Cenozoic Spumellarian Radiolaria With Eccentric Microsphere Author Dumitrica, Paulian Institute of Earth Sciences, Université de Lausanne, Géopolis, 1015 Lausanne, Switzerland; mailing address: Dennigkofenweg 33, 3073 Gümligen, Switzerland Paulian.Dumitrica@unil.ch 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 Homunculodiscus nov. gen. Type species . Stylodictya tainemplekta Caulet, 1991 . Diagnosis . Test circular disc-shaped and very thin consisting of two parallel porous plates interconnected by short bars perpendicular to plates, most of them interconnected also in the equatorial plane of the disc by bars forming characteristic curved structures well visible in transmitted light. Pores circular, disposed commonly in radial rows and increasing slightly in diameter from the centre to periphery. Microsphere without primary radial spines. Deuteroconcha tending to reduce the lobes from three to one. Remarks . This new genus differs from Stylodictya Ehrenberg , to which the type species was originally assigned ( Caulet, 1991 ), by having an eccentric microsphere, a diploconchal initial structure, no primary radial spines, and a different shell structure. The diploconchal structure, and especially the deuteroconcha of this genus, shows a rapid and interesting evolution. In the earliest species ( Homunculodiscus nascens nov. sp. , Fig. 1 , very early Paleocene) this chamber is very small and divided into 3 very small globular chambers. At younger levels of the early Paleocene ( Figs. 2 and 3 ) this chamber is better individualized and the number of chambers starts reducing. At last, in the middle Eocene species Homunculodiscus tainemplecta (Caulet) ( Fig. 3g and Fig. 4 ) this chamber is very well individualized, is larger than the microsphere and together with it makes a well characteristic body that suggests a homunculus, and that is well separated from the rest of the shell by a more or less disturbed oval circle. Etymology . From the Latin homunculus – small man and discus – disc, due to the shape of the central shell of the type species. Masculine gender. Range and occurrence . Lowermost Paleocene to lowermost Oligocene.