42 ELOPIFORM FISHES 



The variations in the caudal skeleton of Anaethalion illustrated by Nybelin (1963, 

 1967b, 1971) and here (Text-fig. 18) do not, however, encompass the type shown by 

 Gaudant (1968 : fig. 5) for A. cirinensis, based on the holotype (Gaudant op. cit. 

 pi. 3, fig. 2). The figure given by Gaudant is unusual for two reasons ; a complete 

 neural arch and spine is shown on the first preural centrum and the third uroneural 

 is elongate and overlaps the second ural centrum. Both these conditions are not 

 met with in elopid (or late leptolepid) fishes, but are usually associated with 

 osteoglossomorph fishes (cf. Hiodon and Lycoptera as figured by Greenwood 1970b). 



From the plate given by Gaudant the apparent discrepancy between his 

 drawing and other species of Anaethalion may be reconciled. The neural structure 

 borne by the first preural centrum appears to represent a neural arch only, there 

 being no indication, even as an impression, of a distal prolongation. The uroneural 

 structure is correctly figured as may be seen by comparing the plate and drawing and 

 inasmuch as there are three visible uroneurals the labelling is accurate. However, 

 the third uroneural figured by Gaudant probably represents the second of other 

 Anaethalion species and elopoids. In length and proximal extension this uroneural 

 is exactly comparable with the second uroneural of elopoids and other species of 

 Anaethalion. Presumably the third uroneural is either missing from the specimen 

 or possibly represented by the splint-like structure shown below the distal extremity 

 of the ' third ' uroneural (Gaudant 1968 : pi. 3, fig. 2). The first two uroneurals 

 (U^ and U 2 of Gaudant 1968 : fig. 5) represent the unfused condition of the first 

 uroneural of elopoids which is known to be a compound element. Thus the first two 

 uroneurals of A. cirinensis resemble those of leptolepids. 



The scales of Anaethalion (unknown in A. vidali) are moderately large, circular 

 and marked by fine circuli which are absent from the central portion of the exposed 

 field. Bone cells are present. Such features are similar to those of Elops. How- 

 ever, the scales of Anaethalion do not show the well-marked anterior radii charac- 

 teristic of all elopiforms. 



In summary, the genus Anaethalion is an assemblage of primitive teleostean fishes 

 most favourably compared with the Elopidae. Anaethalion is more advanced than 

 known leptolepids in showing a reduction of the ethmoid ossification and lacking 

 a basipterygoid process. The suspensorium and dermal jaws are primitive as are 

 many features of the neurocranium and give no indication as to the relationships of 

 most species of Anaethalion. The caudal skeleton is seen to vary from species to 

 species (Nybelin 1971) and it may be of significance that some species show laminar 

 bone, a feature normally associated with euteleosteans. The structure of the caudal 

 skeleton suggests that A. (?) cf. subovatus and A. sp. are closely related; A. 

 knorri, A . angustus and A . angustissimus are probably interrelated species and may 

 be linked to A. sp. and A. (?) cf. subovatus by A. vidali. Anaethalion cirinensis 

 appears to be the most primitive species on the basis of caudal anatomy since it 

 shows three long uroneurals, the first two representing a ' pre-fusion ' state compared 

 with other species of Anaethalion. 



The elopid A. vidali resembles the Megalopidae in some respects. Thus the shape 

 of the body, the position of the pelvic fin and the elongate first anal pterygiophore 

 are similar to Tarpon. In the cranium the otic region of the cranial roof is convex, 



