Helicosphaera alata de Kaenel & Boesiger in Boesiger et al., 2017
Boesiger, T. M., de Kaenel, E., Bergen, J. A., Browning, E., Blair, S. A. , 2017. Oligocene to Pleistocene taxonomy and stratigraphy of the genus Helicosphaera and other placolith taxa in the circum North Atlantic Basin. - Journal of Nannoplankton Research 37(2-3), 145-175.
Helicosphaera alata
de Kaenel & Boesiger in Boesiger et al., 2017
Early Miocene