Igorina tadjikistanensis


Classification: pf_cenozoic -> Truncorotaloididae -> Igorina -> Igorina tadjikistanensis
Sister taxa: I. tadjikistanensis, I. albeari, I. pusilla, I. sp.,

Taxonomy

Citation: Igorina tadjikistanensis (Bykova 1953)
Rank: Species
Basionym: Globorotalia tadjikistanensis
Synonyms:
Taxonomic discussion: This taxon is a distinct component of late Paleocene and earliest Eocene assemblages. Recent examination and SEM reillustration of the holotype specimen of the taxon tadjikistanensis (Plate 11: Figures 4 - 6 ) and convexa (Plate 11: Figures 1-3), described originally from the upper Paleocene of Kazakhstan (Bykova, 1953) and from the zone of conical globorotaliids (= Zones P6-P8) in the Kuban River section near Nal'chik, in the northern Caucasus (Subbotina, 1953), respectively, has shown the two forms to be conspecific, with the former having priority. We essentially follow the interpretation of Blow (1979), although unlike Blow we include certain forms illustrated by Loeblich and Tappan (1957a) from the synonymy of this species. We also include the multichambered variety identified as cf. convexa in this taxon, which presages its descendant /. broedermanni Cushman and Bermudez. [Olsson et al. 1999]

Catalog entries: Globorotalia tadjikistanensis, Globorotalia convexa

Type images:

Distinguishing features: Test small, biconvex, moderately lobulate, densely and finely praemuricate test; axial periphery subrounded to subacute, noncarinate; spiral sutures depressed, strongly recurved, tangential to inner whorl, often obscured by dense murical network; umbilicus small, shallow as a result of tight coiling mode.

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: Relatively small (<0.25 mm in diameter), nonspinose, biconvex, ovate to subcircular, moderately lobulate, densely and finely praemuricate test with 5-7 (rarely up to 9-10) chambers in last whorl; axial periphery subrounded to subacute, noncarinate; umbilical intercameral sutures curved, depressed, spiral sutures depressed, strongly recurved, tangential to inner whorl, often obscured by dense murical network; umbilicus small, shallow as a result of tight coiling mode, surrounded by an irregularly wavy umbilical shoulder formed by undulating periumbilical chamber apices; aperture a low, narrow interiomarginal, umbilical-extraumbilical slit bordered by a distinct lip and extending towards, but, not reaching, the peripheral margin. [Olsson et al. 1999]

Character matrix

test outline:Subcircularchamber arrangement:Trochospiraledge view:Inequally biconvexaperture:Umbilical-extraumbilical
sp chamber shape:Inflatedcoiling axis:Low-moderateperiphery:N/Aaperture border:N/A
umb chbr shape:Inflatedumbilicus:Narrowperiph margin shape:Broadly roundedaccessory apertures:None
spiral sutures:Weakly depressedumb depth:Shallowwall texture:Coarsely pustuloseshell porosity:Finely Perforate: 1-2.5µm
umbilical or test sutures:Weakly depressedfinal-whorl chambers:5.0-9.0 N.B. These characters are used for advanced search. N/A - not applicable

Biogeography and Palaeobiology


Geographic distribution: Igorina tadjikistanensis was broadly distributed in tropical and subtropical latitudes. [Olsson et al. 1999]
Aze et al. 2011 summary: Low to middle latitudes; based on Olsson et al. (1999)

Isotope paleobiology: Igorina tajikistanensis has ∂18O
slightly lighter than coexisting M. velascoensis at equivalent
sizes and has distinctly more negative ∂18O than Subbotina 13
(Shackleton et al., 1985; Berggren and Norris, 1997). The ∂13C of I. tajikistanensis displays a strong increase in ∂13C with increased size, which is similar to Acarinina and Morozovella (Berggren and Norris, 1997). [Olsson et al. 1999]
Aze et al. 2011 ecogroup 1 - Open ocean mixed-layer tropical/subtropical, with symbionts. Based on very heavy δ13C and relatively light δ18O. Sources cited by Aze et al. 2011 (appendix S3): Berggren & Norris (1997)

Phylogenetic relations: This species probably evolved from /. pusilla in middle to upper Zone P3 by developing a more involute coiling mode, increasing the number of chambers in the final whorl, and developing a dense, finely praemuricate ornament. Igorina tadjikistanensis differs from /. albeariin being generally smaller, lower spired, and without a peripheral keel. [Olsson et al. 1999]

Most likely ancestor: Igorina pusilla - at confidence level 4 (out of 5). Data source: Olsson et al. (1999), f5a.

Biostratigraphic distribution

Geological Range:
Notes: Zone P3b to Zone P7. [Olsson et al. 1999]
Last occurrence (top): at top of P5 zone (100% up, 56Ma, in Thanetian stage). Data source: Berggren et al. (2006), f12.1
First occurrence (base): at base of P3b subzone (0% up, 61.3Ma, in Selandian stage). Data source: Olsson et al. (1999), f5a

Plot of occurrence data:

Primary source for this page: Olsson et al. 1999 - Atlas of Paleocene Planktonic Foraminifera, p. 71

References:

Belford, D. J. (1984). Tertiary foraminifera and age of sediments, Ok Tedi-Wabag, Papua New Guinea. Bureau of Mineral Resources, Australia, Bulletin. 216: 1-52. 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

Bykova, N. K. (1953). Фораминиферы сузакского яруса Таджикской депрессии [Foraminifera of the Suzakian Stage of the Tajik depression]. In, unknown (ed.) Microfauna of the USSR, 6. Proceedings of the Oil Research Geological Institute (VNIGRI).. 69: 3-114. gs

Jenkins, D. G. (1971). New Zealand Cenozoic Planktonic Foraminifera. New Zealand Geological Survey, Paleontological Bulletin. 42: 1-278. gs

Leonov, G. P. & Alimarina, V. (1960). Stratigrafiya i planktonnye foraminifery "perekhodnykh" ot mela k paleogeny sloev tsentral'nogo Predkavkazya [Stratigraphy and Plantonic Foraminifera of the Cretaceous-Paleogene "Transition" Beds of the Central Part of the North Caucasus]. In Problema V: Granitsa melovoi i paleogenovoi sistem. Mezhdunarodnyi Geologicheskii Kongress, XXI Sessiya, Doklady Sovetskikh Geologov, Izdatelstvo Akademiya Nauk. 29-60. gs

Loeblich, A. R. & Tappan, H. (1957b). Planktonic foraminifera of Paleocene and early Eocene Age from the Gulf and Atlantic coastal plains. 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: 173-198. gs

Luterbacher, H. P. (1964). Studies in some Globorotalia from the Paleocene and Lower Eocene of the Central Apennines. Eclogae Geologicae Helvetiae. 57: 631-730. gs

McGowran, B. J. (1968). Reclassification of Early Tertiary Globorotalia. Micropaleontology. 14: 179-198. gs

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

Soldan, D. M., Petrizzo, M. R., Silva, I. P. & Cau, A. (2011). Phylogenetic relationships and evolutionary history of the Paleogene genus through parsimony analysis. Journal of Foraminiferal Research. 41: 260-284. gs

Soldan, D. M., Petrizzo, M. R. & Silva, I. P. (2014). Pearsonites, a new Paleogene planktonic foraminiferal genus for the broedermanni lineage. Journal of Foraminiferal Research. 44: 17-27. gs

Stott, L. D. & Kennett, J. P. (1990). The Paleoceanographic and Paleoclimatic signature of the Cretaceous/Paleogene boundary in the Antarctic: Stable isotopic results from ODP Leg 113. Proceedings of the Ocean Drilling Program, Scientific Results. 113: 829-848. gs

Subbotina, N. N. (1953). Foraminiferes fossiles d'URSS Globigerinidae, Globorotaliidae, Hantkeninidae. Bureau de Recherches Geologiques et Minieres. 2239: 1-144. gs


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Igorina tadjikistanensis compiled by the pforams@mikrotax project team viewed: 17-9-2019

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