Heliodiscus Haeckel, 1862

Dumitrica, Paulian, 2019, Cenozoic Spumellarian Radiolaria With Eccentric Microsphere, Acta Palaeontologica Romaniae 15 (1), pp. 39-60 : 52

Genus Heliodiscus Haeckel, 1862

Type species. Heliodiscus phacodiscus Haeckel, 1862 .

Diagnosis. Cortical test lenticular and single with a double medullary shell with eccentric microsphere.

Remarks. Morphologically Heliodiscus resembles very well the Paleogene Phacodiscidae , as for example Astrophacus Haeckel, 1881 , Periphaena Ehrenberg, 1873 , etc., from which it differs in having the double medullary shell with eccentric microsphere. This resemblance is probably the result of a horizontal gene transfer between a phacodiscid species and a species of Excentrodiscus , genus frequent in the Paleogene and later. It could be also the result of a convergence but I do not see how, all radiolarians being planktonic organisms.

Range. Miocene to Recent. It seems that this genus is not present in the Paleogene because no lenticular morphospecies with eccentric microsphere have been illustrated in any Paleogene species (Sanfilippo & Riedel, 1973; Funakawa et al., 2006; Kamikuri, 2015, and others).