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A new species and genus of a large and unusual freshwater hardyhead, Sashatherina giganteus (Pisces: Atherinidae) from West Papua, Indonesia and a comparison with its closest relatives of the genus Craterocephalus.

INTRODUCTION

It appears that the total number of Old World atherinids is related to the amount of exploration that has been done, especially in those parts of the world which were previously not accessible due to insurmountable physical barriers or political constraints. With the relative ease of mobility through recently inaccessible parts of the world, new species of both marine and freshwater fishes are constantly discovered. Two indomitable explorers, Heiko Bleher and the second author, Gerald R. Allen, discovered a considerable number of new species of atherinids (as well as many other species, belonging to different families) which have been described in recent years. New Guinea was of interest to ichthyologists as long ago as the beginning of the last century when Weber (1910) described the first New Guinea freshwater atherinid, Atherinichthys nouhuysi, subsequently placed into the genus Craterocephalus. The second species, C. randi, was discovered by Nichols and Raven in 1934. Later exploration yielded C. lacustis (Trewavas, 1940), C. kailolae (Ivantsoff, Crowley & Allen, 1987), C. pimatuae, (Crowley, Ivantsoff & Allen, 1991) and C. fistularis (Crowley, Ivantsoff & Allen, 1995). It did not come as a surprise, therefore, that exploration of fresh water habitats in southwestern Pacific further yielded C. laisapi (Larson, Ivantsoff & Crowley, 2005) from East Timor and an entirely new freshwater atherinid, Bleheratherina pierucciae (Aarn & Ivantsoff, 2009) from freshwaters of New Caledonia, which was placed into a subfamily of its own. From this study it is obvious that Sashatherina is a close relative of Craterocephalus, nonetheless its morphology suggests placement into a genus of its own.

Atherinids are known from fossils as early as the beginning of the Eocene (Svichenskaya 1952) and evolution and speciation of the family Atherinidae appears to have occurred prior to the split up of Gondwana with this family and its closest relatives, the Melanotaeniidae, Pseudomugilidae and Telmatherinidae all beginning their existence at the head of the Australian Plate and ultimately constrained by the Pacific Plate as the former advanced towards the latter. It is less likely that the radiation of these families has taken place elsewhere since freshwater atherinoids do not occur in the Pacific (other than one species in New Caledonia) or the Indian Ocean. And it is most likely, from some genetic evidence (Crowley 1990) that the freshwater populations of atherinids (Craterocephalus) have split off from the marine/estuarine species (belonging to the C. honoriae group, Crowley & Ivantsoff 1988) during Eocene/Oligocene. Crowley's (1990) proposal that the speciation and radiation of the eyresii group is much older is of significance in the case of the new species herein described, since its affinities with these species are greater than with those of the stercusmuscarum group which have probably speciated later, possibly as late as Miocene/Pliocene.

MATERIALS AND METHODS

14 specimens were collected from West Papua, from Lake Lakamora in the vicinity of Kaimana (3[degrees]41'S 134[degrees]17'E) on 12 June 1995 and 18 July 1995. Specimens were measured from the tip of the snout to the vertical through the hypural joint and their standard lengths (SL) were recorded to the nearest 0.1mm. Measurements were made with electronic callipers with data entered into an Excel file which converted data into proportions of standard length (SL), head length and eye diameter. Counts were made using techniques recommended by Hubbs & Lagler (1958). Table I includes all data obtained by measuring and counting. Standard deviation has been automatically calculated using Microsoft Excel.

[FIGURE 1 OMITTED]
Table I: Morphometric (in mm) and meristic attributes of all type
specimens of Sashatherina giganteus are recorded in columns 1-13.
Pec. L. length of pectoral fin; H max, greatest body depth; Width
max, greatest width taken across head; H min, least body depth;
Pec-anus, distance from dorsal insertion of the pectoral fin to anal
opening; Sn, snout; OD1, origin of first dorsal fin; OD2, origin of
second dorsal fin; OV, origin of ventral fin; TV, tips of ventral
fins; OA, origin of anal fin; TA, origin of last ray of anal fin;
Caud. Ped., caudal peduncle; Prem. Proc., dorsal process of
premaxilla; Midlat sc., scale count along midlateral line; Trans, rows,
number of scale rows along side of body; Pred. sc, predorsal
scales; Interdor. sc., interdorsal scales; D1 Fin, number of
spines in the first dorsal fin; D2 Fin, number of branched rays
in second dorsal fin; Pect.
Fin, pectoral fin rays; Sn -OV, snout to origin of ventral fin;
Gill rak, number of gill rakers in first lower gill arch including
one in the angle of the arch; Anus pos., position of anal opening
in relation to tips of ventral fin, negative number means in
front of. OD1 to TV, position of first dorsal fin in relation
to vertical through tips of ventral fin., OD1 to T. Pec,
position of first dorsal fin in relation to vertical through
tips of pectoral fin; OV to T. Pec, position of tips of ventrals
to vertical through tip of pectoral fin, negative sign indicates
in front of. Vert. Count*, vertebral counts do not necessarily
correspond to the fish recorded in the column.
Specimens in order from left: 1, MZB 19253, holotype, 158 mm
SL; 2, AMS I-45366-001, 153 mm SL; 3, AMS I-45366-001, 118 mm
SL; 4, AMS I-45366-001, 122 mm SL; 5, WAM P.33324-001 138 mm
SL; 6, WAM P.33324-001 126 mm SL; 7, AMS I-45366-, 78 mm SL;
8, AMS I-45366-002. 72 mm SL; 9, WAM P.33325-001, 82.9 mm SL;
10, MZB 19254, 97 mm SL; 11, WAM P.33325-001, 79 mm SL; 12,
WAM P.33326-001, 68.9 mm SL; 13, AMS I-45366-003, 85 mm SL.

               MZB       AMS          AMS          AMS
              19253  I-45366-001  I-45366-001  I-45366-001

                1         2            3            4

IN SL           158          153          118          122

Head             60           57           42         42.9

Pec. L.          23           21           20         19.8

H max.           38           35           23         26.8

Width Max.       27           25           18         18.6

H. Min.          13           12          8.8           10

Pec-anus         52           49           39           45

Sn-OD1           91           90           66         69.1

Sn-OD2          120          118           89         93.3

Sn-OV            76           75           56         60.8

Sn-TV            94           91           72           74

Sn-OA           116          114           87         92.2

Sn-TA           127          125           96          105

IN HEAD

Eye             8.8          9.3          8.4         8.09

Interorbital     17           17           12         11.3

Postorbital      26           27           19         18.6

IN EYE

Snout            23           20           15         16.3

Premaxilla       23           23           16         17.4

Prem. proc.      15           17           11         10.7

MERISTICS

Midlat. sc.      60           63           52           58

Trans. rows      14           16           15           17

Pred. sc.        32           30           31           36

Interdor.        11           11           11           11
sc.

Vert. Count *    38           35           34           35

D1 Fin            8            6            6            7

D2 Fin            8            7            7            7

Anal fin          9            9            8            8

Pect. fin        16           16           14           16

Gill rak.        18           18           18           19

Anus pos.         7            9            4            5

OD1 to TV        -3           -2           -5           -3

OD1 to            5            4            4            3

T.Pec.

OV to T.Pec.     -2           -5           -3           -1

                  WAM          WAM        AMS        AMS
              P.33324-001  P.33324-001  I-45366  I-45366-002.

                   5            6          7           8

IN SL                 138          126       78            72

Head                   49           47       25            23

Pec. L.                22           19       13            12

H max.                 30           27       16            16

Width Max.             22           22       11            10

H. Min.                11           10      6.2           6.6

Pec-anus               45           43       27            24

Sn-OD1                 77           75       41            37

Sn-OD2                103          100       57            53

Sn-OV                  70           65       35            33

Sn-TV                  84           81       45            44

Sn-OA                 104           95       56            51

Sn-TA                 113          107       64            57

IN HEAD

Eye                   9.1          8.6      5.4           5.4

Interorbital           12           11      6.6             6

Postorbital            23           20       11           9.3

IN EYE

Snout                  18           19      8.4           6.5

Premaxilla             20           20      8.2           7.5

Prem. proc.            13          7.3      6.1           5.9

MERISTICS

Midlat. sc.            52           55       57            55

Trans. rows            14           15       13            16

Pred. sc.              32           31       30            30

Interdor.              13           12       11            11
sc.

Vert. Count *          35           36       35            34

D1 Fin                  6            7        7             7

D2 Fin                  7            7        7             7

Anal fin                9            9        8             8

Pect. fin              16           17       15            14

Gill rak.              21           19       18            18

Anus pos.               4            6        5             4

OD1 to TV              -3           -3       -2            -5

OD1 to                5.5            5        5             4

T.Pec.

OV to T.Pec.           -1           -2       -3            -2

                  WAM       MZB       WAM          WAM
              P.33325-001  19254  P.33325-001  P.33326-001

                   9         10         11           12

IN SL                82.9     97           79         68.9

Head                   29     34           27         22.2

Pec. L.              12.3     15           12         10.9

H max.                 17     21           15         13.8

Width Max.           11.9     15           11           10

H. Min.              6.62    7.8          6.3         5.88

Pec-anus             27.3     36           23         23.1

Sn-OD1               46.1     54           42           36

Sn-OD2               62.2     74           58         51.8

Sn-OV                41.2     48           38         31.9

Sn-TV                49.5     60           48         40.4

Sn-OA                58.5     70           56         48.6

Sn-TA                64.4     78           63         55.9

IN HEAD

Eye                  5.96    7.6          6.1         5.53

Interorbital         7.36    9.6          6.7         5.96

Postorbital          13.3     15           12         8.86

IN EYE

Snout                10.1     11          8.9         7.55

Premaxilla           10.7     14          9.5         8.03

Prem. proc.          7.63     12          7.2         6.63

MERISTICS

Midlat. sc.            54     58           59           55

Trans. rows            14     16           15           13

Pred. sc.              29     30           30           30

Interdor.              11     11           13           13
sc.

Vert. Count *          34

D1 Fin                  6      7            6            6

D2 Fin                  8      8            7            7

Anal fin                9      8            9            8

Pect. fin              14     14           17           14

Gill rak.              18     20           18           18

Anus pos.               4      3            4            4

OD1 to TV            -5.2     -6           -7           -5

OD1 to                4.5      5          4.5          5.5

T.Pec.

OV to T.Pec.         -1.2     -2           -2         -1.8

                  AMS
              I-45366-003

                  13

IN SL                  85  MEAN   MIN   MAX    SD

Head                   28  2.88  2.66  3.15  0.16

Pec. L.                13  6.44  5.79   7.4  0.41

H max.                 16  4.76  4.13  5.33  0.34

Width Max.             11  6.69  5.85  7.84  0.57

H. Min.               6.6  12.4  10.9  13.3  0.58

Pec-anus               29  2.98  2.69  3.35  0.16

Sn-OD1                 48  1.81  1.69  1.96  0.08

Sn-OD2                 65  1.33  1.27  1.37  0.03

Sn-OV                  39  2.08  1.95   2.2  0.08

Sn-TV                  49  1.66  1.56  1.75  0.05

Sn-OA                  61  1.38  1.32  1.42  0.04

Sn-TA                  68  1.23  1.16  1.29  0.03

IN HEAD

Eye                   6.2  5.03  4.01  6.78  0.76

Interorbital          7.2   3.8  3.37  4.14  0.23

Postorbital            12  2.29   2.1   2.5  0.11

IN EYE

Snout                 9.3  0.59  0.38  0.83  0.12

Premaxilla             10  0.54  0.37  0.72  0.11

Prem. proc.           8.2  0.79  0.56  1.18  0.15

MERISTICS

Midlat. sc.            58  56.6    52    63  3.05

Trans. rows            14  14.8    13    17  1.19

Pred. sc.              34  31.2    29    36  1.87

Interdor.              13  11.7    11    13  0.91
sc.

Vert. Count *              35.3    34    38  1.15

D1 Fin                  6  6.54     6     8  0.63

D2 Fin                  7  7.23     7     8  0.42

Anal fin                8  8.46     8     9   0.5

Pect. fin              14  15.2    14    17  1.17

Gill rak.              19  18.6    18    21  0.92

Anus pos.               6     5     3     9  1.57

OD1 to TV              -2  -3.9    -7    -2  1.56

OD1 to                  5  4.41   1.8   5.5  1.02

T.Pec.

OV to T.Pec.           -2  -2.1    -5    -1  1.01


One specimen was cleared and stained with Alizarin Red S according to the procedure published by Taylor (1967). This specimen was compared with previously prepared alizarin specimens in the senior author's private collection of Craterocephalus honoriae (WI Ia102, Smiths Lake, N.S.W., Australia), C. marjoriae (WI Ia171, Clarence River, Tabulam, NSW Australia) and C. lacustris (WI70-40c Lake Kutubu, New Guinea). No other comparisons were deemed to be necessary as the new species is without question related closely to the genus Craterocephalus McCulloch but is distinct from it by a number of features. Relevant photographs of alizarin specimens were made at the time of this study. Vertebral counts were made from eight photographic X-ray plates and one alizarin preparation. Disarticulated bones of S. giganteus were photographed through a Leica stereomicroscope equipped with an inbuilt camera. All of the collected specimens were designated as types with the holotype and a paratype deposited in Museum Zoologicum Bogoriense, Cibinong, Java, Indonesia (MZB). The remaining specimens were deposited in the Western Australian Museum, Perth (WAM) and the Australian Museum, Sydney (AMS).

SYSTEMATIC ACCOUNT

Sashatherina n. gen.

Type species: Sashatherina giganteus Ivantsoff and Allen. Sashatherina is monotypic.

Diagnosis: An unusually large freshwater atherinid presently recorded at a maximum length of 180 mm TL (total length) and anecdotally reported to reach lengths of 350 mm total length. Defined by the combination of the following. Dentary protruding before premaxilla. Small lateral process of premaxilla present. Mouthparts very sturdy, ramus of premaxilla not reaching vertical through anterior margin of orbit. Dorsal process of premaxilla reaching to vertical through anterior margin of orbit. Small, pungent villiform teeth in several rows both on dentary and premaxilla. Row of very small teeth on vomer; palatine and ectopterygoid edentulous. Distal end of dentary highly elevated. Lacrimal bone strongly sculptured. Second infraorbital oblong and largest in infraorbital series. Eye quite small compared with other atherinid species. Mesethmoid small distinct bone; nasal quite narrow. Four branchiostegals. Fifth ceratohyals fused. Pectoral girdle unique with long coracoid foramen. Midlateral scales small and crenulated posteriorly, the last, a unique feature for Old World Atherinidae. Up to 63 scales from dorsal origin of pectoral to hypural joint and up to 17 scale rows along side of body.

[FIGURE 1 OMITTED]

Sashatherina giganteus n. sp.

(Figs 2-5 and cover)

[FIGURE 2 OMITTED]

[FIGURE 3 OMITTED]

[FIGURE 4 OMITTED]

[FIGURE 5 OMITTED]

Holotype: MZB 19253, 158 mm SL, Lake Lakamora (or Laamora), east of Kaimana, 3[degrees]41'S 134[degrees]17'E. Creek-like extension of shoreline; water slightly turbid; patchy aquatic vegetation. Collected by hook and line, seine and rotenone. Collectors G. R. Allen and S. Renyaan, 18 July 1995.

Paratypes: MZB 19254, 96.9 mm SL, locality as for holotype, collected by H. Bleher, 12 June 1995, seine. AMS I-45366-001, 3(118-153.5), locality and method of collection as for holotype. AMS I-45366-002, 2 (71.9-77.8), locality as for holotype, collected by H. Bleher, 10 June 1995, seine. AMS I-45366-003, 1 (85.4), locality as for holotype, collected by H. Bleher, seine. AMS I-45366-004, 1 (74.5), alizarin preparation, locality as for holotype. WAM P.33324-001, 2 (126.3-138), data as for holotype. WAM P.33325-001, 2 (78.8-82.9), locality as for holotype, collected by H. Bleher, 10 June 1995, seine. WAM P.33326-001, 1 (68.9), locality as for holotype, collected by H. Bleher, 11 June 1995, seine.

Diagnosis: See generic diagnosis. Sashatherina giganteus n. sp. is the only presently known species of the genus.

Description: Largest known Old World atherinid with recorded size of 235 mm TL (Fig. 4) and an unsubstantiated report of specimens reaching 350 mm TL. Species most closely related to various members of genus Craterocephalus but distinct from them as indicated by generic definition. Exceptionally sturdy fish with strong fleshy mouthparts and with dentary protruding forward beyond premaxilla. Premaxilla not reaching vertical through anterior border of eye. Fleshy lips occluding gape by one third when mouth closed (Figs 2-4).

Observed externally: dorsal process of premaxilla long, reaching vertical through anterior margin of orbit. Blunt, small lateral process of premaxilla present. Maxilla wide and sturdy. Teeth on proximal end of dentary similar to those on premaxilla. Distal end of dentary highly elevated (Fig. 6). Both jaws highly visible externally. Head almost conical in shape with greatest body depth at just past dorsal origin of pectoral fin. Beyond that point, body tapering gently towards hypural joint. Preopercle, opercle and whole body covered with small thin crenulated scales, up to 63 along midlateral band and up to 17 scale rows along side of body; crenulated scales (Fig. 7) a unique feature of Old World Atherinidae.

[FIGURE 6 OMITTED]

[FIGURE 7 OMITTED]

Position of anus variable, up to 9 scales behind tips of ventrals. Gill rakers on first lower gill arch small and stubby, smaller than half diameter of pupil, two specimens with same gill raker number but much more slender. Fin elements quite strong especially in larger specimens; spines of first dorsal about length of preorbital distance.

Spines and rays of second dorsal and anal about same length as spines of first dorsal, with rays slightly shorter than spines and tapering backward in size. Second dorsal and anal fins always with one spine, one unbranched ray and variable number of branched rays. Pectoral fin falcate, inserted high on body, its longest ray about same as those of second dorsal fin. Head 2.9 (2.7-3.2), greatest body depth 4.8 (4.1-5.3), least depth at caudal peduncle 12.4 (10.9-13.3) all in SL. Eye in head 5.0 (4.0-6.8). Snout 0.59 (0.38-0.83), premaxilla 0.54 (0.37-0.72), dorsal process of premaxilla 0.79 (0.56-1.18) last 3 measurements in eye. Midlateral scales 56.6 (52-63), transverse scale rows 14.8 (13-17), predorsal scales 31.2 (29-36) interdorsal scales 11.7 (11-13). Vertebral count 38 (alizarin specimen). Dorsal fin VI-VIII, Ii7-8, anal fin Ii8-9, pectoral fin Ii4-17. Gill rakers on first lower gill arch including one in angle 18.6(18-21). Origin of first dorsal fin from 2 to 7 scales in front of tips of ventrals; origin of ventral fins 1 to 5 scales in front of tips of pectorals. Anus 3-9 scales behind tips of ventrals. Table I includes all meristic and morphometric character of specimens examined.

Colour when live: This description is based on a specimen collected by Heiko Bleher and photographed in the field (Fig. 3). The overall impression is that the fish is predominantly dark yellow in colour but quite variable in tones in different parts of the body. All the fins (membranes and fin elements) are distinctly yellow-brown and in the photographed specimen are in clear contrast to the rest of the body. Above the midlateral band the body is brownish-grey and the scales are more or less outlined by black chromatophores. The midlateral band is silvery, irregular in width, appearing to be wider and more diffuse above the anal fin, ending relatively abruptly at the hypural joint. Its dorsal edge is sharp, clearly separating the dorsum of the fish. The abdomen is silvery and the abdominal cavity is visible, presumably due to the translucent abdominal wall. The opercle and the preopercle are bright and silvery with some peppering of chromatophores towards the edges. The iris is very silvery. The snout is more heavily peppered with chromatophores, forming a distinct black patch immediately behind the premaxilla.

Colour in alcohol: Large preserved specimens (Fig. 5) show more distinctive markings presumably present in larger fish (smaller fish did not show distinctive markings which may, however, be due to preservation). Whilst the colour in fins is indiscernible, the body above midlateral band is much darker brown with each scale clearly delineated with chromatophores. The midlateral band is dark brown with a very thin fine pencil line within. The upper part of the abdomen is lightly pigmented, the lower is uniformly yellow-brown. The opercle is heavily pigmented, the preopercle almost clear other than the presence of chromatophores around the lower part of the orbit. The preorbital region is irregularly pigmented with patches of chromatophores. The mouthparts appear to be devoid of pigmentation.

Osteological description. Small bony mesethmoid present. Nasal narrow and long. Lacrimal highly sculptured and wide, second infraorbital large, third small, oval shaped, fitting closely onto second (Fig. 8). Premaxilla highly protrusible. Both jaws with small, fine villiform teeth in more than one row. Vomer with teeth, palatine and ectopterygoid edentulous. Intercalar small (reduced) and barrel-shaped.

[FIGURE 8 OMITTED]

Hyoid and gill arches not distinct from other Atherinidae; fifth ceratobranchials fused, characteristic of new genus in combination with other attributes (Fig. 9) (C. munroi of the eyresii group as well as some members of the stercusmuscarum group have their fifth ceratobranchials fused or partially fused). Four branchiostegal rays. Gill raker number in first lower gill arch high, up to 21 in some specimens.

[FIGURE 9 OMITTED]

Urohyal (Fig. 10) typical of Atherinidae.

[FIGURE 10 OMITTED]

Vertebral count (34-38) not correlating with number of midlateral scales; more typical of all other Old World atherinids.

Pectoral girdle and postcleithra (Fig. 11) distinct from all Craterocephalus species. Coracoid foramen oblong and large, eroding most of anterior part of coracoid bone. Cleithrum long, forming trough along anterior edge of girdle. Cleithrum dorsal process distinct and finger-like. Scapula small with small scapular foramen. Four proximal radials anterior to short single spine and up to 17 branched rays. Dorsal and ventral post-cleithra attached to one another with ventral postcleithrum overlying first and second pelural ribs with dorsal postcleithrum overlying fifth vertebra and extending dorsally through epipleural ribs.

[FIGURE 11 OMITTED]

Pelvic girdle (Fig. 12) unremarkable but with very small lateral process, possibly distinctive for this species.

[FIGURE 12 OMITTED]

First eight vertebrae with thin and wide neural spines (Fig. 13), anteroposteriorly progressively decreasing in width, becoming thin and pungent; condition typical for all Atherinidae as is remainder of vertebral column.

[FIGURE 13 OMITTED]

Caudal fin unremarkable (Fig. 14) and typical of the Atherinidae. The caudal fin is made up of 17 principal rays of which all but two are branched. There are nine rays in the upper half of the fin and eight in the lower, an invariable feature for all Atherinidae. It is most likely (Patten 1978) that the lower hypural is represented by fusion of two elements with the fin composed of five of these elements, the uppermost being the smallest. Dorsally and ventrally the caudal fin possesses procurrent rays and the hypurals are supported by the terminal half centrum.

[FIGURE 14 OMITTED]

Etymology: The name Sashatherina refers to the first author's son, Sasha, who has assisted his father frequently on collecting trips without any official acknowledgement so far of his being so helpful. The specific epithet giganteus refers to the unusual size of this species, as most Old World Atherinidae rarely exceed 100 mm SL.

DISCUSSION

Until new studies come to hand the latest definition of the Atherinidae by Dyer and Chernoff (1996) is universally accepted with 12 genera grouped into three subfamilies, Atherinomorinae, Craterocephalinae and Atherininiae, the last being the most variable and including the genera Atherina, Atherinason, Atherinosoma, Kestratherina and Leptatherina (Aarn and Ivantsoff 2009). Although Dyer & Chernoff's definition of the Craterocephalinae was not tested (by examining the nasal ventromedial ligament to the palatine with the anterior palatine process directed dorsally and supported by the presence of a large submaxillary meniscus), due to other features there is no doubt that S. giganteus is a member of this subfamily. This new species is found in an area where other freshwater species of this subfamily also occur, such as Craterocephalus fistularis and C. nouhuysi and further to the east C. lacustris, C. pimatuae and C. randi and most easterly in New Guinea, C. kailolae. To the west is found the recently described C. laisapi from East Timor (Larson et al. 2005). Southward, just across the Arafura Sea, other members of this subfamily (and exclusively Craterocephalus spp.) are C. lentiginosus, C. helenae, C. marianae and C. stercusmuscarum. Marine members of this genus, C. mugiloides and C. munroi, also occur off the northern coast of Australia.

The time at which the Craterocephalinae arose is yet to be determined. Members of the Atherininae are known from as early as Eocene and later in Pliocene from what is now the coastline of the north-eastern Mediterranean, all have been attributed to the genus Atherina (Svichenskaya 1973; Gaudant 1978). Ancestral atherinids must have moved together with the Australian continent, an interpretation which is consistent with Talent's opinion (1984) who stated that species must have arisen in Gondwana prior to its fragmentation and as the Gondwanian continents separated, further speciation of the Craterocephalinae must have taken place between the emergent southern part of the island of New Guinea and northern Australia. The collision of the Australian Plate and the Asian Plates is estimated to have taken place in Early Oligocene (about 30 million years ago). This collision resulted in the uplift of the New Guinean highlands by the late Miocene i.e. about 10 million years ago according to a biogeographer Isabel Sanmartin (pers.com.). No freshwater atherinids occur on the northern part of the island confirming that atherinids entered New Guinea only from the south.

Crowley (1990), basing her conclusions on research for her Ph.D. thesis and some subsequent unpublished studies, believed that through constant geomorphological volatility in the northern part of the Australian Plate in post Eocene times, there have been multiple independent incursions both into the southern New Guinea and northern Australia, leading to separate speciation events.

As well, on the basis of genetic evidence, Crowley (1990) suggested that the C. eyresii group migrated into the Australian continent early, probably during the Eocene/Oligocene and then dispersed throughout the continent. Later invasions during Plio/Pleistocene times took place during marine transgressions at many points between Australia and new Guinea. Regression in later time, in Pleistocene, must have resulted in new species of the stercusmuscarum group giving rise to freshwater C. randi and C. nouhuysi in southern Papua New Guinea. Another New Guinea species, C. pimatuae, on the other hand, may have separated earlier after the Miocene uplifting of the central Cordillera on that island. Crowley (1990) further speculated that atherinids must have been euryhaline in earlier times, as many of them are today. Some remained marine and estuarine, ultimately differentiating into the C. honoriae group. Present distribution of Australian continental atherinids is a result of dispersal subsequent to inland incursions of the marine and estuarine species as stated already.

The separation of Sashatherina and members of the genus Craterocephalus must have taken place quite early since S. giganteus shares some of its characters with species which are not geographically contiguous with it, probably separating from Craterocephalus during the late Eocene or early Oligocene. An example is Craterocephalus amniculus (Fig. 15), known only from the environs of Tamworth, NSW (approximate location in north-west NSW, (31[degrees]04'S 150[degrees]53'E), which has up to 48 midlateral scales and up to 18 transverse rows of small scales along side of the body, by far the largest number of all the Craterocephalus species.

[FIGURE 15 OMITTED]

The variability in the shape of the premaxillae in Craterocephalus species is quite subtle which would require a specialist to distinguish. The shape of the dorsal process of the premaxilla in S. giganteus, on the other hand, does not have a slight indentation halfway along the process as the three species figured here have. There is little doubt that the new species is a close relative to Craterocephalus but is distinguished from it by the characters indicated.

The mouth parts of Sashatherina (Fig. 16), specifically the premaxilla, are most similar to members of different species groups of Craterocephalus:

[FIGURE 16 OMITTED]

1. The honoriae species group: C. honoriae is an estuarine species with present distribution on the eastern coast of Australia from approximately southern Tewantin, Queensland (26[degrees]24'S 153[degrees]02'E, some 120 km north of Brisbane and to the south, at Currarong (35[degrees]01'S 150[degrees]49'E) NSW. Other members of the honoriae species group are: C. mugiloides, C. capreoli, C. pauciradiatus (Crowley & Ivantsoff 1988).

2. The eyresii group: C. marjoriae, which occurs in Deep Creek (tributary of Clarence River 28[degrees]53'S 152[degrees]37'E) in northern NSW as well as the Mary River (26[degrees]23'S 152[degrees]45'E, further north in Queensland. Other members of this group are C. laisapi, C. amniculus (see Fig. 15), C. centralis, C. eyresii, C. munroi, C. fluviatilis, C. cuneiceps, C. marianae, C. helenae and C. kailolae (Crowley 1990).

3. The stercumuscarum group: C. lacustris, the distribution of which is essentially restricted to Lake Kutubu in Papua New Guinea (6[degrees]20'S 143[degrees]18'E) (Fig. 17). Other species of this group are: C. dalhousiensis, C. gloveri, C. nouhuysi, C. pimatuae, C. s. fulvus, C.s. randi and C. stramineus (Crowley 1990).

[FIGURE 17 OMITTED]

ACKNOWLEDGEMENTS

We are indebted to Heiko Bleher for providing some of the specimens which he and his team collected in West Papua as well as the photographs of live specimens and the isolated lake Lakamora to which the species is endemic (Fig. 18 and back cover). The second author provided the rest of the specimens by collecting in the same area. The line drawings both of S. giganteus and C. amniculus were made by Ms Barbara Duckworth when the university was in a position to employ a commercial artist. Sasha Ivantsoff is specially mentioned because of the enthusiasm in his younger days by accompanying his father on field trips and helping him in every way. We are also indebted to Dr Lucy Crowley who despite her retirement, has left a legacy by way of information which is still of great value today.

Received: 09 August 2010 - Accepted: 01 November 2010

[FIGURE 18 OMITTED]

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Walter Ivantsoff * (1) and Gerald R. Allen(2)

(1.) Department of Biological Sciences, Macquarie University, North Ryde NSW, 2109 Australia. Postal address: P.O. Box 3753 Marsfield NSW, 2122 Australia. * E-mail walter.ivantsoff@mq.edu.au.

(2.) Western Australian Museum, Locked Bag 49, Welshpool DC, Perth, WA, 6986 Australia.
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