24 



D.J. SIEBERT 



Table 4 Summary table of diagnostic differences among described species of Sundasalanx. 





S. praecox 



S. microps 



S. platyrhynchus 



S. malleti 



5. me sops 



S. mega I ops 



Ipb 3 tooth plate 



large 



small; 1-2 teeth 



small; 2-3 teeth 



large; row of teeth 

 along post, edge 



medium; teeth 

 along post, edge 



small; 4—5 teeth 



Ipb 4 tooth plate 



large 



small 



large 



large 



large 



large 



Palatal and Bb 1 teeth 



present 



absent 



absent 



absent 



absent 



absent 



Gill rakers on 1st arch 



well devel.; 8+1; 

 along whole arch 



minute; 2-3+0 



minute: 2-3+0 



minute; 5+1 



minute; 3+0 



minute; 2+0 



Upper jaw teeth 



10-11 +30 



5-9+ 15-19 



5-7+ 15-19 



4-5+ 15-17 



3-5+ 16-18 



2-3+ 12-14 



Lower jaw teeth 



1 6; 2 rows 



15-16; 2 rows 



15-18; 2 row post. 



10-12 



12-13 



8-10; 2 rows post 



'Vertebrae 



37-JS 



41— #2 



41^/2-43 



40-^2-44 



40-41 



41 



'Branched dorsal rays 



9-10 



9-/0 



9-/0-12 



8-/0-11 



8-9-10 



10 



'Branched anal rays 



13-/4-15 



15-76-17 



14-/6-17 



13-/4-17 



13-/4-16 



14-15 



Eye size 



medium; 4-5% SL 



small; appox. 3% SL 



medium; 4—6% SL 



small; 3-4.5% SL 



medium; 4-6% SL 



large; approx. 6% SL 



Prepectoral spot 



absent 



present 



present 



present 



present 



present 



Cardiac chamber 



absent 



present 



present 



absent 



present 



present 



pigmentation 















Mid-ventral line 



absent 



present 



present 



present 



present 



present 



Basipterygium 



absent 



absent 



absent 



present 



absent 



absent 



pigment ring 















Median value italicised. 



about 7 km SW of Nanga Silat, approx. 0° 19'N 1 1 1° 45 'E, 29-1 V- 

 1990, M.Kottelate/a/. 



PARATYPES. CMK 6979 (12), collection data as for holotype. 

 CMK 7898 (3), c&s, data as for holotype. CMK 6892 (8), Indonesia, 

 Kalimantan Barat, Kapuas River basin, Kapuas R. mainstream at 

 Teluk Ujung Bayur, approx. 0° 50'N 112° 45'E., 27-IV-1990, 

 M.Kottelat et al. 



Diagnosis. A photograph of S. platyrhynchus is presented as Fig. 

 15; selected morphometries are summarised in Table 1 and vertebral 

 and fin-ray counts are summarised in Table 2 and Table 3. It is a 

 species of Sundasalanx with a large head (HL 19.6-23.3% SL, HW 

 10.2-12.0% SL), relatively large eye (4.2-5.7% SL, 21.7-25.9% 

 HL), and short snout (15.3-21.4% HL). Prepectoral mark present; 

 posterior wall of cardiac compartment marked with melanophores; 

 basipterygium without ring of melanophores. Vertebral number 41- 

 43 (median=43);dorsal-fin rays 9-12 (median=10); anal-fin rays 

 14-17 (median=16). Premaxilla with 5-7 teeth; maxilla with 15-19 

 teeth; dentary with 15-18 teeth, arranged in 2 rows in posterior part 

 of dental arcade; 3rd pharyngobranchial tooth plate small, with only 

 2 or 3 teeth; 4th pharyngobranchial tooth plate small, about 1/3 size 

 of pharyngobranchial 4, with principal row of larger teeth along 

 posterior edge. 



Sundasalanx platyrhynchus is easily distinguished from its Kapuas 

 River congener by size of eye and pharyngeal dentition. The eye of 

 S. microps is much smaller (Table 4) and pharyngeal dentition in S. 

 microps is much reduced. Sundasalanx platyrhynchus can be distin- 

 guished from its Barito River congeners by size of eye and vertebral, 

 dorsal- and anal-fin ray counts. S. malleti has a smaller eye; S. 

 megalops has a larger eye. 5. mesops has fewer vertebrae and dorsal- 

 and anal-fin rays. 



DISTRIBUTION. Sundasalanx platyrhynchus is known from the 

 Kapuas River basin, West Kalimantan, Indonesia. 



ETYMOLOGY. The name platyrhynchus is a combination of platys, 

 Greek for broad, and rhynchos, Greek for snout. 



DISCUSSION 



Sundasalanx is very small and much of its anatomy is suggestive of 

 the larvae of lower teleosts generally (as realised by Roberts, 1 984). 

 Evolution of a tiny adult size among clupeiforms is not unusual; it is 

 known both in engraulids (Cervigon, 1982; Nelson, 1986; Roberts. 

 1981; Whitehead et al., 1988) and other clupeids (Poll, 1948; 

 Roberts, 1972; Whitehead, 1988; Whitehead & Teugels, 1985). 

 Among these a good anatomical description is available only for 

 Sierrathrissa leonensis (Whitehead and Teugels, 1985). However 

 'youthful' an impression small size lends to Sierrathrissa leonensis, 

 it nevertheless is more or less a miniature adult. The degree of 

 ossification, development of the intestinal tract, development of the 

 air bladder, fin positions, etc. are all indicative of at least a juvenile 

 stage in the life cycle, if not of an adult. 



Sundasalanx on the other hand is both tiny and underdeveloped. 

 Its level of skeletal and somatic development (straight gut, small air 

 bladder, myotomes not extending ventrally to cover ventral portion 

 of body cavity, presence of ventral fin-fold, undifferentiated 

 cartilaginous plate supporting a rayless pectoral fin, etc.) is compa- 

 rable to that of other unmetamorphosed clupeid larvae. Migration of 

 the dorsal fin forward to a position characteristic of adults is 

 considered to mark the transition between larvae and adults in 

 clupeiforms. The positions of the dorsal fin, anus, and anal fin, in 

 absolute terms and relative to each other, of the largest Sundasalanx 

 specimens studied are similar to the positions reported for other 

 unmetamorphosed spratelloidins (Leis & Trnski, 1989) and there is 

 no difference in the positions of any of these structures between the 

 smallest and largest specimen for any species studied. Sundasalanx 

 appears to have attained the ability to reproduce at a stage of 

 development equivalent to larvae of other clupeids. If this assess- 

 ment of developmental stage of Sundasalanx is correct the size of 

 Sundasalanx may be unusual. Transition, or metamorphosis, in 

 other spratelloidins often begins at sizes of less than half that 

 attained by Sundasalanx. 



Small size, lack of somatic development beyond that of the 



