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Species Parasubbotina inaequispira Subbotina 1953


Diagnosis / Definition:
Pearson et al. (2006):
DESCRIPTION. Type of wall: Symmetrically to asymmetrically cancellate (initially ruber/sacculifer-type wall texture but becoming high porosity, reticulated sacculifer-type in adult morphology and particularly in stratigraphically younger morphotypes Clavigerinella-type with surface thicking), normal perforate, spinose. Test morphology: Test very low trochospiral, globular, lobulate in outline, chambers globular; in spiral view 4-41/2 globular, well separated chambers in final whorl, increasing moderately in size, sutures moderately depressed, straight, final chamber may be slightly reduced in size relative to the penultimate chamber; in umbilical view 4-41/2 globular, well separated chambers, increasing moderately in size, sutures moderately depressed, straight, umbilicus a moderate sized opening, enclosed by surrounding chambers, aperture umbilical to somewhat extraumbilical and directed towards the anterior side of the test, bordered by a narrow continuous, lip, ultimate chamber may be slightly reduced in size relative to the penultimate chamber; in edge view chambers globular in shape, well separated, aperture visible as a low arch, bordered by a narrow lip. Size: Maximum diameter of holotype 0.42 mm, thickness 0.28 mm.
Discussion / Comments:
Pearson et al. (2006):
DISTINGUISHING FEATURES.- Subbotina (1953) alluded to the "Globigerinella-like" coiling style of her species and the small size of the inner whorl in comparison to the outer whorl, the latter feature lending the taxon its name. These features arise from the rapid rate of chamber expansion and their low and slightly irregular trochospiral arrangement, characters that help assign the species to the genus Parasubbotina. The species is distinguished by its lobulate, very low trochospiral test with 4-41/2 chambers in the final whorl and its anteriorly directed umbilical-extraumbilical aperture. The species has been widely identified in previous literature, but often incorrectly so. Parasubbotina inaequispira is distinguished from P. varianta by being more openly coiled and having less closely appressed chambers. It differs from Paragloborotalia griffinoides n. sp. principally in having much less dorso-ventral expansion and lacking the thick, prominent lip ofthat taxon. It differs from P. eoclava in lacking radially elongate chambers and a thick, flaring lip. DISCUSSION.- The holotype of Parasubbotina inaequispira (Subbotina) is illustrated here in SEM for the first time (Pl. 5.11, Figs. 1-3). Blow (1979, p. 1259) regarded P. inaequispira as ancestral to Subbotina crociapertura because of the tendency in P. inaequispira "to produce apertural systems with a slightly expanded to very slightly hooked distal part", which he believed led to the distinctive hook-shaped aperture in S. crociapertura. However, the majority of specimens he illustrated to demonstrate this feature cannot be placed in 19 inaequispira. In fact, Blow's images of inaequispira show different types of wall texture that suggests mixing of separate species. The specimens of S. crociapertura from Tanzania illustrated by Blow, which includes the holotype, have a bulloides-type wall texture whereas P inaequispira has a ruber/sacculifer-type wall texture. Some specimens of P. inaequispira illustrated by Blow (his pl. 177, fig. 3; pl. 180, figs. 2, 3; pl. 185, fig. 9) have a bulloides-type wall texture and may be morphotypes of S. crociapertura. Of particular interest are Blow's images of P. inaequispira from Zones E7 and E8 from the Endeavour Seamount in the North Atlantic Ocean (his pl. 15 1, figs. 5-7; pl. 163, figs. 4-10). These specimens show a fully developed, high porosity, reticulated, sacculifer-type wall texture that is characteristic of the genus Clavigerinella, which apparently first developed in P. inaequispira. Some of the specimens illustrated (his pl. 15 1, figs. 9 and 10) are placed in the intermediate species Parasubbotina eoclava Coxall, Huber, and Pearson that evolved from P. inaequispira and is believed to be directly ancestral to Clavigevinella. The type material of Globigerina achtshacujmensis Khalilov and Globigerina inaequispira var. transversa Khalilov has been viewed by WAB and, despite the poor preservation, both are clearly synonyms of P. inaequispira. The holotype and three paratypes of Globigerina baylissi Samanta were viewed by PNP. Samanta distinguished his taxon from inaequispira by the supposed radial elongation of the final chamber, but this feature is poorly developed and falls within the range of variation here permitted to P. inaequispira. More markedly radially elongate parasubbotinids are assigned to P eoclava Coxall, Huber and Pearson. PHYLOGENETIC RELATIONSHIPS.- Parasubbotina inaequispira appears to have developed from P. varianta (Subbotina) in the earliest Eocene. In turn it gave rise to P. eoclava and P. griffinae in the latest early Eocene. GEOGRAPHIC DISTRIBUTION.- Global in low to mid latitudes. Parasubbotina inaequispira is a common constituent of relatively high productivity environments in the Eocene. STABLE ISOTOPIC PALEOBIOL0GY.- Relatively heavy ò18O indicating cool water (H. K. Coxall, unpublished data).
Systematics:

35
 Ordo Foraminiferida
  Superfamilia Globigerinaceae
   Familia Globigerinidae
    Genus Parasubbotina
     Species Parasubbotina inaequispira
Synonym list:
Pearson et al. (2006):
1953 Globigerina inaequispira Subbotina. - Subbotina : p.84 pl. 6, fig. 1a-c (holotype), 4a-c [lower / middle Eocene Zone of conical Globorotalia, Kuban River, northern Caucasus]; pl. 6, fig. 2a-3c [lower / middle Eocene Zone of conical Globorotalia, Foraminiferal layer, Series F, (bottom), Kuban River, northern Caucasus]
1956 Globigerina achtschacujmensis Khalilov. - Khalilov : p.238 pl. 2; fig. 2a-c ["middle Eocene", Maly Caucasus, Azebaidzhan]
1956 Globigerina inaequispira var. transversa Khalilov. - Khalilov : p.241 pl. 2; fig. 4a-c ["middle Eocene", Maly Caucasus, Azebaidzhan]
1973 Globigerina baylissi Samanta. - Samanta : p.436 pl. 2; fig. 4-6 [middle Eocene Truncorotaloides rohri Zone, Rakhi Nala lacking radially elongate chambers and a thick, flaring section, Pakistan]
1975 Globigerina inaequispira Subbotina. - Stainforth et al. : p.191 fig. 54 1a-c [from Subbotina, 1953]; fig. 54 2a-c [reillustration of holotype]; fig. 54 3-5 [middle Eocene, no locality given]
p 1979 Subbotina inaequispira Subbotina. - Blow : p.1272 pl. 151, fig. 5-7 [lower Eocene Zone E7, KANE 9-Core 42, Endeavour Seamount, eastern North Atlantic Ocean]; pl. 163, fig. 4-8 [middle Eocene Zone E8, KANE 9-Core 42, Endeavour Seamount, eastern North Atlantic Ocean]; pl. 180, fig. 1, 4-7 [middle Eocene Zone E9, DSDP Hole 2 l A, Gulf of Mexico]; pl. 191, fig. 7 [middle Eocene Zone E12, Sample RS.311, Kilwa area, Tanzania]
1985 Globigerina inaequispira Subbotina. - Toumarkine & Luterbacher : p.117 fig. 19-5a-c [reillustration of holotype]
2000 Subbotina inaequispira Subbotina. - Warraich et al. : p.299 fig. 18: 6-8 [Dungan Fm., Sulaiman Range, Pakistan]
2001 Subbotina inaequispira Subbotina. - Warraich & Ogasawara : p.48 fig. 13: 17-19 [Zone E5, Dungan Fm., Sulaiman Range, Pakistan]
2004 Parasubbotina inaequispira Subbotina. - Pearson et al. : p.36 pl. 1; fig. 13 [lower Eocene Zone E617, Tanzania]
2006 Parasubbotina inaequispira Subbotina. - Pearson et al. : p.93 pl. 5.11; fig. 1-15 (Pl. 5.11, Figs. 1-3: new SEMs of holotype of Globigerina inaequispira Subbotina)
Specimen:
VNIGRI collections, St. Petersburg, Inventory number: 3069
VNIGRI collections, St. Petersburg, Inventory number: 4016
VNIGRI collections, St. Petersburg, Inventory number: 4017
VNIGRI collections, St. Petersburg, Inventory number: 4018
References:

Subbotina,N.N. (1953):
Iskopaemye foraminifery SSSR (Globigerinidy, Khantkenininidy i Globorotaliidy) . Trudy Vsesoyznogo Nauchno-Issledovatel'skogo Geologo-razvedochnogo Instituta (VNIGRI) Vol. 76 p. 296

Khalilov,D.M. (1956):
O pelagicheskoy faune foraminifer Paleogenovykh otlozheniy Azerbaydzhana . Trudy Instituta Geologii, Akademiya Nauk Azerbaydzhanskoy SSR Vol. 17

Samanta,B.K. (1973):
Planktonic foraminifera from the Palaeocene-Eocene succession in the Rakhi Nala, Sulaiman Range, Pakistan . British Museum Natural History Bulletin Vol. 22(6) p. 436

Stainforth,R.M.; Lamb,J.L.; Luterbacher,H.P.; Beard,J.H. and Jeffords,R.M. (1975):
Cenozoic planktonic foraminiferal zonation and characteristics of index forms . Paleontological ContributionsArticle 62 p. 425

Blow,W.H. (1979):
The Cainozoic Globigerinida. 3 Vols p. 1413 pp

Toumarkine,M. and Luterbacher,H.P. (1985):
Paleocene and Eocene Planktic Foraminifera.
In: Plankton Stratigraphy p. 87-154

Warraich,M.Y..; Ogasawara,K.. and Nishi,H.. (2000):
Late Paleocene to early Eocene planktonic foraminiferal biostratigraphy of the Dungan Formation, Sulaiman Range, Central Pakistan . Paleontological Research Vol. 4 p. 275-301

Warraich,M.Y.. and Ogasawara,K.. (2001):
Tethyan Paleocene-Eocene planktic foraminifera from the Rakhi Nala and Zinda Pir land sections of the Sulaiman Range, Pakistan . Science Reports of the Institute of Geoscience University of Tsukuba, section B Vol. 22 p. 1-59

Pearson,P.N.; Nicholas,C.J..; Singano,J.M..; Bown,P.R..; Coxali,H.K..; van Dongen,B.E..; Huber,B.T.; Karega,A..; Lees,J.A..; Misaky,E..; Pancost,R.D..; Pearson,M.. and Roberts,A.P.. (2004):
Paleogene and Cretaceous sediment cores from the Kilwa and Lindi areas of coastal Tanzania: Tanzania Drilling Project Sites 1-5 . Journal of African Earth Sciences Vol. 39 p. 25-62

Pearson,P.N.; Olsson,R.K.; Hemleben,C.; Huber,B.T. and Berggren,W.A. (2006):
Atlas of Eocene Planktonic Foraminifera. p. 1-513
Anonymous: Unedited TaxonConcept data
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