44 ELOPIFORM FISHES 



the autosphenotic spine is well developed and the dilatator fossa is relatively deep. 

 These features, and the shape of the parasphenoid, are reminiscent of those seen in 

 megalopids. Further research on A. vidali may justify the inclusion of this species 

 in the Megalopidae. 



Family MEGALOPIDAE Jordan, 1923 



Diagnosis. Elopoid fishes in which the body is compressed. Cranium deep, 

 mouth terminal or (more usually) superior. Cranial roof convex above the otic 

 region. Parietals without evidence of middle pit-lines. Autosphenotic spine and 

 epiotic process well developed. Post-temporal fossae extend forward to orbito- 

 sphenoid and are confluent above the cranial cavity. Dilatator fossa with or without 

 roof. Otophysic connection developed in at least some representatives ; intercalar 

 enlarged, partially or completely surrounding the cranial diverticulum of the swim- 

 bladder. One rostral ossicle. Quadrate/mandibular articulation beneath orbit. 

 Mandible with prominent coronoid process. Pseudobranchiae present (Holstvoogd 

 1965). Pelvic fins originating beneath or anterior to the dorsal fin origin. Anal fin 

 slightly elongated (compared with Elopidae). First anal pterygiophore extending 

 to the vertebral column. Urodermal absent. Scales with three to six basal radii, 

 posterior field ornamented. Lateral line tubes branched. 



Genus TARPON Jordan & Evermann, 1896 



For full generic synonymy see Hildebrand (1963). 



Diagnosis (emended). Megalopid fishes reaching 1800 mm in length. Neuro- 

 cranial roof markedly convex above the cranial vault. Parietals considerably longer 

 than broad in adult. Dilatator fossa broad, shallow and without a roof. Intercalar 

 not entering the lateral wall of the periotic bulla. Jugular canal opening below the 

 level of the subtemporal fossa. Maximum depth of the neurocranium at the occiput. 

 Maxilla extending behind the eye. Scales with three to four anterior (basal) radii. 



Type and only species. Megalops atlanticus Cuvier & Valenciennes, 1846. 



Tarpon atlanticus (Cuvier & Valenciennes) 

 (Text-figs. 20-29) 

 For synonymy see Hildebrand (1963). 



Diagnosis (emended). Tarpon in which the origin of the pelvic fin is in advance 

 of the dorsal fin. Maximum depth of body less than the length of the head. Dorsal 

 fin with 13-15 rays, anal 22-25. Vertebral column with 53-57 vertebrae of which 

 approximately 20 are caudal. Lateral line with 41-48 scales. Fringing fulcra one 

 to four in number. 



Habitat. Atlantic coastal waters of North and South America (from Cape Cod 

 to Brazil), sometimes entering fresh water. Also recorded from tropical West Africa. 



