Nannotax3 - ntax_cenozoic - Reticulofenestra sessilis

Citation: Reticulofenestra sessilis (Lohmann 1912) Jordan & Young, 1990

Basionym: Pontosphaera sessilis Lohmann 1912

Synonyms:

Cyclolithella taiwanea Chen (1980) [my interpretation - JRY 2016]

Taxonomic discussion: Unambiguous Reticulofenestra disappears in the Early Quaternary but there are small reticulofenestrids without bridges though the Quaternary and a couple of extant species, including R. sessilis (see Young 2005), these are conventionally referred to Reticulofenestra but may prove to have descended from Gephyrocapsa by loss of the bridge.

Distinguishing features:
Parent taxon (Reticulofenestra): No bridge, no slits
This taxon: Closed central area. Rather heavily calcified giving irregular form, strongly crenulate margin.

Coccospheres 6-10 µm; liths 2.5-4 µm.

Ecology & Biogeography: Occurs almost exclusively in symbiotic(?) associations with a centric diatom of the genus Thalassiosira. Deep photic.

Geological Range:
Last occurrence (top): Extant. Data source: present in the plankton (Young et al. 2003)
First occurrence (base): within Quaternary Period (0.00-2.59Ma, base in Gelasian stage). Data source: [JRY rough estimate]

References:

Chen, M. -P. (1980). Modern and redeposited coccolithophores for the indication of sediment dispersal pattern around Taiwan offshore region. Acta Oceanographica Taiwanica. 11: 129-156. gs

Lohmann, H. (1912). Untersuchungen über das Pflanzen- und Tierleben der Hochsee, zugleich ein Bericht über die biologischen Arbeiten auf der Fahrt der "Deutschland" von Bremerhaven nach Buenos-Aires in der Zeit vom 7. Mai bis 7. September 1911. Veröffentlichungen des Instituts für Meereskunde an der Universität Berlin, Neue Folge. A. Geographisch-naturwissenschaftliche Reihe. 1: 1-92. gs V O

Okada, H. & McIntyre, A. (1977). Modern coccolithophores of the Pacific and North Atlantic Oceans. Micropaleontology. 23(1): 1-55. gs

Reid, F. M. H. (1980). Coccolithophorids of the North Pacific Central Gyre with notes on their vertical and seasonal distribution. Micropaleontology. 26(2): 151-176. gs

Young, J. R., Geisen, M., Cros, L., Kleijne, A., Probert, I. & Ostergaard, J. B. (2003). A guide to extant coccolithophore taxonomy. Journal of Nannoplankton Research, Special Issue. 1: 1-132. gs V O

Tags	LITHS: placolith, elliptical, CA: ca_conjunct, closed, CSPH: equant, monomorphic, CROSS-POLARS: rim-unicyclic, R-prominent,
Metrics	Lith size: 2.5->4µm; Coccosphere size: 6->10µm; Liths per sphere: 10->30 Data source notes: RCC

Reticulofenestra sessilis

References:

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