. Bulletin of the British Museum (Natural History) Zoology. 26 PH. GREENWOOD •<i^4 Fig. 3. Tilapia guinasana. Oral dentition in part (see also Fig. 9). Anterior and anterolateral region of the right dentary, viewed obliquely from above. The bullate ventrolateral region of the dentary (see p. 30) is clearly visible. Specimen RUSI 35865 (dark blue), mm Magnification x 26. point about midway along their height. Bicuspids situated anteriorly on the dentary have the most pronounced curva- ture, in that way ensuring, because of their low implantation on the jaw, that the crowns are almo
. Bulletin of the British Museum (Natural History) Zoology. 26 PH. GREENWOOD •<i^4 Fig. 3. Tilapia guinasana. Oral dentition in part (see also Fig. 9). Anterior and anterolateral region of the right dentary, viewed obliquely from above. The bullate ventrolateral region of the dentary (see p. 30) is clearly visible. Specimen RUSI 35865 (dark blue), mm Magnification x 26. point about midway along their height. Bicuspids situated anteriorly on the dentary have the most pronounced curva- ture, in that way ensuring, because of their low implantation on the jaw, that the crowns are almost vertically aligned when the mouth is closed. Posteriorly, the outer row of teeth on each side of the dentary has a distinct mediad inclination from a point almost opposite the termination of the inner tooth row (Fig. 9, p. 31). As a result, the dental arcade has an approximately horse-shoe shaped outline in occlusal view (a feature not shared with T. sparrmanii or T. ruweti). Some growth related dental changes are apparent in the sample studied. The larger specimens usually have very weakly bicuspid teeth (almost shouldered unicuspids) interca- lated amongst the true bicuspids, and a few unicuspids occur anteriorly and anterolaterally in both jaws. It is impossible to ascertain whether the shouldered teeth are the result of wear, or are elements in an ontogenetic series; the presence of true unicuspids, however, seems to be explicable on the latter basis. Inner-row teeth in fishes of all sizes are tricuspid, generally with the cusps of equal size and length, but some do have the centre cusp taller and broader than those flanking it. Anteriorly, and to a slight extent anterolaterally, the inner teeth are arranged in several series, narrowing to a single row which never extends along the entire length of the outer row. In fishes mm standard length there are 40-70 (modal range 46-50) outer premaxillary teeth, the number showing no clear-cut correlation with the ind
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