FOSSIL AND RECENT 



189 



55- 



56 

 57 



58 



59 

 60 

 61 



62 



63 

 64 

 65 



66 

 67 

 68 



69 

 70 



Occipital condyle formed by the exoccipitals and basioccipital. Together 

 these elements articulate with a vertebral centrum which is functionally part 

 of the neurocranium. 



Vomer short, with a broad head which bears a paired patch of small teeth. 

 Anterior ceratohyal with an elongate tooth patch plastered along the dorsal 

 margin. 



Branchiostegal rays numerous. 

 Gular plate large, horizontal. 



Premaxilla small, forming little of the functional upper jaw. 

 Gill arches with suprapharyngobranchials associated with the first and 

 second epibranchials. A fifth epibranchial is present. 

 Mandible with low coronoid process situated posteriorly. 

 Posterior infraorbitals broad, covering much of the cheek. 

 Dermosphenotic (sixth infraorbital) large. 



Supratemporals large, meeting one another in the mid-line with the conse- 

 quence that the supratemporal commissure is wholly enclosed by bone. 

 Anterior uroneural with forked base. 

 Seven hypurals. 



Base of the innermost principal fin-ray of each caudal lobe expanded and 

 considerably overlapping the supporting hypural. 

 Urodermal present. 

 Fringing fulcra usually present (but absent in Elops). 



Of the characters listed above, 1-39 and 47-70 are primitive for teleosts, 1 the 

 majority being found in the less specialized representatives of the superorders Clupeo- 

 morpha, Osteoglossomorpha, Protacanthopterygii (sensu Rosen & Patterson 1969) 

 and Ostariophysi. These characters are therefore of little use in indicating rela- 

 tionships ; they merely serve to suggest ways in which the elopiforms have not evolved. 

 No other group of ' lower ' teleosts shows such a wealth of primitive characters and 

 it is clear that the Elopiformes could not have evolved from any extant member (s) 

 of the superorders mentioned above. Indeed, as noted below, it is extremely un- 

 likely that elopiforms evolved from any known fossil teleost group belonging to the 

 other superorders. 



1 Feature 38, the possession of anterior diverticula of the swimbladder is included here as a character 

 which is primitive for teleosts. The evidence is admittedly indirect, since there are no details of swim- 

 bladder anatomy in fossils except where that organ influences osteological development. Within the 

 'lower' teleosts an otophysic connection involving an anterior diverticulum of the swimbladder extend- 

 ing forward to the level of the neurocranium has developed in the Megalopidae (Elopomorpha) , the 

 Clupeomorpha, and in the Notopteroidei and the young growth stages of Mormyriformes (both Osteo- 

 glossomorpha). The development of otophysic connections in these groups, which are presumed to have 

 evolved in parallel (Greenwood et al. 1966), suggests that some rudimentary swimbladder modification 

 was present in the Pholidophoridae. The stage hypothesized for the pholidophorid condition may be 

 seen in Albula, where paired anterior diverticula extend forward to terminate beneath the ventro- 

 lateral surfaces of the basioccipital (Greenwood 1970a) ; such diverticula are present, although poorly 

 developed, in Elops and Pterothrissus. It is of interest to note that ostariophysan fishes, which are 

 thought to have evolved from a group (the Salmoniformes, see Greenwood et al. 1966) without anterior 

 diverticula of the swimbladder, developed an otophysic connection by vertebral and rib specializations 

 (Rosen & Greenwood, 1970). 



