. Annals of the South African Museum = Annale van die Suid-Afrikaanse Museum. Natural history. SOUTHERN AFRICAN RAJIDAE (CHONDRICHTHYES, BATOIDEl) 83 Furthermore, the accessory terminals 3 and 4 might well be derived from laterally positioned dorsal terminal elements. On the evidence presented by their distribution (Hulley 1966: fig. 8), both Raja and Rostroraja, which developed as shelf species from the boreal bathyrajid ancestors, penetrated the Mediterranean Subregion at the beginning of the Pleistocene glacial period (Klausewitz 1968). Possibly at this same time, a complete north-south dis
. Annals of the South African Museum = Annale van die Suid-Afrikaanse Museum. Natural history. SOUTHERN AFRICAN RAJIDAE (CHONDRICHTHYES, BATOIDEl) 83 Furthermore, the accessory terminals 3 and 4 might well be derived from laterally positioned dorsal terminal elements. On the evidence presented by their distribution (Hulley 1966: fig. 8), both Raja and Rostroraja, which developed as shelf species from the boreal bathyrajid ancestors, penetrated the Mediterranean Subregion at the beginning of the Pleistocene glacial period (Klausewitz 1968). Possibly at this same time, a complete north-south distribution on the continental shelf may have been attained by Rostroraja, since equatorial cooling was pronounced along the eastern shores of the Atlantic (Hubbs 1952). The subsequent increase in sea temperatures at the end of the last glacial would have given rise to (?) equatorial submergence in the case of Raja alba (Hulley 1966), and would have induced a southerly spread of the subgenus Raja. This would then support Crowson's (1970) and Parin's (1970) ideas on the correlation between group age and distribution. All other rajid subgenera in the eastern Atlantic can be derived from an ancestor, which possessed a pseudosiphon and long snout, and which had developed a shield and fleshy rhipidion (Fig. 57). In all, the longitudinally segmented pattern of the dorsal terminal cartilages, which form the framework of the dorsal lobe, is retained. This ancestor probably inhabited the archibenthal regions in boreal and antiboreal latitudes. The subgenus Dipturus represents an early split from this ancestor, as indicated by the world-wide distribution of the group, in which the primitive, rigid, rostral bar, with elongate anterior fontanelle and grooved rostrum was retained, but in which the pseudosiphon was lost. The group apparently colonized the edge of the shelf and upper regions of the archibenthal, a fact which probably allowed for their subsequent spread to all oceans (Stehmann 1
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