Selected synonymic references
Undella paradoxa: Cleve, 1900b
Cyttarocylis? (Xystonella) paradoxa: Brandt, 1906-1907
Xystonellopsis paradoxa: Jörgensen, 1924; Kofoid and Campbell, 1929; Balech, 1959; Souto, 1979
Xystonellopsis conicacauda: Kofoid and Campbell, 1939