60 UPPER CRETACEOUS TELEOSTS 
Description. Neurocranium. The neurocranium is shown in dorsal view in 
Text-figure 27. It is elongate and relatively shallow, and with an acutely pointed, 
elongated anterior region. The widest point of the skull-roof is immediately 
posterior to the orbits and is represented by the lateral extension of the sphenotics. 
The major part of the skull-roof is composed of frontals which extend almost back 
to the occipital border. The bones are relatively smooth, only bearing a few weak 
ridges which indicate the course of the sensory canals. The presence or absence of 
a post-temporal fossa is difficult to determine, but in the postero-lateral region of 
the neurocranial roof there is a definite groove which may represent an unroofed 
post-temporal fossa. More anteriorly, however, the frontal is flat and perhaps 
indicates that if the fossa extended into this region then it was roofed. The frontals 
meet in the mid-line and extend backwards to cover the anterior regions of both the 
supraoccipital and the parietals. The supraoccipital thus separates the parietals in 
the mid-line. The supraoccipital bears a prominent posteriorly directed crest 
which does not rise above the plane of the skull-roof. The frontals form the upper 
margins of the orbits and taper anteriorly to insert on to the posterior edges of the 
mesethmoid. The mesethmoid is a long bone composed of two slightly divergent 
posteriorly directed limbs. The frontals are inserted between these projections, 
Fic. 27. Rhynchodercetis hakelensis (Pictet and Humbert). Neurocranium in dorsal 
view. 
