FUSULINIDA Fursenko, 1958

Order FUSULINIDA Fursenko, 1958 View in CoL

Test lenticular, subglobular or fusiform, generally planispirally coiled. Coiling uniform or presence of juvenaria. Terminal uncoilings are rare. Aperture generally basal, central, simple, occasionally replaced by foramina or cuniculi. No cribrate or complex apertures. Endoskeletal secondary deposits represented by pseudchomata, chomata and parachomata; septula of first and second order, axial fillings, and phrenotheceae. Proloculi spherical and small to renifom and larger. Septal folding planar to strongly folded in the whole chamber. Microstuctures and microtextures of wall are considered here as a suborder and superfamily criterion: Wall simple under the form of a dark tectum ( Ozawainelloidea ) or a neosparitized tectum ( Staffelloidea ; bilayered with tectum and protheca ( Schubertelloidea ), multilayered with tectum, tectoria and diaphanotheca ( Fusulinoidea ); coarsely keriothecal ( Schwagerinoidea ); or finely keriothecal ( Neoschwagerinoidea ). Aperture terminal, simple, basal, rarely areal or reduced to cuniculi and/or septal pores.

Remark. Some evolutionary trends are shared by these superfamilies: (1) they are successively: planispiral lenticular, spherical, inflated fusiform, elongate fusiform or cigar-shaped, rarely uncoiled (two genera of Schwagerinoidea and two genera of Schubertelloidea ); (2) Staffelloidea , Ozawainelloidea , and Schubertelloidea are small to medium-sized; Fusulinoidea are large; Schwagerinoidea and Neoschwagerinoidea are large to giant. (3) The gigantic taxa adopt two types of mechanical re-inforcements of the tests: either a very strong septal folding (advanced Fusulinoidea and Schwagerinoidea ), or a more developed endoskeleton with septula and parachomata whereas the septa remain plane ( Neoschwagerinoidea ).