ESPECIALLY MYCTOPHOIDS 171 
Likewise Ichthyotringa cannot be retained in the myctophiform group (in which it 
has often been placed) because of the following characters : 
1. Maxilla enters the gape behind the premaxilla and is toothed. 
2. Premaxilla simple, with no ascending process. 
3. Posterior infraorbitals expanded. 
4. Caudal skeleton with two free ural vertebrae. 
These four characters provide ample justification for separating the Ichthyo- 
tringidae from the Myctophiformes. Additional substantiation for the separation 
is provided by the time of occurrence of the two groups in the fossil record. 
Apateodus first appears in the Albian (Lower Cretaceous) ; Ichthyotringa in 
both the Lower Cenomanian (Ichthyotringa africana, Arambourg 1954) and the 
Middle Cenomanian (Ichthyotringa delicata, Hay 1903) ; whilst Apateopholis, the 
most specialized of the ichthyotringoids, is also from the Middle Cenomanian. 
Thus the Ichthyotringoidei had not only arisen but had radiated to produce highly 
specialized members by the beginning of the Upper Cretaceous. At an equivalent 
time (i.e. Middle Cenomanian) the myctophiform lineage is only represented by basal, 
generalized forms such as Sardinioides. If the Ichthyotringoidei and the Myctophi- 
formes are related then the myctophiforms would presumably have arisen from the 
ichthyotringoids. This view is clearly untenable since the Ichthyotringoidei 
possess several specialized characters which are more advanced than anything seen 
in the basal myctophiformes. These features include : 
1. The long rostrum with its entailed loss of bony elements. 
2. Absence of fulcral scales at the base of the tail. 
3. Absence of a pelvic splint bone. 
4. Absence of accessory radials in front of the dorsal fin radials. 
These four factors are, however, encountered among some of the more advanced 
“alepisauroid myctophiforms ’ (Marshall, 1955; Gosline, Marshall & Mead, 1966). 
For example rostral lengthening and the forward migration of the jaw articulation 
occur in Lestidium and Anotopterus (Text-fig. 78) and the similarity in jaw structure 
between Anotopterus and Ichthyotringa has been pointed out by Arambourg (1954 : 
Fic. 78. Anotopterus phavao. Skull in lateral view. 
