pforams@mikrotax - Igorina tadjikistanensis

Citation: Igorina tadjikistanensis (Bykova 1953)

Basionym: Globorotalia tadjikistanensis

Synonyms:

Globorotalia tadjikistanensis Bykova, 1953:86, pl. 3: fig. 5a-c [Globorotalia tadjikistanensis Zone, Suzakian Stage, southern part of Tadzhik Basin, Ak-Tau, Kazakhstan; given as Eocene].—Leonov and Alimarina, 1960:53, pl. 7: figs. 1, 2, 7 [upper part Globorotalia tadjikistanensis Subzone, eastern facies, Khieu River section, northern Caucasus], figs. 3, 4, 7 [lower part Globorotalia tadjikistanensis Subzone, eastern facies, Khieu River section, northern Caucasus].—Luterbacher, 1964:52, text-fig. 52a-c [Globorotalia pusilla pusilla Zone, Gubbio section, central Apennines, Italy].
Globorotalia convexa Subbotina, 1953:209, pl. 17: fig. 2a-c [holotype], fig. 3a-c [zone of conical globorotaliids, Foraminiferal Layer, Series Fl, Khieu River, Nal'chik, northern Caucasus].—Loeblich and Tappan, 1957a: 188, pl. 48: fig. 4a-c [Zone P4, Vincentown Fm., New Jersey], pl. 50: fig. 7a-c [Zone P4, Hornerstown Fm., New Jersey], pl. 53: figs. 6a-8c [Zone P4, Aquia Fm., Maryland], pl. 57: figs. 5a-6c [Zone P4, Salt Mountain Limestone, Alabama], pl. 63: fig. 4a-c [Zone P4, Velasco Fm., Tamaulipas, Mexico].—Pujol, 1983:644, pl. 3: figs. 1, 2 [Zone P3, DSDP Hole 516F/88/2: 102-103 cm; Rio Grande Rise, South Atlantic Ocean].
Truncorotaloides (Morozovella) convexus (Subbotina).—McGowran, 1968:192, pl. 2: figs. 11-14 [Truncorotaloides (Acarinina) mckannai zonule, Boongerooda Greensand, Australia].
Globorotalia (Acarinina) convexa Subbotina.—Jenkins, 1971:81, pl. 3: figs. 79-83 [Globigerina (Subbotina) triloculinoides Zone, type Teurian, Te Uri Stream section, New Zealand].—Blow, 1979:920, pl. 85: figs. 2-7 [Zone P3, DSDP Hole 47.2/10/2: 80-82 cm], pl. 88: figs. 3, 4 [upper part of Zone P3, DSDP Hole 47.2/10/1: 72-74 cm], pl. 100: figs. 3, 5-9 [Zone P5, DSDP Hole 47.2/9/1: 64-66 cm; Shatsky Rise, northwestern Pacific Ocean].
Globorotalia (Acarinina) convexa cf. convexa Subbotina.—Blow, 1979:921, pl. 100: figs. 1, 2, 4 [Zone P5, DSDP Hole 47.2/9/1: 64-66 cm; Shatsky Rise, northwestern Pacific Ocean].
Globorotalia (Morozovella) tadjikistanensis Bykova.—Belford, 1984:10, pl. 18: figs. 18-23 [upper Paleocene, Wabag Sheet, Papua, New Guinea].
Morozovella convexa (Subbotina).—Stott and Kennett, 1990:560, pl. 3:figs.5, 6 [Zone AP3, near AP3/4 boundary, ODP Hole 690B/19H/4: 36-40 cm; Maud Rise, Weddell Sea, Southern Ocean]. [Olsson et al. 1999]

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]

Distinguishing features:
Parent taxon (Igorina): Test small, biconvex, evolute, margin narrowly rounded or angular, sometimes with a keel; 5-6 chambers in final whorl
Wall, coarsely cancellate, praemuricate, often pustulose.
This taxon: 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.

Description

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]

Biogeography and Palaeobiology

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)

Igorina tajikistanensis has δ18O
slightly lighter than coexisting M. velascoensis at equivalent
sizes and has distinctly more negative δ18O than Subbotina 13
(Shackleton et al., 1985; Berggren and Norris, 1997). The δ13C of I. tajikistanensis displays a strong increase in δ13C 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 _¹³C and relatively light _¹⁸O. Sources cited by Aze et al. 2011 (appendix S3): Berggren & Norris (1997)

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

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. Australia Bureau of Mineral Resources Geology and Geophysics, 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. Trudy Vsesoyuznego Neftyanogo Nauchno-Issledovatel'skogo Geologo-Razvedochnogo Instituta (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 O

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. (85): 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

test outline:	Subcircular	chamber arrangement:	Trochospiral	edge view:	Inequally biconvex	aperture:	Umbilical-extraumbilical
sp chamber shape:	Inflated	coiling axis:	Low-moderate	periphery:	N/A	aperture border:	N/A
umb chbr shape:	Inflated	umbilicus:	Narrow	periph margin shape:	Broadly rounded	accessory apertures:	None
spiral sutures:	Weakly depressed	umb depth:	Shallow	wall texture:	Coarsely pustulose	shell porosity:	Finely Perforate: 1-2.5µm
umbilical or test sutures:	Weakly depressed	final-whorl chambers:	5-9	N.B. These characters are used for advanced search. N/A - not applicable

Igorina tadjikistanensis

Taxonomy

Description

Biogeography and Palaeobiology

Biostratigraphic distribution

References:

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