Original Description Test.- A very low trochospire with a flat spiral side and a convex umbilical side. Primary aperture umbilical. Umbilicus about ⅓ of the maximum diameter. Umbilical system composed of portici bordering the succcssive apertures, leaving proximal accessory apertures, and sometimes composed of tegilla towards the end of the whorl. Chamber profile with one or two moderately developed keels, the keel on the umbiilical side generally less developed or reduced to a row of pustules parallel to the keel situated on the spiral side, or absent. Chamber surface pustulose on the umbilical side, except sometimes towards the end of the last whorl; slightly pustulose on the spiral side; initial chumbers typically globular on the spiral side. Sutures depressed, more or less radial on tbe umbilical side; curved and variably raised on the spiral side. Peripheral outline subcircular, slightly lobate. Size: Etymology: Extra details from original publication Remarks -The combined presence of one or two keels portici and depressed sutures on the umbilical side distinguished Gansserina from all other trochospiral genera (except Helvetoglobotruncana).
Gansserina differs from:
Globotruncana in posessing one or two moderateiy developed keels, an umbilical system composed generally of portici, depressed sutures on the umbilical side, and distinctly globular initial chambers on the spiral stde. The new genus Gansserina is separared from Globotruncana owtng to its phylogenetic links. It evolves probably from an Archaeoglobigerina ancestor.
Helvetoglobotruncana in its phylogenetic ongin: Gansserina probably evolved from double-keeled fonns whereas Helvetoglobotruncana descends from Whiteinella; moreover stratigraphically the two genera are separated by a time-interval of several million years.
Globotruncanita in having a pustulose surface on the chambers at the umbilical side; in the absence of adumbilical and sutural ridges.
Dicarinella in its umbiilcal primary aperture.
Stratigraphic distribution. - From about the middle of the falsostuarti Zone through the mayaroensis Zone (Maastrichtian p.p.). Editors' Notes
Robaszynski, F., Caron, M., Gonzales Donoso, J. M., Wonders, A. A. H. & the European Working Group on Planktonic Foraminifera (1984). Atlas of Late Cretaceous globotruncanids. Revue de Micropaléontologie. 26(3-4): 145-305. gs
Gansserina compiled by the pforams@mikrotax project teamviewed: 6-12-2022