192 UPPER CRETACEOUS- TELEOSTS 
The first obvious difference between the two families is the structure of the neuro- 
cranium and in particular the skull-roof (compare Text-figs. 32 and 44). In the 
Enchodontidae the roof inclines ventrally in its postero-lateral region due to the 
disappearance of the roofs of both the post-temporal and dilatator fossae. In most 
forms in which the roof of the post-temporal fossa is lost the reduction is correlated 
with the tendency for the body to become deepened post-cranially. The epaxial 
musculature of the ‘ neck’ region in deeper bodied fish passes antero-ventrally to 
insert on to the rear end of the skull, the skull-roof and into an unroofed post- 
temporal fossa. In shallow bodied fish the epaxial musculature passes directly 
anteriorly and attaches solely to the rear face of the neurocranium or into a roofed 
post-temporal fossa. This latter condition is seen in the second family, the 
Eurypholidae (Text-fig. 47), where the body is undeepened, the skull-roof flattened 
and the post-temporal fossa roofed. In the Enchodontidae the loss of the roof of the 
post-temporal fossa is associated with a general trend towards body deepening 
(Text-fig. 41). Probably correlated with this postcranial deepening is the tendency 
for the body to become laterally compressed. Throughout the Enchodontidae the 
body is stouter in relation to the head than it is in the Eurypholidae. Eurypholis 
boissiert (Text-fig. 47) has an enormous head compared to the body, and far from 
exhibiting any postcranial deepening the body appears slightly dorso-ventrally 
flattened. The overall neurocranial depth is greater in Enchodus than in Eurypholis, 
and the hyomandibular is deeper. Both of these factors are again correlated with 
the overall tendency for the deepening of the body in the Enchodontidae as opposed 
to the Eurypholidae. 
Body elongation has occurred in both of the families. In the Enchodontidae, 
Palaeolycus has a typical enchodontid head region (comparable to the genus 
Enchodus) but the body has become greatly extended by the multiplication of the 
vertebrae, so that upwards of 70 are present (Text-fig. 43). A corresponding 
elongation has occurred in the anal fin. Within the Eurypholidae, Saurorhamphus 
has an elongated body together with an elongated snout (Text-fig. 55). The body is, 
however, extended not by the multiplication of vertebrae but by the lengthening of 
the precaudal centra. 
The paired fins and associated fin girdles differ somewhat in the two families. 
The Enchodontidae possess a ‘ normal ’ pectoral girdle with a relatively unexpanded, 
curved cleithrum and the pectoral fin is low on the flank (Text-fig. 40). The pelvics 
are abdominal, lying below the origin of the dorsal fin, with a tendency to be reduced 
in size somewhat. Palaeolycus has a minute pair of pelvics but the pectorals are 
enlarged. In contrast, the Eurypholidae have rather more specialized paired fins. 
The cleithrum is greatly expanded both anteriorly and posteriorly, and ventrally is 
turned in towards the mid-line (Text-fig. 46). The cleithrum is extensively 
ornamented and posteriorly extends below the fin insertion. The pectoral fin is 
much higher on the flank than it is in the Enchodontidae. The pelvic bones are 
large and stout and positioned directly behind the posterior cleithral extension. 
The pelvic fins themselves are thus in a sub-thoracic position and are larger than the 
pectorals. 
