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Calcareous algae are common components in the shallow-marine limestones of the Drunka Formation (Early Eocene) cropping out on both banks of Nile between Sohag and Quena. Calcareous algae include: Acicularia valeti Segonzac, Sandalia pavsici Radoicic, Clypeina occidentalis (Johnson and Kaska), C. cf. rotella Jing, Terquemella bellovacensis Munier-Chalmas (Dasycladales), Ovulites arabica (Pfender), O. pyriformis Schwager, O. margaritula (Lamarck), O. elongata Lamarck (Udoteaceae), Halimeda tuna (Ellis and Solander) Lamouroux, H. opuntia (Linneaus) Lamouroux and H. fragilis Taylor (Halimedaceae). Niloporella subglobosa n.gen.n.sp. and Acicularia robusta n.sp. are new calcareous algae. Among fossil Halimeda three evolutionary lineages are recognized in the the Mesozoic and early Cenozoic that derive from Paleozoic Protohalimedaceae: Halimeda cylindracea lineage, H. incrassata, and H. opuntia.
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Dragastan et al. (2002) studied this question.
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