Sphaeroidinellopsis kochi ( Caudri, 1934 )

Fabbrini, Alessio, Zaminga, Ilaria, Ezard, Thomas H. G. & Wade, Bridget S., 2021, Systematic taxonomy of middle Miocene Sphaeroidinellopsis (planktonic foraminifera), Journal of Systematic Palaeontology 19 (13), pp. 953-968 : 957-958

Sphaeroidinellopsis kochi ( Caudri, 1934)

1923 Globigerina sp. Koch: 351, fig. 8a, b.

1934 Globigerina kochi Caudri : fig. 8a, b.

1945 Globigerina grimsdalei ( Keijzer, 1945) : taf. 33a, c.

1959 Sphaeroidinella seminulina kochi (Caudri) ; Blow: pl. 12, figs 78, 79.

1960 Sphaereoidinellopsis seminulina Banner & Blow : pl. 7, fig. 2.

1983 Sphaeroidinellopsis kochi (Caudri) Kennett & Srinivasan : pl. 52, figs 1–3.

1985 Sphaeroidinellopsis multiloba (LeRoy, 1944) ; Bolli & Saunders: pl. 38, figs 15, 16.

1993 Sphaeroidinellopsis kochi Chaisson & Leckie : pl. 10, figs 10, 14, 18.

2013 Sphaeroidinellopsis disjuncta Fox & Wade : fig. 17.8.

2014 Sphaeroidinellopsis disjuncta Sanchez, Berggren & Liska : pl. 3, figs 1–8.

2020 Sphaeroidinellopsis kochi Lam & Leckie : pl. 11, figs 1–4, 6–7.

Test morphology. Low trochospiral and slightly lobate profile. Four to six chambers in the final whorl, often characterized by a radial elongation of the final chamber. This feature might be observable both in kummerforms and normalforms. In umbilical view, four to six chambers are present, and the umbilicus is open, with a low, arched umbilical-extraumbilical aperture. The aperture always presents a thick rim. The final chamber is commonly sac-like and it can be strongly elongated and tilted towards the previous chambers. In spiral view, up to 12 chambers are visible, arranged in three whorls, sutures radial and deeply incised. In edge view, spiral side flat with a low trochospire, with the final sac-like chamber often tilted towards the umbilicus or more rarely towards the spire.

Range. Langhian ( Kennett & Srinivasan 1983)–Zanclean Zone PL 1 ( Wade et al. 2011).

Remarks. This taxon is easily distinguishable from Sphaereoidinellopsis disjuncta due to the elongation of the last chamber, or of the final two chambers. It differs from S. seminulina in having four to six chambers in last whorl, having the final chamber elongated and sac-like, often tilted, and presenting a wider umbilicus and a looser coiling. It can be distinguished from Trilobatus sacculifer by the absence of supplementary apertures on the spiral side and the potential development of a partial or full glassy cortex. Sphaeroidinellopsis kochi differs from Globoturborotalita druryi in its higher number of chambers in the final whorl, the elongation in the final chambers, a looser coiling mode and the potential development of the cortex. This species is also the only one within Sphaeroidinellopsis bearing more than four chambers. A full investigation of the probable synonymies of S. multiloba and similar taxa with S. kochi will be conducted by the Neogene Planktonic Foraminifera Working Group. Also questionable is the synonymy proposed in Bolli & Saunders (1981) with S. hancocki Bandy 1975 , a species described from the Pliocene of the eastern Indian Ocean and presenting some features not compatible with S. kochi as originally described.