240 UPPER CRETACEOUS TELEOSTS 
It now remains to consider the evolution of the teleosts within the Cretaceous 
period. The order Elopiformes is represented in the Cenomanian by Sedenhorstia 
which differs little from the Recent Elops and Megalops (Goody, 1969). Already 
Nybelin (1963) has indicated the presence of an elopiform in the Jurassic, thus the 
elopoid assemblage is an ancient one and would appear to have changed little from 
the Jurassic to the present day. Greenwood, et al. (1966 : 355) have indicated that 
the albuloids were established by at least Eocene times and probably earlier since 
they recognize that the Upper Cretaceous Jstiews shows strong affinities with Ptero- 
thrissus. The two further derivatives of the basal elopomorphs are the eels and the 
notacanths. Both of these groups are represented in the upper Cretaceous ; eels 
by Urenchelys Woodward (1901) and Anguillavus Hay (1903) ; notacanths by the 
halosaur relatives Echidnocephalus von der Marck (1863) and Enchelurus Woodward 
(1g01). These forms are little different from the modern representatives and their 
origin must have been at least in the Lower Cretaceous or even in the Jurassic. 
The basal stock of the Protacanthopterygii probably radiated into marine environ- 
ments at the end of the Jurassic and the beginning of the Cretaceous and is represen- 
ted by the Salmoniformes. Greenwood, e¢ al. (1966) have erected several suborders 
within this order, each representing a small radiation from the basal stock ; the 
Esocoidei, Stomiatoidei, Argentinoidei and Galaxioidei represent certain of these 
radiations. The suborder most closely approaching the basal stock is the Salmon- 
oidei. In the foregoing systematic account four further suborders have been added 
to the Salmoniformes, the Ichthyotringoidei, Cimolichthyoidei, Enchodontoidei and 
Halecoidei, each representing a small radiation of related forms readily separable 
from each other. These fossil suborders represent equivalent groupings to the seven 
or eight salmoniform suborders listed by Greenwood, et al. (1966 : 394). 
The Ichthyotringoidei represents the earliest offshoot from the salmoniform stock 
and is represented in the Gault by Apateodus. This genus existed practically 
unchanged throughout the Upper Cretaceous and finally disappeared in the Maas- 
trichtian. The two families within the suborder, the Ichthyotringidae and the 
Apateopholidae, are both derivable from an Apateodus-like ancestral form by 
extension of the snout (Text-fig. 100). 
The Cimolichthyoidei has been divided into two groups, the cimolichthyid/ 
dercetid group and the prionolepid group. If they are related then the dichotomy 
between the two must have occurred soon after the derivation of the group as a whole 
from the ancestral stock. The Prionolepidae continued into the Turonian without 
diversification. The Dercetidae on the other hand had their origin within the Cimo- 
lichthyidae but radiated quite considerably. For example the very specialized 
long-snouted, long-bodied dercetid Rhynchodercetis extends from the Lower Ceno- 
manian to the Middle Cenomanian and must have arisen in the Lower Cretaceous 
(Albian ?). Pelargorhynchus, although not appearing in the fossil record until 
the Upper Senonian, must have originated from a basal dercetid stock which still 
retained a complete squamation. Since all of the known Upper Cretaceous dercetids 
have a reduced squamation the origin of Pelargorhynchus was presumably well down 
into the Lower Cretaceous, before the origin of the Rhynchodercetis line. Dercetis 
