Salmoniformes 
Salmo 
Parietals meet in mid-line 
Post-temporal fossa roofed 
Orbitosphenoid present 
Basisphenoid present 
No ascending premaxillary 
process 
Articular premaxillary 
process present 
Small, toothed premaxilla 
Large, toothed maxilla 
entering the gape 
2 large supramaxillae 
Teeth on vomer, palatine, 
endopterygoid, 
ectopterygoid 
Supraorbital present 
Antorbital present 
Expanded posterior 
infraorbitals 
Numerous branchiostegals 
Mesocoracoid arch present 
Pectorals low down, 18 rays 
3 postcleithra 
Numerous accessory radials 
Pelvics abdominal, 13 rays 
Pelvic splint bone present 
Imcompletely fused vertebral 
elements 
Numerous epineurals 
No fin spines 
Adipose fin present 
Stegural present 
2 free ural vertebrae 
17 branched caudal rays 
Fulcral scales absent 
Cycloid scales on body 
6 hypurals 
ESPECIALLY MYCTOPHOIDS 
TABLE I 
Myctophiformes 
Sardimioides 
x 
x 
x 
x 
Prominent ascending process 
Prominent articular process 
Very long toothed premaxilla 
Large, untoothed maxilla 
excluded from gape 
2 reduced supramaxillae 
x 
Supraorbital absent 
x 
Unexpanded infraorbitals 
9 (numerous in Aulopus) 
Mesocoracoid absent 
Pectorals on flank, 13 rays 
2 postcleithra 
3 or 4 accessory radials 
Pelvics abdominal, 9 rays 
XS, of 
x 
One free ural vertebra 
x 
Fulcral scales present 
Cycloid/ctenoid scales 
x 
Ctenothrissiformes 
Pattersomichthys 
x 
x 
x 
x 
Small ascending process 
Small articular process 
x 
x 
x 
x 
Supraorbital absent 
x 
Unexpanded infraorbitals 
8 or 9 branchiostegals 
Mesocoracoid absent 
Pectorals on flank, 13 rays 
2 postcleithra 
3 or 4 accessory radials 
203 
Pelvics sub-thoracic, 8-9 rays 
x 
x 
Xx 
2 spinous rays in dorsal 
Adipose fin absent 
x 
One free ural vertebra 
x 
Fulcral scales present 
x 
x 
The differences noticed between the three groups are all relatively minor ones, and 
only one factor in the whole list would exclude a direct descent of the two groups 
from the salmoniforms. This factor is the absence of basal fulcral scales at the base 
of the caudal fin in Salmo. This however is a primitive feature left over from some 
halecostome ancestor and is lost in later myctophiforms and ctenothrissiforms. 
Likewise it has presumably been lost in the Recent salmonoids. 
The list illustrates the strong basal convergence of three groups which are separated 
ordinally. It thus would appear that the sardinioid group and the ctenothrissoid 
group, at the beginning of the Upper Cretaceous, were evolving along similar lines, 
both having been derived from a common ancestral stock within the salmoniforms. 
