FOSSIL AND RECENT 39 



and ethmoid commissure branches) lies within the lachrymal. In Elops the lachry- 

 mal is elbowed and contacts the supraorbital dorsally, the splint-like antorbital 

 lying along the anterior margin of the upright limb. The triradiate division of the 

 infraorbital sensory canal occurs in the skin anterior to the lachrymal. Junction 

 of the lachrymal and supraorbital bones, so excluding the antorbital from the orbital 

 margin, is rare in lower teleosts, although it has been figured for Leptolepis dubia 

 (Patterson 1967a : fig. 4) and is therefore of doubtful phyletic significance. The 

 bone-enclosed branches of the infraorbital sensory canal of Anaethalion are similar 

 to Davichthys but unlike Elops. 



The preoperculum of A. vidali and other species of Anaethalion consists essentially 

 of a vertical limb, the horizontal portion being short. Elops, Davichthys dubius 

 and D. lacostei show a more pronounced horizontal limb and the preoperculum is 

 slightly expanded postero-ventrally. The preopercular sensory canal of all species 

 of Anaethalion opens to the surface within the lower portion of the bone. In A. 

 vidali, as in other elopids, the main canal opens directly to the surface via a series of 

 pores but in other species of Anaethalion there are a few well-developed secondary 

 branches enclosed within the bone. The latter condition is considered the more 

 primitive. 



The postcranial skeleton of A . vidali is similar to that of Elops, with no significant 

 differences in the vertebral column or the paired fins and girdles. The vertebral 

 count of A. vidali (66) is substantially higher than that of most species of Anaethalion 

 (range 42-57). 



In most species of Anaethalion the dorsal fin, although of the same shape and size 

 as the dorsal of Elops, is situated slightly nearer to the caudal peduncle than the 

 occiput. In Elops the dorsal is situated in the centre of the back. Among the 

 species of Anaethalion, A. (?) cf. subovatus and A. vidali show an Elops-like dis- 

 position of the dorsal fin. A. vidali exhibits three features of the fins normally 

 associated with megalopids among Elopiformes : the origin of the pelvic is in advance 

 of that of the dorsal, the anal fin is slightly elongated and the first anal pterygiophore 

 is stout and long, nearly touching the vertebrae above. 



The caudal skeleton of A . vidali (Text-fig. 17) is very similar to that of Elops (or, 

 for that matter, later leptolepids) the main difference being the development of a 

 complete neural spine associated with the second preural centrum. However, a 

 complete neural spine upon the second preural centrum is also seen in Davichthys 

 gardneri among elopids. Unlike Elops, A . vidali shows a single fringing fulcrum, a 

 structure which is also seen in Davichthys dubius. Anaethalion vidali differs from 

 other elopids but resembles some other species of Anaethalion in the development of 

 laminar bone on the anterior margins of the third and fourth preural neural spines. 



The caudal skeleton of the German species of Anaethalion shows several variations 

 from that of A . vidali. Sketches of some of these species are given in Text-fig. 18 

 (see also Nybelin 1971). The development of laminar bone varies ; it is well 

 developed in A . knorri, A . angustus and also in the Spanish A . gigas ; A . angustissimus 

 shows weakly developed laminar bone on the second preural neural spine and as in 

 A. knorri and A. angustus there are well developed projections at the bases of the 

 first few preural neural and haemal spines. 



