Sphaeroidinellopsis disjuncta ( Finlay, 1940 )

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 : 955-957

Sphaeroidinellopsis disjuncta ( Finlay, 1940)

1958 Non Sphaeroidinella cellata Subbotina Bykova : pl. 11, figs 4, 5.

1983 Sphaerodinellopsis disjuncta Kennett & Srinivasan : pl. 51, figs 3–5.

1994 Sphaeroidinellopsis disjuncta Spezzaferri : pl. 10, fig. 4a–c.

2020 Sphaerodinellopsis disjuncta Lam & Leckie : pl. 10, figs 11, 12.

Test morphology. Test compact and mid-trochospiral. In umbilical view, sutures are slightly incised and radial, umbilicus is narrow and deep with a low-arched umbilical aperture bordered by a thick rim. The final chamber tends to be smaller than or the same size as the penultimate chamber. In spiral view two whorls are visible for a total of six to seven chambers, separated by incised straight sutures. In edge view, the profile is rounded and slightly triangular due to the reduced size of the final chamber, chambers from previous whorls visible in the low trochospire. The last whorl presents 31 / 2 to 4 subglobular chambers slowly growing in size as added.

Range. Burdigalian Zone M4 ( Kennett & Srinivasan 1983) to Tortonian Zone M13 ( Kennett & Srinivasan 1983). The extinction of this taxon is reported in Zone N 17 in Bolli & Saunders (1981), and in Zone N 11 in Kennett & Srinivasan (1983). The latest specimens reported here, in this study, are from Zone M10 (= Zone N13).

Remarks. Sphaeroidinellopsis disjuncta can be distinguished from S. kochi by having only four chambers in the final whorl and lacking the peculiar elongation in the final or penultimate chamber. Sphaeroidinellopsis disjuncta can be distinguished from S. seminulina in having 31 / 2 to 4 chambers in the ultimate whorl instead of three. This taxon also has a more open umbilicus than S. seminulina and a wider, higher aperture compared with the slit-like aperture characterizing S. seminulina sensu Schwager 1866 . Sphaeroidinellopsis disjuncta differs from Globoturborotalita woodi by showing a lower aperture bordered with a rim, and by the usually smaller jutting final chamber. The wall shows wider pores and frequently it is covered totally or partially by a shiny cortex. It is distinguished from G. druryi due to the less pronounced apertural rim and the coarser wall texture with cortex development, a feature totally absent in Globoturborotalita .