220 UPPER CRETACEOUS TELEOSTS 
The genus Aulopus described in the preceding pages represents the most primitive 
living representative of the Myctophiformes and many comparable features can be 
seen in the Cretaceous Sardinioides. The similarities can conveniently be listed : 
1. Neurocranium shallow with a roofed post-temporal fossa. 
2. Parietals in contact along the mid-dorsal line. 
3. Both orbitosphenoid and basisphenoid present. 
4. Antorbital present. 
5. Two supramaxillae present, although somewhat reduced in extent. 
6. Maxilla long and narrow except posteriorly where it is deepened. 
7. Premaxilla with ascending and articular processes and a very long 
alveolar arm, 
8. Supratemporal present above the opening to the post-temporal fossa. 
g. Pectoral fin on the flank, the girdle having lost the mesocoracoid arch. 
10. Pelvic fin composed of 9g rays. 
11. In the caudal skeleton preural vertebra one is fused with ural vertebra 
one. 
12. Ural vertebra two present as a small half-centrum. 
13. An adipose fin present (seen in Sardinioides monastert from Sendenhorst, 
Westphalia). 
14. Basal fulcral scales present both above and below the caudal peduncle. 
15. Fin spines absent. 
16. Three or four accessory radials (interneurals) between the occiput and 
the dorsal fin. 
17. Epineurals present on all of the precaudal vertebrae and epipleurals 
present in abundance. 
18. Body scaling extends on to the opercular bones and certain of the head 
bones. 
These numerous similarities in overall construction represent the basic characters 
of the myctophiforms, the differences being few in number and of only minor signi- 
ficance. Firstly, Savdinioides has a narrow parasphenoid below the orbit, but in 
Aulopus the parasphenoid is greatly expanded. The supraorbital bone would 
appear to be absent in Sardinioides but is large and forms part of the orbital border 
in Aulopus. However it may be that what is termed an antorbital in the description 
of Sardinioides minimus (see p. 154) is a supraorbital. The ascending process 
of the premaxilla differs somewhat ; in Sardiniotdes (Text-fig. 70) it is long, but 
in Aulopus (Text-fig. go) it is considerably reduced and rounded. In Sardim- 
otdes the suboperculum is little expanded and the operculum is large, whereas in 
Aulopus the suboperculum has greatly expanded dorsally to form the whole posterior 
edge of the opercular cover, the operculum consequently having become greatly 
reduced. The pelvic fins, although possessing the same number of rays in both 
genera, are abdominal in position in Sardinioides (Text-fig. 71) but seem to have 
migrated to a sub-thoracic position in Aulopus (Text-fig. 92). Sardinioides has a 
pelvic splint bone (Gosline, 1961 : 18) on the outer surface of the dorsal half of the 
