Catalog - Petaloglobigerina simmonsi

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Petaloglobigerina simmonsi

Citation: Petaloglobigerina simmonsi Gradstein, in Gradstein & Waskowska 2021

Type sample (& lithostrat): Tojeira Formation

Type age (chronostrat): Early Kimmeridgian

Type locality: Montejunto area (Estramadura), central Portugal.

Type repository: Krakow; European Micropalaeontology Reference Centre of the MicroPress Europe Foundation at AGH, Krakow, Poland.

Test generally in the 100–150 μm range, trochospiral, low spired. Final whorl large and often almost flat with 3.5–4 petaloide and ovate chambers, rarely finger-like; chamber periphery may become narrow and even pseudo-keeled, but us not imperforate. In larger specimens, individual chambers in the last whorl may slightly twist from the coiling axis; sutures strongly incised; umbilicus narrow or closed; aperture a narrow slit with rim at base of last chamber in umbilical position. A small and incomplete (half) bulla may be rarely present, shielding the aperture. Wall microperforate and densely pustulose, with pustules fusing to form irregular ridges.

The new species name is in honour of Dr. Mike Simmons, who made major contribution to the understand- ing of this group of microfossils with his taxonomic study published in 1997 (Simmons et al. 1997).

Smaller and likely mostly juvenile specimens in the assemblages have been assigned to G. balakhmatovae (Stam 1986; Gradstein et al. 2017a, b) with its characteristic four chambers in the low concave last whorl, shaped in a clover-like pattern; aperture is a slit, and there is no bulla.

We postulate that P. simmonsi nov. gen., nov. sp. shows a morphological transition in its ontogeny from G. balakhmatovae, the latter being its evolutionary ancestor.

There is no stratigraphic record of the P. simmonsi nov. gen., nov. sp. in post (early) Kimmeridgian strata for which we lack sample material with free specimens. Gradstein et al. (2018) proposed the change from specimens, now assigned to P. simmonsi nov. gen., nov. sp. to Clavihedbergella eocretacea Neagu 1975 in the early Berriasian, but more information is essential. In C. eocretacea, chambers in the last whorl expand more in size and the apertural position is umbilical extra-umbilical or interiomarginal, not umbilical as in P. simmonsi nov. gen., nov. sp. Aperture is a low arch or slit with a narrow rim in both taxa. Chambers in both taxa may become somewhat elongated and rather flat, and may twist relative to the plane of coiling. In both taxa, four chambers are commonly found in the last whorl. Both taxa also have an ovate chamber shape, with a tendency to a narrow periphery and a rugulose wall texture.

References:

Gradstein, F. & Waskowska, A. (2021). New insights into the taxonomy and evolution of Jurassic planktonic foraminifera. Swiss Journal of Palaeontology. 140(1): 1-12. gs O

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: Petaloglobigerina simmonsi Gradstein, in Gradstein & Waskowska 2021

Petaloglobigerina simmonsi

References:

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