THE SERRANOCHROMINE GENERA REVIEWED 



37 



characters that are not present in Sargochromis or Pharyn- 

 gochromis, the two other serranochromines with only a single 

 postorbital scale row. These correlated features are an 

 increase in the relative size and bulk of the upper part of the 

 levator arcus palatini muscle, and an anteriorly directed 

 lengthening of the postorbital process from the sphenotic 

 bone, particularly its ventral region associated with the origin 

 of the muscle (see fig. 3 and fig. 8 in Greenwood, 1992). In 

 Sargochromis and Pharyngochromis the muscle is relatively 

 smaller, and the postorbital sphenotic process has the almost 

 uniformly narrow form (Fig. 3) found in the generalised 

 haplochromine skull (and, it may be added, the skulls of 

 Tylochromis and Heterochromis , the genera thought to repre- 

 sent the least derived lineages of African cichlids; see Oliver, 

 1984, and Stiassny, 1989 & 1991). 



The other reason for reconsidering the subgeneric status of 

 Sargochromis is the increased information now available, 

 especially for Chetia (see p. 38), which clearly indicates an 

 extensive overlap in the gill-raker and dorsal fin-ray charac- 

 ters previously used (Greenwood, 1979) to define Serrano- 

 chromis (then including Sargochromis). These characters, 

 therefore, no longer can be considered synapomorphic for 

 Serranochromis and Sargochromis alone. 



With the elimination of those two characters, the only 

 derived feature shared uniquely by Serranochromis and Sar- 

 gochromis is the increased number of abdominal vertebrae. 

 Against that presumed synapomorphy must be set the 

 derived postorbital scale-row character shared only by Serra- 

 nochromis (sensu Regan, 1920) and Chetia, which genera also 

 share two apomorphic features not previously recognised. 

 These are: (i) an increase in the range and modal number of 

 caudal vertebrae (range 15-18, modes 16 and 17 in Serrano- 

 chromis, range 15-17 modes 16 and 17 in Chetia, compared 

 with ranges of 12-16 in Sargochromis , and 14-16 in Pharyn- 

 gochromis, with modes of 14 and 15, and 15 in the genera 

 respectively); (ii) an increase in the range and modal number 

 of circumpeduncular scale, viz. 18-20, rarely 16, in Serrano- 

 chromis and Chetia, neither taxon with a clear-cut modal 

 number, as compared with 16 or 18 (mode 16) in Sar- 

 gochromis and 15 or 16 (mode 15) in Pharyngochromis . The 

 recognition of this feature as an apomorphy is based on the 

 circumpenduncular counts for Tylochromis and Hetero- 

 chromis (see above), where the range, and modes, are 15-16. 



Thus, taking into account the presumed derived characters 

 shared only by Serranochromis and Chetia, it would seem that 

 the higher count of abdominal vertebrae in Serranochromis 

 and Sargochromis should be treated as a homoplasy and not, 

 as previously thought, an apomorphy indicating an immedi- 

 ate common ancestor for the two taxa. For that reason I agree 

 with, and now formally act upon Lippitsch's (1991) conclu- 

 sion that "It seems advisable ... to recognise Sargochromis 

 as a distinct genus. . .". 



The possible relationship of Sargochromis within the serra- 

 nochromines is discussed on p. 41, and a revised generic 

 diagnosis is given on p. 42. 



A few further comments need to be made about the genera 

 Serranochromis and Sargochromis. The number of postor- 

 bital scale rows in certain Serranochromis species can be as 

 high as four or five, and, as far as I can determine, the 

 number of rows is relatively constant intraspecifically. At 

 present insufficient information is available on possible inter- 

 or intraspecific differences in scale ornamentation, or on such 

 variation in the presence or absence of a soft free margin to 

 the scales (see Lippitsch, 1991). The small sample of species I 



Fig. 3. Posterior portion of the neurocranium, in left lateral view, 

 to show differences in the size of the sphenotic postorbital process 

 (Sp.) in Sargochromis, Chetia and Serranochromis. A, 

 Sargochromis carlottae (RUSI: 31204, 89 mm S.L.; B, Chetia 

 brevis (AMG: P1422, 90 mm S.L.) and C, Serranochromis 

 macrocephalus (RUSI: 24175, 112 mm S.L.) Scale bar = 5 mm. 



