Quasicrolanium Kozlova and Vishnevskaya

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 : 788-789

Genus Quasicrolanium Kozlova and Vishnevskaya nov.

Type species: Stichopilidium plaocephala Kozlova, 1976 , Kolguev Island , Borehole 140, depth 472–481 m, Upper Jurassic, Volgian Stage, upper substage .

Etymology: From Greek quasi, “as if”, in allusion to its close similarity to Crolanium .

Diagnosis.—Test multisegmented, trihedral−pyramidal in form, with three ribs extending from top of thorax (rib “D”), or of abdomen (ribs “L”) to distal portion. Cephalis hemispherical, with short conical spines “A”, “ V ” and 2, 1’; remaining segments with concave wall as in Parvicingulidae ; last segment free of ribs may be circular in cross section and turn into a long tube. Abdomen and post−abdominal segments separated externally by concentric circumferential ridges, not circular, but crooked triangle−shaped. Test network regularly hexagonal with four to six transverse rows of small round pores at each segment.

Species included.— Quasicrolanium planocephala ( Kozlova, 1976) .

Remarks.—The new genus is closely related to Crolanium Pessagno, 1977 and Pseudocrolanium Jud, 1994 , having outer ribs in common. The distinguishing feature is the presence of longitudinal ribs on the entire test segments, with exception of the last one; segments and ribs, bearing net on the test wall, resemble to landing−net.

It is doubtful if this new genus can be attributed to the same family as Crolanium and Pseudocrolanium . Quasicrolanium gen. nov. differs from members of the Stichocapsidae by having concave, not convex, segments and transverse circumferential ridges at chamber boundaries. From parvicingulid genera it can be distinguished by possessing three longitudinal ribs and fewer pores at each segment: 4–6 rows (predominantly 6).

Geographic and stratigraphic range.—Late Volgian in height latitudes of Northern Hemisphere; Timan−Pechore Basin and eastern Ural Slope, Russia.