INTERRELATIONSHIPS OF THE ALEPISAUROIDEA 333 



space. 'The adaptive characters involved may be quite broad and varied, as in carnivores and ungu- 

 lates, or may be quite specific, virtually "single characters" in a taxonomic sense, as in rodents and 

 bats.' As already stated, the alepisauroids are bathypelagic fishes and consideration of the group in- 

 volves features such as the dentition, type of gill-raker, loss of scales, acquisition of distensible tissues 

 etc., all of which would seem to be correlated with a predacious, large-prey-seizing habit. Such 

 characters remind one more of the broad and varied features of the mammalian carnivores than of those 

 of the bats. (Perhaps in the type of character-complex, the ceratioid angler fishes are the nearest 

 oceanic equivalents to the bats.) 



Bearing these theorizings in mind, these studies have done little to dispose of the (partly intuitive) 

 idea that the Iniomi may be no more than an assemblage of lineages, each having attained certain 

 morphological features. When the great differences between, say, a myctophid and Anotopterus are 

 considered, the value of keeping the order Iniomi seems questionable. Yet if this is not a compact 

 ' monophyletic ' order, it is at the very least a convenient gathering of those ' isospondyloid ' fishes with 

 more specialized jaws. Furthermore, there is little reason for discarding the two suborders. 



A consideration of the position of the Notosudidae (Notosudis Waite, 1916, and Luciosudis Fraser- 

 Brunner, 193 1), provides something of a test of the usefulness of the classification used in this report 

 (p. 306). The dentition of both genera is somewhat similar to that described for the alepisauroids 

 (p. 305), while the general body-form is reminiscent of certain paralepidids. (Fraser-Brunner, 193 1, 

 regarded Luciosudis as a paralepidid, while Mead and Taylor, 1953, have listed their new species 

 Luciosudis harryi under the Paralepididae.) But the combination of certain features (lath-shaped gill- 

 rakers, anal fins with relatively few rays, lateral pectoral fins with 'axial angles' of more than 45 , 

 pelvic fins set well forward of the mid-standard length and a well-developed scaling) indicates clearly 

 that the Notosudidae have closer affinities with the Myctophoidea. 



Similarly there are certain iniomous fishes (not yet described) in the Discovery Collections with no 

 scales and a single row of teeth on the premaxillae, dentaries and palatines — all alepisauroid features — 

 but with an underlying myctophoid character-complex quite like that described for the Notosudidae. 

 But unlike the Notosudidae, one of these new species appears to have a peculiar system of light organs 

 over the flanks. These new fishes must undoubtedly be placed in a new family and if closer examina- 

 tion confirms the presence of light-organs, then the contrast between the Myctophoidea, having three 

 families in which photophores of peculiar structure have arisen, and the Alepisauroidea, in which 

 photophores have not been evolved, will be further emphasized. 1 



But it is also of interest that in number and arrangement of branchiostegal rays (3-4 + 4-5) the 

 alepisauroids are a more homogeneous suborder than the myctophoids, in which there are three main 

 groups: (1) The Chlorophthalmidae, Ipnopidae, Bathypteroidae, Neoscopelidae and Luciosudis most 

 nearly resemble the alepisauroids in having 3-5+4-8 branchiostegal rays. (2) The Myctophidae have 

 2 + 5-6 + 0-2 rays (numbers on the epihyal, ceratohyal and hypohyal). (3) The third group, which 

 consists of the Aulopidae, Synodontidae and Harpadontidae, has more numerous branchiostegal rays. 

 (Aulopus filamentosus 8 + 7, Hime japonica 7 + 7, Synodontidae 12-16; Synodus lucioceps 8+10, 

 Saurida undosquamis 6+10; Harpadontidae 17-25 : Harpadon nehereus 9+14. One specimen of each 

 species examined.) Furthermore, the orbitosphenoid bone seems to be consistently absent in the 

 alepisauroids, but may be present or absent in the myctophoids (Regan, 191 1 ; Parr, 1929). However, 

 these aspects of the character-complex of the Myctophoidea will be considered in a later paper. 



It is reasonable to conclude that the Myctophoidea and the Alepisauroidea are, at least, useful 

 taxonomic groupings. Each can be adequately defined by a rather loose assemblage of characters and 

 by certain morphological trends. But further discussion of the classification in terms of evolution had 

 1 Apart from the deep-sea Isospondyli, no predacious, bathypelagic fish has an elaborate system of light-organs. 



