pforams@mikrotax - Parasubbotina

Citation: Parasubbotina Olsson, Hemleben, Berggren,&Liu, 1992

Type species: Globigerina pseudobulloides Plummer, 1926.

Taxonomic discussion: In the lower Danian, low trochospiral, cancellate-walled, planktonic foraminiferal species are common and were thought to be phylogenetically linked together. Olsson et al. (1992) showed that two groups can be separated on the basis of a spinose or a nonspinose test morphology. In the earliest Danian, Parasubbotina and Eoglobigerina represent the spinose group and Praemurica represents the nonspinose group. [Olsson et al. 1999]

The genus was originally erected by Olsson and others (1992) to encompass two Danian species, P. pseudobulloides and P. varianta, which are united by a low trochospiral test, high arched aperture and cancellate spinose wall texture. Although they are similar in overall test morphology to closely related Praemurica inconstans and similar forms, their spinose wall texture was considered as being of high taxonomic status, such that Parasubbotina was included in the Family Globigerinidae and Praemurica in the Globorotaliidae. Olsson and others (1992) noted that Parasubbotina ranges at least as high as Zone P4, but the topmost occurrence of P. varianta was not firmly established by them. Thus, initial investigations by the Paleogene Working Group indicated that Parasubbotina might be a short-lived genus restricted to the Paleocene, with the bulk of the Cenozoic spinose radiation stemming from Eoglobigerina (Pearson, 1993).
Parasubbotina was reviewed by Olsson and others (1999). In that work, the stratigraphic range of P. varianta was found to extend at least to the lower Eocene. Further investigations reported here shows that varianta-like morphologies extend as high as the middle Eocene (confirming the original suggestion of Subbotina, 1953) and it now appears that this species was the root of a substantial evolutionary radiation. The new observations indicate that Parasubbotina is closely related to Paragloborotalia, with which it shares the spinose wall, generally low-trochospiral coiling mode and high-arched aperture. The latter genus is distinguished, however, by the thick, continuous lip that rims the aperture and in having a generally slower rate of chamber enlargement, a tighter coiling mode, and more embracing chambers, which tends to result in a quadrate-shaped, more compact test as is typical, for example, in Paragloborotalia nana (Bolli). The number of chambers in the ultimate whorl is usually 4.
A prominent feature of the taxonomy presented here is the inclusion of the frequently decribed species Globigerina inaequispira Subbotina in Parasubbotina, rather than in Subbotina where it has often been placed (e.g., Blow, 1979). This assignment has been made after detailed study of type material on the basis of its coiling mode and the fact that P. inaequispira has been observed to intergrade with other parasubbotinids in high productivity assemblages. [Olsson et al. 2006]

Distinguishing features:
Parent taxon (Globigerinidae): Wall spinose, usually with 3½-6 globular chambers in final whorl, trochospiral or planispiral
This taxon: Very low trochospiral test, chambers increasing rapidly in size; aperture high-arched umbilical-extraumbilical aperture. At most 5 chambers in final whorl.

Description

Test very low trochospiral, globular, lobulate in outline, chambers globular; in spiral view 4-5 globular, somewhat embracing chambers in ultimate whorl, increasing rapidly in size; in umbilical view 4-5 globular, somewhat embracing chambers, umbilicus a small sized opening, enclosed by surrounding chambers, aperture umbilical-extraumbilical.
[Olsson et al. 2006]

Normal perforate, cancellate, spinose. [Olsson et al. 2006]

Biogeography and Palaeobiology

Genus distinguished by low trochospiral test, chambers increasing rapidly in size in ultimate whorl, and high-arched umbilical-extraumbilical aperture with lip of variable thickness, sometimes dentate. Wall cancellate, originally spinose.
[Olsson et al. 2006]

Suggested as having evolved from Hedbergella by Olsson et al. (2006) but Koutsoukos (2014) provided detialed evidence for origin of both Parasubbotina and Eoglobigerina from Praemurica nikolasii. This makes the Globigerinidae polyphyletic, for convenient plotting of the graphs the alternative possibility of Parasubbotina evolving from Eoglobigerina is instead indicated here. NB Alternatively P. nikolasii could be transferred to Eoglobigerina. [editor's comment - JRY 2018]

Biostratigraphic distribution

Geological Range:
Last occurrence (top): at top of O1 zone (100% up, 32.1Ma, in Rupelian stage). Data source: Total of ranges of the species in this database
First occurrence (base): within P0 zone (66.00-66.04Ma, base in Danian stage). Data source: Total of ranges of species in this database

Primary source for this page: Olsson et al. 2006 - Eocene Atlas, chap. 5, p. 96

References:

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

Koutsoukos, E. (2014). Phenotypic plasticity, speciation, and phylogeny in Early Danian planktic foraminifera. Journal of Foraminiferal Research. 44: 109-142. gs

Olsson, R. K., Hemleben, C., Berggren, W. A. & Liu, C. (1992). Wall Texture Classification of planktonic foraminifera genera in the Lower Danian. Journal of Foraminiferal Research. 22(3): 195-213. gs

Olsson, R. K., Hemleben, C., Berggren, W. A. & Huber, B. T. (1999). Atlas of Paleocene Planktonic Foraminifera. Smithsonian Institution Press, Washington, DC. (85): 1-252. gs

Olsson, R. K., Pearson, P. N. & Huber, B. T. (2006c). Taxonomy, biostratigraphy, and phylogeny of Eocene Catapsydrax, Globorotaloides, Guembelitrioides, Paragloborotalia, Parasubbotina, and Pseudoglobigerinella n. gen. In, Pearson, P. N., Olsson, R. K., Hemleben, C., Huber, B. T. & Berggren, W. A. (eds) Atlas of Eocene Planktonic Foraminifera. Cushman Foundation for Foraminiferal Research, Special Publication . 41(Chap 5): 67-110. gs O

Pearson, P. N. (1993). A lineage phylogeny for the Paleogene planktonic foraminifera. Micropaleontology. 39: 193-232. gs

species arranged stratigraphically and by lineage (time control age-window is: 0-800Ma)
			inaequispira & derived species
			Parasubbotina griffinae Test very low trochospiral, globular with strongly inflated chambers; inner whorls partially overlapped by the ultimate whorl. Wall texture Clavigerinella-type (high porosity, reticulated)
			Parasubbotina eoclava Test low trochospiral, 4-4½ chambers in final whorl. Chamber size increases rapidly, and the last 1 or 2 chambers are often radially extended. Aperture small, interiomarginal umbilical-extraumbilical with a broad, flaring lip. Wall texture reticulate (Clavigerinella-type),
			Parasubbotina hagni Large adult test, quadrate. Chambers globular, embracing. Aperture low-arched, umbilical-extraumbilical, with thin irregular lip.
			Parasubbotina prebetica Test symmetrical, compressed with radially elongate, globular to cylindrical chambers.
			Parasubbotina inaequispira Test, lobulate, very low trochospiral, rather openly coiled, 4-4½ chambers in final whorl, which is much larger than inner whorl. Aperture anteriorly directed umbilical-extraumbilical, lacking thick lip
			pseudobulloides-varianta group
			Parasubbotina pseudowilsoni Test small, compact, very low trochospiral, typically<5 chambers in final whorl.
			Parasubbotina variospira Test large (0.4-0.7 mm), loosely coiled, with strongly lobulate outline. Any or all of the last 3-4 chambers with inwardly projecting umbilical teeth. Aperture interiomarginal, umbilical-extraumbilical arch; occasional secondary spiral apertures. Wall spinose and distinctly cancellate with large pore pits.
			Parasubbotina varianta Test with 4 chambers in final whorl, rapidly expanding. Aperture umbilical-extraumbilical, a rounded high arch with fairly broad continuous lip. Umbilicus, small, rounded; deep and open to the surrounding chambers. Wall cancellate spinose with spine holes.
			Parasubbotina pseudobulloides Test medium-sized (>250µm) with 5 chambers in final whorl. Chambers inflated, globular, slightly ovoid; increasing rapidly in size. Aperture interiomarginal, umbilical to extraumbilical, a high rounded arch with a narrow lip. Umbilicus narrow; deep and open to the previous chambers. Wall cancellate spinose, with numerous spine holes
			Parasubbotina aff. pseudobulloides Test small (<225µm), 4½ to 5 chambers in final whorl. Chambers globular, increase rapidly in size. Aperture high arched umbilical-extraumbilical with a thin lip Wall weakly developed cancellate, spinose.
			Parasubbotina sp. Specimens which cannot be assigned to established species

test outline:	Lobate	chamber arrangement:	Trochospiral	edge view:		aperture:	Umbilical-extraumbilical
sp chamber shape:	Globular	coiling axis:		periphery:	N/A	aperture border:
umb chbr shape:	Globular	umbilicus:		periph margin shape:	Broadly rounded	accessory apertures:	None
spiral sutures:	Strongly depressed	umb depth:		wall texture:	Cancellate	shell porosity:	Finely Perforate: 1-2.5µm
umbilical or test sutures:	Strongly depressed	final-whorl chambers:	0-0	N.B. These characters are used for advanced search. N/A - not applicable

Parasubbotina

Taxonomy

Description

Biogeography and Palaeobiology

Biostratigraphic distribution

References:

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