Globorotaloides atlanticus


Classification: pf_cenozoic -> Globigerinidae -> Globorotaloides -> Globorotaloides atlanticus
Sister taxa: G. atlanticus, G. stainforthi, G. eovariabilis, G. hexagonus, G. quadrocameratus, G. suteri, G. testarugosus, G. variabilis, G. sp.,

Taxonomy

Citation: Globorotaloides atlanticus Spezzaferri and Coxall, in Coxall & Spezzaferri 2018
Rank: species
Synonyms:
Taxonomic discussion:

Globorotaloides atlanticus forms part of the plexus of Oligocene bullate Globorotaloides. The most important diagnostic feature of this morphotype is the position of the bulla that extends from the umbilicus around to the equatorial margin. In this respect we view G. atlanticus as being transitional between G. stainforthi, where the bulla is umbilical, to Protentelloides spp., where the bulla forms on the equatorial margin. It is unclear whether or not Globorotaloides atlanticus and contemporaneous G. hexagonus and Protentelloides were spinose. The type material of G. atlanticus shows signs of dissolution and recrystallization, including contact dissolution around other biogenic sediment particles such as sponge spicules (linear impressions in Pl. 4.4, Figs. 1, 9 and 11). This obscures any evidence for or against spines. [Coxall & Spezzaferri 2018]

Catalog entries: Globorotaloides atlanticus;

Type images:

Distinguishing features:

Like G. stainforthi, but with an umbilical-to-equatorial bulla that extends around the peripheral margin, an equatorially directed primary aperture and more numerous chambers in the final whorl.

NB These concise distinguishing features statements are used in the tables of daughter-taxa to act as quick summaries of the differences between e.g. species of one genus.
They are being edited as the site is developed and comments on them are especially welcome.

Description


Diagnostic characters:

Globorotaloides atlanticus differs from Globorotaloides stainforthi, from which it evolved, in having a distinctive umbilical-to-equatorial bulla that extends around the peripheral margin, an equatorially directed primary aperture and more numerous chambers in the final whorl. The bulla in Globorotaloides stainforthi is more strictly umbilical. Globorotaloides atlanticus is distinguished from Protentelloides primitivus, to which it gave rise, by having straight sutures on the spiral side, compared with recurved or sigmoidal sutures in Protentelloides, more inflated chambers and a flattened umbilical-to-equatorial bulla. [Coxall & Spezzaferri 2018]


Wall type: Spinose (?). Normal perforate, coarsely cancellate, sacculifer-type wall texture, with a distinctly honeycomb appearance. Pore density: ~40 pores/50 μm2.

Test morphology: Test outline lobate, axial periphery rounded; 2-2½ whorls of inflated chambers arranged in a flattened globorotaliiform-trochospire; 11-14 chambers in adult tests, 5-7, more frequently 6 slightly compressed chambers in the final whorl, increasing moderately in size. Sutures depressed, radial on both sides, straight, slightly curved on umbilical side. Umbilicus moderately wide, covered by a bulla extending around equatorial margin and having a thickened lip or rim; 2-3 infralaminal apertures around the bulla spanning umbilical sutures, or at the edge of the bulla on the equatorial margin. Where the bulla has broken the primary aperture can be seen as an umbilical-extraumbilical arch at the base of the last chamber, surrounded by a lip. [Coxall & Spezzaferri 2018]

Size: Holotype maximum diameter 0.29 mm, breadth 0.24 mm, thickness 0.15 mm. [Coxall & Spezzaferri 2018]

Character matrix

test outline:Lobatechamber arrangement:Trochospiraledge view:Equally biconvexaperture:Umbilical-extraumbilical
sp chamber shape:Globularcoiling axis:Very lowperiphery:N/Aaperture border:Bulla
umb chbr shape:Globularumbilicus:Wideperiph margin shape:Moderately roundedaccessory apertures:Infralaminal
spiral sutures:Weakly depressedumb depth:Shallowwall texture:Cancellateshell porosity:Macroperforate: >2.5µm
umbilical or test sutures:Moderately depressedfinal-whorl chambers:5.0-7.0 N.B. These characters are used for advanced search. N/A - not applicable

Biogeography and Palaeobiology


Geographic distribution: Low latitude, equatorial. The best-described records are from the equatorial Atlantic Ocean (Spezzaferri, 1994), but it has also been observed in the equatorial Pacific (Quilty, 1976) and Indian Oceans (Spezzaferri, 1995). [Coxall & Spezzaferri 2018]

Isotope paleobiology: Relatively high δ18O and low δ13C compared to other species indicating a deep sub-thermocline habitat (Spezzaferri and Coxall, unpublished) and or life in cool, nutrient rich upwelled water, as has been suggested for Globorotaloides sp. from assemblage-based bioprovince analysis (Spezzaferri, 1995). [Coxall & Spezzaferri 2018]

Phylogenetic relations: Globorotaloides atlanticus evolved from Globorotaloides stainforthi by extension of the bulla towards the equatorial margin. It gave rise to Protentelloides primitivus, which is supported both by morphological similarities and similar pore densities between G. hexagonus and P. primitivus. [Coxall & Spezzaferri 2018]

Most likely ancestor: Globorotaloides stainforthi - at confidence level 3 (out of 5). Data source: Coxall & Spezzaferri 2018.
Likely descendants: Protentelloides primitivus;

Biostratigraphic distribution

Geological Range:
Notes: The range of G. atlanticus has been determined at equatorial Atlantic Ocean DSDP Site 354 and ODP Site 667 as upper Oligocene Zone O7 to lower Miocene Zone M3. This is supported by more sporadic occurrences at South Atlantic Ocean DSDP Site 526 and rare appearances at equatorial Indian Ocean Site 709. These limits are based on the biostratigraphies of Spezzaferri (1994) and new observations made during this study. Globorotaloides atlanticus appears to be most common in O7, where all the examples shown on Plate 4.4 are from. [Coxall & Spezzaferri 2018]
Last occurrence (top): within M3 zone (17.54-19.30Ma, top in Burdigalian stage). Data source: Coxall & Spezzaferri 2018
First occurrence (base): within O7 zone (22.96-25.21Ma, base in Chattian stage). Data source: Coxall & Spezzaferri 2018

Plot of occurrence data:

Primary source for this page: Coxall & Spezzaferri 2018 - Olig Atlas chap.4 p.93

References:

Coxall, H. K. & Spezzaferri, S. (2018). Taxonomy, biostratigraphy, and phylogeny of Oligocene Catapsydrax, Globorotaloides, and Protentelloides. 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: 79-125. gs

Natland, M. L. (1938). New Species of Foraminifera from off the West Coast of North America and from the Later Tertiary of the Los Angeles Basin. Bulletin of the Scripps Institute of Oceanography, Tech. Ser.. 4(5): 137-164. gs

Quilty, P. G. (1976). Planktonic foraminifera DSDP Leg 34, Nazca Plate. Initial Reports of the Deep Sea Drilling Project. 34: 629-703. gs

Spezzaferri, S. (1994). Planktonic foraminiferal biostratigraphy and taxonomy of the Oligocene and lower Miocene in the oceanic record. An overview. Palaeontographia Italica. 81: 1-187. gs

Spezzaferri, S. (1995). Planktonic foraminiferal paleoclimatic implications across the Oligocene-Miocene transition in the oceanic record (Atlantic, Indian, and South Pacific). Palaeogeography, Palaeoclimatology, Palaeoecology. 114: 43-74. gs


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Globorotaloides atlanticus compiled by the pforams@mikrotax project team viewed: 26-6-2019

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