Nannotax3 - ntax_mesozoic - Mitrolithus elegans

Distinguishing features:
Parent taxon (Mitrolithus): Protolith coccoliths with high rim with broad proximal/inner rim cycle; central area filled by a massive boss/spine. Often seen in side view
This taxon: Mitrolithus with steeply sloping, high rim with very wide inner cycle on which sits a lens-shaped spine. Bicyclic rim image in XPL with distinctive broad, bright inner cycle and no central opening. Often seen in side view revealing the distinctive lens-shaped spines. Detached spines are circular in plan view (described as Alvearium dorsetense Black, 1965).

Citation: Mitrolithus elegans Deflandre in Deflandre & Fert, 1954

Synonyms: Alvearium dorsetense Black, 1965

Variants: Mattioli in Abdi et al. 2022, has described three new species of Mitrolithus from the Late Sinemurian of Iran - these are similar to M. elegans but with expanded spines.

Mitrolithus montgolfieri Mattioli in Abdi et al. 2022
Mitrolithus pseudonannoconus Mattioli in Abdi et al. 2022
Mitrolithus tethysiensis Mattioli in Abdi et al. 2022

Geological Range:
Last occurrence (top): within Late Pliensbachian Substage (184.20-188.00Ma, top in Pliensbachian stage). Data source: Bown & Cooper 1998
First occurrence (base): at base of NJ2a subzone (0% up, 199.7Ma, in Hettangian stage). Data source: Bown & Cooper 1998 (fig. 4) - secondary events; Mattioli & Erba 1999

References:

Abdi, A., Mattioli, E. & Bádenas, B. (2022). A new calcareous nannofossil record from the Lower Jurassic of Kermanshah, Western Iran: implications for biostratigraphy and evolutionary reconstructions. Geosciences. 12(59): 1-17. gs

Black, M. (1965). Coccoliths. Endeavour. 24: 131-137. gs

Bown, P. R. & Cooper, M. K. E. (1998). Jurassic. In, Bown, P. R. (ed.) Calcareous Nannofossil Biostratigraphy. British Micropalaeontological Society Publication Series . 34-85. gs O

Bown, P. R. (1987a). Taxonomy, evolution, and biostratigraphy of Late Triassic-Early Jurassic calcareous nannofossils. Special Papers in Palaeontology. 38: 1-118. gs

Bown, P. R. (1987b). The structural development of Early Mesozoic coccoliths and its evolutionary and taxonomic significance. Abhandlungen der Geologischen Bundesanstalt. 39: 33-49. gs

Crux, J. A. (1987b). Early Jurassic calcareous nannofossil biostratigraphic events. Newsletters on Stratigraphy. 17: 79-100. gs

Deflandre, G. & Fert, C. (1954). Observations sur les coccolithophoridés actuels et fossiles en microscopie ordinaire et électronique. Annales de Paléontologie. 40: 115-176. gs

Kristan-Tollmann, E. (1988). Coccolithen aus den Älteren Allgäuschichten (Alpiner Lias, Sinemur) von Timor, Indonesien. Geologisch-Paläontologische Mitteilungen Innsbruck. 15: 71-83. gs

Mattioli, E. & Erba, E. (1999). Synthesis of calcareous nannofossil events in Tethyan lower and middle Jurassic successions. Rivista Italiana di Paleontologia e Stratigrafia. 105(3): 343-376. gs

Prins, B. (1969). Evolution and stratigraphy of cocolithinids from the Lower and Middle Lias. In, Bronnimann, P. & Renz, H. H. (eds) Proceedings of the First International Conference on Planktonic Microfossils, Geneva 1967. E. J. Brill, Leiden 547-558. gs

Rood, A. P., Hay, W. W. & Barnard, T. (1973). Electron microscope studies of Lower and Middle Jurassic coccoliths. Eclogae Geologicae Helvetiae. 66: 365-382. gs O

Mitrolithus elegans

References:

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