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Accepted by F. Lima: 15 Feb. 2018; published: 3 Apr. 2018
ZOOTAXA
ISSN 1175-5326 (print edition)
ISSN
1175-5334
(online edition)
Copyright © 2018 Magnolia Press
Zootaxa 4403 (1): 111
–
122
http://www.mapress.com/j/zt/
Article
111
https://doi.org/10.11646/zootaxa.4403.1.6
http://zoobank.org/urn:lsid:zoobank.org:pub:B8C49CC4-CB0A-4054-A01A-AB7D435843E1
A new species of Myloplus Gill (Characiformes, Serrasalmidae)
from the Tumucumaque Mountain Range, Brazil and French Guiana,
with comments on M. rubripinnis
MARCELO C. ANDRADE
1,4
, MICHEL JÉGU
2
& CECILE S. GAMA
3
1
Universidade Federal do Pará, Programa de Pós-Graduação em Ecologia Aquática e Pesca, and Laboratório de Ictiologia do Grupo
de Ecologia Aquática, Av. Perimetral, 2651, 66077-830, Belém, PA, Brazil. E-mail: andrademarcosta@gmail.com
2
Institut de Recherche pour le Développement, Biologie des Organismes et Ecosystèmes Aquatiques, Laboratoire d´Icthyologie,
Muséum national d’Histoire naturelle, C.P. 26, 43 rue Cuvier, 75231 Paris Cedex 05, France. E-mail: michel.jegu@gmail.com
3
Instituto de Pesquisas Científicas e Tecnológicas do Estado do Amapá, Av. Feliciano Coelho, 1509, 68900-260, Macapá, AP, Brazil.
E-mail: cecile.gama@iepa.ap.gov.br
4
Corresponding author
Abstract
A new species of Myloplus Gill is described from Eastern Tumucumaque Mountain Range, drainages of the Oyapock and
Araguari rivers between Brazil and French Guiana. The new species is diagnosed by having comparatively large scales
on the flanks, resulting in lower counts when compared with congeners, i.e., 59 to 70 total perforated scales on lateral line,
31 to 35 longitudinal scales above lateral line, 24 to 29 longitudinal scales below lateral line, and 22 to 26 circumpedun-
cular scale rows. The new species most closely resembles Myloplus rubripinnis by sharing with this species a general
rounded shape, a similar color pattern, and a high number of rays, i.e., 23 to 25 branched dorsal-fin rays and 35 to 38
branched anal-fin rays in the new species (vs. 24 to 25 and 32 to 40, respectively, in M. rubripinnis). After reviewing the
available type-specimens of all Myloplus species, M. rubripinnis is re-diagnosed as having higher counts of branched dor-
sal-fin rays and anal-fin rays combined to tiny scales on flanks, i.e., 85 to 89 total perforated scales on lateral line, 38 to
45 longitudinal scales above lateral line, 33 to 42 longitudinal scales below lateral line, and 30 to 39 circumpeduncular
scale rows.
Key words: taxonomy, Oiapoque, Araguari, Amapá, Guiana Shield, Ostariophysi
Resumo
Uma nova espécie de Myloplus Gill é descrita para o leste das Montanhas do Tumucumaque, drenagens dos rios Oiapoque
e Araguari entre o Brasil e a Guiana Francesa. A nova espécie é diagnosticada por apresentar escamas comparavelmente
grandes sobre os flancos, resultando em menores contagens quando comparadas com as congêneres, i.e., 59 a 70 escamas
totais na linha lateral, 31 a 35 séries de escamas acima da linha lateral, 24 a 29 séries de escamas abaixo da linha lateral,
e 22 a 26 séries de escamas ao redor do pedúnculo caudal. A nova é mais semelhante a Myloplus rubripinnis por com-
partilharem um formato geral do corpo arredondado, padrão de coloração similar, e elevado número de raios, i.e., 23 a 25
raios ramificados na nadadeira dorsal, e 35 a 38 raios ramificados na nadadeira anal na nova espécie (vs. 24 a 25 e 32 a
40, respectivamente em M. rubripinnis). A revisão do material-tipo disponível de todas espécies de Myloplus permitiu re-
diagnosticar M. rubripinnis como tendo elevadas contagens de raios ramificados nas nadadeiras dorsal e anal combinado
a escamas diminutas, i.e., 85 a 89 escamas totais na linha lateral, 38 a 45 séries de escamas acima da linha lateral, 33 a 42
séries de escamas abaixo da linha lateral, e 30 a 39 séries de escamas ao redor do pedúnculo caudal.
Palavras-chave: taxonomia, Oiapoque, Araguari, Amapá, Escudo das Guianas, Ostariophysi
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Introduction
The family Serrasalmidae includes 16 genera and about 100 valid species (Eschmeyer et al., 2017). Among the
serrasalmid genera, the genus Myloplus Gill is composed by herbivorous species that reach up to 50 cm of standard
length (Andrade, Jégu & Giarrizzo, 2016; Jégu, 2003). Myloplus harbors 13 valid species (Andrade, Ota, Bastos &
Jégu, 2016; Nico et al., 2017) widely distributed throughout South American rivers, presenting its greatest
diversity (11 spp.) at the Amazon basin. Myloplus does not constitute a monophyletic assemblage (Ortí et al., 2008;
Thompson et al., 2014), however, the traditional diagnosis based on morphological features allows characterize
Myloplus primarily by having large abdominal spines, forming a marked prepelvic serra, and premaxilla with two
rows of molariform teeth interspaced from each other, forming a clear gap (Jégu et al., 2003; Jégu et al., 2004).
Although new Myloplus species have been described in recent years (Andrade, Jégu & Giarrizzo, 2016; Andrade,
Ota, Bastos & Jégu, 2016), the analysis of type-specimens, plus additional material deposited in museums continue
to reveal hidden diversity within the genus.
The Tumucumaque Mountain Range lies at the border between Brazil and French Guiana and is drained by
tributaries of the rio Araguari in the Brazilian State of Amapá, and tributaries of the Oyapock River basin between
Brazil and French Guiana. A new Myloplus species closely related to Myloplus rubripinnis (Müller & Troschel) by
sharing with the latter species a general rounded shape and similar coloration pattern was discovered in the area.
The new Myloplus species is promptly distinguished from M. rubripinnis and from the remaining congeners by
having notably larger scales, which results in lower scale counts, in contrast with the tiny scales and consequently
high scale counts of the remaining species belonging to the genus Myloplus. The present contribution aims to
describe this new Myloplus species from drainages of East Guiana Shield, as well as to re-diagnose M. rubripinnis.
Material and methods
Measurements and counts were taken according to Jégu et al. (2003). Measurements of body are expressed as
percentages of standard length (SL) and subunits of head as percentages of head length (HL). Counts are given in
description, followed by the frequency of that count (in parentheses), with the counts of the holotype indicated by
an asterisk (*). Osteological counts and description of head bones were taken from two radiographed specimens
(IEPA 3547 and ZMA 107.638). Vertebrae counts include the Weberian apparatus as four elements and the caudal
centra counted as a single bone. Osteological terminology follows Weitzman (1962), with the modifications
summarized by Mattox et al. (2014). Institutional abbreviations follow Sabaj (2016).
Myloplus tumukumak, new species
(Figs. 1–2, and 4B)
Myloplus rubripinnnis (not Müller & Troschel): Jégu et al., 2004: 143 (in part; specimens from Oyapock River basin).
Holotype. ZMA 107.638, 215.3 mm SL, Brazil, State of Amapá, Motoura River, a tributary of Oyapock River,
02°35’00”N 52°33’00”W, F. d’Aubenton, 11 Oct 1976.
Paratypes. Brazil, State of Amapá: IEPA 3547, 1, 136.0 mm SL, rio Amaparí, rio Araguari basin, Montanhas
do Tumucumaque National Park, 01°35’45”N 52°29’32”W, C.S. Gama, 19 Sep 2004. INPA 2262, 1, 254.5 mm SL,
Nazay River, tributary of Oyapock River, F. d’Aubenton, 18 Apr 1984. MNHN 1981-0541, 1, 152.0 mm SL,
Motoura River, F. d’Aubenton, 11 Oct 1976. French Guiana: IRSNB 20.223, 3, 43.9–53.6 mm SL, Camopi River,
Polydor, S.M. Léopold III & J.P. Gosse, 30 Nov 1969. IRSNB 20.224, 2, 96.7–97.1 mm SL, Oyapock River
downstream Crique Adjoumba between Sikini and Camopi rivers, S.M. Léopold III & J.P. Gosse, 6 Dec 1969.
MNHN 1981-0423, 2, 67.4–93.1 mm SL, Camopi River, Polydor, F. d’Aubenton, 19 Oct 1976. ZMA 107.682, 1,
22.2 mm SL, Sikini Creek, Saut Couachim Tambe, near its confluence with Oyapock River, F. d’Aubenton, 26 Sep
1976. ZMA 107.690, 2, 17.4–19.6 mm SL, Armontabo Creek near its confluence with Oyapock River, F.
d’Aubenton, 22 Oct 1976.
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FIGURE 1. Myloplus tumukumak, ZMA 107.638, holotype, 215.3 mm SL, Motoura River, Oyapock River basin, State of
Amapá, Brazil: photo (A) and x-ray (B), with yellow arrow indicating pectoral-fin origin, and white arrow the anteriormost
spine of prepelvic serra. Scale bars = 10 mm.
Diagnosis. Myloplus tumukumak can be diagnosed from its congeners by having larger scales on flanks,
resulting in lower scale counts. Myloplus tumukumak have 22–26 circumpeduncular scale rows (vs. 38–40 in M.
arnoldi, 31–41 in M. asterias, 34–40 in M. lobatus, 29–33 in M. lucienae, 30–39 in M. rubripinnis, 34–43 in M.
rhomboidalis, 31–34 in M. planquettei, 32–38 in M. ternetzi, and 34–36 in M. zorroi). The new species is further
diagnosed by having fewer scale rows below lateral line, i.e., 24‒29 (vs. 42‒45 in M. arnoldi, 40‒45 in M. asterias,
48‒56 in M. levis, 33‒42 in M. rubripinnis, 46‒57 in M. rhomboidalis, and 32‒37 in M. planquettei). Myloplus
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tumukumak is additionally diagnosed by having 23–25 branched dorsal-fin rays (vs. 18–20 in M. arnoldi, 18–19 in
M. planquettei, 21–22 in M. rhomboidalis, and 18–21 in M. schomburgkii). Myloplus tumukumak further differ
from M. torquatus by having more branched anal-fin rays (35–38 vs. 29–30, respectively). Myloplus tumukumak is
additionally diagnosed from M. lucienae, M. planquettei, and M. zorroi by having anteriormost spine of prepelvic
serra reaching or surpassing anteriorly vertical through pectoral-fin origin (Fig. 1B) (vs. anteriormost spine in M.
lucienae, M. planquettei, and M. zorroi never reaching vertical through pectoral-fin origin). Additional comments
on diagnostic features of the new species are presented under the Discussion.
Description. Morphometric data in Table 1. Largest specimen examined 254.5 mm SL. Body deep and
rounded, highest body depth at dorsal-fin origin. Snout blunt. Dorsal profile of head gently concave, predorsal
profile slightly straight. Dorsal- and anal-fin bases slightly convex. Ventral profiles of head and body convex.
Dorsal and ventral profiles of caudal peduncle convex.
Mouth terminal. Two interspaced rows of premaxillary teeth. Five*(14) molariform teeth in outer premaxillary
row and 2*(14) in inner row. Dentary with 4(2), 5*(10), or 6(1) molariform teeth. Pair*(13) of teeth at dentary
symphysis. Symphyseal tooth with anterior cutting edge. Maxilla edentulous.
Large cycloid scales on flanks. Lower flank scales somewhat larger than in upper flank. Perforated scales from
supracleithrum to hypural plate end 56(1), 57(1), 59(5), 60*(2), 64(3), or 65(1); and total perforated scales on
lateral line from supracleithrum to base of median caudal-fin rays 59(1), 61(1), 62(1), 63(3), 64(2), 65*(1), 67(2),
68(1), or 70(1). Longitudinal scale rows above lateral line to dorsal-fin origin 31(2), 32(4), 33(2), 34*(3), or 35(2);
and longitudinal scale rows below lateral line to pelvic-fin origin 24(1), 25(4), 26(1), 27(3), 28*(3), or 29(1). Scale
rows around caudal peduncle 22(1), 24*(3), 25(6), or 26(3).
Dorsal fin preceded by strong forward-directed spine. Dorsal-fin rays with ii*(14) unbranched, and 23(1),
24*(8), or 25(5) branched fin-rays. Anal-fin rays with ii(4) or iii*(10) unbranched, and 35(2), 36(1), 37*(8), or
38(3) branched fin-rays. Pectoral-fin rays with i*(12) unbranched, and 15(5), 16*(6), or 17(1) branched fin-rays.
Pelvic-fin rays with i*(11) unbranched, and 6(9) or 7*(2) branched fin-rays. Adipose fin small, tear-drop shaped.
Caudal fin forked into two equally-sized lobes.
Ventral keel serrae with well-developed spines. First anterior spine reaching or surpassing vertical through
pectoral-fin origin (Fig. 1B). Prepelvic serra with 24(4), 25*(3), 26(3), 27(2), or 28(1) spines; postpelvic serra with
6(6), 7*(6), or 8(1) simple spines; and with 6*(6), 7(6), or 8(1) pairs of spines around anus. Total serra with 36(3),
38*(4), 39(1), 40(2), 41(2), or 42(1) spines. First branchial arch with 28(1) or 30(1) total gill rakers; upper branch
with 13(1), or 15(1) rakers; lower branch with 14(2) rakers; and 1(2) at cartilage between upper and lower
branches.
Neurocranium triangular, short anteroposteriorly, and with supraoccipital spine very high (Fig. 1B). Ascending
premaxilla process elongated, massif, oblique anteroposteriorly, and well attached to neurocranium. Dentary short,
with rectilinear lower surface. Five supraneurals, with 1st and 5
th
supraneurals positioned anterior to neural spine of
4
th
and 8
th
centra, respectively. Nine predorsal vertebrae, 5 vertebrae between first anal-fin pterygiophore and last
dorsal-fin pterygiophore, and 12 vertebrae posteriorly last dorsal-fin pterygiophore. First dorsal-fin pterygiophore
inserted posterior of neural spine of 9
th
centra. First anal-fin pterygiophore inserted behind haemal spine of 22
nd
centra. Thirty-nine total vertebrae, with 21 precaudal and 18 caudal vertebrae (Fig. 1B).
Color in alcohol. Overall ground color uniformly yellowish brown (Figs. 1A and 2). Ventral surface of head,
belly and base of anal fin pale brown. Fins hyaline to brown, with distal portion of dorsal, anal and caudal fins pale
gray. Outer portion of eyes dark yellowish-brown or predominantly black. Juveniles up to 90 mm SL present a faint
humeral spot roughly positioned above lateral line, extending from 4
th
to 5
th
perforated scales of lateral line (Fig. 2).
Juveniles up to 22 mm SL with six to eight irregular blotches vertically elongated on head and flanks. First blotch
located on head, and last blotch located on caudal peduncle end.
Sexual dimorphism. Mature males of M. tumukumak are recognized by the presence of an additional lobe on
anal fin formed by the extension of the middle branched rays. An additional lobe on anal fin was found only in a
mature male examined (INPA 2262). Conversely, juveniles and females present the first rays of anal-fin longer,
forming a falcated lobe (Fig. 2). No stiff hooks on distal-most lepidotrichia of anal-fin rays or filament extensions
on dorsal-fin rays were found in the single examined mature male.
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TABLE 1 . Morphometric data of Myloplus tumukumak from Tumuk-Humak Montains. Range of larger specimen
measurements includes the holotype data (Hol). SD = standard deviation.
Hol larger specimens youngest specimens
n Range Mean SD n Range Mean SD
Standard length (mm) 215.3 11 43.9‒254.5 118.8 73.9 3 17.4‒22.2 19.7 2.4
Percentages of standard length
Body depth 70.0 11 69.1‒79.5 73.8 3.8 3 53.3‒57.8 55.0 2.4
Head length 26.0 11 25.7‒31.3 27.9 1.8 3 27.8‒29.4 28.9 1.0
Distance from snout to supraoccipital spine 33.6 11 30.1‒39.5 34.0 2.4 3 35.0‒39.7 36.5 2.7
Predorsal length 55.7 11 53.2‒61.2 57.5 2.2 3 52.1‒56.7 54.7 2.3
Dorsal-fin base length 37.2 11 35.1‒38.8 36.8 1.1 3 33.2‒36.3 34.6 1.6
Interdorsal length 11.0 11 5.9‒11.0 8.8 1.7 3 5.1‒7.3 6.3 1.1
Adipose-fin base length 3.9 11 2.9‒3.9 3.5 0.3 3 1.5‒2.4 2.0 0.4
Caudal-peduncle depth 10.1 11 9.0‒10.1 9.6 0.4 3 9.4‒9.9 9.6 0.2
Caudal-peduncle width 4.3 11 2.3‒4.3 3.2 0.6 3 1.7‒1.8 1.7 0.0
Prepectoral length 27.6 11 24.7‒33.4 29.2 2.5 3 30.2‒31.8 31.1 0.8
Pectoral-fin length 23.0 11 21.4‒24.4 22.7 0.8 * * * *
Pelvic-fin origin to anal-fin origin 22.9 11 19.2‒24.3 21.6 1.8 3 16.0‒19.6 17.4 1.9
Pectoral-fin origin to pelvic-fin origin 33.3 11 31.7‒35.8 33.2 1.3 3 21.1‒25.3 23.9 2.4
Prepelvic length 59.7 11 57.5‒67.8 61.2 3.2 3 52.5‒56.8 54.8 2.2
Pelvic-fin length 15.2 11 13.8‒15.6 14.8 0.7 * * * *
Preanal length 78.3 11 75.4‒83.2 78.7 2.5 3 68.2‒75.5 71.1 3.9
Anal-fin base length 38.3 11 37.6‒44.3 41.4 2.3 3 31.0‒35.7 34.0 2.6
First anal-fin lobe length 31.0 10 28.1‒53.2 36.2 9.0 3 18.1‒22.0 20.3 2.0
Second anal-fin lobe length * 1 10.5‒10.5 10.5 * * * * *
Dorsal-fin lobe length 31.1 11 26.2‒53.2 34.7 8.1 3 18.7‒23.5 21.9 2.8
Dorsal-fin origin to anal-fin origin 71.2 11 69.2‒79.3 74.6 3.6 3 53.5‒58.6 55.6 2.7
Dorsal-fin end to anal-fin origin 52.6 11 52.5‒58.8 55.3 2.2 3 36.9‒43.6 39.8 3.4
Dorsal-fin end to anal-fin end 22.2 11 18.6‒23.3 21.1 1.5 3 16.2‒17.8 17.1 0.8
Percentages of head length
Snout length 32.9 11 18.2‒32.9 25.3 4.0 3 17.7‒26.1 22.5 4.3
Mouth length 17.6 11 12.6‒19.8 15.8 2.6 3 8.4‒11.0 9.4 1.4
Mouth width 36.6 11 28.5‒40.1 34.0 4.2 3 15.6‒22.8 19.6 3.6
Interorbital width 58.1 11 40.1‒60.0 48.5 6.9 3 20.9‒30.9 26.1 5.0
Head width 67.6 11 51.8‒67.6 59.2 5.7 3 35.3‒45.0 41.7 5.6
Third infraorbital width 12.7 11 8.9‒15.2 11.5 2.0 3 16.0‒20.0 17.7 2.1
Cheek gap width 9.9 11 8.1‒15.2 11.5 2.0 3 5.7‒8.3 7.1 1.4
Fourth infraorbital width 16.8 11 10.5‒16.8 14.1 2.0 3 17.3‒21.3 19.7 2.1
Eye vertical diameter 39.3 11 37.4‒49.7 46.4 4.6 3 40.2‒43.1 41.1 1.7
Postorbital distance 29.8 11 25.9‒33.0 28.9 2.5 3 31.0‒36.6 34.0 2.8
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FIGURE 2. Myloplus tumukumak, IRSNB 20.223, paratype, 45.9 mm SL, Camopi River, Oyapock River basin, French
Guiana. Scale bar = 10 mm.
FIGURE 3. Distribution map of Myloplus tumukumak (black circles; black star represent type locality), and Myloplus
rubripinnis (white circles). The Tumuk-Humak Mountain Range is represented in gray shade. Symbols can represent more than
one record.
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Growth and ontogeny. Body depth shifts from a low depth in specimens smaller than 45 mm SL (58% SL or
less), to a deeper body in specimens larger than 45 mm SL (greater than 69% SL) (Table 1). Embedded
measurements in standard length, such as preanal and prepelvic lengths, pectoral to pelvic and pelvic to anal
distances have a strong variation between smaller and larger specimens, having lower proportions in smaller
specimens, with a gradual increase in proportional length along growth (Table 1). The first dorsal- and anal-fin rays
are very elongated in specimens around 50–70 mm SL (mean 45.6% SL and 48.0% SL, respectively; see Fig. 2),
compared with smaller specimens (mean 21.9% SL and 20.3% SL, respectively) and in specimens larger than 90
mm SL (mean 29.7% SL and 29.3% SL, for dorsal and anal fin, respectively). A positive allometry is evident in
measurements related with body width, such as caudal peduncle width, and head measurements as interorbital
distance, head, and mouth widths. There is a positive allometry of eye vertical diameter in specimens up to 45 mm
SL (mean 41.1% HL), becoming isometric in specimens larger than 45 mm SL (mean 49% HL in specimens
between 43.9–136.0 mm SL), and presenting a negative allometry in specimens larger than 200 mm SL (mean
38.3% HL in two specimens).
The smaller specimens examined, around 20 mm SL, display molariform teeth with crown edge very high and
spiky, while adult specimens present molariform teeth with crown edge low and rounded. Specimens smaller than
20 mm SL (ZMA 107.690) present premaxillary teeth with spiky crowns with a wide base as well as molariform
teeth, whereas the dentary teeth are sharp and pointed, particularly the four posteriormost teeth, resembling
caniniform teeth by presenting rounded base with general conical shape.
Distribution. Myloplus tumukumak is only known from the Oyapock River and its tributaries between Brazil
and French Guiana, such as Nazay, Camopi, Sikini and Motoura rivers, and also occurring at the rio Amaparí, a
tributary of rio Araguari basin, State of Amapá, Brazil (Fig. 3). The new species occurs in rivers draining two
Conservation Units, both lying at the eastern portion of the Tumuk-Humak mountain range, viz., the Parque
Nacional Montanhas do Tumucumaque in Brazil, and the Parc Amazonien de Guyane in French Guiana.
Etymology. The specific epithet tumukumak refers to the Tumuk-Humak Mountain Range, where the new
species occurs and, as far as known, from where it is apparently endemic. A toponymic adjective.
Discussion
The main distinctive characteristic of M. tumukumak is the size of scales and its consequent lower scale counts
when compared with congeners. The only Myloplus species that also present relatively large-sized scales are M.
lucienae and M. zorroi, which are diagnosed from other species of the genus by presenting other lower meristic
counts such as a lower number of prepelvic spines (Andrade, Jégu & Giarrizzo, 2016, Andrade, Ota, Bastos &
Jégu, 2016). This latter feature clearly diagnoses M. tumukumak from M. lucienae and M. zorroi, since M.
tumukumak present prepelvic spines reaching anteriorly the vertical through the pectoral-fin origin (Fig. 1B),
whereas in M. lucienae and M. zorroi, which possess fewer spines, the prepelvic spines just reach the mid-belly,
never reaching the vertical through pectoral-fin origin. Other feature that diagnose M. tumukumak from the
remaining Myloplus species occurring at the Guiana Shield is the arrangement of the two premaxillary teeth rows.
Myloplus tumukumak can be diagnosed from M. rhomboidalis, M. lobatus, and M. schomburgkii by presenting the
two premaxillary teeth rows with the arrangement of gentle arcs, whereas the latter species present a clear distance
between the two premaxillary teeth rows, forming an arrangement that resembles an uppercase letter A. Myloplus
tumukumak can be readily distinguished from M. ternetzi by always having a pair of symphyseal tooth (vs.
symphyseal tooth always absent). Myloplus tumukumak can be differentiated from M. arnoldi and M. torquatus by
having greater number of total vertebrae (39 vs. 36‒37). Myloplus tumukumak is further diagnosed from congeners
by having flanks and fins without marks (vs. vertical black mark on the middle portion of the flank in M.
schomburgkii; a dense black pigmentation of distal border of anal-fin rays in M. levis and M. tiete; black
pigmentation at first dorsal-fin ray and distal portion of caudal fin in M. arnoldi; and an anterodistal black blotch
on dorsal fin in M. rhomboidalis). In addition, M. tumukumak is diagnosed by presenting a longer dorsal-fin base
(35.1‒38.8% SL, vs. 23.2–32.4% SL in M. lucienae, 26.5–28.2% SL in M. rhomboidalis, 27.8–31.0% SL in M.
planquettei, and 27.6–30.1% SL in M. zorroi).
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FIGURE 4. A) Myloplus rubripinnis, 76.5 mm SL, paralectotype of Myletes rubripinnis, BMNH 1971.5.10.64, Essequibo
River basin, Guyana; B) Myloplus tumukumak, 67.4 mm SL, paratype, MNHN 1981-0423, Camopi River, French Guiana.
Scale bars = 10 mm.
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FIGURE 5. Myloplus rubripinnis, Jari River, Amapá, Brazil. A) IEPA 2863, male, 170.0 mm SL; B) IEPA 2891, female, 155.3
mm SL. Scale bars = 10 mm.
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Myloplus tumukumak is syntopic and morphologically similar to M. rubripinnis, and consequently, comments
on the diagnosis of M. rubripinnis are necessary. Myloplus rubripinnis was redescribed by Jégu et al. (2004), who
assigned this species along with M. asterias to the genus Myloplus, by having molariform teeth and two
premaxillary teeth rows interspaced by a gap. Based on this combination of characters, other serrasalmid species
were subsequently assigned to the genus Myloplus (Andrade, Jégu & Giarrizzo, 2016). It should be pointed,
however, that the major problem of the genus Myloplus concept sensu Jégu et al. (2004) is that the characters
defining the genus are homoplastic and consequently, the monophyly of the genus is uncertain. After an extensive
examination of material, we found that Myloplus rubripinnis as redescribed by Jégu et al. (2004) is a species-
complex composed by at least three different species, which explains the great range variability for the species
reported by the latter authors. Besides M. rubripinnis and M. tumukumak, a third Myloplus species that does not
matches none of the remaining species recorded from the Guiana Shield, and which co-occurs with M. rubripinnis
and M. tumukumak at the rio Araguari (State of Amapá), can be distiguished by presenting lower dorsal-fin ray
counts (19–21 branched dorsal-fin rays), a shorter dorsal-fin base length (27.5–33.7% SL), and 74–79 total
perforated scales on lateral line. The populations assigned by Jégu et al. (2004) to Myloplus rubripinnis from the
rio Xingu (State of Pará) are apparently conspecific with this latter species. A broad, comprehensive analysis
including all Myloplus species is still necessary to clarify species limits within the genus, as well as to provide
more accurate information about the distribution of each species.
Since Myloplus tumukumak is the species which most closely resembles M. rubripinnis in counts and general
body shape, comments on the diagnosis of M. rubripinnis are necessary to clarify the distinctness of both taxa.
Based on the type-material of the M. rubripinnis (Fig. 4A) and additional material from rivers draining the Guiana
Shield, we re-diagnose this species by having higher counts of branched dorsal-fin rays coupled with a longer
dorsal-fin base (24–25, and 29.8–36.9% SL), higher counts of branched anal-fin rays coupled with a longer anal-fin
base (32–40, 32.2–45.3% SL), and by presenting tiny scales with consequently higher counts (85–89 total
perforated scales on lateral line, 38–45 longitudinal scales above lateral line, 33–42 longitudinal scales below
lateral line, and 30–39 circumpeduncular scale rows). As remarked under the Diagnosis, there is a striking
distinction in the scales size on flanks between M. rubripinnis (Fig. 4A) and M. tumukumak (Fig. 4B), the first one
presenting tiny scales, which result in higher counts, in comparison with the latter, that present remarkably large
scales on flanks, mainly in the lower flank (Fig. 4B), which result in noticeable lower scale counts. Although
subtle, there is a difference in general body shape between the two species, M. rubripinnis presents an overall more
rounded body shape (Figs. 4A and 5), while M. tumukumak presenting a more angled shape (Figs. 1A and 4B).
Myloplus rubripinnis was originally described as belonging to the genus Myletes by Müller & Troschel (1844)
based in specimens collected in British Guyana (currently Guyana). Myloplus rubripinnis is herein recognized as a
widespread species occurring throughout Guiana Shield drainages, from the Essequibo River in Guyana to the
Saramacca and Suriname river basins in Suriname; the Maroni/Marowijne river at the Suriname/French Guiana
border, the Mana river basin in French Guiana in Oyapock River between French Guiana and Brazil, and at the rio
Araguari and rio Jari in Brazil (Fig. 3). Conversely, Myloplus tumukumak is only known from the region at the
boundary between Brazil and French Guiana in tributaries of both the Oyapock and Araguari river basins (Fig. 3).
This region harbors mainly headwaters of clearwater rivers, which drain towards the Amazon basin such as the rio
Paru and rio Jari, as well as Atlantic Coastal drainages, such as the rio Araguari and the Oyapock River (Irving,
2004; Lujan & Armbruster, 2011). Myloplus tumukumak should be added to the list of serrasalmid fish species
confined to Guyanese river systems draining directly to the Atlantic Ocean, which also includes Acnodon
oligacanthus, Mylesinus schomburgkii, Myleus knerii, Myleus pacu, Myloplus planquettei, Myloplus ternetzi, and
Tometes lebaili.
Comparative material examined
Myloplus arnoldi: IEPA 2882, 5, 99.1‒118.1 mm SL; IEPA 3552, 1, 30.8 mm SL; IEPA 3553, 1, 83.7 mm SL;
Brazil, Amapá, rio Jari basin. IRSNB 21253, 1, 147.8 mm SL; Brazil, Mato Grosso, rio Xingu basin; ZMB 20812,
syntype, 43.9 mm SL; Brazil, rio Amazonas. Myloplus asterias: BMNH 1971.5.10:61‒62, 2, paralectotypes of
Myletes asterias Müller & Troschel, 115.3‒122.8 mm SL; BMNH 1971.5.10.63, 1, syntype of Myletes ellipticus
Günther, 182.5 mm SL; BMNH 1864.1.21.33, 1, syntype of Myletes ellipticus Günther, 135.9 mm SL; Guyana,
Essequibo River basin. Myloplus lobatus: BMNH 1849.11.8.32‒33, 2 syntypes, 143.6‒152.6 mm SL; BMNH
97.11.26.8, 1, 124.2 mm SL; Brazil, Pará, rio Capim basin. GEA 1988, 1, 166.7 mm SL; Brazil, Amazonas, rio
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NEW MYLOPLUS FROM BRAZIL AND FRENCH GUIANA
Madeira basin. MNHN 0000‒5244, 1, 188.2 mm SL; Amazon River basin. Myloplus lucienae: INPA 30717, 1,
130.7 mm SL; INPA 915, 1, 230.0 mm SL; INPA 916, 4, 279.9‒320.0 mm SL; INPA 917, 2, 286.5‒334.3 mm SL;
INPA 3682, 1, 317.0 mm SL; INPA 3685, 1, 263.4 mm SL; INPA 10213, 1, 286.8 mm SL; INPA 10214, 2,
302.7‒312.3 mm SL; INPA 10216, 4, 260.9‒331.3 mm SL; Brazil, Amazonas, rio Negro basin. Myloplus
planquettei: IEPA 1638, 1, 53.8 mm SL; IEPA 1675, 1, 97.1 mm SL; IEPA 2852, 1, 329.0 mm SL; IEPA 2857, 1,
357.0 mm SL; IEPA 2864, 1, 266.8 mm SL; IEPA 2876, 1, 66.1 mm SL; IEPA 2878, 4, 50.9‒63.1 mm SL; IEPA
3544, 6, 136.4‒167.5 mm SL; IEPA 3545, 1, 108.1 mm SL; Brazil, Amapá, rio Jari basin. INPA 2260, 1, 155.3 mm
SL; INPA 2261, 1, 119.5 mm SL; French Guiana, Mana River. MNHN 1997‒0729, 1 paratype, 66.7 mm SL;
MNHN 1997‒0730, holotype, 112.8 mm SL; MNHN 2001‒1224, 1 paratype, 139.3 mm SL; French Guiana,
Maroni River basin. Myloplus rhomboidalis: IEPA 2833, 1, 90.8 mm SL; IEPA 2865, 1, 162.9 mm SL; IEPA 2870,
1, 145.9 mm SL; IEPA 2887, 1, 77.2 mm SL; IEPA 2894, 1, 68.9 mm SL; IEPA 3056, 1, 42.2 mm SL; IEPA 3559,
1, 43.5 mm SL; Brazil, Amapá, rio Jari basin. IRSNB 20221, 4, 66.9‒95.6 mm SL; IRSNB 20221, 5, 68.0‒87.9
mm SL; French Guiana, Oyapock River basin. MNHN 4423, 1, 150.1 mm SL; Brazil, Amazonas, Amazon River
basin. Myloplus rubripinnis: BMNH 1971.5.10.64, 1 paralectotype of Myletes rubripinnis Müller & Troschel, 76.5
mm SL; Guyana, Essequibo River basin. IEPA 2863, 1, 170.0 mm SL; IEPA 2874, 1, 128.9 mm SL; IEPA 2891, 2,
155.3‒162.4 mm SL; IEPA 3420, 1, 101.7 mm SL; Brazil, Amapá, rio Jari basin. INPA 2251, 3, 106.6‒147.5 mm
SL; French Guiana, Mana River. ZMA 105.565, 2, 168.7‒190.6 mm SL; Suriname, Saramacca basin. MNHN
2000‒0148 [ex A.9870], 3, paralectotypes of Myletes luna Valenciennes, 176.7‒224.4 mm SL; MNHN A.9870, 1,
lectotype of Myletes luna Valenciennes, 285.4 mm SL; French Guiana, Cayenne. RMNH 33704, 1, 183.9 mm SL;
RMNH 33711, 1, 91.6 mm SL; ZMA 120.251, 1, 171.6 mm SL; Surinam, Brokopondo Lake. RMNH 33703, 1,
177.0 mm SL; Surinam, Mamadam, Surinam River. Myloplus cf. rubripinnis: IEPA 2270, 1, 83.8 mm SL; IEPA
2885, 1, 82.6 mm SL Brazil, Amapá, rio Jari. MNHN 1998-0261, 2, 152.1‒259.8 mm SL; Brazil, Amapá, rio
Araguari. Myloplus schomburgkii: GEA 1974, 1 skel., 135 mm SL; Brazil, Pará, rio Xingu basin; GEA 1987, 1,
224 mm SL; Brazil, Amazonas, rio Madeira basin. LIA 316, 2, 44.7‒49.2 mm SL; LIA 451, 1, 51.8 mm SL; Brazil,
rio Xingu basin. Myloplus ternetzi: BMNH 1926.3.2.531‒532, 2 syntypes of Paramyloplus ternetzi, 157.1‒163.2
mm SL; French Guiana, Approuague River basin. IEPA 2847, 2, 178.4‒193.9 mm SL; Brazil, rio Jari basin. IEPA
2866, 2, 161.7‒187.7 mm SL; Brazil, Amapá, rio Araguari basin. IEPA 3560, 5, 98.4‒117.5 mm SL; Brazil,
Amapá, rio Araguari basin. IEPA 3586, 3, 18.1‒29.9 mm SL; Brazil, Amapá, Oyapock River basin. IRSNB 20691,
1, 60.6 mm SL; French Guiana, Oyapock River basin. IRSNB 20225, 2, 48.84‒57.3 mm SL; IRSNB 20226, 3,
27.6‒28.9 mm SL; Brazil, Amapá, Oyapock River basin. IRSNB 20250, 1, 60.8 mm SL; IRSNB 20251, 1, 49.9
mm SL; Brazil, Amapá, rio Amaparí, rio Araguari basin. IRSNB 20689, 3, 57.2‒121.9 mm SL; French Guiana,
Oyapock River basin. RMNH 26467, holotype of Myleus (Paramyloplus) ternetzi goslinei, 178.3 mm SL; RMNH
33828, 6 paratypes of Myleus (Paramyloplus) ternetzi goslinei, 67.1‒142.6 mm SL; Suriname, Suriname River
basin. Myloplus torquatus: NMW 56449, 1 paralectotype, 133.0 mm SL; NMW 56450, lectotype, 122.0 mm SL;
Brazil, Amazonas, rio Branco basin. Myloplus zorroi: INPA 50880, holotype, 326.2 mm SL; INPA 48546, 1
paratype, 249.9 mm SL; INPA 50868, 3 paratypes, 183.8‒339.5 mm SL; Brazil, Amazonas, rio Madeira basin.
Acknowledgments
We thank R. Ruiter (RMNH and ZMA), P. Pruvost (MNHN), O. Crimmen (BMNH), G. Lenglet (IRSNB), L. Rapp
Py-Daniel (INPA), A. Palandacic (NMW), and P. Bartsch (ZMB) for support during visits to their institutions, loan
of comparative material, or for sending information about type specimens. This study was partially supported by
GUYAMAZ Program, a project of the Franco-Brazilian Scientific and University Cooperation. MCA is funded by
Postdoctoral National Fellowship addressed to the Postgraduate Program of Aquatic Ecology and Fishery of UFPA
(PNPD/CAPES # 06/2017).
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