RELATIONSHIPS OF SUNDASALANX 



17 



recessus lateralis. A large fenestra to the rear of the recessus 

 lateralis communicates with the perilymphatic system. 



Laterosensory canals 



No laterosensory canals were observed other than the infraorbital, 

 supraorbital, and temporal canals which converge on the recessus 

 lateralis (Fig. 6). All are short The supraorbital canal does not 

 extend to even over the eye. The temporal canal does not reach the 

 shoulder girdle or form a supratemporal commisure with its counter- 

 part from the opposite side. The infraorbital canal does not extend to 

 beneath the eye. 



Osteology 



No part of the skeleton of Sundasalanx \s heavily ossified. Ossifica- 

 tion of dermal elements appears to be exceptionally slight and many, 

 usually present in other teleosts, may be absent. For example, no 

 parietals or dermal ethmoid element were detected. 



Caudal skeleton 



The caudal skeleton of Sundasalanx is highly consolidated, and 

 somewhat reduced (Fig. 7A). Preural centrum 1 and ural centra 1 

 and 2 are consolidated into a single compound element, to which 

 uroneural 1 is apparently fused. Uroneural 2 is free, and in Barito 

 River Sundasalanx greatly expanded. Only a single epural is present. 

 The parhypural and hypural 1 are fused (observed in an ontogenetic 

 series of cleared and stained materials); the compound parhypural- 

 hypural is autogenous; hypural 2 is fused to the compound centrum; 

 hypural 3 is autogenous; hypural 4 is expanded to about the size of 



hypural 1 ; hypural 5 is present. A hypural 6 was not observed. Bases 

 of caudal-fin rays appear unmodified. 



Pelvic girdle 



The two vertically oriented bones in the pelvic girdle of Sundasalanx 

 Roberts (1981) termed parapel vie cartilages are unknown elsewhere 

 among fishes. The anterior bone is stouter, more vertically oriented, 

 with its ventral end closely associated with the basipterygium and 

 first pelvic ray (Fig. 1 ). The posterior bone is more slender, usually 

 longer than the anterior bone, and is usually inclined forward, often 

 as much as 30° from vertical. It is not as closely associated with the 

 basipterygium as the anterior bone; there is often a considerable gap 

 between the ventral end of the posterior bone and the basipterygium. 

 The greater length and position of the posterior bone relative to the 

 basipterygium results in it extending above the dorsal end of the 

 anterior bone by as much as half its length. The length of the 

 posterior parapelvic bone appears to vary among species. In some 

 specimens of S. praecox the posterior bone is nearly twice the length 

 of the anterior bone whereas in specimen of S. megalops examined 

 the bones are subequal. 



The origin of parapelvic bones is unknown. In some fishes pleural 

 ribs are connected to the pelvic girdle via ligaments and it would not 

 be unreasonable to suggest parapelvic bones might be modified ribs, 

 or ossifications of ligaments associated with the pelvic girdle. 

 Parapelvic bones are similar to pleural ribs in two respects. They are 

 preformed in cartilage (preformation of ribs in cartilage is wide- 

 spread among clupeoids; Patterson & Johnson, 1995), and they lie 

 internal to body musculature, not in myosepta. However, peculiar 



B 



F+G 



Fig. 7 A) Caudal skeleton of Sundasalanx malleti (BMNH 1996.7.18.15), scale = .3 mm; B) Caudal skeleton of Jenkinsia (BMNH 1962.7.21.48-50). 

 scale = .45 mm; A = compound centrum (PU1+U1+U2), B = epural, C = uroneural 2, D = hypural 5, E = hypural 4, F = hypural 1, G = parhypural 



