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ABSTRACT. Phylogenetic analysis of the Early and early Middle Ordovician (Tremadoc and Arenig) ostracod species of Baltoscandia suggests a polyphyletic origin for the suborder Beyrichiocopa. Binodicopes, leiocopes and eridostracans are excluded from the beyrichiocopide clade. An independent origin from the basal ostracods is suggested for the binodicopes and eridostracans. The palaeocopes form a strongly supported monophyletic clade. Within this suborder, the ctenonotellid and the tetradellid families together form a monophyletic clade. The tetradellids are paraphyletic, being a stem-group for the ctenonotellids. Nanopsis nanella, the earliest known ostracod from the Tremadoc, is a basal palaeocope. The early eridostracans Conchoprimitia and Incisua, with their uncomplicated carapace morphology, might be the most primitive ostracods.

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Algae have always been the most diverse and numerous eukaryotic autotrophs in marine ecosystems. Both fossil and molecular data point to an early Proterozoic origin for algae. Although known for their long evolutionary history, the fossil record of algae is sparse and mainly remains of taxa with heavily calcified thalli are preserved. However, fossils of noncalcareous algae, known as extremely sporadic and occasional finds from different parts of the world, provide important insights into the palaeobiology of algal flora in the Earth's past. Here we describe highly diverse flora of noncalcareous thallophytic algae from a Silurian age deposit.

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