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the former Order NOTASPIDEA P. Fischer, 1883 was splitted:
Class: Gastropoda Cuvier, 1797
Subclass: Heterobranchia J.E. Gray, 1840
Infraclass: Euthyneura Spengel, 1881
Subterclass: Tectipleura Schrödl, Jörger, Klussmann-Kolb & Wilson, 2011
Order: Umbraculida Odhner, 1939
Superfamily: Umbraculoidea Dall, 1889 (1827)
Class: Gastropoda Cuvier, 1797
Subclass: Heterobranchia J.E. Gray, 1840
Infraclass: Euthyneura Spengel, 1881
Superorder: Nudipleura Wägele & Willan, 2000
Order: Pleurobranchida J.E. Gray, 1827
Superfamily: Pleurobranchoidea J.E. Gray, 1827
Family: Pleurobranchidae J.E. Gray, 1827
Subfamily: Pleurobranchinae J.E. Gray, 1827