Globigerinoidesella El-Naggar 1971

Genus Globigerinoidesella El-Naggar, 1971

Type species. Globigerina fistulosa Schubert, 1910.

Diagnosis. Type of wall: normal perforate, spinose, cancellate ‘ sacculifer -type’ wall texture, though the ‘ sacculifer -type’ wall texture is commonly obscured by secondary, ‘gametogenic’ calcite, heterogeneously distributed around the test, and particularly concentrated on the distal ends of protuberances. Test morphology: trochospiral, typically four chambers in the final whorl. Adult chambers increasing rapidly in size in the final whorl, initially globular and inflated, with final chambers becoming broad and flattened, possessing one or multiple digitate protuberances on individual chambers; sutures distinct, depressed, straight to slightly curved on both sides; open umbilicus, moderate to large; primary aperture typically umbilical, a broad, low to moderate arch with bordering lip or imperforate band; multiple supplementary apertures on spiral side, four to five visible, one per chamber, situated centrally at the sutures of the previous and third-previous chambers.

Note: diagnosis derives from the original genus concept of El-Naggar (1971), and also that of Banner (1982), Loeblich & Tappan (1987) and Spezzaferri et al. (2015, table 2).

Remarks. Globigerinoidesella El-Naggar, 1971 is distinguished from its ancestral genus Trilobatus Spezzaferri et al., 2015 and also Globigerinoides Cushman, 1927 by the development of one to numerous elongate (‘finger-like’) protuberances on the final one to five chambers. The test size is also generally greater than in Trilobatus or Globigerinoides. Other digitate genera differ in generally possessing only one extension per chamber or simply displaying whole-chamber elongation (without distinct protuberances).

Taxonomic history. El-Naggar (1971) proposed a revised classification for the superfamily Globigerinacea, in which radially elongated tests and/or chambers (i.e. ‘digitate’ forms) were considered a generic-level distinguishing character. Whilst other unrelated genera have been proposed and defined by being digitate, and thus contain exclusively digitate morphospecies, the genus Globigerinoides Cushman, 1927 traditionally encompassed both non-digitate morphospecies and the digitate Globigerinoides fistulosus (Schubert, 1910). Therefore, El-Naggar (1971) proposed the new genus Globigerinoidesella to separate fistulosus from the rest of the non-digitate Globigerinoides morphospecies. El-Naggar (1971) considered the new genus to be monospecific, containing solely G. fistulosa (Schubert, 1910).

Loeblich & Tappan (1994) recognized two further species of Globigerinoidesella. They transferred Belford’ s (1962) Globigerinoides quadrilobatus hystricosus to Globigerinoidesella (i.e. Globigerinoidesella hystricosa) as a “phylogenetically primitive” form of the more developed G. fistulosa. Their G. hystricosa is intermediate in morphology between G. fistulosa sensu stricto and T. sacculifer. They also named a new species, Globigerinoidesella bollii Loeblich & Tappan, 1994, based on the G. trilobus ‘A’ specimens of Bolli (1970) and an additional specimen from Tappan & Loeblich (1982). Their G. bollii form differed from G. hystricosa and G. fistulosa in possessing protuberances that projected in more than one plane (i.e. protruding in different directions). It was also an unfortunate species name selection, as a separate morphospecies had already been described as Globigerinoides bollii by Blow (1959).

Despite these three forms being proposed as species of Globigerinoidesella, El-Naggar’ s (1971) genus concept was not adhered to or accepted by many workers, though notable exceptions include Loeblich & Tappan (1987, 1994) and Hanagata & Nobuhara (2015). Essentially, subsequent publications did not accept Globigerinoidesella, continuing to refer to fistulosa as a species of Globigerinoides (i.e. Globigerinoides fistulosus). Most workers have also not accepted G. bollii and G. hystricosa as valid morphospecies either; specimens of equivalent morphology to Loeblich & Tappan’ s hystricosa and bollii concepts have generally been referred to as Globigerinoides fistulosus.

Spezzaferri et al. (2015) recently re-introduced Globigerinoidesella following El-Naggar’ s (1971) original concept and considered G. fistulosa the sole species. In this study, Globigerinoidesella is also recognized as a distinct genus following El-Naggar (1971) and Spezzaferri et al. (2015). It is here regarded as monospecific, as Globigerinoidesella bollii and Globigerinoidesella hystricosa are considered synonymous with G. fistulosa. Therefore, G. fistulosa is the type and only species.

Stratigraphical range. Middle Pliocene to early Pleistocene (Zone PL 3 [Atlantic]/ PL 5 [Pacific] to Zone PT1) (Wade et al. 2011).