Placenticeras kaffrarium Morph subkaffrarium Spath

Microconch. The shell is compressed to slightly inflated (WB/H = c. 0.71) with subtrigonal whorl section; it is relatively evolute (U/D = 0.3-0.4; Av. = 0.34; S.D. = 0.031). The venter is flat, with clavi. The adult body chamber occupies more than two-thirds of the last whorl. This variant is characterized by shells, each with one row of umbilical tubercles. Umbilical tubercles are pyramidal and clavi appear almost simultaneously in early whorls. Clavi on opposite sides are always alternate

Fig. 5.4 Umkwelanense type of ornament. 1, lateral view, microconch with adult phragmocone and partially preserved body chamber; note uncoiling of body chamber. 2, lateral view, microconch, adult phragmocone; note trace of body chamber showing scaphitoid uncoiling. 3, apertural view. 4, lateral view, macroconch, almost complete. 5, ventral view, note tabulate venter. Scale bar = 1 cm.

Fig. 5.5 Umkwelanense (1) and subkaffrarium (2-5) types of ornament. 1, lateral view, microconch, body chamber; note feeble umbilical tubercles on inner whorl. 2, ventral view, microconch. 3, lateral view, microconch with incompletely preserved adult body chamber. 4, apertural view. 5, lateral view, microconch, adult with partially preserved body chamber; note strong umbilical tubercles. Scale bar = 1 cm.

Fig. 5.5 Umkwelanense (1) and subkaffrarium (2-5) types of ornament. 1, lateral view, microconch, body chamber; note feeble umbilical tubercles on inner whorl. 2, ventral view, microconch. 3, lateral view, microconch with incompletely preserved adult body chamber. 4, apertural view. 5, lateral view, microconch, adult with partially preserved body chamber; note strong umbilical tubercles. Scale bar = 1 cm.

in position and persist to the end of the adult body chamber. Maximum diameter is about 134 mm (Range = 87-134; Av. = 104.97; S.D. = 17.90).

Macroconch. The inner whorls of the macroconch strongly resemble those of the microconch. Shell diameter exceeds 160 mm (Range = 85-160; Av. = 136.28; S.D. = 23.61). The body chamber occupies more than two-thirds of the last whorl. The venter is clavate up to the early mature body chamber; later it becomes broadly rounded. Umbilical tubercles appear early to mid-phragmocone stage and, at the late phragmocone stage, they become subdued and finally disappear on the early part of the body chamber. The whorl section is subtrigonal. Ventral clavi may persist up to the early part of the mature body chamber; after that, the venter becomes smooth and rounded.

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