Bull. nat. Hist. Mus. Lond. (Zool.) 64(1): 97-109 
Issued 25 June 1998 

Revision of Schismatorhynchos Bleeker, 1855 
(Teleostei, Cyprinidae), with the description of 
two new species from Borneo 

DARRELL J. SIEBERT 
Department of Zoology, Natural History Museum, Cromwell Road, London SW7 S5BD, UK 
AGUS H. TJAKRAWIDJAJA 
Balitbang Zoologi, Pusat Penelitian dan Pengembangan Biologi - LIPI, Jl. Juanda No 9, Bogor 16122, Jawa 
Barat, Indonesia 


CONTENTS 
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Materials and Methods ..................... 
GSE LIC PATE ONE ert corer cece cere eta nan Te Mecca cee den eaaws 
SGHISIMATOMINTLENOS WSCC ROTM OOS Meat ics notes sandesrertreaver tecetet es ds uuasts vsaceubiaeahosae savuadyoe ceUpassd ditch Tunana cons twice oi stvesiesusasscovaiascoseacesesss 98 
SIE CIES NEC OES ee etn gm enn. en er ASE LI POO, ono coersa sven ia cceagnyiaxencwepueecussiscinnct srnanssasesceittaseunencensenensdtenensneces 100 
Key OM NE SPECIES ONS GNI ALO I MIIGHOS eee ie, nee taeda. Maken sata sinansus.tavecessincasctaegdttnarere an tuna tenets rtrseniN esr sneionearipextvasesCastcgiees 100 
SCHISINALOMMYNGHO SEL TOMA CHO SN DICEKEN. GIS Ns. itinensssttecnsuecsott csadsantesssevsescanasssancoosass<aessnsesvoassrstlacsecadassseeevadhésaxesede 100 
SC HISIIALOTMNMGHOS- NOLO MYM CHOSYSP MLO Vents: dices eatae aie -aa-suxesncesecx-seseessecesoscccc-sente tt atrewviacsccessaccuevecesocetuicaneterszcseoreessees 104 
SCMISINAT GR DUNG Ost ENC AGATNGDUSNS [ikl O Von asmsws cvs Saeed va acvasueaaavdseesatssssdesassuidvesasvciascussicdesaeascacedtereuseacttvstiivassecausvststts 105 
HEA BLE ILGIC OM AULSO US| metemeeatiemeant decmcvat soOMNtae< ca0s- chee sb orcsscececactes cWardnassterew-ntarivacseocPsneereecerrcecsecrsnceorarescedesurersaresderceecesere 107 
WSIS TTS S1O Ue ene cee ea a poe cera chs Reto ea anu se spy nenes Sct ath tsacapabovaarieesersestavees sateonveretvee Mrumgereesenateastocteheressstedseessieescncteetectanetesttesacee 107 
AMNOta ONS hKeyS Ome ph MIC e nena Of Te meet Onan. ccsux.ccosesecensecenee-cetncrctecesterecessacetes seen fesatssuncscsasesareasusetaeseasascaetenaetace 108 
NEL ERCOWALSLE TENTS IS ceeaeer cole) Ae PORE eee CREEP EPEC apy Glo r r ROT ERR PRR on a ecEiy a oP oe Ri a rei St ea eo a een EE 108 
GEGEN CGS scranase segs ax snes «vated ag sous fo xhi up ssnap as cas cananveticas favacaivadenesi'esanaa feces sterte rive aera us ct aetans sevtewea te scatecetoces tua tavectabeseabietreduevetet east 108 
SYNOPSIS. Schismatorhynchos Bleeker, 1855 is revised: the genus is enlarged to accommodate two new species from Borneo, 
Schismatorhynchos endecarhapis n. sp. is described from the Kapuas and Barito rivers, Kalimantan Barat and Kalimantan Tengah 
and Schismatorhynchos holorhynchos n. sp. is described from the Rejang and Kinabatangan rivers Sarawak and Sabah, Malaysia. 
Schismatorhynchos is characterised by oro-labial features, namely the upper lip not continuous with the lower lip around the 
corner of the mouth, a wide crescentic lower jaw, the lower jaw lightly armoured with a thin, flexible, keratinous cutting edge and 
a lower labial frenulum in which the mandibular laterosensory canal is located. Only S. heterorhynchos (Bleeker, 1853), the type 
species, possesses the eponymous rostral cleft. Nukta Hora, 1942 is excluded from Schismatorhynchos on the grounds it lacks the 
specialisations of the three Sundaland species.A key to species in the genus is provided and annotations to currently used regional 

keys to cyprinid genera are suggested in order to accommodate an enlarged Schismatorhynchos. 
INTRODUCTION 
The cyprinid genus Schismatorhynchos Bleeker, 1855, with a dis- 
junct distribution in Sumatra—Borneo and India, is known by a 
strange rostral modification, a heavily tuberculate snout with a deep 
horizontal cleft (Bleeker, 1853; Weber & de Beaufort, 1916; Hora, 
1942). Two species, each in separate subgenera, are currently included 
in Schismatorhynchos, S. (Schismatorhynchos) heterorhynchos 
(Bleeker, 1853) from Sumatra and Borneo and S. (Nukta) nukta 
(Sykes, 1841) from India. In addition to its unusual snout the 
nominate subgenus is also known for unusual oro-labial morphol- 
ogy which includes: 1) a frenulum connecting the lower lip to the 
anterior gular region; and 2) a lower jaw with an elongated cutting 
edge which separates the upper lip from the lower lip at the corners 
of the mouth — the lips are not continuous around the corner of the 
mouth (Weber & de Beaufort, 1916). Since the description of the 
subgenus Nukta by Hora (1942) Schismatorhynchos has received 
little attention except for listing in faunal reviews. 
© The Natural History Museum, 1998 
Schismatorhynchos heterorhynchos was described from Sumatra 
(Bleeker, 1853) and Weber & de Beaufort (1916) reported it else- 
where only from the Kapuas River, western Borneo. More recently, 
Inger & Chin (1962) identified juvenile specimens from the 
Kinabatangan River, Sabah, Malaysia (northeastern Borneo) as S. 
heterorhynchos (Bleeker, 1853) even though this northeastern Bor- 
neo material lacks a cleft snout. Since the Sabah specimens lack 
tubercles on the snout in the region of the cleft in the snout of S. 
heterorhynchos, and since S. heterorhynchos was known only from 
larger specimens, Inger & Chin implied that the cleft in the snout 
might not develop until maturity. Roberts (1989; Fig. 58) also 
identified some juvenile material without a cleft snout, but from the 
Kapuas River, western Borneo, as S. heterorhynchos. The oro-labial 
morphology of the subgenus Schismatorhynchos is apparently so 
distinctive that both Inger & Chin (1962) and Roberts (1989) were 
able to identify material as belonging to it even in the absence of the 
eponymous rostral cleft. 
We collected juveniles of an unusual fish with a distinctive colour 
