230 UPPER CRETACEOUS TELEOSTS 
Large maxilla supporting two large supramaxillae. 
Incompletely fused vertebral elements. 
Numerous epineurals. 
Parietals meet in the mid-line of the skull-roof. 
Roofed post-temporal fossa. 
17 branched caudal fin rays. 
No true fin spines. (The anteriormost dorsal fin rays are, however, 
unsegmented and spinous.) Woodward (1901) initially indicated that 
Pateroperca libanica had three slender spines at the anterior end of the 
dorsal fin. Patterson (1964 : 371) was of the opinion that these rays 
were segmented distally and not spinous. In Pattersonichthys the first 
two dorsal rays although composed of ray halves basally show no 
evidence of having been segmented. 
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When compared with the genus Ctenothrissa, the genus Pattersonichthys shows 
several characters which appear to be more primitive : 
1. Parietals meet for their entire length along the mid-dorsal line, and the 
supraoccipital is small. 
Post-temporal fossa roofed. 
Head bones unornamented. 
Short ascending process on the premaxilla. 
Maxillary head simple in form. 
Ceratohyal only slightly deepened. 
Pelvics sub-thoracic. 
Scales mainly cycloid. 
Body undeepened. 
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Thus the genus Pattersonichthys is more generalized than Ctenothrissa and lies 
closer to Aulolepis and Pateroperca. Aulolepis, Pateroperca and Pattersonichthys are 
all nearer to the direct ancestry of the Acanthopterygii (sensu Greenwood, é¢ al., 
1966) than is Ctenothrissa itself (see Patterson, 1964). The Ctenothrissiformes as a 
group present a generalized picture with few specializations (except in Ctenothrissa). 
These more generalized ctenothrissiforms can clearly be derived from the basal 
salmoniform stock, Pattersonichthys differing from this stock in a few details. These 
include the absence of a supraorbital ; reduction in the number of branchiostegal 
rays (9) ; reduction in vertebral number ; pelvics sub-thoracic ; mesocoracoid 
arch absent; and only one free ural vertebra. These points have already been listed 
in Table 1 during the consideration of the Myctophiformes. 
The first three of these points are relatively minor changes, whereas the latter three 
features represent more fundamental changes in organization, correlated with a 
greater efficiency in movement. The loss of the mesocoracoid arch is due to the 
migration up the flank of the pectoral fin, from which position the pectoral fin may 
actasa brake. The forward migration of the pelvic fins is correlated with the use of 
the pectorals as brakes, the pelvics being used as stabilizers (Harris, 1938 : 37 ; 
Patterson, 1964 : 452). The consolidation of the caudal skeleton is the first of 
