Catalog - Globuligerina tojeiraensis

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Globuligerina tojeiraensis

Citation: Globuligerina tojeiraensis Gradstein 2017

Type sample (& lithostrat): Tojeira Formation, Montejunto Formation, central Portugal Sample 24/2P "positioned slightly above the thin limestone beds in Fig. 2."""

Type age (chronostrat): Early Kimmeridgian age (Planula-Platynota zones).

Type repository: Krakow; European Micropaleontological Reference Centre of the Micropress Foundation, AGH University, Krakow, Poland

Relatively low to medium high trochospiral, with an H/D ratio of 0.3–05, rarely larger. Test consists of 2–3 whorls with a tiny initial chamber (where visible). No preferred coiling direction observed. Last whorl with four chambers, which strongly increase in width, flaring out. Chambers are rounded with deeply incised sutures; chambers in the last whorl often radially elongate and higher than broad; last chamber often pointing slightly left or right in the equatorial plane. The test has a sunk-in umbilical region; umbilicus small to large (wide open). G. tojeiraensis has this peculiar knack (depressed umbilicus) with surrounding chambers often sticking up two by two. The chambers 2 and 4 of the last whorl stick more up than chambers 1 and 3.
Aperture a low to rarely high arch; it may be slightly asymmetrical in shape, as shown on Fig. 12.5a; aperture generally umbilical in position, rarely umbilical—extraumbilical. A small bulla occurs rarely; it obscures the aperture of the final chamber. Wall pustulose; pustules may fuse to form broken ridges.

Differential diagnosis: G. tojeiraensis differs from G. oxfordiana in its elongated (stretched) chambers in the last whorl, often oblique last chamber (pointing left or right), and often wide open umbilicus. The wall sculpture is densely pustulose, with pustules forming broken ridges; a trend not normally seen in G. oxfordiana. G. tojeiraensis is generally higher spired than G. balakhmatovae and G. oxfordiana and lower spired than G. bathoniana, none of which have elongated chambers, or a wide umbilicus.

Range and occurrence: The type level is the Tojeira Formation, Montejunto Formation, central Portugal of Early Kimmeridgian age (Planula-Platynota zones). The species is common in the Portugese outcrops. A number of small, compact specimens with limited umbilical opening, but typical oblique last chamber occur in swc 50000, Bittern M-62 well, Grand Banks. The sample is of Late Callovian to Early Oxfordian age (Gradstein et al., in prep.). The taxon probably also occurs in the Birmenstorfer Schichten (Oxfordian), Canton Aargau, Switzerland. Non-reticulate specimens of Conoglobigerina caucasica Gorbachik and Poroshina (1979) from the early Berriasian of Azerbijan, shown by Simmons et al. (1997) on their plate 2.6 may belong in Globuligerina tojeiraensis. Possibly, this species extends from Kimmeridgian into Berriasian. More discussion on this is in Gradstein et al. (in prep).

Phylogeny: In Bittern M-62 well, compact specimens with a ‘sideways leaning’ last chamber assigned to G. tojeiraensis have the second chamber of the last whorl typically ‘sticking up’, as in G. oxfordiana. In the Portugese material, where the taxon is common, morphological transitions occur to G. oxfordiana. Hence, this indicates that the latter is a possible ancestor.

References:

Gorbachik, T. N. & Poroshina, L. A. (1979). Новые планктонные фораминиферы из берриасских отложений Азербайджана [New planktonic foraminifera from the Berriasian of Azerbaijan]. Paleontologicheskiy Zhurnal. (3): 22-28. gs

Gradstein, F. M. (2017a). New and emended species of Jurassic planktonic foraminifera. Swiss Journal of Palaeontology. 136(2): 161-185. gs

Simmons, M. D., Boudagher-Fadel, M. K., Banner, F. T. & Whittaker, J. E. (1997). The Jurassic Favusellacea, the earliest Globigerina. In, Boudagher-Fadel, M. K., Banner, F. T. & Whittaker, J. E. (eds) The Early Evolutionary History of Planktonic Foraminifera. British Micropalaeontological Society Publication Series . 17-30. gs

CATALOG OF ORIGINAL DESCRIPTIONS: Globuligerina tojeiraensis Gradstein 2017

Globuligerina tojeiraensis

References:

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