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Trigonostigma truncata, a new species of harlequin rasbora from Malay Peninsula (Teleostei: Danionidae)

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Trigonostigma truncata, new species, is described from the coastal swamp forests along the east coast of the Malay Peninsula. It differs from all congeners, in having a gently sloping lateral head and nape shape, the characteristic black triangular marking, newly termed here as the axine, which is large with its caudal apex not reaching caudal-fin base, presence of orange-red colour on the anal fin, a bluish-lilac coloured sheen on body in life, and a shallower body depth as compared to its most similar congener, T. heteromorpha. A key to the genus Trigonostigma and a brief redescription of T. heteromorpha is also included.
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RAFFLES BULLETIN OF ZOOLOGY 2020
Trigonostigma truncata, a new species of harlequin rasbora from Malay
Peninsula (Teleostei: Danionidae)
Tan Heok Hui
Abstract. Trigonostigma truncata, new species, is described from the coastal swamp forests along the east coast
of the Malay Peninsula. It differs from all congeners, in having a gently sloping lateral head and nape shape, the
characteristic black triangular marking, newly termed here as the axine, which is large with its caudal apex not
reaching caudal-n base, presence of orange-red colour on the anal n, a bluish-lilac coloured sheen on body in
life, and a shallower body depth as compared to its most similar congener, T. heteromorpha. A key to the genus
Trigonostigma and a brief redescription of T. heteromorpha is also included.
Key words. new species, biodiversity, Southeast Asia, acid waters, Cypriniformes
RAFFLES BULLETIN OF ZOOLOGY 68: 421–433
Date of publication: 28 May 2020
DOI: 10.26107/RBZ-2020-0058
http://zoobank.org/urn:lsid:zoobank.org:pub:776F3F8A-8323-45E2-86A0-CF9F1C7278DF
© National University of Singapore
ISSN 2345-7600 (electronic) | ISSN 0217-2445 (print)
Accepted by: Kevin Conway
Lee Kong Chian Natural History Museum, Faculty of Science, National University
of Singapore, 2 Conservatory Drive, Singapore 117377; Email: heokhui@nus.edu.sg
INTRODUCTION
The genus Rasbora has long been known to be a
heterogeneous assemblage of lineages, several of them
easily separated into species groups or complexes (Brittan,
1954b; Kottelat & Vidthayanon, 1993). A few of these
lineages have been recently recognised as separate genera
based on morphological grounds (viz. Boraras by Kottelat
& Vidthayanon, 1993; Sundadanio Kottelat & Witte, 1999;
and Trigonostigma Kottelat & Witte, 1999) and others
more recently recognised as separate genera in conjunction
with molecular phylogenetic work (Brevibora, Kottelatia,
Rasbosoma, Trigonopoma) (Liao et al., 2010).
The genus Trigonostigma was distinguished from Rasbora,
by a small adult size (less than 35 mm SL), unique body
colour pattern (an axine [see below] consisting of a broad
black triangular to dash-shaped pattern along the middle
of the body, with a red to pink to orange body colour), an
incomplete lateral line which is reduced to 6–9 pored scales,
and unique behavioural spawning traits (upside down body
positions of both male and female sh, and egg deposition on
the underside of leaves of submerged macrophytes) (Kottelat
& Witte, 1999; and present study). Trigonostigma currently
includes four species (Kottelat, 2013): T. heteromorpha
(Duncker, 1904), T. hengeli (Meinken, 1956), T. somphongsi
(Meinken, 1958a), and T. espei (Meinken, 1967); all occurring
in freshwater acidic swamp forest habitats. The monophyly
of Trigonostigma has not been disputed since its inception
(see Conway, 2005; Liao et al., 2011), but its phylogenetic
position in relation to Rasbora and related genera is still
inconclusive (Mayden et al., 2007; Rüber et al., 2007;
Conway et al., 2008; Britz et al., 2009, 2014; Fang et al.,
2009; Liao et al., 2010; Tang et al., 2010).
The type species T. heteromorpha was described by Duncker
in 1904, based on a series of specimens from several localities
(Negri Sembilan, Selangor in Peninsular Malaysia and
Singapore). This species is heavily traded in the ornamental
sh trade (Ng & Tan, 1997) based mainly on wild caught
stock, but several selectively bred aquarium varieties are
also available. The subsequent three species were described
by Meinken, all based on aquarium trade shes (Meinken,
1956, 1958a, 1958b, 1967). Trigonostigma hengeli is now
known from two main locations, one in central Jambi and
another in West Kalimantan (Tan & Kottelat, 2009), and
appears sporadically in the aquarium trade. Trigonostigma
somphongsi is the most uncommon of the four species,
supposedly from Menam in southern Thailand (Chao Phraya
drainage) (Kottelat, 2013). It has only been rarely encountered
and always in small numbers during the flood season
(Panitvong N, pers. comm.). Trigonostigma espei was also
described from aquarium trade material, supposedly obtained
from specimens imported from Bangkok (Kottelat, 2013).
This taxon also exhibits a disjunct distribution. Populations in
the eastern range are known from Chantaburi area in eastern
Thailand (Panitvong, 2020), Sihanoukville in Cambodia, and
Phu Quoc island, Vietnam (Bùi, 2011; Vasil’eva et al., 2013).
The disjunct western population is known from Krabi area,
in southwestern Thailand (Panitvong, 2020). For now, these
populations are considered conspecic, but deserve further
investigation. Trigonostigma espei is occasionally available
in the aquarium trade.
Recently, a series of specimens obtained through the aquarium
trade were observed to have a slightly different body shape
Taxonomy & Systematics
422
Tan: New species of harlequin rasbora from Malay Peninsula
and different black marking on the body from true T.
heteromorpha. Upon closer examination of these specimens
and additional material within the Zoological Reference
Collection at Lee Kong Chian Natural History Museum,
these were discovered to be distinct from T. heteromorpha
and represent a new species, described herein.
MATERIAL AND METHODS
The black triangular shape on the posterior half of body is
unique to the genus Trigonostigma (see comparative notes
in Kottelat & Witte, 1999: 54–55), though T. somphongsi
has a much-reduced marking, that is more of a thick black
stripe. Based on its uniqueness, a new term is proposed for
this feature — “axine”. It is a Greek word, meaning wedge.
In reference to the orientation of the axine, there are three
apices — dorsal, ventral and caudal. The dorsal apex is
below the dorsal-n origin, the ventral apex is above the
pelvic-n origin, and the caudal apex is near the caudal n
or at caudal-n base (see Fig. 1).
Specimens were xed in 10% formalin and later transferred
to 75% ethanol for long-term storage. Measurements were
obtained with dial calipers from the left side, according to
Kottelat (1984). Colour pattern terminology follows Brittan
(1954b). Abbreviations used: SL, standard length; HL, head
length.
Specimens examined are deposited in the private collection
of Maurice Kottelat, Delemont, Switzerland (CMK); Natural
History Museum, London (BMNH); and the Zoological
Reference Collection, Lee Kong Chian Natural History
Museum, National University of Singapore, Singapore (ZRC).
TAXONOMY
An articial key to the genus Trigonostigma (based on
freshly preserved mature specimens)
1. Axine large and prominent; distance between dorsal and ventral
apices at least ½ or more than ½ of body depth ...................2
Axine narrow, resembling a thick stripe, with anterior portion
slightly deeper; distance between dorsal and ventral apices
around or less than eye width; known from central Thailand
..................................................... Trigonostigma somphongsi
2. Caudal apex of axine reaching caudal n; anal n with faint
or without orange pigment ......................................................3
Caudal apex of axine not reaching caudal n, with 1–1½ scale
space; anal n always with orange pigment; known from east
coast of Malay Peninsula .........................................................
.......................................Trigonostigma truncata, new species
3. Adult size less than 30 mm SL; axine shallower in depth and
not more than ½ body depth; anal n without anterior black
streak ........................................................................................4
Adult size up to 35 mm SL; axine large and more than ⅔ body
depth; anal n always with anterior black streak; known from
Malay Peninsula, northern Sumatra, and Sumatran islands .....
................................................... Trigonostigma heteromorpha
4. Red/orange pigment restricted to area anterior and dorsal to
axine; dorsal n pale yellow or orange; known from central
Sumatra and west Kalimantan ............. Trigonostigma hengeli
Red/orange pigment throughout body, more intense along
dorsum and caudal regions; dorsal n reddish; known from two
disjunct populations – eastern Thailand to coastal Cambodia and
Vietnamese island of Phu Quoc, and near Krabi in southwestern
Thailand ................................................... Trigonostigma espei
Fig. 1. Trigonostigma heteromorpha with depiction of the axine (Ax) with three apices labelled. A, dorsal apex; B, ventral apex; C, caudal
apex. Specimen from Singapore: Central Catchment Nature Reserve, not preserved.
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RAFFLES BULLETIN OF ZOOLOGY 2020
Trigonostigma truncata, new species
(Figs. 2, 3, 4A, 5)
Rasbora heteromorpha (non-Duncker) – Mohsin & Ambak, 1983:
50 (part); Kottelat et al., 1992: 9, table 1; Kottelat et al., 1993:
63, pl. 18 (part).
Rasbora cf. heteromorpha – Collins et al., 2012: 10, table 3,
supplementary data table S1: 16 (part?).
Trigonostigma heteromorpha (non-Duncker) – Kottelat & Witte,
1999: 54 (part), g. 10; Kottelat, 2013: 170 (part); Panitvong,
2020: 142.
Trigonostigma aff. heteromorpha – Ng et al., 2019: 527 (part).
Material examined. — Holotype: ZRC 61240, 1 ex., 24.2
mm SL; Thailand: Narathiwat Province, stream along road
branching West at about 7 km on road from Waeng to Ban
Bu Ke Ta; Kottelat M et al., 2 November 1995.
Paratypes: SOUTH THAILAND — CMK 12049, 21 ex.,
ZRC 42090, 21 ex., 9.7–24.2 mm SL; same locality as
Fig. 2. Trigonostigma truncata, new species, holotype, ZRC 61240, 24.2 mm SL; Thailand: Narathiwat.
holotype. — ZRC 42131, 2 ex., 17.0–20.3 mm SL; Thailand:
Narathiwat Province, stream about 2 km South of Ban Bu
Ke Ta on road to Ban Sac; Kottelat M et al., 2 November
1995. — ZRC 42076, 6 ex., 15.1–21.6 mm SL; Thailand:
Narathiwat Province, swamp area about 2 km North of
Ban Bu Ke Ta, about 8 km South of Waeng; Kottelat M
et al., 2 November 1995. PENINSULAR MALAYSIA —
CMK 8221, 50 ex., ZRC 24807, 36 ex., 8.2–25.1 mm SL;
Malaysia: Terengganu, stream at about 6 km on road from
Kuala Brang to Kuala Terengganu; Ng PKL et al., 19 March
1992. — ZRC 40234, 40 ex., 11.9–24.7 mm SL; Malaysia:
Terengganu, 5 km Kuala Brang-Kuala Terengganu road; Ng
PKL et al., 16 May 1995. — ZRC 41933, 7 ex., 15.1–21.7
mm SL; Malaysia: Terengganu, Kuala Brang; Ng PKL et
al., October 1997. — ZRC 1966, 27 ex., 9.5–22.3 mm SL;
Malaysia: Terengganu, 17.5 mile Kuala Terengganu-Kuala
Brang road; Alfred ER, 8 July 1958. — ZRC 1714, 6 ex.,
15.3–20.2 mm SL; Malaysia: Terengganu, Kuala Brang;
Tweedie M, August 1950.
Fig. 3. Trigonostigma truncata, new species, live specimen of ca. 30 mm SL (trade material, not preserved).
424
Tan: New species of harlequin rasbora from Malay Peninsula
Table 1. Meristic and morphometric data for Trigonostigma truncata, new species.
Meristics Holotype (ZRC61240) Paratypes (ZRC24807, 42131, 42076,
42090) (n=17) and holotype [mode]
SL (mm) 24.2 17.3–25.1
dorsal n rays i, 7 i, 7
anal n rays i, 6 i, 6
caudal n rays (principle rays) 9+9 9+9
pelvic n rays i, 5 i, 5
pectoral n rays 10 10
lateral scales 27 26–30 [27]
no. of pored lateral line scales 66–8 [7]
predorsal scales 11 11
transverse scales 7–8 [7½]
transverse scales at dorsal 7½–9 [8½]
caudal peduncular scales ½.4.½ ½.4.½
circumpeduncular scales 10 10
dorsal n origin (lat) 10 8–10 [9]
anal n origin (lat) 15 14–15 [14]
pelvic n origin (lat) 98–10 [9]
start of axine in relation to lateral scales 12 10½–12½ [11]
scale rows between lateral and pelvic 32½–3 [3]
min max mean SD
% standard length
total length 130.2 130.2 142.9 138.7 3.34
body length 74.4 68.6 74.4 71.0 1.79
predorsal length 51.7 51.2 56.1 53.3 1.64
preanal length 68.2 64.3 70.7 67.7 1.92
prepelvic length 51.2 48.9 53.3 51.3 1.28
head length 31.0 28.5 31.6 30.2 1.00
body depth at dorsal 33.1 28.3 34.6 32.4 1.88
body depth at anus 24.8 22.5 29.3 25.8 1.68
caudal peduncle depth 14.5 11.0 27.9 14.0 3.98
caudal peduncle length 21.9 15.0 23.7 19.9 2.34
dorsal n base length 15.3 12.9 16.9 15.0 1.02
anal n base length 12.0 10.6 15.2 12.4 1.19
pelvic n length 19.0 15.7 21.6 19.6 1.39
pectoral n length 17.8 17.8 22.9 20.4 1.84
upper caudal lobe length 38.0 33.2 42.7 38.8 3.14
median caudal length 14.9 12.8 20.5 17.0 2.33
lower caudal lobe length 39.3 36.4 43.6 39.7 1.89
% head length
head depth 64.0 62.1 76.9 69.6 4.38
head width 46.7 39.4 51.9 46.8 2.89
snout length 22.7 16.4 25.8 22.1 2.93
orbital diameter 38.7 33.8 40.4 36.8 2.23
interorbital width 36.0 30.1 42.3 36.0 2.97
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Others: ZRC 54736, 4 ex., 29.7–33.7 mm SL; obtained from
aquarium trade, September 2015.
Diagnosis. Trigonostigma truncata, new species, is most
similar to T. heteromorpha, in having a large black axine
starting from approximately mid-body with dorsal apex
near dorsal-n origin, ventral apex near pelvic-n origin,
and caudal apex near caudal-n base; this axine being the
largest amongst all congeners. Trigonostigma truncata differs
from T. heteromorpha in the following characters: a gently
sloping lateral head prole to pre-dorsal region (vs. a steep
convex lateral prole from posterior of head to predorsal
region); sub-superior mouth (vs. terminal mouth); caudal
apex of axine not reaching caudal-n base (vs. reaching
and extending to hypural plate); dorsal and ventral apices
of axine originate posterior to both dorsal-n and pelvic-n
origins by up to three scale-widths (vs. dorsal apex starting
one scale-width posterior to dorsal-n origin and ventral apex
starting at pelvic-n origin; see Figs. 4, 5); faint or indistinct
brown humeral streak just posterior to opercular opening (vs.
a distinct black humeral streak); base of dorsal n hyaline
and its middle reddish-orange in life (vs. anterior two-thirds
of n orange-red); presence of distinct orange-red colour on
anal n in life (vs. faint or absence); having a bluish-lilac
sheen on the body in life (vs. reddish or purplish sheen);
and having a shallower body (depth at dorsal-n origin
28.3–34.6% SL [mean 32.4], vs. 32.6–38.2% [mean 35.8]).
Description. See Figs. 2–4 for general appearance. See Table
1 for meristic and morphometric data. Head pointed, with sub-
superior mouth, barbels absent. Prole of head and anterior
of body gently sloping upwards to dorsal-n origin, absence
of distinct notch between occiput and nape. Orbit relatively
large (orbital diameter 33.8–40.4% HL). Body compressed,
deepest at dorsal-n origin (body depth 28.3–34.6% SL)
and shallowest at caudal peduncle (caudal peduncle depth
11.0–14.5% SL). Dorsal and pelvic ns situated mid-body
(predorsal length 51.2–56.1% SL; prepelvic length 48.9–53.3
% SL), triangular and small (dorsal-n base length 12.9–
16.9% SL). Caudal n forked, symmetrical (upper caudal-n
lobe length 33.2–42.7% SL; lower caudal-n lobe length
36.4–43.6% SL). Anal n triangular, situated down the
body (preanal length 64.3–70.7% SL), and small (anal-n
base length 10.6–15.2% SL). Both pelvic and pectoral ns
triangular. Lateral scale series with 26–30 scales (mode
27), lateral line incomplete and leading horizontally away
from head, perforated lateral line scales 6–8 (mode 7). Both
dorsal-n and pelvic-n origins on vertical through lateral
scale 8–10 (mode 9), anal-n origin at 14–15 (mode 14).
Axine starting at lateral scale series 10½–12½ (mode 11).
Colouration in preservative. See Fig. 2. Base body colour
cream, dorsum dark brown, with dark brown stripe across
dorsum. Head region above eye dark brown. Eye with
silvery iris. Region posterior to opercle opening with faint
brown humeral streak. All ns hyaline, thin black margin
on distal half of anterior edge of dorsal and anal ns. Black
or dark brown axine on mid-body, anterior margin concave
to straight edged, dorsal apex starting about three scales
posterior to dorsal-n origin, ventral apex starting above
pelvic-n origin, caudal apex extending length of caudal
peduncle stopping about 1–2 scales anterior to caudal-n
base; axine surrounded with distinct margin of 1–1½ scale
width. Region of body anterior to triangular marking with
diffused melanophores.
Colouration in life. See Figs. 3, 4. Base body colour pale
yellowish-brown, dorsum can be a darker shade; sometimes
with slight orangish iridescence on anterior half of body and
bright orange blotch at caudal-n base; in fully acclimatised
specimens in captivity, a bluish-lilac sheen can be visible on
body. Region of head above eye dark brown or brown. Eye
with yellowish-orange iris with black dorsal patch, ventral
area silver. Region posterior to opercular opening with faint
brown humeral streak. Large velvety black axine on mid-
body, anterior margin concave to straight edged, dorsal apex
at about three scales posterior to dorsal-n origin, ventral
apex at pelvic-n origin, caudal apex extending length of
caudal peduncle to about 1–2 scales anterior to caudal-n
base; whole axine surrounded with distinct margin of 1–1½
scale width. Paired ns hyaline. Dorsal n base hyaline, thin
black margin on distal half of anterior edge, middle section
orangish-red, distal margin hyaline. Caudal n yellowish with
hyaline distal margin. Anal n base hyaline, thin black margin
on distal half of anterior edge, middle section orangish-red,
distal margin hyaline. Supra-anal region to ventral base of
caudal peduncle with dark brown streak.
No sexual dimorphism or dichromatism observed. From
hobbyists’ observations, males are usually more intensely
coloured.
Distribution. Trigonostigma truncata, new species, is
currently known from the east coast of the Malay Peninsula,
from south of the Isthmus of Kra in Narathiwat province
of southern Thailand to the Malaysian State of Terengganu
(Fig. 6). The map in Fig. 6 also shows the distribution of
all ve species for comparison.
Field notes. This species is found in lowland freshwater
acid swamp-forest stream habitats, usually flowing into
riverine habitats. Syntopic species collected from Mae Nam
Tod Deng swamp forest in South Thailand include the
following: Notopterus notopterus (Notopteridae), Boraras
urophthalmoides, Trigonopoma gracile (Danionidae),
Kryptopterus minor (Siluridae), Clarias meladerma (Clariidae),
Monopterus javanensis (Synbranchidae), Chaudhuria sp.
(Chaudhuriidae), Oryzias minutulatus (Adrianichthyidae),
Indostomus crocodilus (Indostomidae), Betta imbellis, B.
pi, Parosphromenus paludicola, Trichopodus trichopterus,
Trichopsis vittata (Osphronemidae), Channa limbata, and
C. lucius (Channidae).
Syntopic species collected from Kuala Brang in Terengganu
include the following: Osteochilus vittatus (Cyprinidae),
Rasbora bankanensis, R. dusonensis, Trigonopoma gracile
(Danionidae), Acanthopsoides sp., Lepidocephalichthys
furcatus, Pangio cuneovirgata, P. piperata, P. semicincta,
P. muraeniformis (Cobitidae), Homalopteroides nebulosus
(Balitoridae), Nemacheilus selangoricus (Nemacheilidae),
426
Tan: New species of harlequin rasbora from Malay Peninsula
Fig. 4. A, Trigonostigma truncata, new species, ZRC 54736, 33.7 mm SL, trade material; B, T. heteromorpha, ZRC 61239, 28.4 mm SL,
trade material; C, T. espei, ZRC uncat, 28.2 mm SL, trade material (obese individual); D, T. hengeli, ZRC uncat, 23.3 mm SL, Sumatra:
Jambi; E, T. somphongsi, not preserved, ca. 15 mm SL (right-side reversed; photograph by N. Panitvong).
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RAFFLES BULLETIN OF ZOOLOGY 2020
Barbucca diabolica (Barbuccidae), Hemibagrus capitulum,
Nanobagrus fuscus, Pseudomystus stenomus (Bagridae),
Silurichthys hasseltii (Siluridae), Parakysis verrucosus
(Akysidae), Clarias leiacanthus (Clariidae), Neostethus
smithi (Phallostethidae), Bihunichthys sp. (Chaudhuriidae),
Hemirhamphodon pogonognathus (Zenarchopteridae),
Xenentodon canciloides (Belonidae), Doryichthys martensii
(Syngnathidae), Brachygobius xanthomelas (Gobiidae),
Pristolepis grooti (Pristolepididae), Luciocephalus pulcher,
and Parosphomenus paludicola (Osphronemidae).
Syntopic species collected from Dungun swamp in
Terengganu include the following: Barbodes cf. binotatus,
Desmopuntius hexazona, Osteochilus vittatus, O. waandersii
(Cyprinidae), Boraras maculatus, Rasbora einthovenii, R.
cephalotaenia, R. paucisqualis, Trigonopoma gracile, T.
pauciperforatum (Danionidae), Lepidocephalichthys furcatus,
Pangio semicincta (Cobitidae), Homalopteroides nebulosus
(Balitoridae), Nemacheilus selangoricus (Nemacheilidae),
Neostethus smithi (Phallostethidae), Hemirhamphodon
pogonognathus (Zenarchopteridae), Nandus nebulosus
(Nandidae), Betta stigmosa, Luciocephalus pulcher, and
Parosphromenus paludicola (Osphronemidae).
Etymology. From the Latin ‘truncus’, meaning cut off, in
allusion to the caudal apex of the axine not reaching the base
of the caudal-n. Used as a noun in apposition.
Remarks. Trigonostigma truncata, new species, can be
further differentiated from T. heteromorpha in the following
characters: adpressed pectoral n not reaching pelvic-n
origin (vs. reaching); adpressed pelvic n not reaching anal-
n origin (vs. surpassing); more lateral scale count (26–30
[mode 27], vs. 25–28 [mode 26]); perforated lateral line
scales leading horizontally away from head (vs. curving
gently downwards away from head); relatively longer head
(head length 28.5–31.6% SL [mean 30.2], vs. 27.2–31.7%
[mean 28.9]); relatively slimmer caudal region (body depth
22.5–29.3% SL [mean 25.8], vs. 24.4–30.2% [mean 27.9];
caudal peduncle depth 11.0–14.5% SL [mean 12.9], vs.
12.6–15.8% [mean 13.8]); more slender head (head depth
62.1–76.9% HL [mean 69.6], vs. 68.1–80.6% [mean 74.7];
head width 39.4–51.9% HL [mean 46.8], vs. 42.9–53.5%
[mean 49.1]); relatively smaller eye (orbital diameter
33.8–40.4% HL [mean 36.8], vs. 35.6–44.8% [mean 40.2]).
Trigonostigma truncata, new species, can be differentiated
from the other congeners (T. espei, T. hengeli, and T.
somphongsi) by having a larger adult size (up to 33.7 mm
SL, vs. less than 30 mm); large black axine on body with
dorsal and ventral borders not exceeding one scale spacing
to edge of body (vs. 1½–2½ scale width).
In the naming of the new genus Trigonostigma by Kottelat
& Witte (1999: 54, g. 10), they presented a gure of a
preserved specimen of T. heteromorpha which is from the
series ZRC 42076. This is actually part of the type series
for the new species, T. truncata. The two taxa are so similar
that they were misidentied.
Collins’ et al. (2012: 6, g. 4) material of T. heteromorpha
consist of seven specimens from two genetic populations,
with COI divergence of more than 3%. They further
commented on the presence of orange pigments on the anal
n (supplementary table 1), which is congruent with the
present new species; however all of their material is from
the ornamental sh trade, which is without precise locality
data, and thus of limited use for taxonomical studies.
Trigonostigma heteromorpha (Duncker, 1904)
(Figs. 1, 4B, 5, 7)
Rasbora heteromorpha Duncker, 1904: 182, pl. 1, g. 5; Weber
& de Beaufort, 1916: 79; Tweedie, 1936: 21; Herre & Myers,
1937: 55; Fowler, 1938: 57; Brittan, 1954a: 152; 1954b: 187,
g. 44; Menon, 1954: 8; Alfred, 1963: 166; 1966: 19; Mohsin
& Ambak, 1983: 50 (part); Zakaria-Ismail, 1987: 406; Lim &
Ng, 1990: 32; Ng & Lim, 1992: 259, table 3; 1996: 111; 1997:
249; Kottelat et al., 1993: 63, pl. 1; Tan & Tan, 1994: 353;
Ng & Tan, 1997: 84; Sim, 2002: 50; Rachmatika et al., 2006:
64; Rüber et al., 2007: gs. 1–3; Collins et al., 2012 (not all
molecular phylogenetic studies are included in this synonymy
list, as most of them do not include locality data; and many
Fig. 5. Trigonostigma truncata, new species, ZRC 54736, 33.7 mm SL (left); and Trigonostigma heteromorpha, ZRC 61239, 28.4 mm
SL (right); detail of body, showing axine.
428
Tan: New species of harlequin rasbora from Malay Peninsula
Fig. 6. Map of Southeast Asia showing distribution of Trigonostigma: T. heteromorpha (solid circle), T. somphongsi (hollow circle), T.
espei (diamond), T. hengeli (square), and T. truncata, new species (pentagon). Each symbol may represent more than one location.
429
RAFFLES BULLETIN OF ZOOLOGY 2020
also suffer from using the same set of sequence data without
verication of vouchers, thus perpetuating errors [pers. obs.]).
Trigonostigma heteromorpha (Duncker, 1904): Kottelat & Witte,
1999: 54; Ng & Tan, 1999: 352, table 1; Conway, 2005: table
1, g. 11; Tan & Kottelat, 2009: 52; Baker & Lim, 2012: 36;
Kottelat, 2013: 170 (part); Chow et al., 2014: 56; Fahmi-Ahmad
et al., 2015: 34, table 1; Azmai et al., 2020: 74.
Material examined. — ZRC 39918, 2 ex., 19.3–24.2 mm
SL; Malaysia: Perak, Sungei Beriang, 21 km milestone from
Taiping to Segama; Tan HH et al., 18 November 1995. —
ZRC 14383, 1 ex., 28.0 mm SL; Malaysia: Selangor, Sungei
Buloh forest reserve, swampy forest stream; Ng PKL & Lim
KKP, 6 March 1991. — ZRC 13794 sa, 7 ex., 9.8–25.9
mm SL; Malaysia: Johor, Panti forest stream; Ng PKL, 31
August 1990. — ZRC 4903–4914, 11 ex., 15.6–25.0 mm
SL; Malaysia: Johor, Mawai, Sunegi Mupor; Alfred ER,
21 February 1971. — ZRC 55562, 9 ex., 19.0–27.6 mm
SL; Singapore: Central Catchment Nature Reserve, channel
between Upper Peirce and MacRitchie Reservoirs; Tan HH
et al., 18 September 2007 (only the largest specimens were
used for meristic counts and morphometric measurements;
n=20, SL=21.6–27.6 mm).
The following material was also examined but no
measurements or counts taken — BMNH 1905.5.6:2–3 (2
paralectotypes), 22.3–23.2 mm SL; Malaysia: Selangor, Kuala
Lumpur; Robinson HC, 1905. PENINSULAR MALAYSIA
— ZRC 27602, 1 ex., 18.0 mm SL; Malaysia: Selangor,
Sabak Bernam, Sungei Bernam; Ng PKL et al., 19 September
1992. — ZRC 13547, 2 ex., 27.9–28.3 mm SL; Malaysia:
Johor, Pontian, stream adjacent to Gunung Pulai reservoir
I; Ng PKL & Yeong R, 9 September 1988. — ZRC 21243,
4 ex., 17.9–22.9 mm SL: Malaysia: Johor, Sungei Selangi,
15 km Kota Tinggi-Tanjung Sedili Road; Ng PKL et al., 22
April 1992. SINGAPORE — ZRC 2314 (6 paralectotypes);
Singapore: Botanical Garden pond. — ZRC 12405, 4 ex.,
18.4–21.0 mm SL: Singapore: Sime Road forest; Ng PKL
& Lim KKP, 27 October 1989. — ZRC 34601, 18 ex.,
9.0–18.9 mm SL; Singapore: Sime Road forest; Lim KKP
et al., May 1992. — ZRC 34623, 2 ex., 23.0–24.1 mm SL;
Singapore Rie Range road stream; Chang CY et al., 27 May
1993. — ZRC 12386, 4 ex., 17.9–27.0 mm SL; Singapore
Nee Soon swamp forest, second track; Lim KKP & Ng
PKL, 14 April 1990. — ZRC 38248, 7 ex., 17.0–28.5 mm
SL; Singapore Nee Soon swamp forest; Lim KKP, 20 June
1994. INDONESIA: Riau Archipelago — ZRC 14044, 8 ex.,
19.6–30.3 mm SL: Indonesia: Pulau Batam, north-western
part; Ng PKL & Lim KKP, 25 February 1991. — ZRC
33215, 5 ex., 10.0–28.0 mm SL; Indonesia: Pulau Bintan
North; Tan THT et al., 11 May 1993. — ZRC 31540, 10 ex.,
19.1–31.2 mm SL; Indonesia: Pulau Lingga, Daik; Searby
M, November 1996. INDONESIA: Sumatra — ZRC 41950,
8 ex., 11.3–25.1 mm SL; Indonesia: Sumatra: Riau, upper
Indragiri; Tan HH et al., November 1996. — Others: ZRC
61239, 1 ex., 27.8 mm SL; obtained from aquarium trade,
September 2015.
Diagnosis. Trigonostigma heteromorpha shares with T.
truncata, new species, a large black axine starting from
approximately mid-body with dorsal apex near dorsal-n
origin, ventral apex near pelvic-n origin, and caudal apex
near caudal-n base; this axine being the largest amongst
all congeners. Trigonostigma heteromorpha differs from
all congeners in the following combination of characters: a
steep sloping lateral head to pre-dorsal region (shared with
T. espei, vs. a gentle sloping lateral prole from posterior
of head to predorsal region for T. truncata, T. hengeli, and
T. somphongsi); terminal mouth (shared with all except T.
truncata with a sub-superior mouth); caudal apex of axine
reaching caudal-n base (shared with all except T. truncata
with caudal apex not reaching); dorsal and ventral apices of
axine originate near to both dorsal-n and pelvic-n origins
(shared with T. truncata, vs. dorsal apex starting up to three
scale-width posterior to dorsal-n origin and ventral apex
starting two scale-width after pelvic-n origin in T. espei
and T. hengeli; axine reduced to thick black stripe in T.
somphongsi); dorsal n with distinct orange/red pigments
(shared with T. truncata and T. espei, vs. both T. hengeli
and T. somphongsi with almost hyaline dorsal n); and the
largest adult size (up to 35 mm SL).
Description. See Figs. 1, 4B, 7 for general appearance. See
Table 2 for meristic and morphometric data. Head pointed,
with terminal mouth, barbels absent. Prole of head and
anterior of body with a steep slope upwards to dorsal-n
origin, presence of distinct notch between occiput and
nape. Orbit relatively large (orbital diameter 35.6–44.8%
HL). Body compressed, deepest at dorsal-n origin (body
depth 32.6–38.2% SL) and shallowest at caudal peduncle
(caudal peduncle depth 12.6–15.8% SL). Dorsal and pelvic
ns situated mid-body (predorsal length 46.8–54.8% SL;
prepelvic length 47.9–52.5% SL), triangular and small
(dorsal-n base length 13.1–18.4% SL). Caudal n forked,
symmetrical (upper caudal-n lobe length 32.6–39.1% SL;
lower caudal-fin lobe length 33.5–41.6% SL). Anal fin
triangular, origin situated ⅔ down body (preanal length
64.6–70.2% SL), and small (anal-n base length 10.5–15.2%
SL). Both pelvic and pectoral ns triangular. Lateral scale
series with 25–30 scales (mode 26), lateral line incomplete
Fig. 7. Trigonostigma heteromorpha, BMNH 1905.5.6:2–3,
paralectotypes, 22.3 mm SL (top), 23.2 mm SL (bottom); Peninsular
Malaysia: Selangor (copyright of Natural History Museum, London).
430
Tan: New species of harlequin rasbora from Malay Peninsula
Table 2. Meristic and morphometric data for Trigonostigma heteromorpha.
Meristics ZRC55562, 4903, 14383, 39918, 13794 (n=20) [mode]
SL (mm) 21.6–27.6
dorsal n rays i, 7
anal n rays i, 6
caudal n rays (principle rays) 9+9
pelvic n rays i, 5
pectoral n rays 12
lateral scales 25–28 [26]
no. of pored lateral line scales 5–9 [7]
predorsal scales 11
transverse scales
transverse scales at dorsal
caudal peduncular scales ½.4.½
circumpeduncular scales 10
dorsal n origin (lat) 7–9 [8]
anal n origin (lat) 14–16 [15]
pelvic n origin (lat) 8–9 [9]
start of axine in relation to lateral scales 9½–11 [11]
scale rows between lateral and pelvic 2–4 [3]
min max mean SD
% standard length
total length 133.0 142.7 137.2 2.82
body length 67.5 75.0 71.0 1.92
predorsal length 46.8 54.8 52.0 2.19
preanal length 64.6 70.2 67.6 1.69
prepelvic length 47.9 52.5 50.1 1.49
head length 27.2 31.7 28.9 1.18
body depth at dorsal 32.6 38.2 35.8 1.64
body depth at anus 24.4 30.2 27.9 1.55
caudal peduncle depth 12.6 15.8 13.8 0.89
caudal peduncle length 18.6 23.3 21.7 1.24
dorsal n base length 13.1 18.4 15.5 1.38
anal n base length 10.5 15.2 13.1 1.36
pelvic n length 17.6 23.7 20.0 1.60
pectoral n length 17.3 22.9 20.3 1.57
upper caudal lobe length 32.6 39.1 36.4 1.83
median caudal length 13.4 20.2 17.4 1.76
lower caudal lobe length 33.5 41.6 37.8 2.10
% head length
head depth 68.1 80.6 74.7 3.35
head width 42.9 53.5 49.1 2.86
snout length 20.9 28.6 23.8 2.39
orbital diameter 35.6 44.8 40.2 2.63
interorbital width 35.0 41.3 38.6 1.84
and leading horizontally away from head and sloping
downwards, perforated lateral line scales 5–9 (mode 7). Both
dorsal-n and pelvic-n origins on vertical through lateral
scale 7–9 (mode 8) and 8–9 (mode 9) respectively, anal-n
origin at 14–16 (mode 15). Axine starting at lateral scale
series 9½–11 (mode 11).
Colouration in preservative. See Fig. 7. Base body colour
cream, dorsum dark brown, with dark brown stripe across
dorsum, ventrum cream; freshly preserved specimens can
be ushed orange or reddish. Head region above eye dark
brown. Eye with silvery iris. Region posterior to opercle
opening with distinct dark brown humeral streak. All ns
hyaline, thin black margin on distal half of anterior edge of
dorsal and anal ns; for freshly preserved specimens, dorsal
and caudal ns orange or red, anal n with middle portion
orange, paired ns hyaline. Black axine on mid-body, anterior
margin straight edged, dorsal apex starting about one scale
431
RAFFLES BULLETIN OF ZOOLOGY 2020
posterior to dorsal-n origin, ventral apex starting above
pelvic-n origin, caudal apex extending length of caudal
peduncle reaching base of caudal fin; axine surrounded
with distinct margin of 1–1½ scale width. Region of body
anterior to triangular marking with diffused melanophores.
Colouration in life. See Figs. 1, 4. Base body colour orange-
red, dorsum can be a darker shade, belly lighter shade or
silvery; sometimes with slight bluish iridescence on anterior
half of body and bright orange blotch at caudal-n base; in
fully acclimatised specimens in captivity, a purplish sheen
can be visible on body. Region of head above eye dark
brown. Eye with orange iris with black dorsal patch and
ring. Region posterior to opercular opening with diffused
black humeral streak. Large velvety black axine on mid-body,
anterior margin straight edged, dorsal apex at about one
scale posterior to dorsal-n origin, ventral apex at pelvic-n
origin, caudal apex extending length of caudal peduncle to
caudal-n base; whole axine with distinct margin of 1–1½
scale width. Paired ns hyaline. Dorsal n base ushed red
or orange, thin black margin on distal half of anterior edge,
distal margin hyaline. Caudal n reddish-orange with hyaline
distal margin. Anal n base hyaline, thin black margin on
distal half of anterior edge, middle section sometimes with
small patch of orangish-red, rest of n hyaline. Supra-anal
region to ventral base of caudal peduncle with diffused
black streak.
Distribution. Trigonostigma heteromorpha is the most
widely distributed species of the genus, occurring in Malay
Peninsula (Perak, Selangor, Negri Sembilan, Johor, Pahang),
Singapore, Sumatra (North Sumatra and Riau provinces),
Riau archipelago islands of Batam, Bintan, and Lingga,
Bangka island and Belitung island (see Fig. 5). In Sumatra,
T. heteromorpha is found only in North Sumatra and Riau
provinces and is replaced by T. hengeli in Jambi and South
Sumatra provinces (Kottelat & Witte, 1999; Tan & Kottelat,
2009).
Remarks. Duncker’s (1904) description of T. heteromorpha
was based on material collected from Selangor, Negri
Sembilan, and Singapore. Locality data for the type series
was from Negri Sembilan and this had been claried by
Alfred (1963). No holotype was designated at the time of
publication. Ladiges et al. (1958) selected a lectotype from
Negri Sembilan, based in Zoological Museum Hamburg
(Kottelat, 2013). The locality where Duncker collected T.
heteromorpha in Singapore is the Botanical Garden pond
(not specied which pond) which is now depleted of T.
heteromorpha as the surrounding swamp forest habitats
have been destroyed. Surviving populations occur in forest
streams and a remnant swamp forest habitat within the
Central Catchment Nature Reserve (Ng & Lim, 1997; Ho
et al., 2016).
Both T. heteromorpha and T. truncata, new species, are
the largest-sized representatives of the genus. The current
largest documented T. heteromorpha is 35 mm SL (Weber
& de Beaufort, 1916: 80) and for T. truncata is 33.7 mm
SL (present study – ZRC 54736; this specimen has been
kept in captivity before preservation).
Comparative material. Trigonostigma espei — ZRC 40766,
10 ex., 12.3–19.2 mm SL; Thailand: Trat Province, aquarium
material; donor Kubota K, 13 January 1997. Trigonostigma
hengeli — ZRC 38687, 4 ex., 12.4–20.3 mm SL; Indonesia:
Sumatra; Jambi, Pijoan, Sungai Pijoan; aquarium fish
collectors, 28 May 1994. — ZRC 37705, 18 ex., 18.8–24.4
mm SL; Indonesia: Sumatra; Jambi, aquarium material; Lim
KKP et al., June 1994. — ZRC 47139, 47 ex., 13.5–17.2
mm SL; Indonesia: Kalimantan Barat; Pontianak, aquarium
trade; donor Yap P, 8 July 1998.
ACKNOWLEDGEMENTS
The author is grateful to the following: Tan Swee Hee
and Jeremy Yeo, for spotting the new colour form/species;
donation of material from Patrick Yap, Katsuma Kubota;
various eld assistance from Maurice Kottelat, Dennis Yong,
Lukas Rüber, Sebastien Lavoue, Darren Yeo, Ng Heok Hee,
Tan Swee Hee, Peter Ng, Kelvin Lim, Low Bi Wei, Zeng
Yiwen, Liew Jiahuan, Jeffrey Kwik, Jonathan Ho; Kevin
Conway, for processing this manuscript so speedily and
providing references; Rohan Pethiyagoda and an anonymous
reviewer, for the constructive comments and suggestions that
improved the manuscript; Nonn Panitvong, for use of his
image of Trigonostigma somphongsi; Ng Heok Hee for the
base map; numerous research grants (1992–present) from
National University of Singapore; and nancial support from
Lee Kong Chian Natural History Museum.
This species is described in fond memory of the many
occasions on which Tony Whitten (1953–2017) visited the
National University of Singapore and ZRC, always engaging
in stimulating discussions on the taxonomy, ecology, and
biogeography of Southeast Asian shes, amongst other fauna.
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... These include Boraras, Brevibora, Kottelatia, Pectenocypris, Rasbora, Trigonopoma and Trigonostigma (Sholihah et al., 2020;Tan & Armbruster, 2018). The systematics of the subfamily is still confused due to the lack of robust phylogenetic hypothesis of intrarelationships (Brittan, 1972;Hui & Chian, 2020;Kottelat & Vidthayanon, 1993;Kottelat & Witte, 1999;Liao et al., 2010Liao et al., , 2011. However, the monophyly of Rasborinae is supported by both molecular and morphological characters (Saitoh et al., 2006;Stout et al., 2016;Tan & Armbruster, 2018;Tang et al., 2010). ...
Article
Aim Sea-level changes have long been put forward to explain the colonization of Southeast Asian islands by freshwater aquatic organisms. We examined the relative impact of Sundaland geology since the Oligocene and of Pleistocene Eustatic Fluctuations on the mitochondrial lineage diversification of a species-rich subfamily of freshwater fishes widely distributed in Southeast Asia. We specifically tested if the expansion of exposed lands and increased island connectivity during Pleistocene low sea levels (the paleoriver hypothesis) induced bursts of diversification. Location Sundaland. Taxon Rasborinae (Actinopterygii, Cypriniformes, Danionidae). Methods We aggregated 1,017 cytochrome oxidase I sequences and 79 mitogenomes to delineate Molecular Operational Taxonomic Units (MOTUs) and further reconstruct a time-calibrated phylogeny of Rasborinae. Ancestral area estimations were conducted using both island and paleoriver partitioning to examine the impact of island connectivity during Pleistocene sea-level changes on dispersal. Temporal trends of diversification are explored through statistical selection of best-fit models. Results The origin of Sundaland mitochondrial lineages is dated at c. 33 Ma and four major clades are identified, which diversified between c. 31 and 22 Ma. The Island of Borneo and North Sunda paleoriver are identified as the source of Sundaland Rasborinae. Geographical patterns of lineage divergence indicate that most divergence events occurred within islands and diversification under constant birth rate models are the most likely for all clades. Conclusions The geographical and historical context of diversification of mitochondrial lineages in Rasborinae provides little support for the paleoriver hypothesis. The onset of isolation of Borneo from mainland Asia triggered the initial diversification of the group (c. 31–22 Ma). The late colonization of Java and Sumatra occurred through several independent dispersal events, poorly explained by Pleistocene sea-level changes and frequently followed by in situ diversification.
... These include Boraras, Brevibora, Kottelatia, Pectenocypris, Rasbora, Trigonopoma and Trigonostigma(Tan and Armbruster 2018;Sholihah et al. 2020). The systematic of the subfamily is still confused due to the lack of robust phylogenetic hypothesis of relationships within the group(Brittan 1972;Kottelat and Vidthayanon 1993;Kottelat and Witte 1999;Liao et al. 2010Liao et al. , 2011Tan 2020), despite its monophyly is well supported(Saitoh et al. 2006;Tang et al. 2010;Stout et al. 2016;Tan and Armbruster 2018). The Rasborinae encompass ca. ...
Thesis
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Sundaland is one of the most threatened biodiversity hotspots, experiencing a fast increase of threat levels during last decades. Covering Malayan Peninsula, Sumatra, Java and Borneo, this hotspot has one of the highest species richness and endemism for vertebrates in SEA, including freshwater fishes. This level of biodiversity has long attracted the attention of evolutionary biologists, particularly by considering effects of Sundaland complex geological history. This study addressed it by exploring time frame of vicariance and dispersal during diversity build-up of freshwater fish species in Sundaland. To support this, we first aimed to assess the match between distribution of molecular lineages from multiple taxa with palaeoriver boundaries using metadata analysis of existing molecular dataset with representative biological and spatial coverage in Southeast Asia (especially in Sundaland). Second, we focussed on estimating clades’ age and geographic distribution of Rasbora lineages in relation to the Pleistocene Palaeoriver Hypothesis by utilising newly generated empirical data for Rasborinae, a widespread and extremely diversified group of primary freshwater fishes in Sundaland. On both steps, we questioned: 1) if palaeorivers served as corridors of dispersal between islands during Pleistocene sea levels low stands; 2) if palaeoriver watersheds initiated allopatric divergence across their boundaries; and 3) if Pleistocene climatic fluctuation increased rates of species diversification. Overall, this study detected high level of cryptic diversity. Ancestral area reconstructions revealed that Sundaland freshwater fish lineages originated from Mainland Asia, and further colonised the region since Oligocene. This result validated the pre-Pleistocene settlement hypothesis. These lineages entered Sundaland mainly through North Sunda palaeoriver in contemporary Borneo and dispersed to other parts of Sundaland via long distance dispersal, often followed by in situ diversification. These results suggest Bornean part of North Sunda palaeoriver is the most likely centre of origin for Sundaland freshwater fishes. Contrary to the initial hypothesis, we found that although lowered sea level during glacial periods reconnected watersheds within palaeorivers, it did not necessarily open up inter-island dispersal channels for freshwater fishes. Corridors of savanna and seasonal forest ecosystems in the interior of Sundaland served as barrier to dispersal. Also, permeability of the physical boundaries of palaeoriver’s watersheds as well as geomorphological and habitat variabilities within palaeoriver created respectively gene flow between palaeorivers and allopatric speciation within palaeoriver. Moreover, although significant proportion of Sundaland freshwater fish lineages originated during Pleistocene, we found that Pleistocene dynamics did not affect diversification rate as sea level-dependent diversification models poorly account for species proliferation patterns for all clades excepting Channa. Besides, none of the taxa examined has declining diversification rates as suggested by diversity-dependent diversification (DDD) model. It is suggested then that global Pleistocene eustatic fluctuation and regional paleoriver dynamics are not sole drivers for Sundaland freshwater fish diversification, but only a part of abiotic aspects affecting it. Pleistocene Climatic Fluctuations likely interacted with other factors such as: landscape geomorphology, local ecosystem/habitat variability and life history traits of organisms.
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Two new species of Microrasbora are described, M. kubotai from the western (Andaman Sea) slope of Peninsular Thailand and M. nana from the lower Sittang basin in Myanmar. Microrasbora erythromicron is transferred to Danio sensu lato. Two new genera are described, Sundadanio (type species: Rasbora axelrodi) and Trigonostigma (type species: R. heteromorpha). Introduction The genus Microrasbora was created by Annandale (1918: 50) for two species of diminutive cyprinids discovered in Inle Lake, Burma (now Myanmar), M. rubescens (the type species of the genus) (Fig. 1) and M. erythromicron (Fig. 2). Annandale also tentatively placed in the genus two species known from the Malay Peninsula, Rasbora maculata Duncker, 1904 and R . heteromorpha Duncker, 1904. These last two spe­ cies have never been considered as members of Microrasbora by later authors who retained them in the genus Rasbora. Rasbora maculata is now placed in the genus Boraras (Kottelat & Vidthayanon, 1993: 162), while R. heteromorpha and a few other similar-looking species represent a distinct but still unnamed lineage. The genus Microrasbora was considered to be en­ demic to Lake Inle until Herre (1939) described M. gatesi from the vicinity of Rangoon (Myanmar) (Fig. 3). In 1985, MK collected an additional, diminutive species in Peninsular Thailand, and in 1996 KEW collected another one in Myanmar. The species from Thailand has been regularly exported for the aquarium trade since a few years ago. The purpose of the present paper is to make names available for these two species and for two long-recognised but still unnamed genera of diminutive Southeast Asian cyprinids.
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We review the morphological and molecular evidence that Mayden & Chen recently used to infer that the developmentally truncated fish genus Paedocypris is not a member of the teleost order Cypriniformes or carp-like fishes, but is ‘the basal sister group to all Cypriniformes’. This hypothesis contradicts several previous studies that used molecular sequence data or morphological characters. A review of the morphological characters that Mayden & Chen discussed and mapped onto their ‘simplified tree’ shows that these, analysed alone, rather support a close relationship of the cyprinids Sundadanio, Danionella, and Paedocypris. We also present four additional analyses of morphological data, which all contradict Mayden & Chen's result. Despite its highly reductive skeleton, posing a serious problem when analysing its phylogenetic position with skeletal characters, the presence in Paedocypris of the basioccipital masticatory plate is compelling evidence that it is a member of the Cyprinoidei (Cyprinidae plus Psilorhynchidae). Our reanalysis and exploration of their molecular sequence data shows that only a single gene, EGR3, of the six nuclear genes analysed by Mayden & Chen, is responsible for the position of Paedocypris as ‘the basal sister group to all Cypriniformes’. Three independent methods to visualize and analyse phylogenetic signal and conflict of data sets (phylogenetic networks, splits analysis methods or SAMS, and site-wise likelihood analyses) reveal a high level of character conflict and noise in Mayden & Chen's data set. The ‘basal’ position of Paedocypris seems to be the outcome of the interplay of two long-branch effects. We apply the same analytical methods to the data set from Rüber et al.'s molecular analysis of the phylogenetic position of Paedocypris and discuss our findings. We conclude that none of the molecular data sets compiled to date can establish the phylogenetic position of Paedocypris with confidence. Morphological data suggest that Paedocypris and Danionella are sister genera, and that their closest relative is Sundadanio, although the position of these three miniatures among cyprinoids is still unclear. © 2014 The Linnean Society of London
Article
The first phylogenetic analysis of the genus Boraras is addressed. The results indicate that Boraras forms a monophyletic lineage defined by four synapomorphies: (1) the absence of a supraorbital canal, (2) a uniquely shaped urohyal, (3) an elongated 4th pleural rib, and (4) a postcleithrum attached high on the cleithrum. The interrelationships of the five species of Boraras were incompletely resolved and no evidence was found to suggest that Boraras and Trigonostigma are closely related. The phylogenetic position of Boraras in relation to other rasborins remains unclear.