2 Systematic Descriptions
29
a
b
c
Fig. 2.11 a Mature spore, split. b Immature spore. c Immature spore with membranous overlay
a
b
Fig. 2.12 a Permian Tetraedron. b Living alga Tetraedron
specimens encountered are mono-layered; exine smooth. Occasional specimen
was encountered with a membranous ektexine enveloping the smooth thicker
endexine. Membrane is fitting along corpus and loose over apices. The significant
size range is attributed to different maturation stages of the spores belonging to
the same alga.
Dimensions: 70–135 µ (35 specimens measured).
Cf. Tetraedron minimum (Hansgirg 1888).
Occurrence: Sakmarian to Upper Permian of Collie–Muja Basin and Wilga Basin.
Description: Small, quadrangular shape. Distinct thickenings of exine around
apices.
Remarks and comparison: cf. Tetraedron appears identical in morphology to the
living alga of the same name. Tetraedron (Fig. 2.11c) was collected from the southeastern part of the Baltic Sea and photographed by Olenina in 2006 for the Scandinavian Culture Collection of algae, the University of Copenhagen (Figs. 2.12
and 2.13).