Paragloborotalia pseudokugleri


Classification: pf_cenozoic -> Globigerinidae -> Paragloborotalia -> Paragloborotalia pseudokugleri
Sister taxa: P. acrostoma, P. incognita, P. pseudocontinuosa, P. semivera, P. kugleri, P. pseudokugleri, P. mayeri, P. siakensis, P. birnageae, P. continuosa, P. opima, P. nana, P. griffinoides, P. sp.,

Taxonomy

Citation: Paragloborotalia pseudokugleri (Blow, 1969)
Rank: species
Basionym: Globorotalia (Turborotalia) pseudokugleri Blow, 1969
Synonyms:
Taxonomic discussion:

This species is discussed extensively under P. kugleri, above. The holotype chosen by Blow (1969) was originally a paratype of kugleri, as figured by Bolli (1957, pl. 28, fig. 7), from the same locality and level (lower Miocene) as the holotype. Blow (1969) also figured two paratypes. We have also investigated with SEM (not shown) two of Blow’s unfigured paratypes (Natural History Museum, London, Nos P49740 and P49741). The second of these shows slight pinching of the periphery and strongly curved spiral sutures such that we would now assign it to P. kugleri.

There is considerable morphological evolution within the range of P. pseudokugleri, beginning with smaller (<150 μm) ‘primitive’ forms with 5-6 chambers in the final whorl and radial spiral sutures to larger (>150 μm) more ‘advanced’ forms, like the holotype, with up to 7 chambers in the final whorl and moderately curved spiral sutures (e.g., Spezzaferri, 1994). Even specimens with quite strongly curved spiral sutures are assigned to this morphospecies if they show a rounded periphery in edge view. A rounded periphery is the key feature of pseudokugleri s.s.

The nature of the wall has been the subject of some debate, with Spezzaferri (1991) and Rögl (1996) arguing that it is spinose and Pearson and Wade (2009; pl. 6, figs. 6a-f) arguing for a nonspinose wall, having illustrated some well-preserved forms with fused and aligned inner pore ridges which are more typical of the cancellate nonspinose wall. This debate affects the generic designation of the pseudokugleri – kugleri group. The issue was conclusively solved by the discovery of true spines projecting from a well-preserved specimen (Pl. 5.9, Fig. 8).

Li and others (2005) illustrated a suite of very small specimens from the South China Sea. Because of the small size we include these in questionable synonymy, noting that there may be confusion with P. birnageae and heavily encrusted Turborotalita quinqueloba. Paragloborotalia pseudokugleri is distinguished from P. birnageae by its more deeply depressed sutures and lobulate equatorial outline, broadly rounded peripheral margin, and higher aperture with smaller lip (P. pseudokugleri lacks an appressed final chamber with flap-like flange or apertural plate). [Leckie et al. 2018]

Catalog entries: Globorotalia (Turborotalia) pseudokugleri

Type images:

Distinguishing features:

Like P. nana but with 5 or more chambers in the final whorl (typically 6-7) and somewhat less inflated chambers.

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:

A mosaic of characters separate P. pseudokugleri from P. kugleri (see the extended discussion under P. kugleri for means of distinguishing the two species). The most important feature, as described by Blow (1969:391), is that the test is “smoothly rounded, broad, not subacute peripheral margin”, a view that is supported here. Also the chambers are more inflated and less tightly appressed, the outline is more lobulate and circular, and the spiral side sutures are usually either straight or less strongly curved than is typical in kugleri. Earliest forms have straight and radial spiral sutures while later forms have a tendency for curvature, which can be quite marked (e.g., Spezzaferri and Premoli Silva, 1991, pl. 11, fig. 7a-c). Paragloborotalia pseudokugleri is distinguished from its likely ancestor P. nana by having 5 or more chambers in the final whorl (typically 6-7) and by having somewhat less inflated chambers. Early specimens of P. pseudokugleri are distinctly smaller than later Oligocene forms (Leckie and others, 1993; Spezzaferri, 1994). A 5½ chambered specimen, transitional between nana and pseudokugleri is shown on Plate 5.7, Figures 14-16. [Leckie et al. 2018]


Wall type: Normal perforate, coarsely cancellate, sparsely spinose in life, heavy gametogenetic calcification is often present.

Test morphology: Test small to medium in size; low trochospiral, moderately lobulate in equatorial outline, chambers wedge-shaped, moderately inflated, embracing; 5-7 chambers in the ultimate whorl, increasing slowly in size; in spiral view chambers arranged in 2½ -3 whorls, sutures slightly depressed, radial to moderately curved, occasionally strongly curved; in umbilical view chambers wedge-shaped and moderately appressed, sutures slightly depressed, radial, umbilicus narrow, moderately deep; aperture umbilical-extraumbilical, a low slit or very low arch, bordered by a lip; in edge view chambers sub-spherical, spiral side flat to slightly convex, umbilical side slightly convex, periphery broadly rounded. [Leckie et al. 2018]

Size: Maximum diameter of holotype 0.31 mm (original measurement); 0.27 mm (remeasured this study); thickness 0.17 mm (this study). [Leckie et al. 2018]

Character matrix

test outline:Lobatechamber arrangement:Trochospiraledge view:Equally biconvexaperture:Umbilical-extraumbilical
sp chamber shape:Globularcoiling axis:Lowperiphery:N/Aaperture border:Thin lip
umb chbr shape:Subtriangularumbilicus:Narrowperiph margin shape:Broadly roundedaccessory apertures:None
spiral sutures:Weakly depressedumb depth:Shallowwall texture:Cancellateshell porosity:Macroperforate: >2.5µm
umbilical or test sutures:Moderately depressedfinal-whorl chambers:6.0-7.0 N.B. These characters are used for advanced search. N/A - not applicable

Biogeography and Palaeobiology


Geographic distribution: Cosmopolitan, most common at low and mid-latitudes, but in fact it has been found nearly as far north as the Reykjanes Ridge and east Greenland margin in the North Atlantic Ocean (Poore, 1979; Spezzaferri, 1998). [Leckie et al. 2018]

Isotope paleobiology: Poore and Matthews (1984), Pearson and others (1997), and Pearson and Wade (2009) all record this species as a mixed-layer dwelling form. Pearson and others (1997) analyzed this species from a series of consecutive samples through several climate cycles across the Oligocene-Miocene transition, alongside four other species including “Paragloborotalia mayeri” (which would now to assigned to P. siakensis; see discussion under that taxon). Paragloborotalia pseudokugleri had similar oxygen isotope ratios to that species, consistent with a mixed-layer habitat for both taxa, but carbon isotope ratios are distinctly more positive than P. siakensis. This may be evidence of symbiotic association in pseudokugleri but not in siakensis; increasing δ13C with size supports this suggestion (Pearson and Wade, 2009). [Leckie et al. 2018]

Phylogenetic relations: According to its author this species was a descendant of Globorotalia mendacis Blow, but that species is regarded by us as a synonym of P. birnageae and likely evolved from P. pseudokugleri. The ancestry of this species has been the subject of uncertainty because it is very rare near the base of its stratigraphic range and debate about the nature of the wall. Aze and others (2011) suggested that it may have evolved from a nonspinose group. However, the spinose wall texture confirms that it is a true paragloborotaliid and probably evolved from P. nana by an increase in the number of chambers in the final whorl and in development of a more lobulate periphery. Rare intermediate morphologies have been observed near the beginning of the stratigraphic range (Pl. 5.7, Figs. 14-16; Premoli Silva and Spezzaferri, 1990; Leckie and others, 1993; Spezzaferri, 1994). The species gave rise to P. kugleri by gradual transition (see discussion under that species). [Leckie et al. 2018]

Most likely ancestor: Paragloborotalia nana - at confidence level 2 (out of 5). Data source: Leckie et al. 2018.
Likely descendants: Paragloborotalia kugleri;

Biostratigraphic distribution

Geological Range:
Notes: The lowest occurrence of P. pseudokugleri has been observed in mid Zone P22 (Spezzaferri and Premoli Silva, 1991; Leckie and others, 1993; Spezzaferri, 1994) and was used to define the base of Zone O7 by Wade and others (2011), a datum that is supported by this study. The highest occurrence was reported by Blow (1969) as being about half way within the range of P. kugleri (i.e., within Zone M1), but subsequent authors have found it extending to near the top of the range (e.g., at Rio Grande Rise by Pujol, 1983; Ontong Java Plateau by Chaisson and Leckie, 1993; and at Ceara Rise by Pearson and Chaisson, 1997). Recent observations from IODP Site U1337 suggest a ~400 kyr offset between the extinction of P. pseudokugleri and P. kugleri (King and Wade, pers. comm., 2016). [Leckie et al. 2018]
Last occurrence (top): near top of M1b subzone (90% up, 21.3Ma, in Aquitanian stage). Data source: Leckie et al. 2018 f5.1
First occurrence (base): at base of O7 zone (0% up, 25.2Ma, in Chattian stage). Data source: Wade et al. 2011; Leckie et al. 2018

Plot of occurrence data:

Primary source for this page: Leckie et al. 2018 - Olig Atlas chap.5 p.160

References:

Aze, T. et al. (2011). A phylogeny of Cenozoic macroperforate planktonic foraminifera from fossil data. Biological Reviews. 86: 900-927. gs

Blow, W. H. (1969). Late middle Eocene to Recent planktonic foraminiferal biostratigraphy. In, Bronnimann, P. & Renz, H. H. (eds) Proceedings of the First International Conference on Planktonic Microfossils, Geneva, 1967. E J Brill, Leiden 380-381. gs

Blow, W. H. (1979). The Cainozoic Globigerinida: A study of the morphology, taxonomy, evolutionary relationships and stratigraphical distribution of some Globigerinida (mainly Globigerinacea). E. J. Brill, Leiden. 2: 1-1413. gs

Bolli, H. M. & Saunders, J. B. (1985). Oligocene to Holocene low latitude planktic foraminifera. In, Bolli, H. M. , Saunders, J. B. & Perch-Neilsen, K. (eds) Plankton Stratigraphy. Cambridge University Press, Cambridge, UK 155-262. gs

Bolli, H. M. (1957b). Planktonic foraminifera from the Oligocene-Miocene Cipero and Lengua formations of Trinidad, B.W.I. In, Loeblich, A. R. , Jr. , Tappan, H. , Beckmann, J. P. , Bolli, H. M. , Montanaro Gallitelli & E. Troelsen, J. C. (eds) Studies in Foraminifera. U.S. National Museum Bulletin. 215: 97-123. gs

Brönnimann, P. & Resig, J. (1971). A Neogene globigerinacean biochronologic time-scale of the southwestern Pacific. Initial Reports of the Deep Sea Drilling Project. 7(2): 1235-1469. gs

Chaisson, W. P. & Leckie, R. M. (1993). High-resolution Neogene planktonic foraminifer biostratigraphy of Site 806, Ontong Java Plateau (Western Equatorial Pacific). Proceedings of the Ocean Drilling Program, Scientific Results. 130: 137-178. gs

Chaproniere, G. C. H. (1981). Late Oligocene to Early Miocene planktic Foraminiferida from Ashmore Reef no. 1 well, northwest Australia. Alcheringa. 5: 103-131. gs

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Leckie, R. M., Farnham, C. & Schmidt, M. G. (1993). Oligocene planktonic foraminifer biostratigraphy of Hole 803D (Ontong Java Plateau) and Hole 628A (Little Bahama Bank), and comparison with the southern high latitudes. Proceedings of the Ocean Drilling Program, Scientific Results. 130: 113-136. gs

Leckie, R. M. et al. (2018). Taxonomy, biostratigraphy, and phylogeny of Oligocene and Lower Miocene Paragloborotalia and Parasubbotina. 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 5): 125-178. gs

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Pearson, P. N., Shackleton, N. J., Weedon, G. P. & Hall, M. A. (1997b). Multispecies planktonic foraminifer stable isotope stratigraphy through Oligocene/Miocene boundary climatic cycles, Site 926. 154, 441-450. Proceedings of the Ocean Drilling Program, Scientific Results. 154: 441-450. gs

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Paragloborotalia pseudokugleri compiled by the pforams@mikrotax project team viewed: 15-12-2019

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