. Bulletin of the British Museum (Natural History). Zoology . 92 P. H. GREENWOOD The relationship of H. argenteus to the ' estor' species is undoubted, and its place- ment as a separate subgroup is only justified because of the unusual involvement of the ethmo-vomerine region in skull elongation. Finally in this lineage there is the bispecific subgroup of H. dentex and H. bayoni (see p. 89 above), characterized by the fairly sharp decurvature of the ethmo- vomerine skull region (Text-figs 62 and 69(3)). This deviation from the typical skull form of the 'prognathus' lineage is refl
. Bulletin of the British Museum (Natural History). Zoology . 92 P. H. GREENWOOD The relationship of H. argenteus to the ' estor' species is undoubted, and its place- ment as a separate subgroup is only justified because of the unusual involvement of the ethmo-vomerine region in skull elongation. Finally in this lineage there is the bispecific subgroup of H. dentex and H. bayoni (see p. 89 above), characterized by the fairly sharp decurvature of the ethmo- vomerine skull region (Text-figs 62 and 69(3)). This deviation from the typical skull form of the 'prognathus' lineage is reflected in the almost horizontal alignment of the mouth in both species compared with the variously oblique jaws in other members (cf Text-figs 63 and 59-61). Besides this shared similarity in jaw align- ment, both species are unusual in having relatively few (modal number 36-40) and larger outer jaw teeth. Judging from their overall neurocranial morphology, H. dentex and H. bayoni appear to be linked with the ' estor' subgroup (see p. 91 above). Four species, H. dichrourous, H. apogonoides, H. orthostoma and H. parorthostoma (Greenwood, 1967), have not so far been mentioned in this analysis, mainly because there is little information available on their cranial anatomy. Haplochromis dichrourous is known to be piscivorous, but nothing is known about the diet of the three other species. The strong unicuspid teeth and large gape of H. apogonoides suggest that it may be a piscivore, as do the near vertical orientation of the jaws and the large gape in H. orthostoma and H. parorthostoma (Text-fig. 64). Skull and jaw morphology in H. apogonoides is typically that of a generalized H. macrops-\ike species, although the stout, strongly recurved and unicuspid teeth resemble those of H. sauvagei (see pp. 69-70 ; also Greenwood, 1967). Since the skull form of H. apogonoides is not like that of the 'sauvagei' group species (p. 70), and because its teeth could be interpreted as stouter version
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