. Bulletin of the British Museum (Natural History). Zoology . P. H. GREENWOOD. Macropleurodus bicolor Fig. 76. Neurocranial shape in three endemic monotypic genera. (Scale = 3 mm.) bauplan. The relative simplicity of these morphological changes, coupled with the basic anatomical level already reached by the ancestral lake cichlids, has, I believe, given the haplochromine fishes a great 'morpho-potential' with which to meet the environmental opportunities provided in a developing lake (Greenwood, 1973b). Alexander (1967) first drew attention to certain peculiarities in the jaw mech
. Bulletin of the British Museum (Natural History). Zoology . P. H. GREENWOOD. Macropleurodus bicolor Fig. 76. Neurocranial shape in three endemic monotypic genera. (Scale = 3 mm.) bauplan. The relative simplicity of these morphological changes, coupled with the basic anatomical level already reached by the ancestral lake cichlids, has, I believe, given the haplochromine fishes a great 'morpho-potential' with which to meet the environmental opportunities provided in a developing lake (Greenwood, 1973b). Alexander (1967) first drew attention to certain peculiarities in the jaw mechanism of a South American cichlid, Pterophyllum. Subsequently I have been able to show that this specialized type of jaw mechanism occurs in all the Lake Victoria Haplo- chromis species I have dissected ( the majority of species, including most mono- typic genera). These specializations concern functional interrelationships of the premaxillae and maxillae, the effect of which is to allow greater protrusion of the upper jaw, and firmer fixing of that jaw in the protruded position (see Text-fig. 77). As a result, the lower jaw can be closed firmly against the upper jaw whilst the latter is still protruded. The advantages of this system are discussed in detail by Alexander (1967). They are further exemplified by the exploitation of this system in some groups of mollusc. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original British Museum (Natural History). London : BM(NH)
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