Triscutum


Classification: Mesozoic -> Podorhabdales -> Mazaganellaceae -> Triscutum
Sister taxa: Mazaganella, Triscutum,

Distinguishing features: Three-shielded placoliths with a wide central-area spanned by a proximal net or grill.


Daughter taxa: (blue => in age window 0-300Ma)
Triscutum with broad high distal shield and central area spanned by a perforate net.
Triscutum with a wide central area spanned by a net formed from numerous, (~80) thin lateral bars.
A small to medium Triscutum with a relatively narrow central area nearly filled by an axial cross structure.
Triscutum with relatively low and narrow shields.
Triscutum with broad shields and relatively narrow central area.
Specimens not identified to species level

Taxonomy:

Citation: Triscutum Dockerill, 1987
Rank: Genus
Type species: Triscutum beaminsterensis Dockerill, 1987.

Farinacci & Howe catalog pages: Triscutum *

Distinguishing features: Three-shielded placoliths with a wide central-area spanned by a proximal net or grill.


Morphology remarks: Species are often difficult to identify in LM because the distinctive central area structures may be imperceptible or missing. Conversely, several species have been described without observations of central structures (e.g. T. sullivanii, T. tiziense).

Geological Range:
Last occurrence (top): within Oxfordian Stage (157.25-163.47Ma, top in Oxfordian stage). Data source: Total of range of species in this database
First occurrence (base): within Sinemurian Stage (190.82-199.30Ma, base in Sinemurian stage). Data source: Total of range of species in this database

Plot of occurrence data:

References:

Bown, P.R. & Cooper, M.K.E., (1998). Jurassic. In: Bown, P.R. (Editor), Calcareous nannofossil biostratigraphy. British Micropalaeontological Society Publication Series. Chapman & Hall, pp. 34-85.

Dockerill, H.J., (1987). Triscutum, a distinctive new coccolith from the Jurassic. Bulletin des Centres de Recherches Exploration-Production Elf-Aquitaine, 11: 127-131.


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Triscutum compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 20-7-2018

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