Trilobatus quadrilobatus

description

1846 Globigerina quadrilobata d’ Orbigny: 164, pl. 9, figs 7 – 10. 1960 Globigerinoides quadrilobatus (d’ Orbigny); Banner & Blow: 17, pl. 4, fig. 3 a, b. 1983 Globigerinoides quadrilobatus (d’ Orbigny); Kennett & Srinivasan: 66, pl. 14, figs 1 – 3. 2003 Globigerinoides quadrilobatus (d’ Orbigny); Li, McGowran, & Brunner: 20, pl. P 6, figs 16, 17. 2012 Globigerinoides quadrilobatus (d’ Orbigny); Rögl: 188, pl. 2, figs 3, 4. 2013 Globigerinoides quadrilobatus (d’ Orbigny); Fox & Wade: 400, fig. 11.4. 2018 Trilobatus quadrilobatus (d’ Orbigny); Spezzaferri, Olsson, & Hemleben: 296 – 298, pl. 9.12, figs 1 – 20. Description. Type of wall: spinose, coarsely cancellate sacculifer - type wall texture. Test morphology: low trochospire, 3.5 to typically 4 globose, near-spherical chambers in the final whorl increasing slowly-moderately in size as added; sutures distinct, depressed, straight to slightly curved on both sides; umbilicus narrow; primary aperture extraumbilical-umbilical or umbilical, generally a low arch, often broad, typically no bordering rim; prominent supplementary apertures on spiral side, one per chamber, placed at the sutures of the preceding chamber and third-previous ch

Systematic taxonomy of the Trilobatus sacculifer plexus and descendant Globigerinoidesella fistulosa (planktonic foraminifera)

discussion

Remarks. Trilobatus quadrilobatus is distinguished from T. sacculifer in possessing a globular, near-spherical final chamber as opposed to a sac-like final chamber. Trilobatus sacculifer also possesses a distinct lip bordering the primary aperture, whilst T. quadrilobatus has no lip (though gradation between the two morphospecies occurs). Trilobatus quadrilobatus also shows morphological gradation with T. immaturus, but differs in having a lower chamber expansion rate and a more open umbilicus and typically having four spherical chambers in the final whorl. Trilobatus quadrilobatus has a broad resemblance to the short-ranging Oligo – Miocene morphospecies Trilobatus primordius (Blow & Banner 1962), but T. primordius only possesses one supplementary aperture on the spiral side and may not have a strictly sacculifer - type wall texture (the original description of T. primordius by Blow & Banner [1962, p. 115] states it has a “ markedly cancellate and punctate ” surface).

Systematic taxonomy of the Trilobatus sacculifer plexus and descendant Globigerinoidesella fistulosa (planktonic foraminifera)

materials_examined

Type locality. Nussdorf (= Nubdorf), Rara, Vienna Basin, Austria. Taxonomic history. d’ Orbigny (1846) described Globigerina quadrilobata from the Vienna Basin, Austria. He noted that the final four chambers were of almost equal size, increasing only marginally in size as added (d’ Orbigny 1846, p. 164). The original illustrations (d’ Orbigny 1846, pl. 9, figs 7 – 10; also reproduced numerous times, e. g. in Papp & Schmid 1985, pl. 54, fig. 7 and Bolli & Saunders 1985, p. 193, fig. 20.18) clearly show this low chamber expansion rate in the final whorl. No supplementary apertures are visible in the illustrations or are recorded in the original description, although, as also discussed by Banner & Blow (1965), this omission does not preclude the possibility of supplementary apertures having been present on the specimen. Unfortunately, the original vial labelled ‘ G. quadrilobata ’, examined by Banner & Blow (1960) and later Papp & Schmid (1985), did not contain d’ Orbigny’ s (1846) figured specimen, but it was found to contain a suite of 11 specimens of at least three different morphospecies. According to Banner & Blow (1960), only five specimens were of the quadrilobate form. Despite

Systematic taxonomy of the Trilobatus sacculifer plexus and descendant Globigerinoidesella fistulosa (planktonic foraminifera)