50 UPPER CRETACEOUS TELEOSTS 
cavity. All of the vertebrae bear neural arches and spines dorsally, those spines in 
the precaudal region being long and very slender. In the caudal region the neural 
spines become shorter and much stouter. The centra are slightly longer than deep 
and are mesially constricted. Each centrum is strengthened by one or two lateral 
longitudinal ridges. Epineurals and epipleurals occur on the precaudal vertebrae. 
The pectoral fins are low down on the flanks and each fin appears to consist of 
approximately 12 rays. The rays are stout and well ossified with the first ray 
unbranched. The pelvic fins are abdominal, situated below the mid-point of the 
dorsal fin. Each pelvic fin consists of 10 or 11 rays. The pelvic bones are large 
triangular plates meeting in the mid-line of the ventral body wall. The pelvic 
fins are almost as large as the pectoral fins. The dorsal fin lies within the anterior 
half of the trunk and is relatively short based. It is composed of approximately 
15 rays, but more may have been present. The anal fin is only shown by a few. 
imperfect fragments, and all that can be said is that possibly as many as Io rays 
were present ; it is remote in position, quite close to the caudal fin. The caudal 
fin is not represented but part of the caudal skeleton can be seen. The preural 
vertebrae are about four in number and the centra are reduced in length. The 
neural and haemal spines are enlarged and somewhat flattened. The first preural 
vertebra is fused with the first ural vertebra, and the compound centrum so pro- 
duced supports the parhypural (the haemal spine of the first preural vertebra) and 
the first two hypurals. These hypurals are fused into a single compound element. 
Scales. The trunk is devoid of normal squamation but bears two rows of scutes 
on each flank, one placed dorso-laterally, the other ventro-laterally. The scutes 
(Woodward 1902, pl. 12, fig. 5) are overlapping and ‘ arrowhead ’ shaped, those in 
the anterior region of the dorso-lateral row being the largest. Each scute bears a 
longitudinal raised keel, and the posterior region is broader and slightly corrugated. 
The scales are longer than they are broad with the anterior region narrow, smooth 
and slightly lengthened. At the base of the pelvic fin, one of the scutes in the 
ventro-lateral row has its lower margin excavated to allow for the fin insertion. 
Family DERCETIDAE Pictet, 1850 
D1aGnosis (emended). Body elongated and very shallow ; head elongated to a 
greater or lesser extent. Post-temporal fossa never completely roofed. Maxilla 
enters gape and supports a single tooth row. Supraorbital and supramaxilla absent. 
Vertebrae 60-80 in number of which approximately 30 are caudal. Anterior 
precaudal vertebrae often elongated. Ribs borne on prominent laminar transverse 
processes. Neural and haemal spines always short. Intermuscular bones extremely 
abundant. Scales normally confined to one or more continuous rows of enlarged 
triradiate scutes along the flank, occasionally the remainder of the body covered by 
much smaller scales. 
