Globigerinatheka subconglobata


Classification: pf_cenozoic -> spinose -> Globigerinidae -> Globigerinatheka -> Globigerinatheka subconglobata
Sister taxa: G. barri, G. curryi, G. euganea, G. index, G. korotkovi, G. kugleri, G. luterbacheri, G. mexicana, G. semiinvoluta, G. subconglobata, G. tropicalis, G. sp.,

Taxonomy

Citation: Globigerinatheka subconglobata Shutskaya 1958
Rank: Species
Basionym: Globigerinoides subconglobatus subconglobata
Synonyms:
Taxonomic discussion: The specimens illustrated by Subbotina (1953) as G. conglobatus (pl. 14, figs. 2a-5b) are attributable to (or fall within the variability of) G. tropicalis as suggested by Blow and Banner (1962) and followed by Bolli (1972). Even though some of Subbotina’s specimens exhibit a subrectangular outline similar to G. index, they do not possess the high semicircular aperture or the incised sutures typical of the latter species. The specimen illustrated by Subbotina (1953, pl. 13, figs. 19a,b) as G. rubriformis, which has a very low spire and high-arched primary and supplementary apertures, is here considered very similar, if not identical, to G. tropicalis. The specimen illustrated by Jenkins (1971, pl. 21, figs. 633-634) as G. (G.) semiinvoluta appears very similar to G. tropicalis with its low-arched, non-subcircular primary and supplementary apertures and more sub-rectangular test shape. The specimen illustrated by Krasheninnikov and Basov (1983) as Globigerapsis index (pl. 7, fig. 1) due to its outline, appears closer to G. tropicalis, while the specimen of G. aff. tropicalis illustrated by the same authors seems to have a long inner spire, so it is doubtfully attributed to Blow and Banner’s species G. tropicalis. [Premoli Silva et al. 2006]

Catalog entries: Globigerinoides subconglobatus subconglobata;

Type images:

Short diagnosis: The distinctly depressed sutures, medium low spire and mainly subcircular apertures with rims characterize G. tropicalis. Globigerinatheka tropicalis has frequently been confused with G. index. According to Blow and Banner (1962), G. tropicalis differs from G. index in lacking the very thick wall, deeply incised sutures, and heavily granular surface characteristic of G. index. In addition, G. tropicalis exhibits a less compact outline, smaller and less subcircular primary aperture without a thick lip, and more numerous smaller secondary apertures than G. index. Bolli (1972) agreed with Blow and Banner (1962) in including some of his specimens identified as G. index in G. tropicalis. Meanwhile, it is hard to separate Globigerinatheka lindiensis from G. tropicalis, except for the presence of bullae in the former, and in agreement with Bolli (1972), we consider G. lindiensis a junior synonym of G. tropicalis. Blow (1979) considered G. tropicalis as junior synonym of G. mexicana mexicana (p. 825), but in our opinion, these two taxa are not conspecific. Globigerinatheka tropicalis differs from G. semiinvoluta by its less compact test, less embracing final chamber, distinct sutures and mainly high arched apertures.

NB The short diagnoses are used in the tables of daughter-taxa to act as quick summaries of the differences between e.g. species of one genus. They have initially been copied from the diagnostic characters/distinguishing features sections of the Eocene and Paleocene Atlases, they will be edited as the site is developed.

Description


Diagnostic characters: The distinctly depressed sutures, medium low spire and mainly subcircular apertures with rims characterize G. tropicalis. Globigerinatheka tropicalis has frequently been confused with G. index. According to Blow and Banner (1962), G. tropicalis differs from G. index in lacking the very thick wall, deeply incised sutures, and heavily granular surface characteristic of G. index. In addition, G. tropicalis exhibits a less compact outline, smaller and less subcircular primary aperture without a thick lip, and more numerous smaller secondary apertures than G. index. Bolli (1972) agreed with Blow and Banner (1962) in including some of his specimens identified as G. index in G. tropicalis. Meanwhile, it is hard to separate Globigerinatheka lindiensis from G. tropicalis, except for the presence of bullae in the former, and in agreement with Bolli (1972), we consider G. lindiensis a junior synonym of G. tropicalis. Blow (1979) considered G. tropicalis as junior synonym of G. mexicana mexicana (p. 825), but in our opinion, these two taxa are not conspecific. Globigerinatheka tropicalis differs from G. semiinvoluta by its less compact test, less embracing final chamber, distinct sutures and mainly high arched apertures. [Premoli Silva et al. 2006]

Wall type: Spinose, cancellate, rather thick, with pores about 4 µm in diameter, frequently recrystallized. [Premoli Silva et al. 2006]

Test morphology: Test globular to nearly spherical, formed by 3 whorls, initially coiled in low trochospire becoming progressively higher and slightly streptospiral in the last whorl; chambers globular, small and very slowly increasing in size as added up to half of the second whorl, then increasing gradually but progressively faster; the first chamber of the last whorl is about half the size of the antepenultimate, the latter and penultimate chamber have a very similar size, the last chamber is typically smaller and flattened; initially 4 to 5 chambers per whorl, and typically 4 chambers in the last whorl; in spiral view chambers of the last whorl longer than wide, elongate in coiling direction, in umbilical view the last chamber is small and straddles the three previous chambers; sutures distinct throughout, weakly depressed in the inner coils, then moderately depressed; primary aperture umbilical, a low rather wide arch at the base of the last chamber, one to two small low arched secondary apertures at the intersections between the base of the last chamber and previous sutures, apertures frequently poorly visible. [Premoli Silva et al. 2006]

Size: The size of specimens is highly variable ranging in diameter from 0.30 mm to 0.65 mm; medium sized specimens are rather common. Diameter of the lectotype (Shutskaya, 1958, pl. 1, fig. 8) ca. 0.50 mm. [Premoli Silva et al. 2006]

Character matrix

test outline:Circularchamber arrangement:Trochospiraledge view:Equally biconvexaperture:Umbilical
umb chamber shape:Globularcoiling axis:Lowperiphery:N/Aaperture border:N/A
sp chbr shape:Globularumbilicus:Narrowperiph margin shape:Broadly roundedaccessory apertures:Sutural
umbilical or test sutures:Moderately depressedumb depth:Deepwall texture:Spinoseshell porosity:Finely Perforate: 1-2.5
spiral sutures:Moderately depresseddiameter mm:0.5width mm:breadth mm:
final-whorl chambers:4.0-4.0

Biogeography and Palaeobiology


Geographic distribution: Jenkins (1971) considered G. tropicalis to be the tropical equivalent of G. index, a taxon that, according to Blow (1969), is largely restricted to cooler water habitat. Bolli (1972) extended the distribution of G. tropicalis to mid latitudes. [Premoli Silva et al. 2006]
Aze et al. 2011 summary: Cosmopolitan; based on Premoli Silva et al. (2006)

Isotope paleobiology: No data available. [Premoli Silva et al. 2006]
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): Pearson et al. (1993)

Phylogenetic relations: Globigerinatheka tropicalis evolved from G. index. [Premoli Silva et al. 2006]

Biostratigraphic distribution

Geological Range:
Notes: The appearance of G. tropicalis is poorly constrained; it occurs in the upper middle Eocene (upper Zone E13) and is common in Zone E14. It has been suggested that G. tropicalis is the last globigerinathekid to disappear (see Bolli, 1972). At middle latitudes Nocchi and others (1988) showed that the extinction of G. tropicalis occurs in the latest Eocene at the same level as the extinction of hantkeninids (= Eocene/Oligocene boundary), postdating the disappearance of G. index and Turborotalia cunialensis. [Premoli Silva et al. 2006]
Last occurrence (top): within E13 zone (37.99-39.97Ma, top in Bartonian stage). Data source: Eocene Atlas
First occurrence (base): within E8 zone (43.85-45.72Ma, base in Lutetian stage). Data source: Eocene Atlas

Plot of occurrence data:

Primary source for this page: Premoli Silva et al. 2006 - Atlas of Eocene Planktonic Foraminifera, chapter 7, p. 201

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, 1413 pp.

Bolli, H.M., (1957). Planktonic foraminifera from the Eocene Navet and San Fernando formations of Trinidad. In: Loeblich, A.R., Jr. et al. (Editors), Studies in Foraminifera: U.S. National Museum Bulletin 215. U.S. Government Printing Office, Washington, D.C., pp. 155-172.

Bolli, H.M., (1972). The genus Globigerinatheka Bronnimann. Journal of Foraminiferal Research, 2(3): 109-136.

Cushman, J.A., (1925). New foraminifera from the Upper Eocene of Mexico. Contributions from the Cushman Foundation for Foraminiferal Reseach, 1(1): 4-9.

Finlay, H.J., (1939). New Zealand foraminifera: Key species in stratigraphy - no. 2. Transactions of the Royal Society of New Zealand, 69(1): 89-128.

Fleisher, R.L., (1974). Cenozoic planktonic foraminifera and biostratigraphy, Arabian Sea, Deep Sea Drilling Project, Leg 23A. Initial Reports of the Deep Sea Drilling Project, 23: 1001-1072.

Pearson, P.N.; Shackleton, N.J. & Hall, M.A., (1993). Stable isotope paleoecology of middle Eocene planktonic foraminifera and multi-species isotope stratigraphy, DSDP Site 523, South Atlantic. Journal of Foraminiferal Research, 23: 123-140.

Poag, C.W. & Commeau, J.A., (1995). Paleocene to middle Miocene planktic foraminifera of the southwestern Salisbury Embayment, Virginia and Maryland: Biostratigraphy, allostratigraphy, and sequence stratigraphy. Journal of Foraminiferal Research, 25: 134-155.

Premoli Silva, I.; Wade, B.S. & Pearson, P.N., (2006). Taxonomy, biostratigraphy, and phylogeny of Globigerinatheka and Orbulinoides. In: Pearson, P.N. et al. (Editors), Atlas of Eocene Planktonic Foraminifera, Cushman Foundation Special Publication 41. Allen Press, Lawrence, Kansas, pp. 169-212.

Pujol, C., (1983). Cenozoic planktonic foraminiferal biostratigraphy of the South-Western Atlantic (Rio Grande Rise): Deep Sea Drilling Project Leg 72. Initial Reports of the Deep Sea Drilling Project, 72: 623-673.

Shutskaya, E.K., (1958). Variability in some lower Paleogene planktonic foraminifera from the northern Caucasus. Voprosy Mikropal, Moscow, 1958(2): 86.

Snyder, S.W. & Waters, V.J., (1985). Cenozoic planktonic foraminiferal biostratigraphy of the Goban Spur Region, Deep Sea Drilling Project Leg 80. Initial Reports of the Deep Sea Drilling Project, 80: 439-472.

Stainforth, R.M.; Lamb, J.L.; Luterbacher, H.; Beard, J.H. & Jeffords, R.M., (1975). Cenozoic planktonic foraminiferal zonation and characteristics of index forms. The University of Kansas Paleontological Contributions, 62: 1-425.

Toumarkine, M., (1971). Etude des Foraminifères planctoniques de deux sondages (H-S49 et PGYT-31) dans l’ Eocène de la Montagne du Bakony (Transdanubie, Hongrie). Annales Instituti Geologici Publici Hungarici, 54: 283-299.

Toumarkine, M., (1975). Middle and Late Eocene planktonic foraminifera from the northwestern Pacific Ocean: Leg 32 of the Deep Sea Drilling Project. Initial Reports of the Deep Sea Drilling Project, 32: 735-751.

Toumarkine, M., (1978). Planktonic foraminiferal biostratigraphy of the Paleogene of Sites 360 to 364 and the Neogene of Sites 362A, 363 and 364 Leg 40,. Initial Reports of the Deep Sea Drilling Project, 40: 679-721.

Toumarkine, M., (1983). Les Foraminifères planctoniques de l’Eocène moyen et supérieur des régions tropicales à temperées chaudes. PhD Thesis, Université Pierre et Marie Curie, Paris 6, 83-05, 1-219 pp.


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Globigerinatheka subconglobata compiled by the pforams@mikrotax project team viewed: 19-8-2017

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