Место издания:The University of Kansas Lawrence, Kansas
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Аннотация:More recent studies have related the class Radiocyatha most closely to the Early Ordovician–Permian receptaculitaleans, a group popularly allied with calcareous algae, though most recently regarded as problematic (neither sponges, nor dasycladalean algae). In the receptaculitalean model, homology is drawn between the recep- taculitalean merom (consisting of shaft, inner platelike foot and outer quadribra- chial structure with surmounting head plate) and the radiocyathan radial rod connecting corresponding inner and outer nesasters. This proposed affinity with receptaculitaleans is consistent with microstructural (Kruse & Debrenne, 1989) and mineralogical comparisons. Nevertheless, because of continuing uncertainty regarding their affinities, the Radiocyatha are included in the present Treatise revision.