. Bulletin of the British Museum (Natural History). PELMATOCHROMIS, TILAPIA AND SAROTHERODON 13 THE RELATIONSHIP BETWEEN PELMATOCHROMIS AND TILAPIA To include as Thys (1968b : xxvii-xxix) does Pelmatochromis buettikoferi, P. ocellifer, P. nigrofasciattis, Pt. congicus and Tilapia bnsumana in the same subgenus requires a definition full of alternatives. I will proceed to examine the characters on which he relies and some others that seem to me to be relevant to the relation- ship. Dentition of jaws We have no P. ocellifer smaller than 63 mm SL and in this the teeth are unisucpid, curved cones o
. Bulletin of the British Museum (Natural History). PELMATOCHROMIS, TILAPIA AND SAROTHERODON 13 THE RELATIONSHIP BETWEEN PELMATOCHROMIS AND TILAPIA To include as Thys (1968b : xxvii-xxix) does Pelmatochromis buettikoferi, P. ocellifer, P. nigrofasciattis, Pt. congicus and Tilapia bnsumana in the same subgenus requires a definition full of alternatives. I will proceed to examine the characters on which he relies and some others that seem to me to be relevant to the relation- ship. Dentition of jaws We have no P. ocellifer smaller than 63 mm SL and in this the teeth are unisucpid, curved cones of the adult type. The same is true of the smallest P. buettikoferi examined, a specimen of 28 mm SL. The teeth of P. nigrofasciatus from SL 22 mm to the adult have been described on p. 6 and fig. 4. The only species of Tilapia in which the very early development of the teeth has been described is T. tholloni. Fishelson (1966 : 197) states that they are unicuspid at first appearance, but at the 15th day after fertilization there are already tricuspid teeth. In his fig. 23 of a 16-day larva one minor cusp is visible on each clearly defined tooth. This goes on to develop into the well-known Tilapia dentition, with bicuspid outer and tricuspid inner teeth. O 10. mm A I' t ^ I mm B. mm Fig. 9. Tilapia btisumana. A, isolated teeth from a specimen of SL 156 mm; above, one of the 22 outer lateral simple teeth from right ramus of upper jaw and one of the 11 bicuspid anterior outer teeth from the same; below, inner teeth from respectively the row next to the bicuspids and the inmost row; the open lower ends of the outer teeth are seen because of the curve of the axis of each in a plane at right angles to the page. B, dentition of lower jaw, with enlarged drawings of three of the teeth in a fish of SL iii 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
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