Toweius


Classification: ntax_cenozoic -> Isochrysidales -> Prinsiaceae -> Toweius
Sister taxa: Futyania, Hornibrookina, Neobiscutum, Prinsius, Toweius

Taxa ordered alphabetically (time control age-window is: 0-800Ma)
robust bars on distal surface define pores which are clearly visible in LM
Toweius serotinus
Medium sized (6-8 µm) with >=10 pores
Toweius pertusus
Small to medium-sized (4-6 µm) with >=10 peforations.
Toweius tovae
Medium to large with 5-9 (frequently 6) large pores 
Toweius eminens
Medium sized (typically 6-8 µm) with 4 large pores.
Toweius occultatus
Medium to large with 2 large openings in the central area.
Finely perforate central plate
Toweius reticulum
Very small (2-3µm); narrowly elliptical; central area wide, spanned by radial bars.
Toweius selandianus
Very small to small (2-4µm); narrowly elliptical; central area narrow, spanned by a net.
Toweius rotundus
Small (~<4 µm); sub-circular to circular; central area narrow, spanned by a plate with perforations too small to resolve in LM.
Toweius patellus
Medium sized; broadly elliptical to sib-circular; central area broad, spanned by a plate with perforations too small to resolve in LM.
Toweius callosus
Medium sized (4-8 µm); elliptical to sub-circular Toweius; central area spanned by a fine proximal net that is not typically discernible in LM.
Toweius magnicrassus
Large to very large (8-15 µm); broadly elliptical to subcircular; central area narrow. Shields are moderately birefringent and tube cycle is highly birefringent.
Central plug
Toweius gammation
Medium sized; circular; central area with bright central plug crossed by strongly curving swastika-like extinction lines. Shield elements are usually conspicuous in LM.
Unidentified
Toweius sp.
Specimens which cannot be assigned to any established species

Taxonomy:

Citation: Toweius Hay and Mohler, 1967
Rank: Genus
Type species: Toweius craticulus Hay and Mohler, 1967, a junior synonym of Toweius pertusus (Sullivan, 1965) Romein, 1979
Synonyms: Girgisia Varol 1989 - proposed as separate genus for T. gammation

Distinguishing features:

Elliptical to circular prinsiacean placoliths with central areas that are typically spanned by a proximal net and/or distal conjunct nets or bars. Typically medium sized.

Farinacci & Howe catalog pages: Toweius * , Girgisia *


Morphology:

 Intergrade with Prinsius but distinguished by wider,better-developed, central area nets.

Search data:
TagsLITHS: placolith, circular, elliptical, CA: ca_conjunct, grill, vacant,
CSPH: equant, monomorphic, CROSS-POLARS: rim-bicyclic, V-prominent, R-prominent,
MetricsLith size: 2->16µm;
The morphological data given here can be used on the advanced search page. See also these notes

Geological Range:
Notes: Toweius was one of the dominant placolith groups of the late Paleocene to early Eocene but declined, broadly coincident with the appearance and rise of the reticulofenestrid group in the early Eocene (zones NP12–13) (e.g., Agnini et al. 2006). The extinction of Toweius has remained poorly constrained with reports ranging from Zone NP12 (Bralower & Mutterlose 1995) to Zone NP15 (Perch-Nielsen, 1985). Relatively common Toweius coccoliths were documented in equatorial Pacific sites up to Zone NP15 by Bown & Dunkley Jones (2012) and similarly we see Toweius through to Subzone NP15b in the Exp. 342 sites (e.g. Site U1409), confirming this later extinction level. [Bown & Newsam 2017]
Last occurrence (top): in upper part of Lutetian Stage (74% up, 42.9Ma, in Lutetian stage). Data source: Total of range of species in this database
First occurrence (base): in upper part of Danian Stage (63% up, 63.2Ma, in Danian stage). Data source: Total of range of species in this database

Plot of occurrence data:

References:

Agnini, C., Muttoni, G., Kent, D. V. & Rio, D. (2006). Eocene biostratigraphy and magnetic stratigraphy from Possagno, Italy: The calcareous nannofossil response to climate variability. Earth and Planetary Science Letters. 2241: 815-830. gs

Agnini, C., Fornaciari, E., Raffi, I., Rio, D., Rohl, U. & Westerhold, T. (2007a). High-resolution nannofossil biochronology of middle Paleocene to early Eocene at ODP Site 1262: Implications for calcareous nannoplankton evolution. Marine Micropaleontology. 64: 215-248. gs

Agnini, C., Fornaciari, E. & Raffi, I. (2008). Three new species of calcareous nannofossil from Late Palaeocene and Early Eocene assemblages (Ocean Drilling Program Site 1262, Walvis Ridge, SE Atlantic Ocean). Journal of Nannoplankton Research. 30(1): 51-56. gs V O

Bown, P. R. & Dunkley Jones, T. (2012). Calcareous nannofossils from the Paleogene equatorial Pacific (IODP Expedition 320 Sites U1331-1334). Journal of Nannoplankton Research. 32(2): 3-51. gs V O

Bown, P. R. & Newsam, C. (2017). Calcareous nannofossils from the Eocene North Atlantic Ocean (IODP Expedition 342 Sites U1403–1411). Journal of Nannoplankton Research. 37(1): 25-60. gs V O

Bralower, T. J. & Mutterlose, J. (1995). Calcareous nannofossil biostratigraphy of Site U865, Allison Guyot, Central Pacific Ocean: a tropical Paleogene reference section. Proceedings of the Ocean Drilling Program, Scientific Results. 143: 31-74. gs V O

Hay, W. W. & Mohler, H. P. (1967). Calcareous nannoplankton from Early Tertiary rocks at Point Labau, France and Paleocene-Early Eocene correlations. Journal of Paleontology. 41(6): 1505-1541. gs

Perch-Nielsen, K. (1985a). Cenozoic calcareous nannofossils. In, Bolli, H. M., Saunders, J. B. & Perch-Nielsen, K. (eds) Plankton Stratigraphy. Cambridge University Press, Cambridge 427-555. gs

Romein, A. J. T. (1979). Lineages in Early Paleogene calcareous nannoplankton. Utrecht Micropaleontological Bulletin. 22: 1-231. gs V O

Sullivan, F. R. (1965). Lower Tertiary nannoplankton from the California Coast Ranges. II. Eocene. University of California Publications in Geological Sciences. 53: 1-74. gs

Varol, O. (1989b). Eocene calcareous nannofossils from Sile (northwest Turkey). Revista Española de Micropaleontología. 21: 273-320. gs V O


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Toweius compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 18-4-2021

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Short stable page link: https://mikrotax.org/Nannotax3/index.php?id=1413 Go to Archive.is to create a permanent copy of this page - citation notes



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