Zeugrhabdotus


Classification: ntax_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)
Zeugrhabdotus blowii
Unicyclic, small; bar divided longitudinally, darkest at 0°
Zeugrhabdotus burolletii
Unicyclic(?), very small; with additional lateral bars [only known from EM]
Zeugrhabdotus burwellensis
Unicyclic, small (4-6 µm); bar complex; broad rim/small openings
Zeugrhabdotus erectus
Unicyclic, small; bar split perpendicular to length; narrow rim/large openings
Zeugrhabdotus fissus
Unicyclic, small; bar divided longitudinally, darkest at 0°
Zeugrhabdotus moulladei
Unicyclic, small; bar complex
Zeugrhabdotus noeliae
Unicyclic (or bicyclic?), small (or medium); bar complex, wide rim/small openings
Unicyclic - medium (5-8 µm)
Zeugrhabdotus bicrescenticus
Unicyclic, medium; bar divided longitudinally, darkest at 45°; rim broad/openings small
Zeugrhabdotus diplogrammus
Unicyclic, medium; bar divided longitudinally, darkest at 60°
Zeugrhabdotus fluxus
Unicyclic, medium; bar split perpendicular to length, darkest at 45°
Zeugrhabdotus howei
Unicyclic or diffusely bicyclic, medium; bar complex, darkest at 45°
Zeugrhabdotus petrizzoae
Unicyclic, medium; bar divided longitudinally and parts offset , darkest at 45°
Zeugrhabdotus reticulatus
Unicyclic, medium; reticulate net on proximal surface [only known from EM]
Zeugrhabdotus scutula
Unicyclic or diffusely bicyclic, medium-large (6-9µm); bar complex; narrow rim/large openings
Unicyclic - large (8-12 µm)
Zeugrhabdotus biperforatus
Unicyclic, large; bar divided longitudinally; very wide rim/very small openings
Zeugrhabdotus kerguelenensis
Unicyclic, large; with very broad spine, often seen in side view; broad rim/small openings
Zeugrhabdotus large spine
Zeugrhabdotus with simple rim and large spine ending in very large calyx
Zygodiscus clubhousensis
Medium to large Zeugrhabdotus with massive conical spine
Bicyclic - small to medium (4-6 µm)
Zeugrhabdotus clarus
Bicyclic, small to medium; bar split perpendicular to length, tapers at both ends.
Zeugrhabdotus acanthus
Bicyclic, medium sized; bar complex, flaring slightly as it meets the rim, can appear x-shaped.
Zeugrhabdotus trivectis
Bicyclic, medium sized (5-6µm); bar complex
Zeugrhabdotus xenotus
Bicyclic, medium sized; bar divided longitudinally, darkest at 0°, can appear x-shaped.
Bicyclic - medium to large (6-12 µm)
Zeugrhabdotus angelozziae
Diffusely bicyclic, medium-large; bar oblique to length and divided longitudinally
Zeugrhabdotus cooperi
Diffusely bicyclic, medium to large and high; bar split perpendicular to length; broad rim/ narrow openings
Zeugrhabdotus embergeri
Bicyclic, large; bar split perpendicular to length, spine often prominent
Zeugrhabdotus praesigmoides
Bicyclic, medium-large; bar complex; bright inner rim broadest where it meets bridge, very narrow tends of central area.
Zeugrhabdotus sigmoides
Bicyclic, medium-large; bar complex; bright inner rim broadest where it meets bridge, very narrow tends of central area.
Zeugrhabdotus simplex
Bicyclic, large; bar simple (formed of one unit); rim narrow/openings large
Zeugrhabdotus streetiae
Bicycle, large; bar complex, appears x-shaped in some views.
Zeugrhabdotus sp.
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:
Taxonomic 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: Long-ranging group (late Triassic-early Eocene) and often common to dominant.

Search data:
TagsLITHS: murolith, ca_disjunct, process, bar, CROSS-POLARS: rim-bicyclic, rim-unicyclic, V-prominent,
MetricsLith size: 2->14µm;
Data source notes: 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: 20-1-2021

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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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