Cenozoic Spumellarian Radiolaria With Eccentric Microsphere Author Dumitrica, Paulian text Acta Palaeontologica Romaniae 2019 2019-04-25 15 1 39 60 http://dx.doi.org/10.35463/j.apr.2019.01.04 journal article 10.35463/j.apr.2019.01.04 1842-371x 10520604 57C54916-CC13-4BA1-BA82-2A99A822D9D1 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).