. Annals of the South African Museum = Annale van die Suid-Afrikaanse Museum. Natural history. UPPERMOST CENOMANIAN-BASAL TURONIAN AMMONITES FROM SALINAS, ANGOLA 125 Ornament comprises rather weakly developed umbilical bullae from which arise slightly prorsiradiate main ribs, separated by 1-2 intercalatories. There are 18 ribs per half whorl, generally with upper and lower ventro-lateral clavi. The. —f—o —o Fig. 33. Watinoceras coloradoense (Henderson) (?). Suture-line of SAM-PCA2730 at about 48 mm diameter. upper ventro-lateral clavi are very close together and stand out above the ribbing, gi
. Annals of the South African Museum = Annale van die Suid-Afrikaanse Museum. Natural history. UPPERMOST CENOMANIAN-BASAL TURONIAN AMMONITES FROM SALINAS, ANGOLA 125 Ornament comprises rather weakly developed umbilical bullae from which arise slightly prorsiradiate main ribs, separated by 1-2 intercalatories. There are 18 ribs per half whorl, generally with upper and lower ventro-lateral clavi. The. —f—o —o Fig. 33. Watinoceras coloradoense (Henderson) (?). Suture-line of SAM-PCA2730 at about 48 mm diameter. upper ventro-lateral clavi are very close together and stand out above the ribbing, giving the venter a concave aspect. There is no sign of siphonal tubercles at any stage. Measurements No. D H W W/H U SAM-PCA2730 48 21 (44) 17 (35) 0,81 15(31) 5? 35 16 (46) 12 (34) 0,75 9(26) SAM-PCA2753 41 17 (41) 13 (31) 0,76 14 (34) Discussion As shown above, Watinoceras coloradoense (Henderson), W. reesideiWaxren and W. amudariense (Arkhangelsk^) are conspecific, the oldest available name being W. coloradoense. There appears to be a wide range of variation, both ontogenetic and intra- specific, within Henderson's species. The variation in rib density within the macroconch is well shown by Cobban & Scott (1972) (see also Fig. 34), while these authors record 1-3 intercalatories between main ribs in this species. Arkhangel'skii's (1916, pi. 8 (figs 8, 14)) juvenile macroconchs, however, show only simple, main ribs. Moreover, the diameter at which the course macroconch ornament first appears is also variable. Thus, typical' Watinoceras coloradoense- type' ornament appears at only 25 mm diameter in 'Acanthoceras' amudariense var. horridum, whereas the Angolan example still retains ' Watinoceras reesidei- type' ornament at 48 mm diameter. A similar amount of variation would also. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly r
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