.–Venezuela: Zulia: MCZ 37222
(1, PT), Rio Motatan, 09◦28N, 70◦37W, 17.III.1942. UF
25447 (1, 191), Rio Catatumbo, 09◦2259N, 71◦4359W,
17.VI.1974. UMMZ 157671 (2, 195–228, PT), Rio Palmar,
10◦11N, 71◦52W, 21.II.1942. USNM 121567 (17, 160–426),
Rio Socuy, Lago Maracaibo, 24.II.1942.
Sternopygus sp. ‘cau’. – Venezuela: Bolivar: AMNH
58643 (2, 263–267), Rio Caura, 7◦38N64
◦53W, 22.XI.1985.
Sternopygus xingu. – Brazil: Mato Grosso: MZUSP
48374 (1, 182, HT), Rio Batovi, 13◦S, 53◦30W,
19.VIII.196464.VIII. MZUSP 48375 (4, 162–260,PT), Rio
Batovi, 13◦S, 53◦30W, 19.VIII.196464.VIII. UMMZ 228961
(4, 206–265, PT, 2 C&S), Rio Batovi, 13◦S, 53◦30W,
VIII.1964. USNM 218830 (15, 175–265, PT, 2 C&S), Rio
Batovi, 13◦S, 53◦30W, 19.VIII.196464.VIII. USNM 326120
(3, 380–525, PT), Rio Batovi, VIII.1964. USNM 338273 (14,
72–304, PT), Rio Batovi, VIII.1964. USNM uncat. (28, 91–
240, PT, 2 C&S), Rio Batovi, VIII.1964. Par´
a: INPA 6418 (1,
353), Rio Tocantins, Tucuru´
ı, 03◦42S, 49◦42W, 31.X.1980.
INPA 6420 (1, 485), Rio Tocantins, Itupiranga, 05◦0805S,
49◦1936W, 29.VII.1982. INPA 6425 (1, 270), Rio Tocantins,
Breu Branco, 04◦0159S, 49◦40W, 11.VII.1982. INPA 6426
(1, 446), Rio Tocantins, Lago Taua, 03◦42S, 49◦42W,
31.X.1980. INPA 6427 (1, 455), Rio Tocantins, Lago Grande,
05◦09S, 49◦20W, 21.XI.1981. INPA 6918 (1, 354), Rio
Tocantins, 05◦01S, 50◦40W, XI.1980.
Appendix 2: Sternopygus branch list
Steps in parentheses are unambiguous character-state changes
on tree topology of Figure 17. Clade A–G named in Table 7.
Abbreviations listed in Materials and methods. Additional ab-
breviations include: consistency index (CI), rescaled index (RI)
and rescaled consistency (RC).
Clade A: (steps: 17)
14 Gape: larger or equal to eye diameter (CI: 1.00, RI: 1.00,
RC: 1.00)
17 Infraorbitals 3–4: enlarged, bony (CI: 0.50, RI: 0.67, RC:
0.33)
21 Ventral ethmoid: long (CI: 1.00, RI: 1.00, RC: 1.00)
22 Mesethmoid: robust (CI: 1.00, RI: 1.00, RC: 1.00)
432 Kevin G. Hulen et al.
23 Lateral ethmoid cartilage: contacting maxilla (CI: 1.00,
RI: 1.00, RC: 1.00)
25 Lateral ethmoid anterior process: long, extending lateral
to dorsal margin of vomer (CI: 0.50, RI: 0.67, RC: 0.33)
30 Neurocranium depth: moderate, mean 30.1–34.9% NL
(CI: 0.40, RI: 0.57, RC: 0.23)
35 Premaxilla shape: gracile, triangular in dorsal view (CI:
0.50, RI: 0.80, RC: 0.40)
37 Meckel’s cartilage ossification: dorsal margin ossified
completely in adults (CI: 1.00, RI: 1.00, RC: 1.00)
43 Hyomandibular PM opening: emerging from anterior shelf
(CI: 0.50, RI: 0.50, RC: 0.25)
46 Opercle, ratio of long axes: dorsal margin moderate, mean
70–75% distance of anterio-ventral margin (CI: 0.50, RI:
0.67, RC: 0.33)
48 Gill rakers: complex (see text), separated by unmineralized
tissue (CI: 1.00, RI: 1.00, RC: 1.00)
51 Posttemporal: not fused with supracleithrum (CI: 1.00, RI:
1.00, RC: 1.00)
55 Pectoral fin length: short, mean P1 51–60% HL (CI: 1.00,
RI: 1.00, RC: 1.00)
56 Pectoral fin rays: few, mode P1R 13–16 (CI: 0.50, RI: 0.50,
RC: 0.25)
63 Anterior vertebrae: not compressed (see text) (CI: 1.00,
RI: 1.00, RC: 1.00)
65 Anal-fin ray structure: unbranched (CI: 1.00, RI: 1.00, RC:
1.00)
Clade B: (steps: 4)
2 Pale lateral stripe: present in juveniles and adults (CI: 0.50,
RI: 0.80, RC: 0.40).
8 Head: wide, mean HW 42–47% HL (CI: 0.33, RI: 0.33,
RC: 0.11).
11 Interorbital distance: wide, mean IO 25–28% HL (CI: 0.50,
RI: 0.75, RC: 0.38).
30 Neurocranium: deep, mean HD 35–50% NL (CI: 0.40, RI:
0.57, RC: 0.23).
Clade C: (steps: 2)
3 Dark bars: present in juveniles (CI: 1.00, RI: 1.00, RC:
1.00).
15 Eye: large, mean ED 12–16% HL (CI: 0.50, RI: 0.67, RC:
0.33).
Clade D: (steps: 2)
12 Internarial distance: long, NN 19–23% HL (CI: 0.67, RI:
0.50, RC: 0.33).
13 Mouth: broad; mean MW16–19% HL (CI: 0.25, RI: 0.25,
RC: 0.06).
Clade E: (steps: 3)
5 Body: deep, BD 12–15% LEA (CI: 1.00, RI: 1.00, RC:
1.00).
6 Head: long, HL 14–15% LEA (CI: 0.67, RI: 0.75, RC:
0.50).
54 Pectoral distal radials: 3 and 4 fused (CI: 0.50, RI: 0.75,
RC: 0.38)
55 Pectoral fin: very short, P1 40–50% HL (CI: 1.00, RI: 1.00,
RC: 1.00).
Clade F: (steps: 3)
26 Vomer: long, narrow, length more than five times width
(CI: 0.50, RI: 0.67, RC: 0.33).
28 Frontal margin: straight dorsal to lateral ethmoid (CI: 0.50,
RI: 0.67, RC: 0.33).
46 Opercle, ratio of long axes: dorsal margin long, mean 76–
90% distance of anterio-ventral margin (CI: 0.50, RI: 0.67,
RC: 0.33).
Clade G: (steps: 5)
10 Snout profile: dorsal margin strongly concave (CI: 0.50,
RI: 0.50, RC: 0.25).
11 Interorbital: narrow, IO 17–24% HL (CI: 0.50, RI: 0.75,
RC: 0.38).
30 Neurocranium: moderate, ND 30–34.9% NL (CI: 0.40, RI:
0.57, RC: 0.23).
32 Parasphenoid width at prootic foramen: as wide or broader
than (PaS) at (PtS)–(OrS) junction (CI: 1.00, RI: 1.00, RC:
1.00).
36 Maxilla width: midlength half width of area near palatine
articulation (CI: 0.50, RI: 0.50, RC: 0.25).
