ESPECIALLY MYCTOPHOIDS 195 
myodome (Greenwood, et al., 1966 : 372, fig. 5), but a large basisphenoid is retained. 
In enchodontoids the basisphenoid is never present and the prootic is complete. 
4. The shape of the ethmoid region in stomiatoids (Weitzman, 1967 : 514, 
fig. 7) is also quite unlike that of the enchodontoids. 
5. The peculiar specialization of the anterior vertebrae of the stomiatoids (Regan 
& Trewavas, 1930) also sets them apart from the enchodontoids. 
These five points provide sufficient evidence to assume that the two groups are 
not closely related. They do, however, share the features that ally them to the 
salmoniform complex within the Protacanthopterygii, for example, no fin-spines, 
abdominal pelvics, large number of branchiostegal rays, etc. A further feature 
which is shown by both groups is an adipose fin. This structure, or rather an 
impression of it in the matrix, is seen in a specimen of Enchodus gracilis from Senden- 
horst, Westphalia (Woodward, 1gor : 202). Impressions of an adipose fin are also 
seen in other specimens from Sendenhorst e.g. Sardinioides monastert. 
The second major group with which the enchodontoids have been linked is the 
scopelids (Myctophiformes), and Woodward (1901) went as far as to suggest that they 
might furnish the ancestors of the myctophiforms. The hypothesis is untenable in 
the light of the host of specialized features in the enchodontoids which are more 
advanced than those shown by the basal myctophiform stock (e.g. Sardinioides and 
Aulopus). These specialized enchodontoid features are as follows : 
1. Basisphenoid and orbitosphenoid absent. 
Supraorbital and antorbital absent. 
Nasal bones absent. 
Supramaxillae absent. 
Interoperculum absent. 
No fulcral scales at the base of the tail. 
Incomplete squamation. 
No pelvic splint bone. 
et ON eS 
These features which are absent or reduced in the enchodontoids are present in 
Aulopus, and all except the supraorbital are present in Sardimioides. Thus although 
the enchodontoids could not conceivably be ancestral to the Myctophiformes, they 
could still possibly be related to them. Again this latter proposition is negated by 
several factors : 
1. The maxilla enters the gape and is toothed in some genera of enchodontoids. 
In the Myctophiformes the maxilla never enters the gape and is never toothed. 
2. The premaxillary region in the enchodontoids might also set them apart since 
all of the Myctophiformes possess a true ascending process and an articular process. 
The enchodontoids do not appear to have a true ascending process, but have an 
enormously expanded articular process (Goody, 1968 : 228). 
3. The occurrence of the two groups in the fossil record also clearly separates 
them. At the base of the Cenomanian the Myctophiformes is represented by the 
primitive and generalized Sardinioides. The enchodontoids first occur in the Lower 
Cenomanian (Enchodus venator Arambourg, 1954 : 125) and are considerably more 
advanced in structure than the basal myctophiforms. 
