Globigerinatheka mexicana


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

Taxonomy

Citation: Globigerinatheka mexicana (Cushman 1925)
Rank: Species
Basionym: Globigerina mexicana
Synonyms:
Variants: sm
Taxonomic discussion: As reported by Bolli (1972, p. 129), Cushman’s species mexicana “has been misinterpreted more than any other of the Globigerinatheka” (see the synonymy list) owing to the inadequate original description and illustrations and to the fact that specimens with different features and of much larger sizes than the holotype have been identified as mexicana, including by Cushman himself (1927). Saito (1962), in emending mexicana, regarded it as being very closely related to barri, which he interpreted as the bullate form of the former. Saito’s view was followed by Bolli (1972, p. 129) who, based on Beckmann’s observation of the original types, considered mexicana s. s. and barri as subspecies of Globigerinatheka mexicana. Bolli (1972) also included in mexicana his species kugleri, again as a subspecies of it, based on his finding intermediate forms, a view rejected here (see above). For instance, the specimen illustrated by Bolli (1972, pl. 2, fig. 5, the spiral view) as G. mexicana mexicana for its subtriangular outline is attributable to G. kugleri. Toumarkine (1978) illustrated as G. mexicana mexicana some specimens that do not possess the last large enveloping chamber and have a rather short, not flat initial spire; they may be closer to G. barri. The specimen attributed by Samanta (1970, pl. 2, figs. 20-21) to G. barri in our opinion exhibits a large last chamber that is more characteristic of G. mexicana. Blow (1979, p. 789) referred Globigerinatheka kutchensis Singh and Tewari, 1967 to G. mexicana mexicana because it possesses abortive chambers and not true bullae. Blow and Saito (1968a) regarded mexicana as synonymous with semiinvoluta, whilst Blow (1979) considered mexicana as synonymous with tropicalis. We recognise all these species as separate taxa (also see Bolli, 1972 for discussion). [Premoli Silva et al. 2006]

Catalog entries: Globigerina mexicana;
Globigerinatheka kutchensis;

Type images:

Distinguishing features: Test nearly spherical. Last chamber large (ca ½ test), inflated. Sutures not vey distinct.

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: Globigerinatheka mexicana is characterized by its nearly spherical test and large inflated last chamber that comprises about half of the entire test. It differs from G. semiinvoluta by its less embracing last chamber and smaller secondary apertures that lack a rim, from G. barri by its larger hemispherical last chamber, less depressed sutures throughout, spherical outline and less common bullae, and from G. kugleri by its more spherical test and less distinct sutures. [Premoli Silva et al. 2006]

Wall type: pores about 4 mm in diameter.

Test morphology: Test very close to spherical, early chambers arranged in a low trochospire composed of at least 6 subglobular chambers initially gradually increasing in size as added, then increasing much more rapidly; last chamber hemispherical constituting almost half of the entire test totally covering the umbilical side of the earlier chambers; sutures poorly visible except between the last two to three chambers where they are very slightly depressed; three visible apertures at the base of the last chamber, small to medium-sized arches close to subcircular, apparently located at the junctions of previous chambers. [Premoli Silva et al. 2006]

Size: The diameter of the holotype measures 0.30 mm, much smaller than that indicated by Cushman (1925, diameter 0.40-0.60 mm). [Premoli Silva et al. 2006]

Character matrix

test outline:Circularchamber arrangement:Trochospiraledge view:Equally biconvexaperture:Biapertural
umb chamber shape:Globularcoiling axis:Lowperiphery:N/Aaperture border:N/A
sp chbr shape:Globularumbilicus:Narrowperiph margin shape:Broadly roundedaccessory apertures:None
umbilical or test sutures:Weakly depressedumb depth:Deepwall texture:-shell porosity:Macroperforate: >2.5µm
spiral sutures:Weakly depressedfinal-whorl chambers:3.0-3.5

Biogeography and Palaeobiology


Geographic distribution: Low to mid latitudes. [Premoli Silva et al. 2006]

Isotope paleobiology: Globigerinatheka mexicana has oxygen and carbon isotopic ratios indicative of a mixed layer habitat (Boersma and others, 1987; Wade, 2004). [Premoli Silva et al. 2006]

Phylogenetic relations: Bolli (1972, p. 114) stated that mexicana “branched off from G. subconglobata micra near the base of G. subconglobata subconglobata Zone (= upper part of Zone E8), while the subspecies barri and kugleri originated from mexicana s.s. in subsequent order always within the G. subconglobata subconglobata Zone”. Besides Bolli (1972), other authors (i.e., Stainforth and others, 1975; Blow, 1979; Toumarkine, 1983) all agree that mexicana appears first, followed slightly later by barri. Consequently, G. mexicana probably descended from the G. subconglobata plexus close to the E8/E9 zonal boundary. Through Zone E13, the sutures of G. mexicana become less pronounced, the final chamber more spherical and apertures semicircular to circular in outline. In uppermost Zone E13 and lowermost E14 in the western North Atlantic (ODP Site 1052), transitional forms are evident to G. semiinvoluta (Plate 7.8, Fig. 11). [Premoli Silva et al. 2006]

Most likely ancestor: Globigerinatheka subconglobata - at confidence level 3 (out of 5). Data source: Premoli Silva et al. 2006 f7.1.
Likely descendants: Globigerinatheka semiinvoluta;

Biostratigraphic distribution

Geological Range:
Notes: Globigerinatheka mexicana appears in the lower middle Eocene and its first occurrence was used to identify the base of Zone P11 (=E9) sensu Stainforth and others, 1975; Blow, 1979; Toumarkine, 1983. Although the appearance of G. mexicana is poorly calibrated it seems it occurs very close to that of G. kugleri. It ranges up to the topmost part of E14. [Premoli Silva et al. 2006]
Last occurrence (top): within E14 zone (35.89-37.99Ma, top in Priabonian stage). Data source: Premoli Silva et al. 2006 f7.1
First occurrence (base): within E9 zone (43.23-43.85Ma, base in Lutetian stage). Data source: Premoli Silva et al. 2006 f7.1

Plot of occurrence data:

Primary source for this page: Premoli Silva et al. 2006 - Eocene Atlas, chap. 7

References:

Baumann, P., (1970). Mikropalaentologische und stratigraphische Untersuchungen der obereozaenen-oligozaenen Scaglia im zentralen Apennin (Italien). Eclogae Geologicae Helvetiae, 63: 1133-1211.

Berggren, W.A., (1992). Paleogene planktonic foraminifer magnetobiostratigraphy of the southern Kerguelen Plateau (sites 747-749). Proceedings of the Ocean Drilling Program, Scientific ResultsOcean Drilling Program, College Station, Texas, 551-568 pp.

Blow, W.H. & Banner, F.T., (1962). The mid-Tertiary (Upper Eocene to Aquitanian) Globigerinaceae. In: Eames, F.E. et al. (Editors), Fundamentals of mid-Tertiary Stratigraphical Correlation. Cambridge University Press, Cambridge, pp. 61-151.

Blow, W.H. & Saito, T., (1968). The morphology and taxonomy of Globigerina mexicana Cushman, 1925. Micropaleontology, 14(3): 357-360.

Blow, W.H., (1969). Late middle Eocene to Recent planktonic foraminiferal biostratigraphy. In: Bronnimann, P. and Renz, H.H. (Editors), Proceedings of the First International Conference on Planktonic Microfossils, Geneva, 1967, Leiden, Netherlands, pp. 380-381.

Blow, W.H., (1979). The Cainozoic Globigerinida: A study of the morphology, taxonomy, evolutionary relationships and stratigraphical distribution of some Globigerinida (mainly Globigerinacea), 2. E. J. Brill, Leiden, 1413 pp.

Boersma, A.; Premoli Silva, I. & Shackleton, N.J., (1987). Atlantic Eocene planktonic foraminiferal paleohydrographic indicators and stable isotope paleoceanography. Paleoceanography, 2: 287-331.

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.

Brönnimann, P., (1952). Globigerinoita and Globigerinatheka, new genera from the Tertiary of Trinidad, B.W.I. Contributions from the Cushman Foundation for Foraminiferal Reseach, 3(1): 25-28.

Cushman, J.A., (1925). New foraminifera from the Upper Eocene of Mexico. Contributions from the Cushman Laboratory for Foraminiferal Research, 1(3): 4-9.

Cushman, J.A., (1927). Some characteristic Mexican fossil foraminifera. Journal of Paleontology, 1(2): 147-172.

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.

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

McKeel, D.R. & Lipps, J.J., (1975). Eocene and Oligocene planktonic foraminifera from the Central and Southern Oregon Coast Range. Journal of Foraminiferal Research, 5(4): 249-269.

Mohan, M. & Soodan, K.S., (1970). Middle Eocene planktonic foraminiferal zonation of Kutch, India. Micropaleontology, 16: 37-46.

Nishi, H. & Chaproniere, G.C.H., (1994). Eocene-Oligocene subtropical planktonic foraminifers at Site 841,. Proceedings of the Ocean Drilling Program, Scientifc Results, 135: 245-266.

Poore, R.Z. & Brabb, E.E., (1977). Eocene and Oligocene planktonic foraminifera from the Upper Butano sandstone and type San Lorenzo formation, Santa Cruz Mountains, California. Journal of Foraminiferal Research, 7(4): 249-272.

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.

Raju, D.S.N., (1971). Upper Eocene to Early Miocene planktonic foraminifera from the subsurface sediments in Cauvery Basin, India. Jahrbuch der Geologischen Bundesanstalt, Sonderband, 17: 7-68.

Saito, T., (1962). Eocene planktonic foraminifera from Hahajima (Hillsborough Island). Transactions and Proceedings of the Paleontological Society of Japan, New Series, 45: 209-225.

Samuel, O. & Salaj, J., (1968). Microbiostratigraphy and Foraminifera of the Slovak Carpathian Paleogene. Geologicky Ustav Dionyza Stura, Bratislava: 1-232.

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.

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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.

Wade, B.S., (2004). Planktonic Foraminiferal biostratigraphy and mechanisms in the extinction of Morozovella in the Late Middle Eocene. Marine Micropaleontology, 51: 23-38.


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Globigerinatheka mexicana compiled by the pforams@mikrotax project team viewed: 15-12-2018

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