204 UPPER CRETACEOUS TELEOSTS 
From the above considerations it can be seen that any division between the three 
will be somewhat arbitrary. One feature, the presence of a definite ascending 
process on the premaxilla, separates the myctophiforms and ctenothrissiforms from 
the salmoniforms. However the ancestral forms from which these arose presumably 
must have had at least the forerunner of an ascending process. Points for and 
against ordinal separation can be argued, but in view of the potential within each 
group, especially the Ctenothrissiformes, it is convenient to give both groups ordinal 
separation. 
Turning to a consideration of the myctophiforms alone, a direct comparison can be 
made between the Cenomanian Sardinioides and the recent genus Aulopus. This 
latter genus has often been cited in phylogenetic considerations of teleosts (Patterson, 
1964), and the skull has been figured by both Woodward, 1902 and Regan, IgII. 
A complete osteological description has been compiled for comparative purposes 
and is set out below. 
Aulopus filamentosus (Bloch) 
(Text-figs. 86-93) 
Neurocranium. The neurocranium is shown in dorsal, ventral and lateral views 
in Text-figures 86, 87 and 88. In general shape the neurocranium is long and broad. 
The skull-roof is flattened but inclines ventrally in the postero-lateral region. The 
neurocranium attains its greatest width posteriorly in the region of the pterotics. 
Much of the skull-roof is formed from the large frontals which are somewhat con- 
stricted between the orbits but widen posteriorly. The surface of the frontal is 
smooth although some surface markings in the form of feeble ridges occur above the 
curved orbital margin. The sensory canals run within the bone and their course is 
indicated externally by broad ridges. The frontals meet in a more or less straight 
suture in the mid-line. Postero-laterally the frontal contacts the sphenotic and 
pterotic and posteriorly the broad parietal. The tube which contained the supra- 
orbital sensory canal opens postero-laterally above the sphenotic and posteriorly just 
in front of the parietal. A further posterior branch extends back into the parietal. 
The tube passes anteriorly, where it receives a further tube from the medial region 
of the frontal. This medial connection is continuous across the skull-roof (the 
frontal commissure of Gosline, Marshall & Mead, 1966: 7). Weitzman (1967 : 
527) points out that this cross-connection is a common occurence in the myctophi- 
forms, but is rare among the salmoniforms. Anteriorly the frontal meets the 
rear end of the mesethmoid, and just posterior to this the supraorbital sensory 
canal opens on to the nasal. A prominent supraorbital bone, at the anterior end of 
the orbit, is attached to the lateral edge of the frontal. 
The lateral ethmoid extends from beneath both the frontal and the supraorbital 
forming the anterior limit of the orbit. It is large and well ossified and attached 
mainly to the dorsal surface of the parasphenoid. Ventro-laterally the lateral 
ethmoid is free from the parasphenoid and has a cartilaginous connection with 
the postero-dorsal region of the palatine. In the mid-line the lateral ethmoids 
