36 ELOPIFORM FISHES 



37048 ; A.gigas, B.M.N.H. P.10927, P.10377, P. 10380 ; A. vidali, B.M.N.H. P.10375 

 and P.10376. 



Anaethalion has been referred to the Leptolepididae by Woodward (1895), Berg 

 (1940), Bertin & Arambourg (1958), Danil'chenko (1964) and Romer (1966). 

 Nybelin (1967b) did not firmly suggest a familial position although he hinted strongly 

 at a relationship with Elops. Similarly Gaudant (1968) could not reconcile Anaetha- 

 lion with the Leptolepididae and erected a new family, the Anaethalionidae. 



I would agree with both Nybelin and Gaudant that Anaethalion should be 

 excluded from the leptolepids. There are several features of dissimilarity from 

 leptolepids which, at the same time, are points of similarity with Elops. The neuro- 

 cranium is shallow ; there is a connection between the supraorbital and infraorbital 

 sensory canals ; the supratemporal bone is large (unlike Upper Jurassic leptolepids) ; 

 the infraorbital and preopercular sensory canals show few branches ; there is no 

 basipterygoid process ; both the maxilla and dentary are shallow, the latter bearing 

 only a weakly defined coronoid process posteriorly ; and the dentition upon the 

 dermal jaws consists of broad bands of villiform teeth. 



Although Anaethalion is unlike leptolepids, it must also be said that definite 

 evidence of elopid affinity is lacking for most species of Anaethalion. It is true 

 that Anaethalion is most favourably compared with Elops and Davichthys, but a 

 positive association with elopids could only be made on finding rostral ossicles, an 

 associated leptocephalus larva or a pectoral splint. A pectoral splint is present in 

 Anaethalion vidali and consequently this form may be assigned to the Elopidae with 

 some degree of certainty (but see footnote p. 190). The other species may or may 

 not be elopids. In caudal anatomy there is some variability from species to species 

 within the genus Anaethalion. These caudal variations and their possible implica- 

 tions in understanding the relationships of Anaethalion species are discussed below 



(P- 39)- 

 The following remarks on the genus are based primarily on A. vidali, the only 



species definitely referable to the Elopidae. 



To describe the anatomy of A. vidali would essentially be a repetition of the 

 description given for Elops, so alike are the two forms. The differences that exist 

 are minor and many are bridged by Davichthys. 



The skull roof of Anaethalion differs from that of Elops only in the form of the 

 dermethmoid, which bears ventro-laterally directed processes similar to those seen 

 in young Tarpon and Megalops. Such horns are absent in Elops but may be seen 

 in Davichthys gardneri and probably represent a primitive teleostean condition. 



Little is known concerning the neurocranium of any species of Anaethalion. 

 What is known suggests that the neurocranium is primitive, closely resembling that 

 of Elops. Within the otic region the pars jugularis is long with separate openings 

 as in Elops, the subtemporal fossa is deep and there is a prootic-intercalar bridge in 

 at least A. vidali and A. knorri. Posteriorly the first vertebral centrum is incor- 

 porated with the neurocranium (also figured for A. knorri by Nybelin 1967b) and this 

 centrum bears a large neural arch. 



The snout of A . vidali resembles that of Elops ; the mesethmoid must have been 

 unossified and the lateral ethmoid is represented by a thin sliver of perichondral 



