Tranolithus


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

Distinguishing features: Murolith (loxolith) coccoliths with central area spanned by complex transverse structures principally constructed from two or four projections. Delicate lateral bars may also be present but are generally only seen in exceptional preservation.


Daughter taxa: (blue => in age window 0-800Ma)

Small murolith (loxolith) with narrow rim and central area spanned by a transverse structure formed from two projections from the rim.
Species with 4 blocky rim elements extending into central area and defining anvil-shaped opening. Low bridge
Projections are a pair of perforate angular blocks.

Loxolith coccoliths with a transverse structure/bar composed of four lateral struts, a median granular component, and a central hollow spine base. In addition, the coccolith has a proximal grill composed of lateral bars.
Medium sized (c. 5.0 µm) murolith coccolith with a transverse bar composed of four, short, triangular-shaped struts and a median granular section. The struts, which protrude from the inner rim edge, are conspicuous when the coccolith is orientated parallel to the polarising directions; the median part of the tranverse bar is only visible when the coccolith is rotated to 45°.

Tranolithus species with small transerve bar and strongly birefringent inner cycle, composed of four plates that fill the central area and surround two openings aligned with the long axis
Specimens not identified to species level

Taxonomy:

Citation: Tranolithus Stover, 1966
Rank: Genus
Type species: Tranolithus manifestus Stover, 1966. Probably conspecific with T exiguus and T. phacelosus, described by Stover, and T. orionatus described by Reinhardt, 1966. T. orionatus is probably the most widely used of these names.
Synonyms: Pontilithus Gartner 1968 (the type species P. obliquicancellatus is a j. synonym of T. orionatus)
Barringtonella Black 1972 (the type species B. flabellosa is a j. synonym of T. orionatus)
- see also extended discussion of Lambert (1987)

Farinacci & Howe catalog pages: Tranolithus + + + + + * , Pontilithus * , Barringtonella *

Distinguishing features: Murolith (loxolith) coccoliths with central area spanned by complex transverse structures principally constructed from two or four projections. Delicate lateral bars may also be present but are generally only seen in exceptional preservation.


Morphology remarks: Defined by Stover (1966) for coccoliths similar to Zeugrhabdotus but which have central area bars, projections or ‘structures’ which are divided longitudinally, the structures having the same or similar crystallographic orientation as the adjacent rim. In practise Tranolithus has come to be used for murolith coccoliths which possess central structures composed of two or four blocks (e.g., Perch-Nielsen, 1985, p. 408; Bown & Young, 1997). The phylogenetic relationships between species grouped in Tranolithus is uncertain.

Geological Range:
Last occurrence (top): at top of Maastrichtian Stage (100% up, 66Ma, in Maastrichtian 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:

Black, M. (1972). British Lower Cretaceous Coccoliths. I-Gault Clay (Part 1). Palaeontographical Society Monograph. 126: 1-48. gs

Bown, P. R. & Young, J. R. (1997). Mesozoic calcareous nannoplankton classification. Journal of Nannoplankton Research. 19(1): 21-36. gs

Bown, P. R., Rutledge, D. C., Crux, J. A. & Gallagher, L. T. (1998). Early Cretaceous. In, Bown, P. R. (ed.) Calcareous Nannofossil Biostratigraphy. British Micropalaeontological Society Publication Series. 86-131. gs

Gartner, S. (1968). Coccoliths and related calcareous nannofossils from Upper Cretaceous deposits of Texas and Arkansas. The University of Kansas Paleontological Contributions. Article 48 (Protista 1): 1-56. gs

Lambert, B. (1987). Nannofossiles calcaires de l'Albien supérieur et du Vraconnien du Cameroun méridional. Cahiers de Micropaléontologie. 2(2): 33-60. gs

Perch-Nielsen, K. (1985b). Mesozoic calcareous nannofossils. In, Bolli, H. M. , Saunders, J. B. & Perch-Nielsen, K. (eds) Plankton Stratigraphy. Cambridge University Press, Cambridge 329-426. gs

Reinhardt, P. (1966b). Zur Taxonomie und Biostratigraphie des fossilen Nannoplanktons aus dem Malm, der Kreide und dem Alttertiär Mitteleuropas. Freiberger Forschungshefte. C196: 5-109. gs

Stover, L. E. (1966). Cretaceous coccoliths and associated nannofossils from France and the Netherlands. Micropaleontology. 12: 133-167. gs


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Tranolithus compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 15-12-2019

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