236 UPPER CRETACEOUS! TELEOSTS 
the early Jurassic, competing with the leptolepids and pholodophorids, as well as 
the majority of the Holostei. The elopids and the leptolepids thus appear to 
represent independent attainments of the teleost level, if the leptolepids are considered 
to be teleosts. 
The similarities between the Pholidophoridae, Elopidae and Leptolepidae can 
conveniently be listed : 
1. No articular or ascending processes on the premaxilla. 
Rostral elements with a bone enclosed ethmoidal commissure. 
Several supraorbitals. 
Fringing fulcral scales. 
Gular plate present. 
Many posterior branches from the preopercular sensory canal. 
No stegural. 
No adipose fin. 
The Salmoniformes represent a further teleost stock which shows a wide divergence 
from the Elopiformes. This divergence has been indicated by Greenwood, et al. 
(1966) who have given superordinal rank to these two phyletic lineages. The basal 
salmoniform stock exhibits many differences not only from the elopiforms, but from 
the pholidophorids and the leptolepids. These differences include : » 
1. Articular process on the premaxilla. 
No separate dermal rostrals, no bone enclosed commissure. 
One small supraorbital. 
No fringing fulcra. 
No gular plate. 
No posterior branches of preopercular sensory canal. 
Stegural present. 
Adipose fin present. 
Several further dissimilarities are seen between the Recent forms Megalops and 
Salmo. Megalops has an otophysic connection, a leptocephalus larva, parasphenoid 
teeth and a subtemporal fossa. 
Discussion of the origin of the Salmoniformes is rendered difficult by the complete 
absence of fossil material below the Albian stage of the Lower Cretaceous. However, 
any one of these features in which the Salmoniformes differ from the Pholidophoridae 
could have been derived directly by reduction or loss through intermediate forms, as 
yet unknown, presumably within the Jurassic. For example, Nybelin (1967 : 244) 
has shown that the bone enclosed ethmoidal commissure of the elopoids is homologous 
with the canal system embedded in the soft tissue of the snout of clupeoids, and the 
pit-line on the snout of salmonoids. The commissure, then, in the salmonoids, has 
lost its bony surround together with any other rostral elements, except for the 
antorbital. Gardiner (1960 : 351) has said that the Salmonidae and Characinidae 
can be derived much more easily from a pholidophorid ancestor than from a lepto- 
lepid one, not just on scale structure, but on general disposition, in particular of the 
jaws. From my own observations I think it impossible to derive a basal salmoni- 
form from a leptolepid such as Leptolepis africana Gardiner (1960 : 314, fig. 48) 
DI AAR WS 
DI AAR WS 
