16 



G.J. HOWES 



me 



esc 



so 



Fig. 4. Neurocranium of M. zugmayeri in A, dorsal and B, ventral views. In A, the right parietal, right nasal and left posttemporal have 

 been removed. In B, dashed outline circles on the prootic and intercalar indicate the positions of the otoliths. 



Cranium (Figs 4-8). 



In its overall shape the cranial roof is almost square, the most 

 noticeable feature being the deep indentation of the lateral 

 frontal border anterior to the sphenotic, and the prominent 

 anterolateral projections of the lateral ethmoid wings 

 (Fig. 4A). 



The ethmoid dorsal surface (rostrodermosupraethmoid) is, 

 in keeping with that of other gadoids (Howes & Crimmen, 

 1990: 166), being narrow and cruciform with a steep anterior 

 slope (Fig. 5B). The ossified anterior wall of the ethmoid 

 forms most of the nasal cavity and a thin, vertical septum of 

 ethmoid cartilage separates the cavities medially. A shallow 

 bed of cartilage separates the base of the ethmoid and the 

 vomer. The vomer has a thick, broadly rounded head bearing 

 on either side 6 or 7 teeth in smaller specimens and 10-12 in 

 larger (Figs 4B, 6A). In smaller specimens of both species the 

 teeth are more or less arranged in a single row but in larger 

 specimens the posterior teeth tend to be in a patch with one 

 or two stout and caniniform being almost twice the length of 

 their neighbouring teeth and three times that of the symphy- 

 seal teeth (Fig. 6A). The vomerine shaft is relatively short, 

 extending to just beyond the posterior level of the lateral 

 ethmoid. The base of the lateral ethmoid is long and broad 

 and where it meets the vomer bears a deep cavity into which 

 inserts the palatine ligament. The wall of the lateral ethmoid 

 is thin and projects forward at an angle of 45°. The postero- 



medial wall extends backward to directly contact the 

 pterosphenoid. 



The nasals (Fig. 4A) are large, almost entirely covering the 

 lateral ethmoid and are narrowly separated from one another 

 in the midline by the rostrodermosupraethmoid. Each bone 

 has prominent anterior and posterolateral processes, two 

 dorsal processes, lateral and medial, are folded inward to 

 form curved flanges which support the skin roofing the 

 sensory canal. In large specimens the nasals tend to become 

 narrow with attrition of the anterior process (Fig. 6B). 



The frontals are nearly square except that the posterior half 

 of the lateral border is deeply indented. Anteriorly, close to 

 the midline is a high, arch-shaped crest (afc, Fig. 4A), a 

 similar but longer arch is situated in the centre of the bone 

 and is sometimes divided into two separate crests (cfc. 

 Figs 4A, 5B), posteriorly is a low, diagonal crest (pfc, 

 Fig. 4A). All these crests shelter a neuromast foramen and 

 serve to support the skin covering the frontal canal system. 

 Posteriorly, the frontal margin meets the pterotic, is over- 

 lapped by the parietal and partially overlaps the anterior 

 border of the supraoccipital. There are no ventral frontal 

 laminae. The parietals (Figs 4A, 5B) are thin, near-diamond 

 shaped bones each with a single neuromast foramen and 

 posterolaterally covered by the median extrascapular. There 

 is no parietal crest. 



The autosphenotic (Figs 4A,B, 5B) has a prominent, 

 bluntly rounded lateral process and is overlapped by the 



