INTERRELATIONSHIPS OF THE ALEPISAUROIDEA 33> 



Considering all fishes known to swallow relatively large prey, the striking fact emerges that all are 

 scaleless or have a very reduced squamation. Omosudis, Alepisaurus and Evermannella are completely 

 naked, while Anotopterus has scale-like segments only along the lateral line. Other fishes with dis- 

 tensible stomachs and body-walls (the Melanostomiatidae, Idiacanthidae, Astronesthidae, Malacos- 

 teidae, Lyomeri, Giganturoidea, Chiasmodus niger and Melanocetus have no scales). The only known 

 scaled fishes which can engulf large prey are Stomias and Chauliodus. In Chauliodus — and probably in 

 Stomias — the scales, which are very thin and do not overlap, lie between the epidermis and the pig- 

 mented layer of the corium (Brauer, 1908). Moreover, the scales are not held in pockets, which sug- 

 gests that fishes cannot have both a normal overlapping scale system and a highly distensible body- 

 wall. Presumably the connective tissue pattern associated with an imbricating squamation sets a limit 

 to the degree of tissue distensibility. However this may be, there is no record of a fish with well- 

 developed, overlapping scales being able to cope with large prey. It is interesting that the scaleless 

 (or virtually scaleless) paralepidids, Lestidium, Macroparalepis and Sudis have relatively larger teeth 

 on the palatines and mandibles than the fully scaled Magnisudis, Paralepis and Notolepis. Is it pos- 

 sible that the larger toothed genera are able to capture (and retain) larger prey and that the loss of 

 scales is an adaptation towards distensibility of the stomach and body wall? On the other hand the 

 scopelarchids with a formidable dentition of stabbing, barbed teeth are completely scaled. A study 

 of the food of these fishes would be of particular interest. (In the stomach of Scopelarchus gnentheri 

 of standard length 65 mm. I found the remains of copepods and ostracods and a mass of nematocysts, 

 probably of Siphonophora.) 



The alepisauroids, which are all pelagic, may be compared and contrasted with the pelagic members 

 of the Myctophoidea, the Myctophidae, Luciosudis and Notosudis. These latter fishes are fully scaled, 

 the myctophids feeding particularly on copepods and smallish members of the zooplankton (Beebe 

 and Vander Pyl, 1944). There is no evidence that any myctophid fish is able to tackle large prey. 

 Harpadon, which of all myctophoid fishes has a dentition most like an alepisauroid, feeds on small 

 fishes and shrimps (Hora, 1934). 



To summarize : among the pelagic families of the Iniomi the predominant evolutionary trend in the 

 alepisauroids has been towards adaptations for dealing with nektonic prey, extraordinary elasticity 

 of the tissues of the stomach and body wall being associated with a loss or marked reduction in the 

 scaling. By contrast, the Myctophidae, which feed on planktonic animals, have a complete scaling. 



INTERRELATIONSHIPS OF THE ALEPISAUROIDEA 



Considerations of the interrelationships within the Alepisauroidea are inseparable from the question 

 whether the suborder represents a natural group, but before attempting to deal with this problem the 

 similarities and differences between the families must be elaborated. 



Parr (1929) considered that the Scopelarchidae and Evermannellidae were fairly closely related. 

 Moreover, the other four families, the Alepisauridae, Anotopteridae, Omosudidae and Paralepididae 

 have certain common features. 



The characters of these two groups can be listed as follows : 



Group 1 . Scopelarchidae and Evermannellidae 

 Intermuscular bones absent : parietals fused with the frontals ; anus near to origin of anal fin or mid- 

 way between pelvic and anal fins; 1 body short to moderately elongate; definite trend towards develop- 

 ment of tubular eyes. 



1 In larval or juvenile scopelarchids, the anus is closer to the pelvics than to the origin of the anal fin, e.g. in Neoscopel- 

 archoides linguidens (Mead and Bohlke, 1953) and in Benthalbella larvae. 



