. Annals of the South African Museum = Annale van die Suid-Afrikaanse Museum . owth striae, butthese are variably developed and lacking from the largest specimen, SAM-PCA1961. Measurements Specimen D H W H/W U SAM-PCA1727 c. 50 26 (52) ? ? c. (14) SAM-PCA1726 c. 71 c. 38 (54) c. (45) ? SAM-PCA1915 67 35 (52) (26) (13) Discussion As noted by Klinger & Kennedy (1989), Placenticeras kaffrarium Etheridge displayshigh intraspecific variability, manifest in the degree of inflation of the whorls, theprominence of the lateral bulges and umbilical tubercles, and the rounding of
. Annals of the South African Museum = Annale van die Suid-Afrikaanse Museum . owth striae, butthese are variably developed and lacking from the largest specimen, SAM-PCA1961. Measurements Specimen D H W H/W U SAM-PCA1727 c. 50 26 (52) ? ? c. (14) SAM-PCA1726 c. 71 c. 38 (54) c. (45) ? SAM-PCA1915 67 35 (52) (26) (13) Discussion As noted by Klinger & Kennedy (1989), Placenticeras kaffrarium Etheridge displayshigh intraspecific variability, manifest in the degree of inflation of the whorls, theprominence of the lateral bulges and umbilical tubercles, and the rounding of the features are sexually linked, with larger macroconchs being more inflated, withmore conspicuous flank bulges and a broadly rounded venter at relatively early stage,when compared with the microconch. Namibian Placenticeras merenskyi Haughton (1930: 363, pi. 11; Klinger 1977, fig. 7)differs from the present species in being more compressed, with smaller, more numerousumbilical (12) tubercles per whorl. Contrary to Howarth (1985) and Klinger & Kennedy. v * •. i ^ Figure 17Vascoceras cf. proprium (Reyment). x Lateral and anterior views of SAM-PC A1896. UPPER CRETACEOUS (TURONIAN-CONIACIAN) AMMONITES FROM SAO NICOLA U, ANGOLA 121 (1989), the numerous small umbilical bullae exclude P. merenskyi from the presentspecies and, the writer believes, it should fall into the synonymy of P. memoria-schloenbachi (Laube & Bruder) (1887: 221, pi. 23 (fig. 1)), an Upper Cenomanian-Turonian species. Proplacenticeras fritschi (de Grossouvre 1894: 124, pi. 5 (figs 1-2)) from theConiacian of La Ribochere, differs from P. kaffrarium in having ventrolateral clavi pairedacross the venter. Although most workers regard Proplacenticeras a subjective juniorsynonym of Placenticems, in the context of hoplitacaean phylogeny the oppositeventrolateral clavi are phyletically and taxonomically meaningful and, here,Proplacenticeras is regarded a valid taxon. Stratigraphical occurrence Place
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