Zeugrhabdotus


Classification: Mesozoic -> Eiffellithales -> Chiastozygaceae -> Zeugrhabdotus
Sister taxa: Amphizygus, Archaeozygodiscus, Gorkaea, Placozygus, Reinhardtites, Tranolithus, Zeugrhabdotus, Chiastozygus, Staurolithites, Diadorhombus, Rhabdophidites, Ahmuellerella, Bukrylithus, Diloma, Heteromarginatus, Misceomarginatus, Monomarginatus, Vacherauvillius, Braloweria, Clepsilithus, Crepidolithus, Loxolithus, Neocrepidolithus, Tubirhabdus,

Distinguishing features: Murolith (loxolith) coccoliths with central area spanned by variably constructed transverse bar. The bar is usually spine bearing. Inner/proximal rim cycle is variably developed and so the LM image may be unicyclic or bicyclic. Delicate lateral bars may also be present but are generally only seen in exceptional preservation.


Daughter taxa: (blue => in age window 0-800Ma)
Unicyclic - small (3-5µm)
Unicyclic, small; bar divided longitudinally, darkest at 0°
Unicyclic(?), very small; with additional lateral bars [only known from EM]
Unicyclic, small; bar split perpendicular to length; narrow rim/large openings
Unicyclic, small; bar divided longitudinally, darkest at 0°
Unicyclic, small; bar complex
Unicyclic (or bicyclic?), small (or medium); bar complex, wide rim/small openings
Unicyclic - medium (5-8 µm)
Unicyclic, medium; bar divided longitudinally, darkest at 45°; rim broad/openings small
Unicyclic, medium; bar divided longitudinally, darkest at 60°
Unicyclic, medium; bar split perpendicular to length, darkest at 45°
Unicyclic or diffusely bicyclic, medium; bar complex, darkest at 45°
Unicyclic, medium; bar divided longitudinally and parts offset , darkest at 45°
Unicyclic, medium; reticulate net on proximal surface [only known from EM]
Unicyclic or diffusely bicyclic, medium-large (6-9µm); bar complex; narrow rim/large openings
Unicyclic - large (8-12 µm)
Unicyclic, large; bar divided longitudinally; very wide rim/very small openings
Unicyclic, small (4-6 µm); bar complex; broad rim/small openings
Unicyclic, large; with very broad spine, often seen in side view; broad rim/small openings
Bicyclic - small to medium (4-6 µm)
Bicyclic, small to medium; bar split perpendicular to length, tapers at both ends.
Bicyclic, medium sized; bar complex, flaring slightly as it meets the rim, can appear x-shaped.
Bicyclic, medium sized (5-6µm); bar complex
Bicyclic, medium sized; bar divided longitudinally, darkest at 0°, can appear x-shaped.
Bicyclic - medium to large (6-12 µm)
Diffusely bicyclic, medium-large; bar oblique to length and divided longitudinally
Diffusely bicyclic, medium to large and high; bar split perpendicular to length; broad rim/ narrow openings
Bicyclic, large; bar split perpendicular to length, spine often prominent
Bicyclic, medium-large; bar complex; bright inner rim broadest where it meets bridge, very narrow tends of central area.
Bicyclic, medium-large; bar complex; bright inner rim broadest where it meets bridge, very narrow tends of central area.
Bicyclic, large; bar simple (formed of one unit); rim narrow/openings large
Bicycle, large; bar complex, appears x-shaped in some views.
Specimens not identified to species level

Taxonomy:

Citation: Zeugrhabdotus Reinhardt, 1965
Rank: Genus
Type species: Zygolithus erectus Deflandre in Deflandre and Fert, 1954, designated by Reinhardt, 1965.
Synonyms:
Notes & discussion: The taxonomy of Zeugrhabdotus is notoriously confused. We have attempted here to characterise the described species in terms of a limited set of criteria, using both the orginal descriptions and reliably identified images:
Most species can be characterised using these criteria but there are a few problematic names which seem to have been applied with variable meanings - notably Z. erectus, Z. noeliae and Z. burwellensis. These names should be used with caution.
Co-ordinating names between electron microscopy and light microscopy is another problem. On the one hand neither the unicyclic/bicyclic division nor the bar-structure types are easy to apply in EM. on the other hand aspects of structure readily vislble in EM may not be applicable in LM. Consequently most species are only well-known from LM. It would be useful if more SEM studies were undertaken of samples where the taxonomy was well-established in the LM. Conversely there are a couple of species which are only known from the EM - Z. buroletii and Z. reticulatus. [JRY 2020]

Farinacci & Howe catalog pages: Zeugrhabdotus + + * , Glaukolithus + * , Microrhabdulinus * , Lordia * , Rectapontis *

Distinguishing features: Murolith (loxolith) coccoliths with central area spanned by variably constructed transverse bar. The bar is usually spine bearing. Inner/proximal rim cycle is variably developed and so the LM image may be unicyclic or bicyclic. Delicate lateral bars may also be present but are generally only seen in exceptional preservation.


Morphology remarks: Long-ranging group (late Triassic-early Eocene) and often common to dominant.

Search data:
Tagsmurolith, process, bar, V-UNITS: V-prominent, DETAILS: ca_disjunct, rim-bicyclic, rim-unicyclic,
MetricsLith size: 2->14µm;
Data source notes: size range of included species
Sources: size range of included species
The morphological data given here can be used on the advanced search page. See also these notes

Geological Range:
Last occurrence (top): at base of Ypresian Stage (1% up, 55.9Ma, in Ypresian stage). Data source: Total of range of species in this database
First occurrence (base): at base of Pliensbachian Stage (0% up, 190.8Ma, in Pliensbachian 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. (ed.) Calcareous Nannofossil Biostratigraphy. British Micropalaeontological Society Publication Series. 34-85. 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

Deflandre, G. (1963). Sur les Microrhabdulidés, famille nouvelle de nannofossiles calcaires. Comptes Rendus Hebdomadaires des Séances de l'Académie des Sciences, Paris. 256: 3484-3487. gs V O

Reinhardt, P. (1964). Einige Kalkflagellaten-Gattungen (Coccolithophoriden, Coccolithineen) aus dem Mesozoikum Deutschlands. Monatsberichte der Deutschen Akademie der Wissenschaften zu Berlin. 6: 749-759. gs V O

Reinhardt, P. (1965). Neue Familien für fossile Kalkflagellaten (Coccolithophoriden, Coccolithineen). Monatsberichte der Deutschen Akademie der Wissenschaften zu Berlin. 7: 30-40. gs V O

Varol, O. & Girgis, M. (1994). New taxa and taxonomy of some Jurassic to Cretaceous calcareous nannofossils. Neues Jahrbuch für Geologie und Paläontologie, Abhandlungen. 192: 221-253. gs

Varol, O. & Jakubowski, M. (1989). Some new nannofossil taxa. INA Newsletter. 11: 24-29. gs V O


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Zeugrhabdotus compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 23-9-2020

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Short stable page link: http://mikrotax.org/Nannotax3/index.php?id=11319 Go to Archive.is to create a permanent copy of this page - citation notes



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