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ISSN 0206-0477. NEW CONTRIBUTIONS TO FRESHWATERFISH RESEARCH

ST. PETERSBURG, 2001 (PROCEEDINGS OF THE ZOOLOGICAL INSTITUTE, VOL. 287)

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ÑÀÍÊÒ-ÏÅÒÅÐÁÓÐÃ, 2001, ÒÎÌ 287

A REVISION OF ALTAI OSMANS OF THE GENUSOREOLEUCISCUS (CYPRINIDAE: LEUCISCINAE) WITH

A DESCRIPTION OF A NEW SPECIES, O. ANGUSTICEPHALUS,FROM RIVER KOBDO (HOVD) SYSTEM, WEST MONGOLIA

N.G. Bogutskaya

Zoological Institute, Russian Academy of Sciences,Universitetskaya nab., 1, St. Petersburg, 199034, Russia

A comparative morphological study of Altai osmans, the genus Oreoleuciscus, fromdifferent parts of its distribution was performed. Besides non-type samples, materialexamined includes syntypes and holotypes of most species and varieties described earlier.An analysis of 33 morphometric and meristic characters, 14 craniological parameters aswell as other features of skeletal structure including vertebrae counts and degree ofossification of the dorsal unbranched rays, and cephalic sensory canals confirmed aconclusion (Bogutskaya, 1990c) that the genus Oreoleuciscus contains three species.The Nogon Nuur narrow-headed osman is described here as a new species,O. angusticephalus. The main diagnostic characters are the number of branched rays inboth dorsal and anal fins, structure of the last unbranched dorsal ray, the number ofpores in the sensory canals, the relative width of the head in its different parts, the shapeof the supraethmoid and the pterotic posterior process. Key for the identification ofspecies of the genus and synonymies are given.

Species of the genus Oreoleuciscus (Altai osmans, or mountain daces)are the most typical representatives of the ichthyofauna of Central AsianInternal Basin (North-West Mongolia), a comparatively small area,geomorphologically subdivided into the west Mongolian Great LakesValley and Gobi Valley Lakes (or Lake Valley). The basin consistspredominantly of large lentic water masses without outlets beyond it.They are fed by relatively short upland streams or rivers that drain thesouthern slopes of Tanny-Ula, the Hangayin (Hangay) and northen slopesof the Mongolian Altai mountain ranges. Beyond this region Altai osmansoccur only in the basin of the Upper Ob River.

Altai osmans are nearly eurybiont inhabiting fresh and brackish waterlakes, rivers, streams, situated at an altitude from 700 to 2000 m abovesea level. Variability of environmental conditions and the poverty of

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ichthyofauna determining a nearly complete absence of competition withfishes of other genera apparently favoured great morphological andecological diversity of this genus.

The initial phase of the systematic studies of Altai osmans ischaracterized by the tendency to describe morphologically distinct groupsof specimens or single deviating specimens as species or varieties. ThusWarpachowski (1889) in his excellent monograph distinguished thefollowing species and varieties: Oreoleuciscus potanini, O. potanini var.recurviceps, O. pewzowi, O. pewzowi var. altus, O. pewzowi var.longicaudus, O. humilis, O. humilis var. phoxinoides, O.similis, O.dsapchynensis, O. herzensteini, O. gracilis and (based on a head alone)O. choerocephalus. Later, O. ignatowi Nikolski, 1902 and O. ignatoviDorogostaiski, 1908, were described. A part of these forms were reducedto synonyms by Berg (1912, 1949, and others) who distinguished threemain species, O. humilis, O. potanini and O. pewzowi, and also O.recurviceps and O. similis.

The next phase is characterized by a study of Altai osmans on arelatively larger material, mainly from water bodies of mountain Altaiand Tuva in the USSR. Application of the characters used byWarpachowski (1889) and Berg (1912, 1949, and others) showed thatthey do not always permit an accurate identification of species of Altaiosmans (Gladkov, 1938; Kafanova, 1961; and others). The great variationand age-and-size variability of morphometric characters (in particularrelative length of the head and body depth, length of the lower jaw relativeto minimum depth of the body, length of the operculum) determineddoubts concerning species status of O. humilis (Krivoshchekov, 1959;Egorov, Zhamsaran, 1961) and O. pewzowi (Iohansen, 1940; Nichols,1930) which were later synonymized with O. potanini (Svetovidova,1965).

Relatively extensive collections of Altai osmans from Mongolia(from both the Kobdo (Chovd Gol, Hovd) River basin and from theLake Valley) were studied by Dashdorzh and co-authors (Dashdorzh etal., 1969). A detailed analysis of morphometric and some meristiccharacters confirmed existence of differences between O. potanini andO. humilis, that are particularly conspicuous in the number of branchedrays in the dorsal and anal fins, and also showed distinctiveness ofspecimens, identified as O. pewzowi (without comparison with syntypesof this species), from O. humilis. It is important that geographic separationof the two groups of Altai osmans was revealed: O. potanini was recordedonly in the basin of the Kobdo River, whereas O. humilis and O. pewzowi

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were connected with water bodies of Hangayin and the Lake Valley(except one sample from Achit Nuur). One of the characters dividing thetwo groups mentioned above is the structure of simple rays in the dorsalfin. As a whole these data correlate well with the results of a comparativeanalysis of Altai osmans from basins of the Kobdo River on the onehand and forms inhabiting water bodies of the Ubs-Nur (Uvs Nuur) Valleyon the other (Gundrizer, 1962, 1976). It should be noted that many authors(Svetovidova, 1965; Gundrizer, 1976; Dashdorzh et al., 1969) acceptedthe characters used by Warpachowski (1889) and Berg (1912, 1949) asthe key characters without a re-examination of type specimens of theearlier described species and varieties. Without a comparison with thelatters the systematic revisions were incomplete and even somenomenclature inaccuracies arose (see below).

The third phase in the study of Altai osmans is associated with thework of joint Soviet-Mongolian biological expedition in 1975-1980. Thedata obtained by the expedition became the basis of a number ofsummarizing reviews on morphology and mode of life of species of thegenus Oreoleuciscus within the limits of a larger part of its distributionarea in Mongolia (Dgebuadze, 1982; Baasanzhav et al., 1983, 1985;Borisovets et al., 1984, 1985a, 1985b, 1985c, 1987, etc.). Without aspecial revision of taxonomic status of individual groups of Altai osmansand referring them all to species O. potanini these authors paid moreattention to the analysis of diversity of these fishes. Based on the studyof a large number of morphometric and meristic characters conclusionswere made on the occurrence of five morpho-ecological forms, or types,in the studied water bodies. These forms are conventionally calledherbivorous, sharp-snouted, piscivorous, dwarf and lake forms of Altaiosman. The former three are associated with the basins of rivers Kobdoand Dzavhan Gol, the latter two occur in water bodies of the slopes ofHangayin, and Lake Valley. It is shown that the dwarf and lake form arerelatively close and form a single group, the differences of which fromall osmans of the Kobdo basin are approximately equal to the differencesbetween the herbivorous and piscivorous forms (Borisovets et al., 1985c).Taxonomic status of the latter two forms was analyzed by Vasilieva(1982). The study of a number of craniological characters showedconsiderable differences between two forms of Altai osmans from LakeNogon-Nuur and somewhat later (Vasilieva, 1985) differences betweenthese both forms and Altai osmans from River Taytzyn-Gol (Tatsain Gol)and Lake Taytzyn-Tsagaan-Nuur (Tatsain Tsagaan Nuur). In the samepublication, the author also analyzed the degree of thickening and

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segmentation of the last simple dorsal ray and divided all Altai osmansinto two large groups. The first group includes osmans with a relativelyrigid ray (corresponds to O. potanini), the second group uniting soft-rayed Altai osmans is represented by two subgroups: one is characterizedby a wider skull and a lower number of pores of the sensory canal on thedentary (corresponds to O. humilis), the other by a narrower skull with alarge number of pores (Lake Nogon-Nuur). Two hypotheses have beenproposed for the taxonomic status of O. humilis: it is either a distinctspecies capable of forming lake forms, or the dwarf osman is an eco-morphological form of the soft-rayed narrow-headed osman. The latteris given a name O. pewzowi though the author clearly showed that thesyntypes of Leuciscus pewzowi belong to O. potanini (Vasilieva, 1985).According to this, Leuciscus pewzowi had to be considered as a juniorsynonym of Chondrostoma potanini, and the soft-rayed osman from LakeNogon-Nuur had to be given a new name in case of the first hypothesis.

Analysis of variation of a number of characters, osteological onesincluded, and topography of sensory canals on the head (Bogutskaya,1990c) confirmed that, in spite of the comparatively large intraspecificvariation of a number of characters, three groups of forms can bedistinguished within the genus Oreoleuciscus, which are given the rankof species (O. humilis, O. potanini, Oreoleuciscus sp.). They differ inthe structure of simple dorsal rays, the number of pores in sensory canals,general configuration of neurocranium and a number of other characters.These data in many respects conformed to the main conclusions of theprevious authors (Gundrizer, 1976; Vasilieva, 1985; Borisovets et al.,1985a, 1985b, 1985c) concerning the taxonomy of the genusOreoleuciscus if one discards the nomenclatural confusion related tousage (Gundrizer, 1976; Vasilieva, 1985) of the name “pewzowi”.

The purpose of the present study is to straighten out the accumulatedsystematic data on Altai osmans on the basis of a comparativemorphological study of specimens from different localities all over thearea of distribution of the genus and their comparison with type specimensof species and varieties for defining validity of names and taxonomicstatus of individual “forms” of Altai osmans.

The question of taxonomic composition of the genus Oreoleuciscusis closely related to the question of taxonomic status of the genusAcanthorutilus Berg, 1912. Initially only one species, O. dsapchynensis,based on a single specimen from River Dzavhan Gol (ZISP 6410), wasplaced into this genus. Later, four more species from Asia Minor wereadded to Acanthorutilus: A. anatolicus Hanko, A. handlirschi Pietschman,

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A. maeandricus Ladiges and A. crassus Ladiges. An opinion becameestablished in the literature that the genus Acanthorutilus is close toMediterrranean Pseudophoxinus Heckel, 1843 and Phoxinellus Heckel,1843 and possesses the disrupted distribution range (Sychevskaya, 1983;Bãnãrescu, 1960; and others). Karaman (1972) excluded Asia Minorspecies from Acanthorutilus and referred them to Phoxinellus. A moredetailed revision of Asia Minor leuciscins shed more light on taxonomyof the genera Pseudophoxinus and Phoxinellus (Bogutskaya, 1991, 1997).The four species mentioned were included in Pseudophoxinus, a genuswhich is essentially different from Oreoleuciscus being a member of thetribe Leuciscini in contrast to the latter which is a member of the tribePseudaspinini. The holotype of O. dsapchynensis is similar toO. potanini by all diagnostic characters (see below) and, accordingly,Acanthorutilus should be regarded as a junior synonym of OreoleuciscusWarpachowski, 1889, which confirms the point of view of the previousauthors (Gundrizer, 1976; Dashdorzh et al., 1969).

Material and Methods

In total, 763 specimens of Altai osmans form water bodies of Altai,Tuva and North-West Mongolia including 120 osteological preparationshave been examined. Material included specimens deposited in thecollections of the Zoological Institute, Russian Academy of Sciences,St. Petersburg (ZISP), Natural History Museum of the National Academyof Sciences of Ukrain, Kiev (NMU), Zoological Museum of the MoscowUniversity (ZM MGU) and also uncatalogued specimens collected duringthe Soviet-Mongolian expedition. Material for each species is given inrespective places of descriptions.

One hundred and fifteen specimens were radiographed. Mostosteological preparations were made after clearing and staining withalizarin red “S“, some from salted specimens. The last two branchedrays in both the dorsal and anal fins are counted as two, not one ray. Porecounts were made from both left and right sides of the head; the numberof canal opening on an individual bone includes entry and exit ones. Finrays were specifically examined in radiographs in parallel with traditionalbinocular observations to reveal accurate border of an articulated simpleray section and a point of dichotomy of a branched ray.

Abbreviations used are:l. l. - number of lateral line scales on the left side of the body, SL -

standard length, D - dorsal fin, A - anal fin, sp. br. - gill-rakers , vert. -

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total vertebrae (including four Weberian vertebrae and the fused preural-ural centrum as the last one), abd. vert. - abdominal vertebrae (includingintermediate ones; precaudal vertebrae auctorum), interm. vert. –intermediate vertebrae (transitional vertebrae auctorum; abdominalvertebrae with parapophyses fused to centra and non-articulated withribs), preD vert. - predorsal abdominal vertebrae (vertebrae anterior tothe first dorsal pterygiophore), caud. vert. - caudal vertebrae;

cephalic sensory canals: CIO - infraorbital canal, CPM -preopercular-mandibular canal, CSO - supraorbital canal, CST -supratemporal canal;

skull measurements: H eth - depth of ethmoid region, H soc - depthof occipital region, L bas. n. - length of neurocranial base (from anteriorend of vomer to posterior end of basioccipital without pharyngealprocess), L cr. r., length of cranial roof (from anterior margin ofsupraethmoid up to origin of supraoccipital crest), Lt eth - width ofneurocranium between lateral margins of lateral ethmoids, Lt spho - widthof neurocranium between lateral margins of sphenotic lateral processes,Lt pto - width of neurocranium between lateral margins of pterotics;

bones and their elements: aart - anguloarticular, boc - basioccipital,dn - dentary; ectpt - ectopterygoid, entpt - entopterygoid, eoc - exoccipital,epo - epiotic, eth.l. - lateral ethmoid, f - frontal, f. car. - carotid foramen,f. dil. op. – dilatator fossa, f. st - subtemporal fossa, hm - hyomandibular,ic - intercalar, iop - interorperculum, keth - kinethmoid, meth -mesethmoid, mtpt - metapterygoid, mx - maxilla; op - operculum, orbs -orbitosphenoid, p - parietal, p. m. - masticatory plate of pharyngealprocess, pal - palatine, peth - preethmoid, pmx - premaxilla, pr. cor. -coronoid process, pr. p.-lat. - postero-lateral process of pterosphenoid,pr. pto - posrerior pterotic process, pr. spho - lateral process of spherotic,pro - prootic, ps - parasphenoid, pto - pterotic, pts - pterosphenoid, qu -quadrate, rart – retroarticular, s - symplectic, seth - supraethmoid, soc -supraoccipital; sop - suboperculum, spho - sphenotic, v - vomer.

Oreoleuciscus Warpachowski, 1889

Oreoleuciscus Warpachowski, 1889: 27 (type-species: Chondrostomapotanini Kessler, 1878)

Acanthorutilus Berg, 1912: 81 (type-species: Leuciscus dsapchynensis[Herzenstein, nom. mus.] Warpachowski).

Body elongated, not laterally compressed; abdominal keel is lacking.Bases of dorsal and anal fins short. D III(IV)(7)8, 9; A III (7)8-10. Dorsal

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fin posteriorly placed so that predorsal distance larger than postdorsalone. Dorsal fin origin above ventral fin base. Scales small, 80-120 in l.l. Lateral line scales larger than other scales; the number of scales of thelateral row above the lateral line can attain 138. Throat and abdomenoften scaleless or covered with small, rounded, non-overlapping scaleslike those on back in front of dorsal fin and flanks below lateral line(except caudal peduncle). In most cases shape of scales changes fromhead to posterior end of the body, being more elongated on caudalpeduncle. Lateral line usually complete, sometimes lacking from 1 to 4last scales or slightly interrupted (absent from 1 to 6 scales) along body.Pharyngeal teeth in one row, 6-5 or 5-5, sometimes hooked. Gill-rakersrelatively short or long particularly in central part of arch, 15-43 on outerside of first arch. Gill-rakers compressed and bear small but conspicuousdenticles along medial margin. CSO shortened and commonly terminatesat posterior margin of frontal. CST usually interrupted and medial endsof its lateral branches bent backwards. CPM not connected with CIOterminating at upper end of operculum. CPM always interrupted betweenlower jaw and preoperculum.

Total vertebrae from (40)41 to 46, rarely 47 or 48. Abdominal regionis relatively long, being commonly 6 to 9 vertebrae longer than caudalregion. Intermediate vertebrae numerous, often 5. Second and thirdvertebrae fused. Anal fin origin markedly in front of first caudal vertebra:anteriormost 3 to 5 pterygophores of anal fin located under 2 or 3 posteriorintermediate vertebrae.

Neurocranium shallow, elongated. Supraethmoid with roundedanterior and narrowed posterior part; its anterolateral corners notpronounced and attachment of ligaments from palatines occurs not onanterior margin of supraethmoid, but on its lateral edges. Frontalelongated with shallow long orbital notch. Interorbital septum oforbitosphenoid not pronounced in specimens of middle and large size.Unlike the majority of leuciscins, contact of pterosphenoid through itspostero-lateral process with ascending process of parasphenoid very long.Origin of adductor arcus palatini muscle spread forward expanding ontolateral surface of pterosphenoid. Levator arcus palatini muscle attachednot only to lateral sphenotic process like in most leuciscins but also toventral surface and lateral margin of frontal along dilatator fossa up toits very anterior end. Supraoccipital takes part in formation of subtemporalfossa on both sides of head, a character typical only of the tribePseudaspinini sensu Bogutskaya (1990c). This bone bears a pair ofanterolateral cone-shaped extensions each located in notch of respective

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epiotic and forming posterior apex of subtemporal fossa. Third andsubsequent infraorbitals with narrow lamellate portions, often of irregularshape or reduced. Number of infraorbitals posterior third one varies from1 to 4 due to fragmentation of bones according to segments of CIO.Suboperculum with narrow but high anterodorsal process. Hyomandibularshallow, relatively wide, with very short ventral branch (nearly notpronounced in large specimens). Cleithrum has deep notch on anteriormargin.

Males have longer abdominal fins, elongated cone-shaped urogenitalpapilla, and also epithelial tubercles during spawning season.

Howes (1984) placed the genus Oreoleuciscus in the “aspinine-group”together with genera Luciobrama, Aspiolucius, Aspius, Pseudaspius,Elopichtys, Aspiopsis, Pogonichtys, Genghis, and Tribolodon. Our data(Bogutskaya, 1990b, Bogutskaya, 1994) indicate that this is a mixed groupuniting large, mostly predatory leuciscins belonging to separate phylogeneticlineages. Oreoleuciscus is included into the tribe Pseudaspinini (Bogutskaya,1990b) which contains also Pseudaspius, Tribolodon, Phoxinus. Thedistinguishing characters of this tribe are the presence of a notch on thecleithrum, the hyomandibular with a short ventral branch anddiscommunicated CPM and CIO, CPM on the operculum being alwaysabsent. Most similar to the genus Oreoleuciscus is the genus Phoxinus,possessing a similar type of arrangement and connection of cephalic canalsas well as position of the anterior anal fin pteriogyphores.

According to the paleontological data (Sychevskaya, 1983), andothers) a representative of the Leuciscinae similar to Oreoleuciscus hasbeen reported for the Late Pleiocene in Dzagso Khairkhan (Mongolia);at the same time, in the Neogene ichthyofauna of Siberia this genus isunknown. Apparently Oreoleuciscus is a primary endemic of the WesternMongolian Province having its origin in the Eurosiberian Neogeneichthyofauna of phoxinoid leuciscine cyprinids.

Key for the identification of species of the genus Oreoleuciscus

1(2). Eight branched rays in dorsal and anal fins. Eight to ten, rarely 11,pores in supraorbital sensory canal. Less than 22 pores ininfraorbital canal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . O. humilis

2(1). Commonly 9 or 10 branched rays in the dorsal and anal fins. Morethan 11 pores in the supraorbital canal. More than 22 pores in theinfraorbital canal

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3(4). Last simple dorsal fin ray thickened, segmented for less than 1/2of its length. Head wide, its width between margins of pterotics 50% of skull roof length, width between lateral margins of sphenoticlateral processes equal to or ecxeeds 40 % of skull roof length.Posterior pterotic process short, does not reach basioccipitalarticulatory surface level . . . . . . . . . . . . . . . . . . . . . . O. potanini

4(3). Last simple dorsal fin ray soft, segmented for more than 1/2 of itslength. Head narrow, its width between margins of pterotics doesnot exceed 50 % (up to 52% in small specimens only) ofskull rooflength, width in the region of processes of sphenotica is not morethan 40 % (in small specimens not more than 42%) of skull rooflength. Posterior pterotic process long, reaches much behindbasioccipital articulatory surface level . . . . O. angusticephalus

Oreoleuciscus humilis Warpachowski, 1889

dwarf Altai osman (Fig. 1)

Leuciscus potanini (part.; misidentification) - Herzenstein in Potanin, 1883: 244 (part.:ZISP 6381, 8079, 8080 River Chuya near Koschagatch [Kasch-Agatch, Kosh-Agach);Ulangom [Ulaangom] in the basin of Lake Ubs-Nur [Uvs Nuur])

Oreoleuciscus humilis Warpachowski, 1889: 50, Tabl. 2, Fig. 3 (Ulangom; River Chuyanear Kosch-Agatsch [a settlement of Petropavlovskoje])

Oreoleuciscus humilis var. phoxinoides Warpachowski, 1889: 54, Tabl. 2, Fig. 4(Ulangom; Kosch-Agatsch)

Oreoleuciscus ignatovi (non Nikolskji) (nonem nudum) - Dorogostaiski, 1908: 238(Lake Kandy-Nur [Handi Nuur] and Bust-Nur [Bust Nuur])

Oreoleuciscus humilis - Berg, 1912: 85 (Upper Ob River; basin of Lake Ubs-Nur).Oreoleuciscus pewzowi altus (misidentification) - Nichols, 1930: 16 (Lake Orog-Nuur

[Orog Nuur] and Kolobolkhi-Nur).Oreoleuciscus potanini (misidentification) - Nichols, 1930:16 (Lakes Bon-Tsagaan-

Nuur [Böön Tsagaan Nuur] and Kolobolkhi-Nur).Oreoleuciscus pewzowi pewzowi (misidentification) - Nichols, 1930: 16 (Lake Bon-

Tsagaan-Nuur)Oreoleuciscus humilis - Iohansen, 1940: 164 (Upper Chuya River).Oreoleuciscus humilis - Berg, 1949: 541 (Chuya River; basin of Lake Ubs-Nur)Oreoleuciscuis pewzowi - Berg, 1949: 540 (part.: Lake Kandy-Nur and Bust-Nur)Oreoleuciscus pewzowi var. altus - Berg, 1949: 540 (part.: Lake Orog-Nuur)Oreoleuciscus potanini (misidentification) - Egorov, Zhamsaran, 1961: 42 (Lake Ubs-

Nur)Oreoleuciscus potanini - Svetovidova, 1965: 24 (part.: Lake Terekhol)Oreoleuciscus humilis - Dashdorzh et al., 1969: 290 (Lake Telmen Nuur, rivers Tazarhain,

Tuin Gol, Taytzyn Gol, Tess [Tesiyn Gol])Oreoleuciscus pewzowi (misidentification) - Dashdorzh et al., 1969: 290 (part.: River

Baydrag-Gol [Baidarik, Baydarag Gol], lakes Bon-Tsagan-Nur, Orog-Nuur, Sangijn-Dalai-Nur [Sangiyn Dalay Nuur])

Oreoleuciscus potanini pewzowi (misidentification) - Gundrizer, 1976: 162, Fig. 1(lake and river ecotypes, basin of Lake Uvs Nuur, Lake Orog Nuur)

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Fig.

1. L

ecto

type

of O

. hum

ilis,

ZISP

637

8. S

l 96.

0 m

m. U

laan

gom

(bas

in o

f Lak

e U

bv N

uur)

.

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Oreoleuciscus potanini - Baasanzhav et al., 1983: 146, Fig. 22 (part.: dwarf form,water bodies of Lake Valley)

“Altai osman” - Borisovets et al., 1985c: 1200, Fig. 2 (part.: dwarf and lake forms)Oreoleuciscus humilis – Vasilieva, 1985: 204 (River Tatsain Gol, Lakes Böön Tsagaan

Nuur, Tatsain Tsagaan Nuur)Oreoleuciscus pewzowi – Vasilieva, 1985: 201 (part.: Lakes Tere Khol, Orog Nuur,

Böön Tsagaan Nuur, Hari Nuur, basin of Lake Uvs Nuur)Oreoleuciscus potanini – Travers, 1989: 193, Fig. 12 (Lake Böön Tsagaan Nuur, River

Tsagaan Gol, Lake Biger Nuur)Oreoleuciscus humilis - Bogutskaya, 1990c: 114, Fig. 1-4 (River Chuya; Lake Uvs

Nuur system, water bodies in Lake Valley)Oreoleuciscus humilis – Dgebuadze, 1995: 239 (Lake Valley: Baydrag-Gol, Bon-

Tsagaan-Nuur, Tuyn-Gol, Orog-Nuur, Taytzyn-Gol, Taytzyn-Tsagaan-Nuur, Ungijn-Gol[Ongiiyn Gol])

Oreoleuciscus humilis – Golubtsov et al., 1999: 890 (Lake Terekhol)Material: ZISP 6378 (1, lectotype of O. humilis, Ulaangom), ZISP

50026 (2, paralectotypes, of O. humilis, Ulaangom), ZISP 8079 (4,paralectotypes of O. humilis, Kosh-Agach), ZISP 6377 (11, syntypes ofO. humilis var phoxinoides, Ulaangom), ZISP 6381 (10, syntypes of O.humilis var. phoxinoides, Kosh-Agach), ZISP 6382 (3, ? syntypes of O.humilis var phoxinoides, Kosh-Agach), ZISP 10554 (3, Ulaangom), ZISP8080 (7, syntypes of O. humilis var phoxinoides, Kosh-Agach), ZISP14787 (1, River Chuya), ZISP 15285 (2, Lake Handi Nuur), ZISP 15286(1, Lake Bust Nuur), ZISP 16320 (1, Lake Handi Nuur), ZISP 21676 (5,Lake Orog Nuur), ZISP 21678. (1, Lake Orog Nuur), ZISP 22081 (1,River Tuyn Gol), ZISP 22096 (2, Lake Orog Nuur), NMU 2485 (13,River Tesiyn Gol), NMU 2568 (20, River Tesiyn Gol), NMU 2571 (14,River Tesiyn Gol), NMU 2715 (21, Lake Terekhol), ZM MGU P-15904(9, Lake Orog Nuur), uncat. (39, Lake Böön Tsagaan Nuur); uncat. (30,River Tatsain Gol), uncat. (18, Lake Tatsain Tsagaan Nuur), uncat. (40,Lake Bayan Nuur), uncat. (50, Lake Terekhol), uncat. (35, Lake UvsNuur), uncat. (15, Lake Biger Nuur), uncat. (18, River Tesiyn Gol); 65osteological preparations (rivers Baydrag Gol, Tatsain Gol, LakeTerekhol, Tatsain Tsagaan Nuur, Bayan Nuur, Uvs Nuur).

Lectotype: Female with ripe eggs. SL 96.0 mm. Morphometriccharacters are given in Tabl. I. D III 8, the last simple ray is articulatedalong 52 % of its length; A IV 8; dent. 6-5; l.1. 90; sp. br. 25, vert. 41,abd. vert. 24, caud. vert. 17, preD vert. 14, interm. vert. 4; CSO 8/81 ,CIO 17/14, CPM 7+82 /6+9, CST 3+2.

Paralectotypes: four males and two females. SL 82.1-95.4 mm.Morphometric characters see Tabl. 1. D III 8, the last simple ray is

1 Number of pores on the left and right side.2 Number of pores in two canal fragment (on the lower jaw and preoperculum)

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articulated along 51-54 % of its length; A III, IV 8; dent. 6-5, 5-5; l.1.83-94; sp. br. 23-25, vert. 41, 42, abd. vert. 24, 25, caud. vert. 17, 18,preD vert. 14, 15, interm. vert. 4, 5; CSO 8, 9, CIO 14-18, CPM [6(7)]+[6-8(9)], CST [2, 3]+[2, 3].

Diagnosis. Usually 8 branched rays in both dorsal and anal fins.Vertebrae few, total number 40 to 43. Gill-rakers numerous, 22-43.Cephalic pores relatively few: 8-10, rarely 11 pores in CSO, 14-19,seldom to 21, pores in CIO. Simple dorsal rays not thickened, soft; lastsimple ray segmented for more than one half of its length. Supraethmoid

Table 1Morphometric characters of O. humilis

Character LectotypeZISP 6378

ParalectotypesZISP 8079

n=4

Lake Boon–Tsagaan Nuur

n=20

Lake Orog Nuurn=12

SL, mm 96.0 82.2–95.4 161.8–174.2 179.5–210.5Percents of SL

Snout length (1) 6.6 5.8–6.5 7.9–9.1 7.1–9.0Eye diameter (2) 5.6 5.2–5.9 3.7–4.9 3.8–4.5Postorbital distance (3) 15.3 14.5–15.1 17.1–20.9 18.0–20.4Head length (4) 25.0 25.8–27.5 28.5–34.4 30.0–34.2Head depth at nape (5) 13.6 13.0–14.7 14.3–16.7 15.1–16.7Head width at nape (6) 10.5 10.5–11.0 12.2–14.6 11.9–13.3Interorbital distance (7) 5.8 5.9–6.2 6.5–7.8 6.4–7.3

Maximum body depth (8) 15.5 14.6–17.2 20.9–22.0 19.1–22.5Minimum body depth (9) 8.0 7.7–8.7 9.4–10.5 8.0–10.2Predorsal distance (10) 54.0 51.9–33.6 53.0–57.4 54.2–57.4Postdorsal distance (11) 37.5 36.9–39.7 32.1–36.4 33.5–38.3Caudal peduncle length (12) 19.5 20.0–22.9 18.2–21.2 18.4–21.8Dorsal fin length (13) 10.4 10.8–12.2 9.8–11.1 9.5–10.8Dorsal fin depth (14) 19.2 18.2–22.8 17.5–20.3 18.0–19.8Anal fin length (15) 8.7 8.6–10.8 9.0–11.1 8.7–10.5Anal fin depth (16) 13.9 14.2–17.3 14.4–17.7 14.7–16.5Pectoral fin length (17) 15.4 14.9–17.7 16.3–17.8 15.4–17.5Pelvic fin length (18) 13.0 13.2–14.7 12.0–15.5 12.0–14.1P–V distance (19) 23.1 22.5–24.1 24.5–25.7 23.7–25.7V–A distance (20) 20.1 18.7–20.9 18.6–20.4 17.1–19.8Upper jaw length (21) 6.9 6.2–6.8 7.3–8.2 7.3–8.5Lower jaw length (22) 9.7 8.8–9.6 10.3–12.2 10.4–11.8Cranial roof length (23) 18.5 17.3–18.6 18.8–22.1 19.88–22.2

Percents of operculum lengthOperculum depth (24) 84.5 75.8–84.1 73.1–90.5 70.0–84.6

Percents of cranial roof lengthLt pto (25) 55.6 55.4–57.7 52.9–60.6 52.1–58.8Lt spho (26) 47.3 46.4–48.7 42.6–47.9 40.9–49.3Lt eth (27) 34.3 33.1–36.9 35.8–39.5 31.7–35.1

Percents of Lt ptoLt spho (28) 84.3 83.7–87.0 76.1–88.5 77.7–89.3

Percents of Lt sphoLt eth (29) 71.3 70.0–76.4 74.7–84.7 67.2–78.6

17

broad, particularly in large specimens. Neurocranium wide, Lt pto 52-60% of L cr. r.

Description. The throat and, to a certain extent, the abdomen arescaleless; in most specimens there are also areas on the back and on thesides that are covered by small not overlapping scales. Lateral line scalesare notably larger that the others, 81-114.

There are usually 8 branched rays in the dorsal fin. In our material(377 specimens examined) there was only one specimen with 9 rays. Inthe anal fin there are also 8 branched rays, 9 were found only in 1.3% ofspecimens. Dorsal fin rays are soft; the last (third or fourth) simple ray isnot thickened, flexible for 51-60% (seldom up to 68%) of its length,rarely articulated part of the ray is slightly shorter (48-50%). The next tolast simple ray is short. Its length is 33-52% of the length of the lastsimple ray.

Gill-rakers are strongly compressed, as a rule long, dense, (22-24)25-40(43). The most numerous gill-rakers were found in Altai osmans fromLake Böön Tsagaan Nuur and Orog Nuur.

In CSO there are 8-10(11), most commonly 8 or 9 pores (there are6-8(9) canal openings on the frontal, 2 or 3 on the nasal). In CIO (14)15-19(20, 21), more frequently 16 or 17 pores (there are 4 or 5, rarely 6,canal openings on the 1-st infraorbital). In CPM pores are arranged inthe following way: on the lower jaw there are (3,5)6,7(8,9) pores with 3to 8, commonly 5 or 6, canal openings on the dentary and (6)7-9(10)pores on the preoperculum. In CST which is usually interrupted in themiddle, there are 3 to 6, more frequently 4 or 5 pores.

The total number of vertebrae (38 specimens examined) is 40 (2specimens), 41 (12), 42 (17) or 43 (7). Number of abdominal vertebrae24 (25), 25 (12) or 26 (1). Predorsal vertebrae 13 (1), 14 (23) or 15 (14).Intermediate vertebrae 4 (24) or 5 (14). Number of caudal vertebrae 16(2), 17 (19) or 18 (17). Vertebral formulae 24+17 (12), 24+18 (11),25+17 (6), 25+18 (6), 24+16 (2).

The mouth is terminal; the tip of the mouth is on the level of themiddle of the eye or slightly lower. The general appearence of fish changeswith growth, especially the shape of the head. The most pronouncedchanges are an increase of the postorbital distance, the snout length, thehead length, and length of the lower jaw (Tabl. 1), a flattenning of thedorsal surface of the head, a general increase of the mouth size, a reductionof the eye size. Shape and proportions of the head directly reflect theshape of the skull and correlation of its separate elements. An analysisof a number of osteological characters shows that many of them are

18

subject to relatively high age-and-size variability (Bogutskaya, 1990c).The neurocranium width Lt eth increases while its Lt pto and Lt sphodecreases, the ratio of the latters remains relatively constant (Lt sphoconsititutes 76-80% of Lt pto). The supraethmoid width, length of thelower jaw, depth and length of the operculum, length of the hyomandibularare positively correlated with fish size, but the depth of the hyomandibularis negatively correlated (the length of the hyomandibular becomes nearlyequal to its depth in large specimens, whereas in the small ones itconstitutes slightly more than a half of it) (Tabl. 2). There are also changesin shape of the bones of the ethmoid region, of the orbitosphenoid,parasphenoid, jaw bones (Bogutskaya, 1990c). Although variability ofmany characters indicated is relatively high, some to a certain extent aretypical of the species. Thus the neurocranium (see in Bogutskaya, 1990c,Fig.1, 3) is wide in general, in specimens of different sizes values of Ltpto and Lt spho are within the ranges of 52.1-60.6 and 40.9-49.3% of Lcr. r. respectively. The supraethmoid is broad, in specimens of middleand large size it is markedly wider than the underlying bones of theethmoid region and its width is up to 14% of L bas. n. The lateral spenoticprocess bears a relatively deep notch on the posterior margin, so that thepostlateral end of the process bends backwards as a hook. The posteriorpterotic process is narrow, directed backwards. Its length slightly increaseswith the increase of body size and the end of the process can reach thelevel of articulatory surface on the basioccipital. The pharyngeal processis low; the masticatory plate is concave, often quite strongly. Its shapevaries from oval to nearly pentagonal, but lateral edges are alwayssmoothed, angles are not pronounced. The preoperculum does not changeits shape in connection with the increase of fish size, its horizontal branchis always equal in length to the ascending branch.

Comparative remarks. Oreoleuciscus humilis differs from two otherspecies of the genus by a low number of branched rays in the dorsal andanal fins (no one specimen was found among O. potanini or O.angusticephalus sp. n. with 8 branched rays in D and A at the sametime), by a low number of pores in the cephalic sensory canals(particularly in CSO and CIO), a wide supraethmoid and also a lownumber of vertebrae and more numerous and longer gill-rakers.Oreoleuciscus humilis differs from O. potanini also by the followingfeatures: not thickened simple rays in the dorsal fin, the last one segmentedalong more than one half of its length, a hooklike posterior end of thesphenotic process directed backwards, a pointed posterior pterotic

19

process, and, in large specimens, an elongated operculum and a longlower jaw (Tabl. 2).

Oreoleuciscus humilis is similar to O. angusticephalus sp. n. inhaving soft nonthickened highly segmented simple rays in the dorsal finand an elongated head, but differs notably from this species, in additionto the above mentioned characters, also by a wider skull, particularly inthe region of pterotics.

The Ubs-Nur osman described by Gundrizer (1976) under the nameO. potanini pewzowi corresponds to the species O. humilis. Unfortunately,this author, having made a conclusion that typicalO. pewzowi described from the Kobdo River system is Potanin’s osmanand in no way relates to the Ubs-Nur osman, continued using the name“pewzowi”. A wrong conclusion is made also concerning the status of O.humilis as a species described on the basis of a mixed group of specimens.However all syntypes of O. humilis, as can be seen also from descriptionsgiven above, are similar in their diagnostic characters between themselvesand with the Ubs-Nur osman. The latter according to the data of Gundrizer

O. humilis O. potanini O. angusticephalus

Character n=35 n=30 n=25 n=20 n=2 n=4

SL, mm 108–176 200–442 159–220 over 250 218; 300 over 300

Percents of L bas. n.

Lt pto 42.5–48.1 40.8–47.5 43.6–46.9 40.2–47.8 39.3; 37.5 34.0–38.6

Lt spho 32.9–40.0 30.4–39.0 32.2–37.9 29.2–39.5 25.7; 29.6 21.7–26.6

Lt eth 24.9–30.1 27.0–33.6 25.4–31.6 26.2–32.6 23.5; 26.0 23.2–25.3

H soc 22.6–26.8 22.8–27.8 25.1–29.2 25.5–30.3 24.3; 24.7 24.0–26.0

H eth 6.1–8.1 6.5–8.3 7.5–13.1 6.9–13.8 6.3; 6.9 6.0–6.7

Supraethmoid width 8.9–11.7 10.3–13.9 7.8–10.2 8.4–10.5 7.5; 7.6 7.2–8.9

Lower jaw length 38.9–49.1 45.6–57.1 39.2–46.6 40.2–52.2 49.4; 54.9 53.5–57.6

Operculum length 39.1–47.4 40.0–49.3 35.5–44.3 36.1–42.3 45.4; 47.3 41.4–49.1

Percents of hyomandibular depth

Hyomandibulare length 54.0–72.5 67.4–94.5 54.2–64.2 51.4–81.8 76.1; 79.5 99.3–103.1

Table 2Data of skull measurements of Altai osmans

20

(1976) is characterized by fewer dorsal and anal fin branched rays, fewerthan in O. potanini number of vertebrae and scales in the lateral line.

Morphological differences of O. humilis from other forms of Altaiosmans were shown also by Borisovets and his co-authors (1985c, andothers). Species status of O. humilis is confirmed also by electrophoreticanalysis of muscle proteins (Timofeyev, Dgebuadze, 1985).

Distribution. This species inhabits lakes and rivers of Lake Valleyfrom Biger Nuur in the west to Ongiyn Gol in the east where this speciesis the only one from the genus Oreoleuciscus. For a detailed descriptionof this region see Dgebuadze (1999). Oreoleuciscus humilis also occursin the system of Lake Uvs Nuur with tributaries (the largest one is RiverTess, or Tesiyn-Gol), in some water bodies probably historicallyconnected with this drainage in Tuva and Mongolia, for example, LakeTerekhol, lakes Handi Nuur, Bust Nuur and Sangiyn Dalay Nuur in theeast, and also in Telmen Nuur. The question if O. humilis is spread in theUpper Ob’ River needs a special remark. An opinion that O. humilis andO. potanini are sympatric at least in River Chuya is originally basedupon a fact that some from syntypes of O. humilis and O. humilis var.phoxinoides are labelled “Kosch-Agatch” (the Chuya drainage) and thislocality is respectively given as a type-locality for these names (togetherwith Ulaangom in the Uvs Nuur basin) by Warpachowski (1889).However, no reliable recent data exist on occurrence of O. humilis in theUpper Ob’ system. A special investigation was undertaken by Golubtsovwith co-authors (1999) who only found O. potanini in seven localitieswithin the systems of rivers Argut, Chuya, Bashkaus and Chulyshman.These authors believe that “Warpachowski (1889) … identified somespecimens of O. potanini from the headwaters of the Ob’ system asrepresentatives of O. humilis.” (p. 893-894). However, the present studyundoubtedly shows that all syntypes of O. humilis and O. humilis var.phoxinoides from both Ulaangom and Kosh Agach as well as non-typeZISP 14787 labelled “Tchuya” belong to one and the same species. Untillit is proved that the Kosh Agach syntypes are mislabelled, O. humilisstill has the River Chuya system as one from its type-localities. Localitieswhere this species is studied from are given on a map in Fig. 2.

Mode of life. Two eco-morphological forms, conventionally termeda dwarf form and a lake form, can be distinguish within a species O.humilis (Baasanzhav et al., 1983, 1985; Borisovets et al., 1985a, 1985b,and others). According to the data of these authors, the dwarf form (lengthof individuals up to 214 mm) occurs in shallow waters of lakes and riversfalling into them. In rivers, it prefers sections with slow water (raceways

21

Fig

. 2.

Loca

litie

s fo

r spe

cim

ens

exam

ined

: 1 –

O. h

umili

s, 2

– O

. pot

anin

i,3

– an

gust

icep

halu

s sp

. n.

- 1 - 2 - 3

22

Fig.

3. L

ecto

type

of O

. pot

anin

i, ZI

SP 4

210.

SL

191.

4 m

m. D

ain-

gol,

Upp

er D

zavh

an G

ol.

23

and pools). Its feeds on invertebrates (mainly insect latvae), plants anddetritus. The lake form is much larger (length up to 550 mm), inhabitsonly lakes and when it length attains 180-200 mm it passes to piscivorousfeeding. Individuals of the dwarf form matures at smaller sizes (at SLabout 70 mm and four years of age) than the lake form. Spawning ofboth forms occurs in June-August, in the dwarf form slightly earlier thanin the lake form. Spawning areas of these fishes inlude parts of deltacoasts and river flood plains covered by water during floods. Spawningis portioned, eggs are laid on plants and sand.

The dwarf and the lake forms of O. humilis from Lake Valley areinvestigated in conditions of periodic droughts accompanying thedisappearance of lakes and some part of rivers in a paper by Dgebuadze(1995). It is shown that during the drought both forms disappear fromthe lakes and populations of the dwarf form remain in the rivers; afterthe lakes are filled again, the lake form originates anew from the riverdwarf form.

Oreoleuciscus potanini (Kessler, 1879)

Altai osman, or Potanin’s osman (Fig. 3)

Chondrostoma Potanini Kessler, 1879: 307 (“Quellzuflussen des Daingol” [Lake Dain-gul, or ? Dayan Nuur], upper reaches of River Kobdo)

Chondrostoma Potanini – Kessler, 1880: 267 (“Quellzuflussen des Daingol”)Leuciscus Potanini – Herzenstein in Potanin, 1883: 244 (part.: River Chuya [ZISP

6382], River Tchonokhoraikh [Tchon-Hariha, a channel between Har Nuur and Durgen-Nur[Dörgö Nuur], River Tatche-teli [Tel, a channel between Har Nuur and Dzavhan Gol], RiverKobdo)

Leuciscus latifrons (nomen nudum) – Herzenstein, 1883: 244 (Ulaangom)Leuciscus Pewzowi (nomen nudum) – Herzenstein, 1883: 244 (Chonokhoraikh)Oreoleuciscus Potanini – Warpachowski, 1889: 30, Tabl. 3, Fig. 1 (basin of River

Kobdo; River Chuya)Oreoleuciscus Potanini var. recurviceps Warpachowski, 1889: 38, Tabl. 3, Fig. 2 (locality

unknown, probably River Naryn in Upper Kungui [Hüngüy] system)Oreoleuciscus Pewzowi Warpachowski, 1889: 41, Tabl. 1, Fig. 2 (Tchon-Charicha)Oreoleuciscus Pewzowi var. altus Warpachowski, 1889: 45, Tabl. 1, Fig. 3 (Tatche-

Teli)? Oreoleuciscus pewzowi var. longicaudus Warpachowski, 1889: 49, Tabl. 3, Fig. 3

(Tatche-teli)Oreoleuciscus similis (nom. mus. by Herzenstein) Warpachowski, 1889: 57, Tabl. 2,

Fig. 1 (Dsapchyn [River Dzavhan Gol])Oreoleuciscus dsapchynensis (nom. mus. by Herzenstein) Warpachowski, 1889: 61,

Tabl. 2, Fig. 2 (Dsapchyn)Oreoleuciscus Herzensteini Warpachowski, 1889: 65, Tabl. 1, Fig. 1 (River Kungui)Oreoleuciscus gracilis Warpachowski, 1889: 68, Tabl. 1, Fig. 4 (Ulangom)? Oreoleuciscus choerocephalus Warpachowski, 1889: 72, Tabl. 3, Fig. 4 (Airik-Nor

[Ayrag Nuur])

24

Oreoleuciscus ignatowi Nikolskji, 1902: 188 (“Tscheibok-kol in montibus Altai, insyst. fl. Baschkaus” [Choebak Khol])

Oreoleuciscus potanini - Berg, 1912: 86 (River Kobdo; basin of the Upper Ob River)Oreoleuciscus pewzowi - Berg, 1912: 88 (part.: basin of River Kobdo)Oreoleuciscus pewzowi var. altus - Berg, 1912: 88 (Lake Choebak Khol)Oreoleucsicus pewzowi - Gladkov, 1938: 296 (Lake Choebak Khol)Oreoleuciscus potanini - Iohansen, 1940: 164 (part.: basin of the Upper Ob River)Oreoleuciscus potanini - Berg, 1949: 539, Fig. 311 (part.: lake of the Lower Kobdo

River)Oreoleuciscus pewzowi - Berg, 1949: 540 (basin of River Kobdo)

Morphometric characters

CharacterLectotype,O. potaniniZISP 4210

Paralectotypes,O. potaniniZISP 4211,

50027

Holotype,O. dsapchynensis

ZISP 6410

Syntype,O. gracilisZISP 6376

Holotype,O. similisZISP 6411

SL, mm 191.4 148.3–192.5 226.3 87.0 226.5Percents of SL

(1) 5.7 5.9–7.3 6.2 6.9 7.4(2) 4.6 4.1–4.6 3.9 6.7 3.4(3) 16.0 15.1–19.2 13.5 16.3 20.7(4) 26.2 25.9–27.3 24.1 27.6 32.0(5) 14.5 13.9–15.2 13.5 15.9 16.7(6) 10.4 10.8–12.2 10.9 11.7 12.5(7) 6.3 5.4–7.0 6.2 7.2 6.9(8) 17.4 17.7–19.6 20.2 18.8 20.7(9) 9.1 8.9–10.1 9.5 9.3 10.3(10) 53.3 50.4–53.9 45.5 50.6 54.6(11) 37.3 36.1–39.4 42.0 37.9 36.2(12) 19.6 17.3–20.7 21.6 23.2 18.4(13) 11.6 10.9–12.3 13.0 11.8 11.6(14) 20.3 20.0–23.1 − 24.9 −(15) 10.7 10.4–12.6 11.8 12.1 11.1(16) 15.2 16.0–17.9 − 18.6 −(17) 16.2 15.7–17.5 − 15.9 −(18) 15.3 14.7–16.1 − 16.1 −(19) 25.0 22.9–27.2 20.7 20.1 24.2(20) 24.0 24.0–23.0 24.7 21.0 20.4(21) 5.6 6.2–6.7 5.7 7.2 9.2(22) 8.4 8.1–9.5 9.3 9.3 12.3(23) 18.1 17.0–19.1 16.3 18.4 19.3

Percents of operculum length(24) 92.6 73.4–89.7 99.4 88.2 75.9

Percents of cranial roof length(25) 53.6 51.3–58.8 55.7 58.1 54.9(26) 46.1 41.7–47.2 48.9 50.0 44.9(27) 33.6 30.7–38.9 32.4 33.1 31.6

Percents of Lt pto(28) 86.8 78.3–91.3 87.9 86.0 81.7

Percents of Lt spho(29) 74.8 72.3–78.0 65.3 66.3 70.4

25

Oreoleuciscus pewzowi var. altus - Berg, 1949: 540 (part.: basin of River DzavhanGol; Upper Ob River)

Oreoleuciscus potanini - Svetovidova, 1965: 246 (part.: basin of River Kobdo; LakeChoebak Khol)

Oreoleuciscus potanini - Dashdorzh et al., 1969: 290 (basin of River Kobdo)Oreoleuciscus potanini - Baasanzhav et al., 1983: 146, Fig. 23, 25 (part.: herbivorous

and sharp-snouted forms, basin of River Kobdo)“Altai osman” - Borisovets et al., 1985c: 1200, Tabl. 1, Fig. 2 (part.: herbivorous and

sharp-snouted forms, basin of rivers Kobdo and Dzavhan Gol)

Holotype,O. herzensteini

ZISP 6412

Holotype,O. pewzowi

var.longicaudusZISP 7761

Holotype,O. potanini

var.recurvicepsZISP 6413

Syntypes,O. pewzowi

ZISP 6386

Syntypes,O. pewzowi

var.altus

ZISP 6380

Syntypes,O. ignatowi

ZISP 11193193.1 116.4 147.2 217.0; 250.1 75.5–142.0 207.8–352.0

Percents of SL7.2 8.2 6.2 7.2; 7.9 4.7–7.9 8.8–9.63.9 6.7 4.9 4.0; 4.8 4.5–6.6 3.6–5.0

17.0 18.4 17.3 18.1; 21.8 14.5–18.8 19.8–23.327.7 32.6 28.3 30.5; 34.1 24.1–31.1 32.7–37.716.1 16.0 16.1 15.4; 16.2 14.7–15.4 16.1–18.713.0 11.6 12.2 10.2; 12.6 10.2–11.8 11.6–14.46.8 6.5 6.3 5.6; 6.1 6.2–6.5 7.4–8.9

23.9 17.9 21.9 17.1; 18.6 17.0–20.3 19.6–21.710.8 8.0 9.5 8.8; 8.4 7.6–10.0 7.4–10.053.8 54.0 53.9 54.0; 54.7 50.7–54.8 54.5–59.235.2 37.2 36.7 37.1; 35.5 35.8–38.1 31.7–34.316.6 20.3 20.0 19.7; 17.5 18.8–21.9 17.3–19.512.5 10.7 9.5 10.4; 11.2 10.6–12.6 11.6–12.018.6 21.3 21.0 17.7;17.1 21.5–24.6 19–21.811.7 10.8 10.9 10.2; 10.4 9.7–11.8 11.0–11.611.4 16.8 15.6 15.3; 13.9 16.4–18.4 14.1–16.015.3 15.7 − 14.6; 15.9 17.9–18.8 15.9–17.2− 14.5 − 13.4; 14.5 14.5–16.3 12.5–14.6

26.2 19.5 24.0 21.2; 22.2 19.1–22.5 19.8–25.323.0 18.9 23.6 21.8; 21.2 19.2–20.4 20.2–22.17.6 9.6 6.9 8.0; 9.7 7.5–8.8 8.4–10.19.6 12.6 9.4 10.9;12.9 10.2–11.6 12.0–14.1

18.4 21.6 18.6 19.0; 21.7 19.6–20.0 19.8–23.1Percents of operculum length

82.3 78.0 82.1 72.7; 67.6 78.4–90.3 76.9–90.1Percents of cranial roof length

56.9 48.8 53.3 49.8–51.4 51.6–55.4 50.8–52.247.3 39.6 42.0 38.7–41.6 42.5–46.9 40.8–43.233.8 28.8 31.0 32.8–34.5 28.2–34.8 29.2–30.1

Percents of Lt pto83.2 82.0 79.0 73.7–81.9 80.3–90.0 78.2–85.1

Percents of Lt spho71.4 70.0 73.9 80.0–86.6 73.2–80.7 69.4–71.6

Table 3of O. potanini

26

Oreoleuciscus potanini – Vasilieva, 1985: 199 (upper Ob River; basin of River Kobdo)Oreoleuciscus potanini - Bogutskaya, 1990c: 126 (Upper Ob River; basin of rivers

Kobdo and Dzavhan Gol)Oreoleuciscus potanini – Golubtsov et al., 1999: 894 (rivers Argut, Chuya, Bashkaus

and Chulyshman)Material: ZISP 42101 (1, lectotype; Daingol), ZISP 50027

(separated from 4210) (2, paralectotypes; Daingol), ZISP 4211 (4,paralectotypes; Daingol), ZISP 6376 (2, bearers of a name Leuciscuslatifrons nom. nud. by Herzenstein and syntypes of O. gracilisWarpachowski; Ulangom), ZISP 6379 (2, River Kobdo), ZISP 6380 (7,syntypes of O. pewzowi var. altus; Tatche-teli), ZISP 6383 (5, RiverChuya near Kasch-Agatch), ZISP 6385 (3, Tschon-Charicha), ZISP 6386

Fig. 4. Neurocranium: a - O. potanini, L bas. n. 105.1 mm, Lake Nogon Nuur,b - O. angusticephalus sp. n., L bas. n. 111.8 mm, Lake Nogon Nuur.

a b

pr. spho pr. spho

pr. ptopr. pto

1 I have found only seven specimens in total deposited in ZISP under the numbers 4210 and 4211(syntypes) though Kessler (1879) and Warpachowski (1889) gave a total number of ten.

27

a

b

d

f

c

e

seth

peth meth

pto p

epo

boc

proorbs

ff.dil.op.

pspts

Fig. 5. Skull of O. potanini, L bas. n. 105.1 mm, Lake Nogon Nuur:a - neurocranium, lateral view, b - neurocranium, ventral view, c - neurocranium,

posterior view, d - hyomandibular and palato-quadrate complex,e - bones of opercular cover, f - jaw bones

eth.l.

v

pr.pto

eocp.m.

ic

f.st

pr.p.-lat.

f.car.sphosoc

epo

eoc

palentpt mtpt

hm

squ

ectpt

keth

pmx

mx

dnpr.cor.

aart

rart

pop

op

iopsop

28

(2, syntypes of O. pewzowi; Tschon-Charicha), ZISP 6387 (1, syntypeof O. pewzowi, deform.; Tschon-Charicha), ZISP 6408 (1, River BuyantGol), ZISP 6409 (1, River Chuya), ZISP 6410 (1, holotype of O.dsapchynensis; Dzavhan Gol), ZISP 6411 (1, holotype of O. similis;Dzavhan Gol), ZISP 6412 (1, holotype of O. herzensteini; River Hüngüy),ZISP 6413 (1, holotype of O. potanini var. recurviceps, localityunknown), ZISP 7761 (1, holotype of O. pewzowi var. longicaudus;Tatche-teli), ZISP 8078 (1, 1; locality unknown), ZISP 10553 (1, RiverChuya), ZISP 11193 (3, syntypes of O. igantowi; Lake Choebak Khol);ZISP 11194-11200 (65, Lake Choebak Khol), ZISP 12024 (12, LakeTash-Obolon-Bashi), ZISP 12645 (2, River Kobdo), ZISP 14788 (3, LakeChoebak Khol), ZISP 15755 (3, Tzagan-Nur1 ), ZISP 15757 (3, RiverHüngüy), ZISP 15762 (6, River Chuya), ZISP 20813 (9, Lake Ureg-Nur[Örög Nuur]), ZISP 10814 (8, Lake Ishtyk Khol, basin of River Chuya),ZISP 20815 (1, Lake Ishtyk Khol), ZISP 26699 (3, River Ob), ZISP39052 (3, channel between lakes Khirgis-Nur [Hyargas Nuur] and Airik-Nur [Ayrag Nuur]), ZISP 39053 (6, Lake Örög Nuur), NMU 2715 (1,Lake Örög Nuur), ZM MGU P-15900 (1, Lake Nogon Nuur), ZM MGUP-15902 (3, Lake Hara-Nur [Har Nuur]), uncat. (26, Lake Dzhulukul[Dzulu Khol]), uncat. (27, Lake Khuh Nuur, Upper Dzavhan Gol) andalso 49 osteological preparations (Dzavhan Gol, Lakes Khuh Nuur,Nogon Nuur, Dzulu Khol, channel between lakes Hyargas Nuur and AyragNuur).

Lectotype: Female with ripe eggs. SL 191.4 mm. Morphometriccharacters are given in Tabl. 3. D III 9, the last simple ray is articulatedalong 35 % of its length; A III 10; 5th ceratobranchials absent; l.1. 87, sq.l. 91; sp. br. 18, vert. 44, abd. vert. 25, caud. vert. 19, preD vert. 15,interm. vert. 5; CSO 6+7/13, CIO 30/27, CPM 6+9/6+2+12, CST 5+5.

Paralectotypes: four males and two females. SL 148.3-192.5 mm.Morphometric characters see Tabl. 3. D III 9, the last simple ray isarticulated along 37-48% of its length; A III 9, 10; dent. 6-5, 5-5; l.1. 84-99; sp. br. 18, 19; vert. 44, 45, abd. vert. 25, 26, caud. vert. 18, 19, preDvert. 14, 15, interm. vert. 4, 5; CSO (11)12-14, CIO 24-30, CPM [(7)8-10]+[10-13], CST [3-5]+[3-5].

Diagnosis. Usually 9 branched rays in dorsal and 9 or 10 in analfins. Vertebrae numerous, total number 43 to 46. Gill-rakers not very

1 There are several lakes called “Tzagan (Tsagaan) Nuur” in West Mongolia. These specimens arecollected by K.V. Yurganova, 14.07.1911; judging on description of her trip (Kerzhner, 1972), atthis date she was in the surroundings of Uliastay which is located on Bogdyn Gol, a tributary ofSurgyn Gol (Upper Dzavhan Gol).

29

dense, 15 to 25. Cephalic pores relatively numerous: 12-18, very rarely11 pores in CSO, 22-33, commonly 25-30, pores in CIO. Simple dorsalrays thickened, slightly or notably rigid; the segmented part of the lastray usually constitutes less than 1/2 of its length. Supraethmoid narrowin specimens of all sizes. Neurocranium wide, Lt pto and Lt sphorespectively 52-60% and 40-52% of L cr. r. Posterior pterotic processshort, does not reach the level of articulatory surface of basioccipital.

Description. The body including the throat up to the isthmus is oftencovered by the overlapping scales or scales on the ventral side is reducedto a certain extent. There are 82 to 116 lateral line scales. There arecommonly 9, seldom 8 (8%) or 10 (1%) branched rays in the dorsal finand 9, sometimes 10 (10%), in the anal one. The last (most commonlythe third) simple ray in the dorsal fin is thickened to a certain extent,often quite rigid. Articulated part of this ray constitutes as a rule lessthan 1/2 (more frequently 38-48 %) of length of this ray and striation ofthe ray (traces of fusion of the segments) is seen along a relatively shortportion below. A relatively small number of specimens (from both LargeLakes Hollow and form the upper Kobdo and Dzabkhan rivers) was foundwith the third simple dorsal ray relatively soft and .articulated along 48-52% of its length. The most thickened and to the least degree articulatedray has been noted in specimens form Lake Choebak Khol, Lake NogonNuur, Dzavhan Gol River, in which segments are not fused for only 25-40% of the ray which frequently has the appearance of a spine, flexibleonly on the very apex (for example, in the holotype of O. dsapchynensis,specimens of the sharp-snouted form from Lake Nogon-Nuur). Theindicated structural features of the last simple dorsal ray are found inspecimens from 65-70 mm SL. In individuals of smaller sizes (SL 30.4-32.5 mm: Lake Tash-Obolon-Bashi) this ray is segmented over 50-55%of its length. Anterior part of the dorsal fin is more rigid also because ofthe frequently thickened, comparatively long next to last simple ray (itslength is 50-78% of the length of the last simple ray).

Gill-rakers are relatively short, (15)16-24 (25) on the outer side ofthe first gill arch.

In CSO there are 11 to 18, most commonly 12 to 15 pores (there are(7)8-11(12) canal openings on the frontal, 3 to 5 on the nasal). In CIO22 to 33, more frequently 25 to 30 pores (there are 5 to 12, commonly 6or 7, canal openings on the first infraorbital). In CPM pores are arrangedin the following way: on the lower jaw there are (7)8-11(12) pores with3 to 9, commonly 5 to 8, canal openings on the dentary and 8 to 14,

30

usually 9 to 12, pores on the preoperculum. In CST which is usuallyinterrupted in the middle, there are 6 to 10 pores.

The total number of vertebrae (46 specimens examined) is 43 (4specimens), 44 (21), 45 (16) or 46 (5). Number of abdominal vertebrae24 (2), 25 (13), 26 (21), 27 (9) or 28 (1). Predorsal vertebrae 12 (2),13 (4), 14 (23), 15 (13) or 16 (3). Intermediate vertebrae 4 (2), 5 (25) or6 (18). Number of caudal vertebrae 17 (3), 18 (20), 19 (16), 20 (6) or 21(1). Most frequent vertebral formulae 26+18 (11), 26+19 (7), 25+19(7), 27+18 (6), 25+20 (3).

The mouth is terminal, subinferior or seldom almost superior, sothat the tip of the mouth is on the level of the upper margin of the eye.The snout is usually stout. The jaws are not long: length of the upper andlower jaw constitutes up to 9 and 11% of SL respectively. Dorsal surfaceof the head is weakly convex. Length of the head normally does notexceed 30% of SL. The neurocranium (Fig. 5, 6) is relatively short (L cr.r. is 16-20% of SL), wide (Tabl. 2), slightly narrowing in the central part(in the region of sphenotics). According to the data of measurements of90 undissected specimens (SL more than 70 mm) from lakes Khuh Nuur,Dzulu Khol, Choebak Khol, Tash-Obolon-Bashi, Nogon Nuur, HüngüyRiver and Chonokhoraikh, Lt pto is 52.2-62.4 (on the average 55.8), Ltspho is 41.4-51.6 (44.9), Lt eth is 31.8-38.5 (36.1) % of L cr. r.; Lt sphois 76.7-92.8 (85.2) % of Lt pto and Lt eth is 64.3-80.0 (75.3) % of Ltspho. The operculum is relatively deep, its depth is 76.8-102.4 (on theaverage 86.6) % of the bone length. Comparison of specimens of differentsizes shows that width of the skull within the regions indicated does notchange or changes insignificantly with the increase of fish body size(Tabl. 3). Thus specimens (ZISP 12024) with SL 30.4-32.5 mm have thesame wide head as specimens with the length of 70.5-109.0 mm: Lt ptois 52.1-58.3 and 54.4-58.0% of L cr. r. respectively. These data areconfirmed by results of the measurement of skulls in dissected specimensof O. potanini (Tabl. 2). The shape of neurocranium and also of otherelements of the skull shows a relatively low variability. Some differenceshave been revealed between specimens from River Chuya and upperDzavhan Gol on one hand and specimens from Lake Nogon Nuur on theother hand. The latter differs in having a slightly more elongatedneurocranium, a small hyomandibulare, a more elongated and smalloperculum (Bogutskaya, 1990c).

Characters of the neurocranium structure (Fig. 4a, 5) distinguishingO. potanini show comparatively low variability. The supraethmoid isnarrow, its width does not exceed 10.5% of L bas. n. The lateral sphenotic

31

process has an obliquely cut or weakly concave posterior margin whichnever has the shape of a pronounced hook. The dilatator fossa even inlarge specimens is narrow and short (Fig. 4a), does not exceed 35% of L.bas. n.; the fossa is medially deepened and possesses a well developedroof formed from the frontal and pterotic. The posterior pterotic processis relatively blunt at the end, relatively short even in the largest specimens,it does not reach the level of the articulatory surface of the basioccipital.The pharyngeal process, its masticatory plate and preoperculum aresimilar in shape with those of O. humilis.

Specimens of the sharp-snouted form having a narrow elongatedsnout differ from typical O. potanini described above only in the shapeof the snout. The neurocranium of the sharp-snouted forms differs onlyby a shallower and more elongated ethmoid region – H eth is about 6%,length of the ethmoid region 20-21% of L bas. n. (vs. 7-14 and 16-17%respectively in the typical form).

Fig. 6. Head, dorsal view: a - O. potanini, SL 220.5 mm, ZISP 39052,b - O. angusticephalus sp. n., SL 216.4 mm, ZISP 50164, both from the channel

between lakes Hyargas Nuur and Ayrag Nuur.

a b

32

In a number of examined samples of O. potanini there are specimens,which to a certain extent differ in some characters from the typical formbeing closer to O. angusticephalus sp. n.. Thus among specimens fromLake Choebak Khol (collected by Igantov, 1901) there are threespecimens (syntypes of O. ignatowi Nikolski; SL 207.8-352.0 mm)possessing a relatively large head (length of the head 32.7-37.7% SL)and a long lower jaw (12.0-14.1% SL). However, in the structure of thedorsal simple rays and other morphometric characters they do not differfrom typical O. potanini (Tabl. 3). A similar “large-headed” specimen(SL 335.0 mm) was found also in the upper reaches of River DzavhanGol (ZISP 15755) (length of the head and length of the lower jaw 36.0and 14. 5% SL respectively). The holotype of O. similis (SL 226.5 mm)differs by a long head (32.0 % SL), a long lower jaw (12.3% SL) and anelongated operculum (depth is 75.9% of length of the bone), but itpossesses a rigid last simple dorsal fin ray and a broad skull (Tabl. 3),which are typical of O. potanini.

Different from typical specimens of O. potanini caught inChonokhoraikh (a channel between lakes Har Nuur and Dörgö Nuur)(ZISP 6380) are three specimens (syntypes of O. pewzowi) caught in thesame water body. They are characterized by a slightly narrower and longerhead, a longer lower jaw and an elongated operculum (Tabl. 3). Becausethe last simple ray of the dorsal fin is thickened, articulated for only 35-42% of its length, syntypes of O. pewzowi were referred to O. potanini(Vasilieva, 1985; Bogutskaya, 1988, 1990c). A comparison of the headwidth in these specimens with that in typical O. potanini and specimensof O. angusticephalus sp. n. of the same size (SL 216-238 mm) alsoshows that the syntypes of O. pewzowi (Lt pto is 49.8-51.4, Lt spho is38.7-41.6% of L cr. r.) is closer to O. potanini than to O. angusticephalussp. n. (44.4-47.6 and 34.2-37.0% of L cr. r. respectively).

Comparative remarks. O. potanini is clearly distinguishable fromO. humilis by the number of branched rays in the dorsal and anal fins,number of vertebrae, number of cephalic pores as well as in having athickened rigid last simple ray in the dorsal fin accompanied by arelatively long next to last ray and a narrow supraethmoideum.

Besides the structure of the dorsal simple rays, differences betweenO. potanini and O. angusticephalus sp. n. are related basically to thecranial width and some other features of skull structure. Thus in O.potanini the neurocranium is relatively wider in all regions, which isparticularly pronounced when specimens of middle and large size arecompared (Fig. 6, Tabl. 2). In undissected specimens of O. potanini

33

Lt pto is more than 50%, and Lt spho more than 39 % of L cr. r., whereasin O. angusticephalus sp. n. only a few of the smallest specimens had Ltpto up to 52% and Lt spho up to 42% of L. cr. r. Considerable differencesare also observed in the shape of the lateral sphenotic process, posteriorpterotic process, dilatator fossa, masticatory plate, preoperculum,operculum and hyomandibular.

Using characters of cranial structure is not always possible, so, thestructure of the last simple ray in the dorsal fin and the relative width ofthe skull are key characters of external morphology for distinguishingbetween O. potanini and O. angusticephalus sp. n. However, twospecimens were found among all studied of Altai osmans (Tatche-teli;one of syntypes of O. pewzowi var. altus, ZISP 6380, SL 94.5 mm andthe holotype of O. pewzowi var. longicaudus ZISP 7761, SL 116.4 mm),possessing characters of both species. Like all other specimens fromTatche-teli they have the hard last simple dorsal ray segmented for only35-47% of its length, but differ by a narrow, long head: L cr. r. constitutes21.2 and 24.3% of SL, Lt pto is 49.0 and 48.8% of L cr. r. respectively,which coincides with values of these parameters in one-size specimensof O. angusticephalus sp. n. I have identified them as O. potanini on thebasis of the presence of hard thickened ray in the dorsal fin. It is possiblethat they can be hybrids of O. potanini and O. angusticephalus.

Distribution. Lakes and rivers of the Upper Ob drainage; basin ofrivers Kobdo and Dzavhan Gol including water bodies of the westMongolian Great Lakes Valley and Lake Örög Nuur (without outlet, southfrom the Tsagaan Shibetu mountain). Localities where this species isstudied from are presented on a map in Fig. 2. with one exception forZISP 6376 (syntypes of O. gracilis Warpachowski) with a locality“Ulangom” given on the label. An analysis of literature and my own datagives no reliable recent evidence for occurrence of O. potanini in thebasin of Lake Uvs Nuur.

Mode of life. According to data of a number of authors (Baasanzhavet al., 1985; Borisovets et al., 1985c) Potaninin’s osman inhabits lakesand parts of rivers with slow current. It does not migrate at long distances,avoiding areas with rapid current. It feeds mostly on aquatic vegetation,and also invertebrates; larger specimens consume fish. Maximum sizesin water bodies of Mongolia are 40-50 cm; for the Upper Ob River thereare indications of catching larger fishes (Krivoshchekov, 1959). Lengthof the sharp-snouted form do not exceed 30 cm. Life duration is 31 to 34years. This fish attains maturity at an age of 7-8 years at a length of 170-190 cm, but individuals are met that mature earlier (at a length of 80-100 cm

34

Fig.

7. P

arat

ype

of O

. ang

ustic

epha

lus

sp. n

. ZM

MG

U P

-159

01. S

L 23

7.8

mm

. Lak

e N

ogon

Nuu

r.

35

and an age of 4-5 years) and die having smaller sizes (140-150 mm).Spawns in channels and coastal areas of lakes. Spawning lasts from earlyMay until August.

Oreoleuciscus angusticephalus, sp.n.

narrow-headed Altai osman (Fig. 7)

Oreoleuciscus pewzowi (non Warpachowski) – Vasilieva, 1985: 202 (part.: Lake Nogon-Nuur)

? “Altai osman” – Borisovets et al., 1985c: 1203 (part.: piscivorous form, Lake NogonNuur and Dörgö Nuur)

Oreoleuciscus sp. – Bogutskaya, 1990c: 128 (Lake Nogon Nuur).Etymology. Latin translation of the name “narrow-headed”, which

reflects the most typical character of this new species.Material: ZISP 50163 (1, holotype; channel between lakes Khirgis-

Nur and Airik-Nur), ZISP 50164 (7, paratypes, the same locality), ZMMGU P-15901 (3, paratypes, SL 136.2, 159.2, 237.8 mm; Lake NogonNuur), 6 osteological preparations (Lake Nogon Nuur; channels betweenHyargas Nuur and Ayrag Nuur).

Holotype: immature female. SL 175.5 mm. Morphometric charactersare given in Tabl. 4. D III 9, the third simple ray is soft, articulated along55 % of its length; A III 10; dent. 5-5; l.1. 91; sp. br. 20, vert. 44, abd.vert. 26, caud. vert. 18, preD vert. 15, interm. vert. 5; CSO 15/16, CIO29/27, CPM 12+10/11+10, CST 4+4.

Paratypes: SL 115.2-237.8 mm. Morphometric characters see Tabl.4. D III (IV)9 (8 in one specimen), the last simple ray is articulatedalong 52-56% of its length; A III 9, 10; dent. 6-5, 5-5; l.1. 89-105; sp. br.16-20; vert. 44, 45, abd. vert. 25, 26, caud. vert. 18, 19, preD vert. 14,interm. vert. 5; CSO 13-17, CIO 26-33, CPM [10-12]+[10-14], CST [3-5]+[3-5].

Diagnosis. Usually 9 branched rays in dorsal and anal fins. Vertebraenumerous, total number 43 to 47. Gill-rakers not very dense, 15 to 22.Cephalic pores numerous: 13-18 in CSO, 26-35, commonly 27-33, poresin CIO. Simple dorsal rays soft; the segmented part of the last ray usuallyconstitutes more than 1/2 of its length. Supraethmoid narrow in specimensof all sizes. Neurocranium narrow, Lt pto and Lt spho respectively 44-52%and 33-44% of L cr. r. Posterior pterotic process long, its end reaches muchbehind the level of articulatory surface of basioccipital.

Description. The troat and anterior part of the abdomen (lessfrequently the entire abdomen) are scaleless, adjoining parts of the bodyare covered by non-overlapping scales. There are 89 to 108 lateral line

36

scales. There are three, rarely four, simple and 9, rarely 8 or 10, branchedrays in both the dorsal and anal fins; not a single specimen with 8 branchedrays simultaneously in both fins A have been found. The last simple raysare never thickened and rigid, but segmentation of the last one isdeveloped slightly less than that in O. humilis - in the majority ofspecimens an articulated part of the ray consitutes only a little bit morethan 1/2 (seldom up to 56-65%) of the ray length; sometimes the ray issegmented for 50-46% of its length. The next to last simple ray is longer

Table 4Morphometric characters of O. angusticephalus sp. n.

Character Holotype,ZISP 50163

Paratypes,ZISP 50164

Paratypes ZM MGUP–15901

Non–type,Nogon–Nur

SL, mm 175.5 115.2–216.4 136.2–237.8 79.4–149.1Percents of standard length

(1) 8.3 6.9–8.4 8.3–8.7 6.6–8.7(2) 4.7 4.6–5.8 4.2–5.5 4.2–6.4(3) 22.2 18.7–22.6 28.8–21.8 17.4–21.8(4) 35.3 31.7–35.4 32.7–34.7 30.0–35.0(5) 16.2 15.1–16.6 15.2–16.0 14.4–17.2(6) 11.4 10.4–11.6 10.8–11.4 10.9–12.8(7) 6.3 5.6–6.4 6.5–7.2 5.9–7.8(8) 19.0 17.9–19.7 16.0–19.1 16.0–21.9(9) 7.6 7.8–8.3 8.0–8.9 7.6–9.3(10) 53.3 51.0–54.2 53.5–57.1 52.0–58.0(11) 36.4 34.3–39.9 35.2–39.3 35.2–42.5(12) 18.7 17.9–21.4 19.7–22.5 19.7–24.0(13) 11.6 10.8–12.0 10.4–11.9 10.4–13.1(14) 22.1 19.8–26.0 21.4–24.5 20.1–26.0(15) 11.4 10.7–12.1 9.2–11.2 9.2–12.5(16) 17.5 16.9–19.2 16.5–18.0 15.9–19.6(17) 15.6 14.2–20.2 14.8–15.5 13.9–17.1(18) 14.5 13.7–15.6 13.4–15.2 13.4–16.7(19) 20.7 20.2–23.9 19.3–20.7 17.4–22.7(20) 19.9 16.7–21.1 15.7–17.6 15.2–22.1(21) 9.1 7.7–9.6 7.9–9.6 7.8–9.6(22) 13.1 11.8–13.7 11.7–13.2 10.7–13.4(23) 22.2 20.6–21.8 21.0–21.4 19.9–22.8

Percents of operculum length(24) 71.6 69.1–74.1 71.1–76.9 70.5–83.5

Percentsof cranial roof length(25) 46.9 44.2–48.2 44.4–47.6 46.8–52.0(26) 33.8 34.2–38.7 35.4–37.0 35.5–42.2(27) 28.7 28.6–31.3 30.7–33.3 30.4–35.4

Percent of Lt pto(28) 72.1 72.5–80.7 75.8–77.5 75.2–83.2

Percents of Lt spho(29) 86.8 77.8–89.6 88.4–97.1 75.8–92.5

37

than in O. humilis and constitutes 58-72% of the length of the last simpleray.

Gill-rakers are relatively short and few, 15-22 on the outer side ofthe first gill arch.

Range of variation of the number of pores in certain canals on thehead and those of O. potanini overlap; but on the wholeO. angusticephalus sp. n. have a somewhat larger number of pores: inCSO there are 13-17(18), more frequently 14 to 16 pores (in the nasalthere are 4-6 canal openings and (9)10-13(14) on the frontal). In CIOthere are (26)27-33(34, 35), commonly 28 to 31, pores (on the firstinfraorbitale there are 7-11(12), more frequently 9 to 11 canal openings).In CPM pores are arranged in the following way: on the lower jaw thereare 8 to 13, more frequently 10 to12 pores (7 to 13 canal openings on thedentary) and on the preoperculum there are 10 to 15, usually 11 to 14,pores. In CST which is interrupted for rare exceptions there are (6, 7)8-10 pores.

The total number of vertebrae (31 specimens examined) is 43 (4specimens), 44 (17), 45 (7), 46 (2) or 47 (1). Number of abdominalvertebrae 25 (7), 26 (19), 27 (4) or 28 (1). Predorsal vertebrae 13 (6), 14(22) or 15 (3). Intermediate vertebrae 4 (4), 5 (22) or 6 (5). Number ofcaudal vertebrae 17 (4), 18 (13), 19 (13) or 20 (1). Most frequent vertebralformulae 26+18 (10), 26+19 (6), 25+19 (5), 27+17 (2), 25+18 (2).

The mouth is terminal; the lower jaw is protruding forward,particularly in larger specimens. The snout is pointed. The head is long,30-35% SL. The lower jaw is long, constitutes more than 11% SL evenin the smallest specimens.

The neurocranium (Fig. 4b, 8) is relatively long (length of the cranialroof is 20-23% of SL), narrow (Tabl. 2), notably narrowing in the regionof sphenotics. According to data for all 44 specimens Lt pto constitutes44.2-52.0 (on the average 47.8), Lt spho 33.4-42.2 (36.3), Lt eth 28.6-35.4 (33.5) % of L cr. r.; Lt spho is 72.5-83.4 (79.1) % of Lt pto; Lt ethis 75-97.1 (86.2) % of Lt spho. The operculum is elongated, particularlyin larger specimens; its depth is 69.1-85.5 (on the average 76.4) % of itslength. Comparison of specimens having different sizes showed that withfish growth width of the neurocranium on the level of sphenotics andpterotics decreases, Lt spho can attain or be even less than Lt eth (thelatter constitutes up to 90-107% of Lt spho); length of the lower jawencreases, the hyomandibular becomes more elongate (in large specimensits length can be nearly equal or higher than the depth) (Tabl. 2).

38

Fig. 8. Skull of O. angusticephalus sp. n., L bas. n. 111.8 mm, Lake Nogon Nuur:a - neurocranium, lateral view, b - neurocranium, ventral view,

c - neurocranium, posterior view, d - hyomandibular and palato-quadrate complex,e - bones of opercular cover, f - jaw bones.

f.dil.op.

c

e

a

b

d

f

op

spho pr.pto

ic

p.m.v

39

The supraethmoid is narrow, its width does not exceed 9% of L bas. n.The lateral sphenotic process with a concave posterior margin, so that theposterior end of the process is turned into a small sharp hook. The dilatatorfossa is wide, long, its length is 37-42% of L bas. n. (Fig. 4b). The frontaldoes not form the roof of the fossa and its medial edge is smoothed. Theposterior pterotic process is directed backwards, narrow, pointed at the end,long, particularly in large specimens. Its end (in lateral view) is notablybehind the articulatory surface on the basioccipital. The masticatory plateon the pharyngeal process is weakly concave or flat of elongated pentagonalshape with pronounced postlateral angles. The preoperculum with anelongated horizontal branch exceeding the ascending branch in length (Fig. 8).

Comparative remarks. Oreoleuciscus angusticephalus sp. n. issimilar with O. humilis by the presence of a soft last simple dorsal ray,segmented for more than one half of its length, elongated head andoperculum, an elongated lower jaw, especially in specimens of largersize. However these species are clearly distinct in particular in the numberof vertebrae, in the number of pores in all canals on the head, generalwidth of the neurocranium, width of the supraethmoid, number ofbranched rays in the dorsal and anal fins.

Oreoleuciscus angusticephalus sp. n. shares with to O. potanini acertain number of characters such as the number of rays is the dorsal andanal fins, the number of vertebrae and gill-rakers . Ranges of the numberof pores in individual cephalic canal in both species are quite wide andoverlapping but if modal ranges are concerned the species can be welldistinguished. Thus, in CSO on the frontal the modal ranges of pores are10 to 13 in O. angusticephalus and 8 to 11 in O. potanini, in CIO 28 to31 and 25 to 30 with respectively 9 to 11 and 6 or 7 canal openings onthe first infraorbital. In CPM on the lower jaw the modal ranges of thenumber of pores are 10 to 12 and 8 to 11 respectively with 8 to 10 and 5to 8 canal openings on the dentary.

Differences between O. angusticephalus sp. n. and O. potanini concernmainly the structure of the simple rays in the dorsal fin, shape of the skulland its different regions and bones. Differences in shape of the neurocranium(Fig. 3), hyomandibular, operculum and preoperculum are better pronounedin fish of larger size. By the diagnostic external characters O. angusticephalusdiffers distinctly from O. potanini (including the specimens of the sharp-snouted form from Lake Nogon Nuur examined in this study). The mostdifferentiating external character is the relative width of the skull since somespecimens of O. potanini possess relatively soft simple dorsal rays and along head. Comparison of groups of one-size specimens of O. potanini from

40

different water bodies (SL more than 100 mm) with one size O.angusticephalus sp. n. has shown that values of width of the neurocraniumbetween the lateral margins of pterotics and sphenotics in them do not overlap,in the majority of cases a chiatus is comparatively wide. Thus, Lt pto and Ltspho in O. angusticephalus from the channel between lakes Hyargas Nuurand Ayrag Nuur (paratypes, SL 115-216 mm) constitutes 44.2-48.2 and 34.2-38.3 as compared to 53.2-58.0 and 44.5-51.2% of L cr. r. in specimens fromLake Choebak Khol (SL 104-220 mm). In same degree the indicatedspecimens of O. angusticephalus sp. n. differ form specimens of O. potanini(ZISP 39052, SL 119-334 mm) (Fig. 5) caught simultaneously with them inthe same channel (in the latter Lt pto and Lt spho are respectively 51.5-53.9and 40.3-48.0% of L cr. r.). The relative length of the upper and lower jawsas well as the degree of operculum elongation are also differentiating in themajority of cases (Tabl. 3, 4).

For the first time O. angusticephalus sp. n. was considered as a distinctspecies in our concept by Vasilieva (1982, 1985), but unfortunately this wasnot supported by a pertinent taxonomic procedure. Data of this author andalso results of the present work confirm occurrence in the lakes of the lowerreaches of River Kobdo of two groups of Altai osmans, which can receivethe rank of species because of certain morphological differences describedabove. A further study of diversity of Altai osmans using additional characters,will possibly provide new data for understanding taxonomic relations of O.potanini and O. angusticephalus sp. n..

Distribution. Lakes of the lower reaches of Kobdo and DzavhanGol. Sympatric with O. potanini.

Mode of life. Oreoleuciscus angusticephalus sp.n. apparently correlateswith the piscivorous form of Altai osman of a number of authors (Borisovetset al., 1985c, and others). Individuals of this form differ by large sizes (lengthup to 100 cm) and long life duration — more than 40 years. They reachmaturity at an age of 8-9 years at body length of 200-240 mm. The youngfeed on plankton, fish is predominant in the diet of adult fishes. Spawningoccurs in May and June. Eggs are laid on the sand, pebble, vegetation. Timeand places of spawning partly coincide with those ofO. potanini.

Acknowledgements

I am very thankful to Drs. E. D. Vasilieva, Yu.Yu. Dgebuadze andO.N. Pugachev for specimens given at my disposal from their collections.The study was sponsored by grants from the Russian Foundation for

41

Basic Research (98-04-48524, 00–15–97794, 01-04-49552) the“Biodiversity” Program (1998-2001), and a grant “Scientific collection”,USC ZIRAS, 03-16.

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ÀÍÍÎÒÀÖÈß

ÓÄÊ. 597.5.CyprinidaeÍ.Ã. Áîãóöêàÿ

Çîîëîãè÷åñêèé èíñòèòóò ÐÀÍ

ÐÅÂÈÇÈß ÀËÒÀÉÑÊÈÕ ÎÑÌÀÍÎÂ ÐÎÄÀ OREOLEUCISCUS(CYPRINIDAE: LEUCISCINAE) Ñ ÎÏÈÑÀÍÈÅÌ ÍÎÂÎÃÎ ÂÈÄÀ,

O. ANGUSTICEPHALUS, ÈÇ ÁÀÑÑÅÉÍÀ Ð. ÊÎÁÄÎ, ÇÀÏÀÄÍÀß ÌÎÍÃÎËÈß

Ïðîâåäåíî ñðàâíèòåëüíî-ìîðôîëîãè÷åñêîå èçó÷åíèå àëòàéñêèõ îñìàíîâ ðîäàOreoleuciscus (Leuciscinae, Cyprinidae) èç ðàçíûõ ìåñò àðåàëà, â òîì ÷èñëå ñèíòèïîâè ãîëîòèïîâ îïèñàííûõ ðàíåå âèäîâ è âàðèåòåòîâ. Íà îñíîâàíèè àíàëèçà 33ïëàñòè÷åñêèõ è ìåðèñòè÷åñêèõ ïðèçíàêîâ, 14 êðàíèîëîãè÷åñêèõ ïàðàìåòðîâ, àòàêæå äðóãèõ îñîáåííîñòåé ñòðîåíèÿ ñêåëåòà, (â òîì ÷èñëå ïîçâîíî÷íèêà è ñòåïåíèîêîñòåíåíèÿ íåâåòâèñòûõ ëó÷åé), è êàíàëîâ ñåéñìîñåíñîðíîé ñèñòåìû íà ãîëîâåïîäòâåðæäåí âûâîä (Áîãóöêàÿ, 1990c) î òîì, ÷òî ðîä Oreoleuciscus ïðåäñòàâëåí3 âèäàìè. Óçêîãîëîâûé îñìàí èç îç. Íîãîí-Íóð, íå èìåâøèé âàëèäíîãî íàçâàíèÿ,îïèñûâàåòñÿ êàê O. angusticephalus sp. n. Îñíîâíûìè äèàãíîñòè÷åñêèìèïðèçíàêàìè ÿâëÿþòñÿ ÷èñëî âåòâèñòûõ ëó÷åé â ñïèííîì è àíàëüíîì ïëàâíèêàõ,ñòðîåíèå ïîñëåäíåãî íåâåòâèñòîãî ëó÷à â ñïèííîì ïëàâíèêå, ÷èñëî ïîðñåéñìîñåíñîðíûõ êàíàëîâ íà ãîëîâå, îòíîñèòåëüíàÿ øèðèíà ãîëîâû â ðàçíûõîòäåëàõ, ôîðìà supraethmoideum è çàäíåãî îòðîñòêà pteroticum. Ïðèâîäÿòñÿîïðåäåëèòåëüíàÿ òàáëèöà âèäîâ ðîäà è ïîäðîáíàÿ ñèíîíèìèÿ.