PLOTNIKOVINA Mikhalevich, 1981

 

 

Type species: Gaudryina (Siphogaudryina) compressa Cushman, 1935 (*778), p. 3; OD.

Plotnikovina Mikhalevich, 1981 (*2110), p. 38.

Test elongate, with short early triserial and triangular stage and later biserial stage, with flattened to rhomboid section, chambers broad and low, lateral extremities distinctly produced at the chamber angle, an internal vertical partition then isolating a small distal cham­berlet, inner partitions of successive cham­bers approximately in vertical alignment, the tip of the chamberlets commonly broken to leave a small opening at the surface; sutures slightly depressed, straight, at a slight angle from the horizontal; wall finely agglutinated, extremely thin outer wall of the lateral pro­jections formed by the chamberlets, septa and vertical partitions canaliculate; aperture an interiomarginal arch. Holocene; Atlantic; Caribbean; S. Pacific.

 

Remarks: Both Plotnikovina and Siphoni­feroides were proposed in 1981 and both orig­inally included Textularia siphonifera Brady. Plotnikovina is here recognized in a more restricted sense, for species with flattened tests or with rhomboidal section in the bise­rial stage and with chamberlets restricted to the lateral angles. Siphoniferoides has rows of chamberlets on the chamber faces as well as the lateral edges and a nearly circular sec­tion in the biserial stage. Both genera were said to have lateral supplementary apertures, but both instead have lateral chamberlets cut off by vertical internal partitions; openings present in some specimens are due to second­ary breakage of the chamberlet tips, rather than apertures communicating with the cham­ber lumen. The canaliculate wall was not mentioned for either genus, but sectioned specimens of their type species clearly dem­onstrate this.