ESPECIALLY MYCTOPHOIDS 175 
Roofed post-temporal fossa. 
Orbitosphenoid and basisphenoid present. 
Posterior infraorbitals expanded. 
No ascending process on the premaxilla. 
Mesocoracoid arch (A pateodus). 
Abdominal pelvic fins. 
Supraorbital bone (A pateodus). 
Oo en is 
io 
These characters are all, however, merely indicative of a primitive grade of organi- 
sation, and could equally ally the Ichthyotringoidei with the salmonoids. Certain 
features, however, definitely separate the ichthyotringoids from the elopoids : 
No rostral bones, and no ethmoidal commissure. 
No antorbital. 
No nasal. 
No supramaxillae. 
No gular plate. 
Development of a trigemino-facialis chamber in the prootic (A pateodus) 
as opposed to the separate intraosseus passages seen in the elopoids 
(Greenwood, et al., 1966). 
7. No teeth on the parasphenoid. 
NE a Age ee 
These features are sufficient clearly to separate the ichthyotringoids from the 
elopoids and are features which are present in the more progressive salmoniforms. 
Greenwood, et al. (1966 : 350), in the erection of their new superorder Protacantho- 
pterygii, suggested that the salmonoids constitute the principal and basal element of 
this group, possessing none of the limitations of the elopoids, and the salmonoids 
would appear to have the requirements to give rise to the major radiations within 
the Protacanthopterygii and Acanthopterygii. The salmonoids possess the following 
basal osteological characters : parietals in contact in the mid-line ; orbitosphenoid 
and basisphenoid ; supraorbital and antorbital ; expanded posterior infraorbitals ; 
maxilla large and toothed ; incipient ascending process of premaxilla ; two large 
supramaxillae ; teeth on vomer, palatine, endopterygoid and ectopterygoid ; 
numerous branchiostegal rays ; mesocoracoid arch ; three postcleithra ; as many 
as 18 pectoral rays ; anterior neural spines consisting of separate lateral elements ; 
numerous supraneurals ; numerous epineurals ; transverse processes not fused 
to centra ; pelvic fin with 11 rays ; pelvic splint bone ; no fin spines ; two free 
ural vertebrae ; stegural with one or two further uroneurals ; 17 branched caudal 
rays ; six hypurals ; cycloid scales. 
The Ichthyotringoidei agree with the majority of these characters, differing in the 
features related to rostral elongation, and the absence of a stegural, accessory 
radials and a pelvic splint bone. In conclusion, then, the ichthyotringoids represent 
a small radiation commencing in the Lower Cretaceous. Apateodus is the least 
specialized genus and continued little changed throughout the Upper Cretaceous 
(Gault to Maastrichtian). It was a generalized predator which may possibly have 
given rise to the other more advanced ichthyotringoids. The elongate rostral region 
