Lithostrobus borealis Kozlova and Vishnevskaya, 2012

Vishnevskaya, Valentina S. & Kozlova, Genrietta E., 2012, Volgian and Santonian-Campanian radiolarian events of the Russian Arctic and Pacific Rim, Acta Palaeontologica Polonica 57 (4), pp. 773-790 : 786

Lithostrobus borealis Kozlova and Vishnevskaya sp. nov.

Fig. 7H–J .

Etymology: With reference to the Boreal Realm.

Holotype: GIN N K22−1−57 (see Fig. 7J ).

Type locality: Borehole 22, Ust−Manja, western Siberia, Russia.

Type horizon: Lower Campanian, Upper Cretaceous.

Diagnosis.—Low conical domed multisegmented Lithostrobus with large perforate spheroidal cephalis bears high conical apical horn.

Description.—Test subconical, multisegmented with 3–4 post−abdominal segments becoming cylindrical distally. Cephalis subspherical, poreless, bearing a very strong short apical horn with two grooves. Thorax bears two lateral spines. Post−abdominal segments slightly increasing in width, but constant in height. All segments visibly separated. Test wall thick with transverse rows of polygonal pore frames; four rows per segment.

Measurements (in µm).—Total height 200–250, maximum width 140–150, height of cephalis and thorax together 60–80.

Remarks.—Differing from congeners in having of lateral spines, an apical horn with two grooves, but not circular in cross−section and four rows of pores per segment.

Geographic and stratigraphic range.—Lower Campanian; Western Siberian Basin, Russia.

Figures

Fig. 7. Scanning electron micrographs of Late Cretaceous (Early Campanian) radiolarians from siliceous rocks of the Russian Arctic Margin (western Siberia, borehole 22, Ust−Manja, sample 57), except for D which is from the Volga Basin, Uljanovsk region, Shilovka section, sample 7−1. A–C. Spongurus arcticus Kozlova and Vishnevskaya sp. nov. A. Holotype, GIN N K22−2−57. B. GIN N K22−2a−57. C. GIN N K22−2b−57. D–F. Prunobrachium articulatum (Lipman, 1952). D. GIN N K22−15a−57. E. GIN N K22−15b−57. F. GIN N K22−15c−57. G, K–N. Lithostrobus ex gr. rostovzevi Lipman, 1960. G. GIN N K22−1a−57/1.K. GIN N K22−1b−57/1. L. GIN N K22−1c−57/2. M. GIN N K22−1c−57. N. GIN N K22−1d−57. H–J. Lithostrobus borealis Kozlova and Vishnevskaya sp. nov. H. GIN N K22−1a−57. I. GIN N K22−1b−57. J. Holotype, GIN N K22−1−57. O. Lithostrobus longus Grigorieva, 1975; GIN N K22−11−57. P–R. Immersothorax marinae (Gorbovets, 1966). P. GIN N K22−12−57. Q. GIN N K22−12a−57. R. GIN N K22−12b−57. S. Amphipyndax stocki (Campbell and Clark, 1944), GIN N K22−13−57.