Diagnosis: Test triserial throughout or with an adult biserial stage; chambers with backward-oriented peripheral projections; aperture subterminal bearing a toothplate.

Description: Test with serial chamber arrangement, with a short triserial stage followed by a biserial one, approximately two times longer in the primitive species and triserial throughout in the adult one. Earlier chambers are globular, those in the adult stage of the evolved species subangular and with lateral projections. Sutures are deeply incised and distinct. Aperture is subcircular in shape and subterminal in position. A supplementary suture is present on the apertural face between the aperture and suture between the last-formed two chambers. Chamber surface is smooth. Test wall is calcitic, hyaline and nannoperforate.

Remarks.– Haigella is proposed to accommodate a distinct lineage that evolved from Praeplanctonia and is confined to upper Albian sediments. The life span of Haigella is of approximately 900,000 years according to the depth-age model for the upper Albian sediments at ODP Site 1050C (Huber in Petrizzo & Huber, 2006). This genus differs from Archaeoguembelitria nov. gen. by the presence of the chamber peripheral projections in the evolved species and the presence of the elongate biserial adult stage of the primitive one. Noteworthy, a supplementary suture on the apertural face is known also in Pyramidina Brotzen, 1948 of the Upper Cretaceous (Santonian)-Eocene. This genus exhibits substantial variability with respect to the position of the aperture, which is situated at the base of the last-formed chamber and becomes subterminal due to the symmetrical extensions of the test wall near the base of the aperture (Brotzen, 1948; Hofker,1957). Accordingly, Haigella and Pyramidina appear to have evolved separately and there is no phylogenetic relationship between them.

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