Annals of the South African Museum = Annale van die Suid-Afrikaanse Museum . tes, although application of this criterion sometimes becomes subjectiveas the Zululand material shows. Unless the inner whorls are preserved to reveal details of ontogeny, it isdifficult to distinguish between late representatives of Submortoniceras, johannisludovici Collignon, and smooth forms of Menabites {Delawarella). The Zululand specimens of Menabites are very large, with diameters of upto 700 mm in one M. {Delawarella) species. This, combined with the generallack of the early inner whorls, makes it diff
Annals of the South African Museum = Annale van die Suid-Afrikaanse Museum . tes, although application of this criterion sometimes becomes subjectiveas the Zululand material shows. Unless the inner whorls are preserved to reveal details of ontogeny, it isdifficult to distinguish between late representatives of Submortoniceras, johannisludovici Collignon, and smooth forms of Menabites {Delawarella). The Zululand specimens of Menabites are very large, with diameters of upto 700 mm in one M. {Delawarella) species. This, combined with the generallack of the early inner whorls, makes it difficult to identify these specimens withthe much smaller species described from Madagascar. Difficulties occur especi-ally in the interpretation of M. {Australiella) species. Apart from the fact that allthe Zululand representatives of this subgenus are highly variable, they grow tomuch larger diameters, and in doing so pass from the typically trituberculateAustraliella stage to a pentatuberculate Menabites or Bererella stage. Unfortu- CRETACEOUS FAUNAS FROM SOUTH AFRICA 283. Fig. 216. Bevahites sp. B. gr. ex. B. subquadratus CoUignon, 1948. NMB-D1067. x 1. 284 ANNALS OF THE SOUTH AFRICAN MUSEUM nately, the authors have insufficient data on the Madagascan material to findout whether these Australiella species were, in fact, all adult or immature. Phylogenetic relationships between Menabites and the other texanitinegenera, and even between the subgenera within Menabites, are not quite clear. In Madagascar, Menabites starts appearing in the upper part of theLower Campanian, Zone of Menabites boulei and Anapachydiscus arrialoorensis,but is replaced by representatives of Australiella, Delawarella and Bererellain the Middle Campanian. Data on the first appearance of Menabites in Zulu-land are scant, but the abundant occurrence of Australiella and Delawarellaat the south-western tip of the Nibela Peninsula seems to suggest the sametemporal sequence. This, however, is at varian
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Keywords: ., bookcentury1800, bookdecade1890, booki, booksubjectnaturalhistory
