Homunculodiscus nascens, Dumitrica, 2019

Dumitrica, Paulian, 2019, Cenozoic Spumellarian Radiolaria With Eccentric Microsphere, Acta Palaeontologica Romaniae 15 (1), pp. 39-60 : 41

Homunculodiscus nascens nov. sp.

Figures 1 a-g

Description. Shell disc-shaped, circular or subcircular, very thin and with irregular margins. Margins with very small and thin spines. Shell consists of two perforate cortical plates interconnected by irregularly or radially arranged transversal bars that look like black points in transmitted light giving the shell a punctiform ornamentation. Transversal bars free or interconnected by equatorial bars arranged in short arches of different directions. Pores circular, most of them radially distributed. Diploconchal structure consisting of a very small eccentric microsphere and a small crescent shaped deuteroconcha divided into two or three chambers much smaller than the microsphere. Microsphere with circular pores smaller than those of the disc.

Material. Eight photographed specimens of which only 3 mounted on fig. 1.

Holotype. Figure 1a, 1b ., coll. MGL 103554 .

Dimensions. Diameter of microsphere 13 μm, of shell 173-249 μm.

Etymology. From the Latin word nascens – that is giving birth, because it is the first species that started the lineage of this genus.

Remarks. This is the oldest and most frequent species of this genus in the studied samples. It differs from the younger species of the genus in having the deuteroconcha rather disorderly formed and rather small.

Range and occurrence. Lowermost Paleocene, DSDP 21- 208-32 CC and 31 CC, north Lord Howe Rise, southwestern Pacific.

Figures

Fig. 1 a-g. Homunculodiscus nascens nov. gen., nov. sp. a-b – holotype; b, detail, double magnification of central part of fig. a; c-e – paratype 1, d-e detail of central part, double magnification of fig. c, focused at two levels. f-g. paratype 2; g – double magnification of central part of fig. f. a, c, DSDP 21-208-32CC, early Paleocene. f, DSDP-21-208-31CC, early Paleocene. Scale bars for a, b, c, f = 50 μm.