. Bulletin of the British Museum (Natural History). Zoology . EVOLUTION OF A CICHLID SPECIES FLOCK 73. Fig. 42. Haplochromis viponianus. (Natural size.) The skull of H. obtusidens taken as an entity is, however, more like that of H. empodisma (cf Text-figs 32 and 43), an insectivorous, bottom-detritus eating species (see p. 63 above). Thus, although I have previously indicated a close relationship between H. obtusidens and the H. ishmaeli pair (Greenwood, i960) and therefore a possible phyletic lineage of increasing specialization, I now suspect that this was an error. Recent anal
. Bulletin of the British Museum (Natural History). Zoology . EVOLUTION OF A CICHLID SPECIES FLOCK 73. Fig. 42. Haplochromis viponianus. (Natural size.) The skull of H. obtusidens taken as an entity is, however, more like that of H. empodisma (cf Text-figs 32 and 43), an insectivorous, bottom-detritus eating species (see p. 63 above). Thus, although I have previously indicated a close relationship between H. obtusidens and the H. ishmaeli pair (Greenwood, i960) and therefore a possible phyletic lineage of increasing specialization, I now suspect that this was an error. Recent analysis of various character complexes suggests that although H. empodisma and H. obtusidens are related (and are members of the 'empodisma* lineage, see p. 63) and although H. ishmaeli and H. pharyngomylus are also inter- related, the latter species pair belong to a distinct lineage (Text-fig. 70). The most likely plesiomorph sister species for H. ishmaeli and H. pharyngomylus is H. humilior (Text-figs 5C and 43 ; see also Greenwood, 1960). In H. humilior the pharyngeal mill is moderately developed (and shows a high degree of intraspeciflc variability, see Greenwood, op. cit.) and the pharyngeal apophysis shows some depar- ture towards the ' ishmaeli' condition (an increased area of basioccipital in the facet; see Text-fig. 44C). But the overall form of the neurocranium in H. humilior is of the basic insectivore type, with a short and decurved preorbital face (see Text-fig. 43). Apart from the larger pharyngeal apophysis, the neurocranium in H. ishmaeli is identical with that of H. humilior (Text-fig. 43). Haplochromis humilior could well be derived from a species like H. pallidus, a taxon in which there is already some slight hypertrophy of the lower pharyngeal teeth (see p. 59). The close correlation that can exist between the relative massive- ness of the pharyngeal bones (and their teeth) and the degree to which the neuro- cranial apophysis is developed has been clearly demon
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