Protentelloides primitivus


Classification: pf_cenozoic -> Globigerinidae -> Protentelloides -> Protentelloides primitivus
Sister taxa: P. dalhousiei, P. primitivus, P. sp.,

Taxonomy

Citation: Protentelloides primitivus Zhang and Scott, 1995
Rank: species
Basionym: Protentelloides primitiva Zhang and Scott, 1995
Synonyms:
Taxonomic discussion:

We change the species name to its masculine form to accord with Article 31.2 of the ICZN (“a species-group name, if it is or ends in a Latin or latinized adjective or participle in the nominative singular, must agree in gender with the generic name with which it is at any time combined”). Thus Protentelloides primitiva becomes P. primitivus. Protentelloides primitivus has a similar wall texture to the proposed ancestor G. atlanticus. Pore density is much lower than in G. variabilis and G. stainforthi. Longer ranging than its descendant, it exhibits a wide range of morphological variability in both the number of final whorl chambers and the nature of coiling. The morphologies assigned to this morphospecies clearly shows overlap with P. dalhousiei. We choose to separate the two due to the slightly higher stratigraphic appearance of forms that consistently have near-planispirally coiled and an elaborate aperture system. There are no published occurrences of this taxon since its description in 1995. In our recent studies of Oligocene material we find it in ODP Site 667, which is near to DSDP Site 366, but not outside of the eastern equatorial Atlantic Ocean where these two sites lie. [Coxall & Spezzaferri 2018]

Catalog entries: Protentelloides primitiva

Type images:

Distinguishing features:

Large, laterally compressed, low trochospiral/pseudoplanispiral, 4-6 chambers in the final whorl, final chamber reduced and bulla-like, sutures depressed, straight to curved; aperture an elongated slit at the base of the bulla-like final chamber.

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:

Large and distinctive, Protentelloides primitivus differs from Globorotaloides atlanticus n. sp., from which it evolved, by the more irregularly shaped and inflated chambers, the deeply depressed sutures, more lobate peripheral outline and the distinctly equatorial position of the terminal bulla-like chamber. It differs from Globorotaloides hexagonus (Natland) in possession of a bulla and the equatorial-umbilical aperture. It is distinguished from Protentelloides dalhousiei in the slightly more involute coiling, the transitional position of the primary aperture, which is umbilical to extraumbilical, and in lacking accessory apertures. It also typically has fewer chambers in the final whorl than P. dalhousiei. It differs from Protentella prolixa Lipps (1964) in the lower stratigraphic range, possession of a bulla-like final chamber and the coarse cancellate wall. The tendency towards elongation of the final chamber represents another example of evolutionary convergence on a digitate form. [Coxall & Spezzaferri 2018]


Wall type: Normal perforate, coarsely cancellate, sacculifer-type to ruber/sacculifer-type. Possibly spinose. Pore density: ~40 pores/50 μm2.

Test morphology: Large, lobate to strongly lobate, laterally compressed, low trochospiral/pseudoplanispiral, 2 whorls, axial periphery rounded; internal whorl 4-5 rounded chambers, well-defined and clearly visible in spiral view, 4-6 chambers in the final whorl, increasing rapidly in size, final chamber reduced and bulla-like, variably cantilevered slightly towards the umbilical or spiral side; spiral sutures depressed, straight to curved; umbilical sutures radial, depressed, straight, becoming curved, small umbilicus; primary aperture an elongated slit at the base of the bulla-like final chamber extending from the equatorial margin to the umbilicus, bordered by an imperforate rim or well-defined lip. [Coxall & Spezzaferri 2018]

Size: The maximum diameter of the holotype as figured by Zhang and Scott (1995) is 0.52 mm. [Coxall & Spezzaferri 2018]

Character matrix

test outline:Lobatechamber arrangement:Pseudoplanispiraledge view:Equally biconvexaperture:Extraumbilical-peripheral
sp chamber shape:Globularcoiling axis:Very lowperiphery:N/Aaperture border:Bulla
umb chbr shape:Globularumbilicus:Wideperiph margin shape:Broadly roundedaccessory apertures:Intralaminal
spiral sutures:Weakly depressedumb depth:Shallowwall texture:Cancellateshell porosity:Finely Perforate: 1-2.5µm
umbilical or test sutures:Weakly depressedfinal-whorl chambers:4.0-6.0 N.B. These characters are used for advanced search. N/A - not applicable

Biogeography and Palaeobiology


Geographic distribution: So far found only in the eastern equatorial Atlantic Ocean. [Coxall & Spezzaferri 2018]

Isotope paleobiology: No data available. [Coxall & Spezzaferri 2018]

Phylogenetic relations: Protentelloides primitivus evolved from Globorotaloides atlanticus n. sp. by compression and radial spreading of the test and migration of the bulla-like chamber from the umbilicus to the equatorial periphery. It gave rise to Protentelloides dalhousiei by development of the equatorially centered bulla. [Coxall & Spezzaferri 2018]

Most likely ancestor: Globorotaloides atlanticus - at confidence level 3 (out of 5). Data source: Coxall & Spezzaferri 2018 f4.1.
Likely descendants: Protentelloides dalhousiei;

Biostratigraphic distribution

Geological Range:
Notes: Zhang and Scott (1995) report a short range for Protentelloides primitivus (~1.3 myr range), restricted to upper Oligocene Zone O7 (upper P22) (Spezzaferri, 1994; Zhang and Scott, 1995). Our recent studies based on ODP Site 667 material suggest this range can be extended into the early Miocene (Zone M1) (Fig. 4.1). [Coxall & Spezzaferri 2018]
Last occurrence (top): in mid part of M1b subzone (50% up, 21.8Ma, in Aquitanian stage). Data source: Coxall & Spezzaferri 2018 f4.1
First occurrence (base): near base of O7 zone (10% up, 25Ma, in Chattian stage). Data source: Coxall & Spezzaferri 2018 f4.1

Plot of occurrence data:

Primary source for this page: Coxall & Spezzaferri 2018 - Olig Atlas chap.4 p.119

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(Chap 4): 79-124. gs

Lipps, J. H. (1964). Miocene planktonic foraminifera from Newport Bay, California. Tulane Studies in Geology and Paleontology. 2: 109-133. 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

Zhang, J. & Scott, D. B. (1995). New planktonic foraminiferal genus and species from the upper Oligocene, DSDP Hole 366A, Leg 41. Micropaieontology. 41(1): 77-83. gs


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Protentelloides primitivus compiled by the pforams@mikrotax project team viewed: 12-11-2019

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