Protentelloides dalhousiei

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


Citation: Protentelloides dalhousiei Zhang and Scott, 1995
Rank: species
Basionym: Protentelloides dalhousiei Zhang and Scott, 1995
Taxonomic discussion:

This species exhibits a very wide range of morphological variability in the shape of the final chamber or bulla and the structure and complexity of the aperture system. The test is superficially planispiral (pseudoplanispiral), however, unlike Eocene Hantkenina and Pseudohastigerina that are truly planispiral (biumbilicate), umbilical and spiral sides are recognizable due to asymmetry of the apertural lip on the two sides, which rotates slightly into the umbilicus. Protentelloides dalhousiei has a similar wall texture to G. atlanticus. Pore density in P. dalhousiei is much lower than in G. variabilis and G. stainforthi.  [Coxall & Spezzaferri 2018]

Like its ancestor Protentelloides primitivus, this taxon has not been recorded since its description in 1995, or outside its type locality in the eastern equatorial Atlantic Ocean. We recognize it as a distinct species that represents a branch of the Globorotaloides lineage. Described from DSDP Site 366 (Zhang and Scott, 1995), this morphology was recorded informally as Clavatorella aff. C. oveyi Buckley by Spezzaferri (1994) from the equivalent level (Zone O7) in ODP Site 667, 150 km to the northeast of Site 366. The Site 366 sequence has been restudied for the purposes of this work. Together with Protentelloides primitivus, P. dalhousiei has been suggested as an accessory marker for recognizing the Oligocene/Miocene boundary in tropical settings (Zhang and Scott, 1995) (see below), however, this is of limited use because it has not been found elsewhere (e.g. Leckie and others, 1993; Spezzaferri, 1994; Pearson and Chaisson, 1997). Moreover, Spezzaferri (1994) who recorded this morphotype as Clavatorella aff. C. oveyi at nearby ODP Site 677, indicate the range of Protentelloides (species undifferentiated) to extend sporadically across the Oligocene/Miocene boundary up to Zone N4 (lower Miocene Zone M1 of Berggren and others, 1995).  [Coxall & Spezzaferri 2018]

Zhang and Scott (1995) tentatively suggested Protentelloides dalhousiei as the ancestor of Clavatorella bermudezi (Bolli). This is based on a single specimen of C. bermudezi recorded (not illustrated) occurring 8-9 m above the highest occurrence of Protentelloides spp. in DSDP Hole 366A, still within Zone O7 (Zhang and Scott, 1995:82, Table 1). Oligocene to Miocene biostratigraphic studies of DSDP Hole 366A by Krasheninnikov and Pflaumann (1977), however, record ‘(rare) C. bermudezi only’ in the upper part of the lower Miocene (Praeorbulina glomerosa Zone) (= M4/M5, Berggren and others, 1995), and middle Miocene (Orbulina suturalis-Globorotalia peripheroronda and Globorotalia peripheroacuta zones = M6), which is consistent with the range of this species based on observations from other sites (Quilty, 1976; Spezzaferri, 1994; Pearson and Chaisson, 1997). The single specimen is described as being “well-preserved…and… thin-walled” (Zhang and Scott, 1995:82). This is inconsistent with the heavily cancellate wall of Clavatorella and is instead suggestive of Quilty’s (1976) species Quiltyella nazcaensis described from the Oligocene (Zones N2-N4 = O4-O7 of Wade and others, 2011) in the equatorial Pacific Ocean (see Chapter 6, this volume). Based on this reasoning we conclude that the range of Protentelloides and C. bermudezi do not overlap, and thus, that P. dalhousiei is not the ancestor of C. bermudezi but that Zhang and Scott’s (1995) specimen is a rare, protentelloidid homeomorph (as indicated by the higher stratigraphic range of the morphotype recorded at Site 667, Spezzaferri, 1994) or possibly Quiltyella nazcaensis, which is related to Globigerinella (see Chapter 6, this volume). This trend of becoming digitate, as we presume Zhang and Scott’s C. bermudezi to be, occurs repeatedly in a variety of Eocene to Recent low latitude tropical taxa (Coxall and others, 2007). [Coxall & Spezzaferri 2018]

Catalog entries: Protentelloides dalhousiei

Type images:

Distinguishing features:

Like P. primitivus but with more evolute, near-planispiral coiling; apertural system, more variable and complex, with tendency to become ‘cribrate’.

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.


Diagnostic characters:

Protentelloides dalhousiei is a rare but conspicuous species. It differs from Protentelloides primitivus from which it evolved in the more evolute coiling, near-planispiral coiling, less conspicuous inner whorl, equatorially centered final chamber and primary aperture, and the great variability and complexity of the apertural system, including the tendency to become ‘cribrate’. It differs from all other globorotaloidids in the tendency to form a cribrate aperture system. It can also be distinguished from Globorotaloides hexagonus, to which some forms bear a close resemblance, by its tendency to possess an equatorial-umbilically positioned bulla-like final chamber. Also by the nature of the primary aperture, which possess distinctive lips, as well as, commonly, accessory apertures. There is a tendency for the final chambers of P. dalhousiei to become slightly radially elongate, but as not dramatically as in Clavatorella bermudezi Blow, 1965, and Protentella Lipps, 1964. [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: Laterally compressed, evolute, low trochospiral/pseudoplanispiral, strongly lobate; 2-2½ whorls, 5 rounded chambers in the innerwhorl, 5-6 chambers in the final whorl, increasing very rapidly in size, rounded at first with the final 3-4 becoming radially elongate to comma-shaped, final chamber maybe reduced in size, bulla-like, centered at the equatorial margin, variable in morphology; spiral view, sutures depressed, straight between early chambers, becoming curved and later sigmoidal, pre-adult whorls visible, flattened into center; umbilical view, sutures radial, depressed, straight, becoming curved to sigmoidal, small but deep umbilicus; primary aperture equatorial to slightly umbilical, highly variable in morphology: an elongated equatorial slit or low arch at the base final chamber with one ray extending into the umbilicus, bordered by an imperforate rim that may be elongated into a protruding lip; the primary aperture may occur with or without one or more rimmed circular to elongated accessory openings (‘cribrate’) within the final chamber or apertural lip, or along the equatorial face where converging apertural lips divide the primary opening. [Coxall & Spezzaferri 2018]

Size: The maximum diameter of the holotype as figured by Zhang and Scott (1995) is 0.675 mm. All new observations of this species and its close relative P. primitivus are considerably smaller. [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:Thick flange
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:5.0-6.0 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: Protentelloides dalhousiei registers positive δ18O and negative δ13C compared to other species indicating a deep sub-thermocline habitat (Spezzaferri and Coxall, unpublished) consistent with many other independently evolved flattened, clavate forms (Coxall and others, 2007). [Coxall & Spezzaferri 2018]

Phylogenetic relations: Protentelloides dalhousiei evolved from Protentelloides primitivus. [Coxall & Spezzaferri 2018]

Most likely ancestor: Protentelloides primitivus - at confidence level 3 (out of 5). Data source: Coxall & Spezzaferri 2018 f4.1.

Biostratigraphic distribution

Geological Range:
Notes: Zhang and Scott (1995) report a short range for Protentelloides primitivus (~0.45 million years) restricted to Zone O7 (Spezzaferri, 1994; Zhang and Scott, 1995). At DSDP Site 366 Zhang and Scott (1995) recorded the first occurrence of Protentelloides dalhousiei stratigraphically above the first occurrence of Protentelloides primitivus with the two disappearing simultaneously ~0.5 million years before the origin of Paragloborotalia kugleri. This led the authors to suggest this bioevent as an accessory marker for recognizing the Oligocene/Miocene boundary in tropical settings (Zhang and Scott, 1995). Spezzaferri (1994), however, recorded this morphotype as Clavatorella aff. C. oveyi at nearby ODP Site 677, extending the range of Protentelloides (species undifferentiated) up to Zone N4 (=lower Miocene Zone M1), i.e. above the first appearance of Paragloborotalia kugleri. This is confirmed by our latest studies of this core. [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): in lower part of O7 zone (20% up, 24.8Ma, 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.117


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Protentelloides dalhousiei compiled by the pforams@mikrotax project team viewed: 6-7-2020

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