. Annals of the South African Museum = Annale van die Suid-Afrikaanse Museum. Natural history. 194 ANNALS OF THE SOUTH AFRICAN MUSEUM terized by their lozenge-shaped disc, short tail and single mid-dorsal row of stout thorns. The distribution and interrelationships of this group have been discussed by Krefft (1968&). In appearance and type of spination, R. radiata falls into the heavily- spined sub-group of the radiata-complex. R. radiata is so closely allied to R. doellojuradoi, recorded from the western South Atlantic, that Bigelow & Schroeder (1953: 255) point out that 'no reliable
. Annals of the South African Museum = Annale van die Suid-Afrikaanse Museum. Natural history. 194 ANNALS OF THE SOUTH AFRICAN MUSEUM terized by their lozenge-shaped disc, short tail and single mid-dorsal row of stout thorns. The distribution and interrelationships of this group have been discussed by Krefft (1968&). In appearance and type of spination, R. radiata falls into the heavily- spined sub-group of the radiata-complex. R. radiata is so closely allied to R. doellojuradoi, recorded from the western South Atlantic, that Bigelow & Schroeder (1953: 255) point out that 'no reliable criteria have been found to distinguish the one from the other'. Pozzi (1935, 1936) and Norman (1937) hold that in R. radiata the tail is longer, so that the vent is nearer to the tip of the snout than to the end of the tail; the teeth are more numerous (38-46 rows in upper jaw in R. radiata; 31-34 rows in R. doellojuradoi); there are only 2 scapular thorns; and the spines on the disc are less well developed, there being less than 10 in the mid-line of the tail posterior to the axils of the pelvics. Krefft (personal communication), in comparing six specimens of R. radiata from the northern Atlantic with five specimens of R. doellojuradoi from the western South Atlantic, has found that there is no difference in the number and distribution of the median thorns and no difference in spination except in the number of scapular thorns. Whereas in R. radiata two large scapular thorns exist, the third one being either vestigial or much smaller than the outer ones, in R. doellojuradoi the three scapular thorns are of the same size. In the South African specimens, tooth count favours their identity with R. radiata, and while size at first maturity may be a questionable taxonomic character, the size of the two specimens is well above the 530 mm total length limit for R. doellojuradoi (Krefft, personal communication). Furthermore the raj id distribution of the Atlantic suggests that the Sou
Size: 2145px × 1164px
Photo credit: © Library Book Collection / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, bookdecade1890, booksubjectnaturalhistory, booky
