Catalog - Globigerinoides rublobatus

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Globigerinoides rublobatus

Citation: Globigerinoides rublobatus Latas et al. 2023

Type specimens: Holotype (Figs. 1b, 4.1, 5.1 and 12) is curated at the Natural History Museum (NHM), London, United Kingdom (PF 75381)

Type sample (& lithostrat): IODP exp 363 U1483A/9H/2/50–52 cm

Type age (chronostrat): Pleistocene (Planktonic Foraminifera Subzone PT1a).

Type locality: Scott Plateau, E Indian Ocean

Type repository: London; Natural History Museum

Diagnosis. Large test with distinctly flattened ultimate and penultimate chambers. Primary aperture elongated, low-arched and positioned over the single suture, which separates the penultimate and antepenultimate chamber. The morphospecies occurs in two pigmentation variants (chromotypes) represented by pinkand white-coloured forms.

Description. The test is large, compact and tightly coiled in a trochospiral manner, giving it a globular to subglobular overall morphology. The outline in the equatorial view ranges in shape from subquadrate to subcircular. The final whorl consists of three chambers, gradually increasing in size as added, each progressively more radially compressed than the previous one. The umbilicus is narrow, and sutures are slightly curved, deeply incised and well defined. The primary aperture is umbilical, elongated and low-arched with a thin lip. Usually, it is positioned centrally over the suture separating penultimate and antepenultimate chambers, but in some cases it is off-centre, which tends to be more pronounced in the largest specimens of the white variant. Several supplementary apertures are located at sutural junctions of the spiral side. The test is spinose with the surface perforated and a cancellate wall texture. Globigerinoides rublobatus n. sp. occurs in two pigmentation variants, represented by pink and white forms. Apart from the obvious difference in colouration, some other morphological differences can be observed between the variants. White forms are generally around 50% larger than their pink counterparts; the mean area size value for the former is 362701μm² as opposed to 227417μm² in the case of the latter (Fig. 9). Qualitative observations of broken specimens suggest that their tests may also have thicker walls, with well-developed gametogenic calcite crust in some of the largest specimens (Figs. 4.13–4.15, 15.2–15.4 and 5.13– 5.15), which Hemleben et al. (2018) define as “conglobatus-type” wall texture. Accessory apertures on the spiral side of the white specimens are typically narrower and more elongated than those in pink specimens, in which they are more rounded and widely open. We regard these minor morphological differences as representing variation within a single morphospecies.

The holotype has a maximum diameter of 685μm, which falls within the typical size range for an adult form of the pink-pigmented variant. White-coloured forms of this morphospecies are on average ∼50% larger, with some extremely large specimens reaching almost 1000 μm in diameter.

The species name rublobatus reflects the reddish pigmenta- tion seen in some specimens (ruber is Latin for “red”) and the lobate outline; it is also a contraction of two other Globigeri- noides species names, ruber and conglobatus, to reflect the mosaic morphology of the newly erected species. We thank IODP Expedition 363 scientist Kelly Gibson for the suggestion.

? Globigerinoides gomitulus (Seguenza) – Kaneps, 1973, p. 734 (no figures).
? Globigerinoides gomitulus (Seguenza) – (plesiotype) – Saito, Thompson and Breger, 1981 p. 57, pl. 14, fig. 2a– d.
Globigerinoides gomitulus (Seguenza) pink-coloured variety – Beiersdorf, Bickert, Cepek, Fenner, Petersen, Schönfeld, Weiss and Won, 1995, p. 48, pl. 3, figs. 4–6.
Globigerinoides sp. cf. conglobatus (pink) – Rosenthal, Holbourn, Kulhanek, Aiello, Babila, Bayon, Beaufort, Bova, Chun, Dang, Drury, Dunkley Jones, Eichler, Fernando, Gibson, Hatfield, Johnson, Kumagai, Li, Linsley, Meinicke, Mountain, Opdyke, Pearson, Poole, Ravelo, Sagawa, Schmitt, Wurtzel, Xu, Yamamoto, and Zhang, 2018b, p. 18, fig. 17.
Not Globigerinoides gomitulus Seguenza, 1880, pl. XVII, fig. 16 (Pliocene section in Riace, Calabria region, southern Italy) (inadequate illustration; no type specimen designated; neotype designated by Mistretta 1962, p. 202, fig. 1 (Globigerinoides elongatus) subsequently lost from the micropalaeontological collection of the Institute of Geology and Paleontology at the University of Palermo)

5.3 Holotype specimen of Globigerinoides rublobatus n. sp. (Figs. 1b, 4.1, 5.1 and 12) is curated at the Natural History Museum (NHM), London, United Kingdom (PF 75381). Before deposition in the museum collection, holotype was CT-scanned to produce its detailed digital 3D model, allowing for extraction of comprehensive morphological data and providing an efficient method for future data curation of the newly designated species. Regrettably, the original pink pigmentation of the holotype specimen was accidentally removed in the scanning process, most likely due to prolonged exposure to X-ray radiation, resulting in the classic white colouration of a calcite foraminifera test. Fortunately, the true nature of the holotype pink pigmentation is preserved in the form of photographic evidence presented in this paper (Figs. 1b, 4.1, 5.1 and 12).

5.4 Paratypes We have selected both pink and white specimens as paratypes, as we consider them to be variants within the same morphospecies. All 14 paratype specimens of Globigerinoides rublobatus n. sp. are curated at the Natural History Museum (NHM), London, United Kingdom. Figures 4.2, 5.2 and 13.1a–d – PF 75382; Figs. 4.3, 5.3 and 13.2a–d – PF 75383; Figs. 4.4, 5.4 and 13.3a–d – PF 75385; Figs. 4.5, 5.5 and 13.4a–d – PF 75385; Figs. 4.6, 5.6 and 13.5a–d – PF 75386; Figs. 4.7, 5.7 and 14.1a–d – PF 75387; Figs. 4.8, 5.8 and 14.2a–d – PF 75388; Figs. 4.9, 5.9 and 14.3a–d – PF 75389; Figs. 4.10, 5.10 and 14.4a– d – PF 75390; Figs. 4.11, 5.11 and 14.5a–d – PF 75391; Figs. 4.12, 5.12 and 15.1a–d – PF 75392; Figs. 4.13, 5.13 and 15.2a–d – PF 75393; Figs. 4.14, 5.14 and 15.3a–d – PF 75394; Figs. 4.15, 5.15 and 15.4a–d – PF 75395.

5.5 Material The collection of 15 type specimens representing the adult form of both pink and white variants of G. rublobatus n. sp. was selected from core samples recovered from IODP Sites U1482, U1483 and U1486. Morphometric study of G. rublobatus n. sp. was carried out on a series of 284 specimens picked from nine consecutive core samples from the IODP Site U1483 (Table 1).

5.6 Type locality & horizon. Morphospecies presence confirmed so far in the core samples from the eastern Indian Ocean (IODP Sites U1482 and U1483) and western Pacific Ocean (IODP Site U1486) (Fig. 2). 5.7 Age The holotype specimen and series of paratypes are all of Pleistocene age (Planktonic Foraminifera Subzone PT1a). 5.10 Distribution Morphospecies presence confirmed so far in the core samples from the eastern Indian Ocean (IODP Sites U1482 and U1483) and western Pacific Ocean (IODP Site U1486) (Fig. 2).

5.11 Remarks Globigerinoides rublobatus n. sp. differs from Globigerinoides ruber (d’Orbigny, 1839) by having on average a much larger test (Fig. 9) with distinctively flattened chambers (especially ultimate and penultimate chambers) and by possessing a low-arched and elongated primary aperture, which can in some cases be slightly offset from the centre. It can be distinguished from Globigerinoides conglobatus (Brady, 1879) by having only 3 chambers in the final whorl, with a primary aperture positioned over the single suture that separates the penultimate and antepenultimate chamber, and by also occurring as a pink variant in addition to regular white forms. Unexpected holotype specimen bleaching during laboratory analyses indicates that pigment is still chemically active and could be potentially extracted from fossil specimens, which provides the opportunity for future studies of its nature and chemical composition.

5.12 Phylogenetic relationship Our study suggests that G. rublobatus n. sp. shares more similarities with G. conglobatus than with G. ruber, which is supported by combined evidence from morphological observations (e.g. large test, characteristic flattening of the final chamber and shape of the primary aperture) and collected morphometric data recording the size and shape of the test (Figs. 7–11). It is likely that G. rublobatus n. sp. evolved from G. conglobatus, but the transition has not been observed.

References:

Hemleben, C., Olsson, R. K., Premec Fucek, V. & Hernitz Kucenjak, M. (2018). Wall textures of normal perforate Oligocene planktonic foraminifera. In, Wade, B. S., Olsson, R. K., Pearson, P. N., Huber, B. T. & Berggren, W. A. (eds) Atlas of Oligocene Planktonic Foraminifera. Cushman Foundation for Foraminiferal Research, Special Publication . 46(Chap 3): 55-78. gs

Latas, M., Pearson, P. N., Poole, C. R., Fabbrini, A. & Wade, B. S (2023). Globigerinoides rublobatus – a new species of Pleistocene planktonic foraminifera . Journal of Micropalaeontology. 42: 57-81. gs O

Seguenza, G. (1880). Le foramazioni terziarie nella provincia di Reggio (Calabria),. Rendiconti Atti della Reale Accadamia dei Lincei. (6): 1-466. gs O

CATALOG OF ORIGINAL DESCRIPTIONS: Globigerinoides rublobatus Latas et al. 2023

Globigerinoides rublobatus

References:

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