New Ordovician mitrates (Echinodermata, Stylophora) from the Ancenis Basin (South Armorican Domain, France): Palaeogeographic and palaeoenvironmental implications.

8 pages; International audience; Fossil echinoderms are extremely rare in Ordovician deposits of the South Armorican Domain (SAD), a structurally complex area stacked to the Medio-North Armorican Domain during the Hercynian orogeny. Two new occurrences of mitrate stylophorans are documented in the eastern part of the SAD (Ancenis Basin). The youngest known specimen of Lagynocystis pyramidalis is described from the Schistes du Fresne Formation (Late Ordovician). Mitrocystites mitra is reported from the Pierre Meliere Formation (Middle Ordovician), and for the first time, outside of Bohemia. The presence of these two cool-adapted taxa (both abundant in the Prague Basin) in the Ancenis Basin d…