120 UPPER CRETACEOUS TELEOSTS 
Dermal upper jaw. The dermal upper jaw is shown in lateral view in Text-figure 
54. The premaxilla is large and has a prominent pedicel anteriorly, lying at 90° to the 
lateral region of the bone. The premaxillary pedicels meet in the mid-line and lie in 
the same plane as the anterior part of the skull-roof and form a direct continuation 
of it, the pedicels articulating with the anterior edge of the mesethmoid. Each pedicel 
contains an oval fenestra through which the enlarged anteriormost tooth of the dent- 
ary projects when the jaws are closed. Between the premaxillary pedicel and the 
lateral face of the bone there is a groove running to the anterior edge of the snout, 
this groove is continuous with the anterior opening of the supraorbital sensory canal 
on the lateral edge of the frontal. The premaxilla is closely associated with the 
lateral face of the palatine and extends back to a point below the centre of the orbit. 
The lateral face of the premaxilla is triangular and ornamented with four or five rows 
of bony tubercles which radiate backwards and outwards from the anterior snout 
region. Postero-dorsally the lateral face is overlapped by the ventral expansion 
of the lachrymal bone, and a lateral groove devoid of ornamentation extends 
anteriorly. This groove may have contained an anterior prolongation of the 
infraorbital sensory canal. The premaxilla decreases in depth below the lachrymal 
and tapers posteriorly. 
The maxilla enters the gape behind the premaxilla and along its whole length is 
closely attached to the premaxilla making the demarcation line between the two 
bones difficult to define. The maxilla is continued on the internal face of the pre- 
maxilla and is firmly fused to it. The maxilla is smooth and rod-like with no 
ornamentation. There isa single marginal row of teeth on the premaxilla which does 
not extend on to the maxilla. The teeth are small, evenly spaced, acutely pointed 
and merely seem to be a slightly enlarged marginal row of bony tubercles similar 
to the tubercular ornamentation on the other dermal bones of the skull. 
Mandible. The mandible is shown in medial and lateral views in Text-figures 53, 
54. The dentary forms almost the whole of both dorsal and ventral margins of the 
mandible and over half of the lateral face. The posterior edge of the dentary is 
deeply indented into a V-shape. The mandible is elongate and relatively shallow 
with the ventral region strongly inflected towards the mid-line. Dorsally the dentary 
bears a medial flange on which the teeth are borne ina single row. The teeth are like 
those found on the palato-pterygoid arcade, i.e., conical, acutely pointed, hollow, 
slightly recurved, laterally compressed, and with expanded bases. The dentary also 
bears a ventro-medial flange which diverges from the dorsal flange in the anterior 
mandibular region. The deep V-shaped groove left between the dorsal and ventral 
flanges on the internal face of the mandible served to house the remains of Meckel’s 
cartilage. 
The articular facet is concave and transverse, limited medially by a small vertical 
flange, and laterally by a large vertical upgrowth of the articular. This lateral 
flange completely covers the articular facet so that it is not visible in lateral view. 
The articular extends anteriorly to occlude the posterior indentation of the dentary, 
and is inserted on to the medial face of the dentary. The mandibular sensory canal 
entered the articular region of the mandible behind the articular facet and passed 
