Distinguishing features:
Parent taxon (Eiffellithales): Murolith coccoliths with an upper/outer cycle of clockwise-imbricate V-units and a lower/inner cycle of R-units.
This taxon: Typical Eiffelithales - rim with well outer/upper clockwise-imbricate V-units and lower/inner R-units. Central area open or spanned by disjunct cross or bar supporting a spine.
: Genera arranged by main structure in central area, then alphabetically (time control age-window is: 0-800Ma) | Granddaughter taxa | ||||
Transverse bar in central area | |||||
Amphizygus Muroliths with bicyclic rim and tranverse bar formed from laths which continue around the inner edge of the rim, delineating the two circular perforations. | |||||
Archaeozygodiscus Bicyclic (LM) murolith with a birefringent, spine-bearing bar. Distal/outer-cycle displays anticlockwise imbrication, unlike all other Mesozoic loxoliths. Triassic genus. | |||||
Gorkaea Bicyclic (LM) muroliths with broad, bright inner-cycle and robust, birefringent, transverse bar. | |||||
Placozygus Murolith with distal/outer-cycle that shows little or no imbrication and central area spanned by transverse bars; rim exhibits spiral interference pattern. | |||||
Reinhardtites Unicyclic muroliths with very broad rim and narrow central-area spanned or filled by a tranverse bar. | Reinhardtites anthophorus Reinhardtites levis Reinhardtites clavicaviformis Reinhardtites elkefensis Reinhardtites sp. | ||||
Tranolithus 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. | Tranolithus bitraversus Tranolithus gabalus Tranolithus incus Tranolithus macleodiae Tranolithus minimus Tranolithus orionatus Tranolithus praeorionatus Tranolithus salillum Tranolithus simplex Tranolithus sp. | ||||
Zeugrhabdotus 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. | Zeugrhabdotus blowii Zeugrhabdotus burolettii Zeugrhabdotus burwellensis Zeugrhabdotus erectus Zeugrhabdotus fissus Zeugrhabdotus moulladei Zeugrhabdotus noeliae Zeugrhabdotus bicrescenticus Zeugrhabdotus diplogrammus Zeugrhabdotus fluxus Zeugrhabdotus howei Zeugrhabdotus petrizzoae Zeugrhabdotus reticulatus Zeugrhabdotus scutula Zeugrhabdotus biperforatus Zeugrhabdotus kerguelenensis Zeugrhabdotus large spine Zygodiscus clubhousensis Zeugrhabdotus clarus Zeugrhabdotus acanthus Zeugrhabdotus trivectis Zeugrhabdotus xenotus Zeugrhabdotus angelozziae Zeugrhabdotus cooperi Zeugrhabdotus embergeri Zeugrhabdotus praesigmoides Zeugrhabdotus sigmoides Zeugrhabdotus simplex Zeugrhabdotus streetiae Zeugrhabdotus sp. | ||||
Diagonal cross in central area | |||||
Chiastozygus Murolith (loxolith) coccoliths with relatively narrow rim and wide central area spanned by diagonal bars. Inner/proximal rim cycle is variably developed and so the LM image may be unicyclic or bicyclic. | Chiastozygus amphipons Chiastozygus bifarius Chiastozygus lamprostauros Chiastozygus litterarius Chiastozygus platyrhethus Chiastozygus spissus Chiastozygus antiquus Chiastozygus garrisonii Chiastozygus stylesii Chiastozygus trabalis Chiastozygus propagulis Chiastozygus quadriperforatus Chiastozygus synquadriperforatus Chiastozygus tenuis Chiastozygus sp. | ||||
Simple axial cross in central area | |||||
Staurolithites Loxolith muroliths with relatively narrow rim and wide central area spanned by axial cross bars. The cross is usually spine bearing. Inner/proximal rim cycle is variably developed and so the LM image may be unicyclic or bicyclic. NB The bicyclic/unicyclic separation is simply controlled by how far the inwards the R-units develop so, although it is a useful identification criterion, it almost certainly has no real phylogenetic significance and would be a very poor character for defining genera. | Staurolithites dibrachiatus Staurolithites stradneri Staurolithites dentatus Staurolithites eiffellithoides Staurolithites flavus Staurolithites halfanii Staurolithites minutus Staurolithites ngurumahambaensis Staurolithites quadriarcullus Staurolithites siesseri Staurolithites coroniformis Staurolithites gausorhethium Staurolithites leptostaurus Staurolithites ormae Staurolithites handleyi Staurolithites laffittei Staurolithites dorfii Staurolithites lumina Staurolithites imbricatus Staurolithites dicandidula Staurolithites mitcheneri Staurolithites angustus Staurolithites mutterlosei Staurolithites zoensis Staurolithites aachenus Staurolithites aenigma Staurolithites ellipticus Staurolithites elongatus Staurolithites integer Staurolithites mielnicensis Staurolithites parma Staurolithites sp. | ||||
Diadorhombus Square-shaped loxolith cococoliths with cross bars that run parallel to the coccolith sides. | |||||
Rhabdophidites Spinose forms with minute basal loxolith coccolith with axial cross bars. The spines are long, parallel sided (?or tapering) and cruciform in section. | Rhabdophidites moeslensis Rhabdophidites parallelus Staurolithites pseudocarinolithus Rhabdophidites sp. | ||||
Complex axial cross in central area - &/or cross fills central area | |||||
Ahmuellerella Muroliths with complex axial cross structure or plate, typically incorporating 8 near-axial or radial bars or suture lines. | Ahmuellerella alboradiata Ahmuellerella frankiae Ahmuellerella octoradiata Ahmuellerella regularis Ahmuellerella sp. | ||||
Bukrylithus Loxolith coccoliths with narrow unicyclic rim and central area spanned by a plate incorporating broad, fibrous, tapering axial-cross-bars. Dark overall image in XPL. | |||||
Diloma Elliptical loxoliths with a rim that appears tricyclic, composed of inner and outer rim cycles and a proximal plate. The outer rim cycle and proximal plate are only weakly birefringent, while the blocky inner rim cycle is brightly birefringent. Central structures are variable but include cross bars, lateral bars and curving concentric bars. | |||||
Heteromarginatus Bicyclic muroliths with axial cross and additional small bars in the central-area. | |||||
Misceomarginatus Muroliths with narrow, bicyclic rim and wide central-area spanned by axial cross bars and a perforate plate. | |||||
Monomarginatus Muroliths with narrow, unicyclic rim and wide central-area spanned by axial, concentric and lateral bars. | |||||
Vacherauvillius Muroliths with axial, lateral and concentric bars spanning the central-area. | |||||
Others | |||||
Braloweria Loxoliths with central area filled with a tall, columnar to bulbous boss borne on a plate. Seen in side view. Spine has a thick wall, narrow axial canal and is formed from two crystallographically distinct units. | |||||
Clepsilithus Small loxolith coccoliths with multiple central area radial bars supporting a central spine. | |||||
Crepidolithus Murolith (loxoliths) with a robust, broad, high rim and central area that may be vacant, closed or spanned by bars or grill. | Crepidolithus crassus Crepidolithus crucifer Crepidolithus granulatus Crepidolithus parvulus Crepidolithus perforatus Crepidolithus pliensbachensis Crepidolithus timorensis Crepidolithus cantabriensis Crepidolithus impontus Crepidolithus sp. | ||||
Loxolithus Loxolith coccoliths with broad, open central-area, probably spanned by a rarely preserved, finely perforate net | |||||
Neocrepidolithus Murolith (loxolith) coccoliths with broad, high rim and narrow or closed central-area, which may be spanned by bars. | Neocrepidolithus cohenii Neocrepidolithus cruciatus Neocrepidolithus ruegenensis Neocrepidolithus watkinsii Neocrepidolithus sp. | ||||
Tubirhabdus Narrowly elliptical loxolith coccoliths with a central-area structure that supports a broad, hollow, flaring spine. | |||||
Chiastozygaceae - unidentified unidentified specimens, often in side view |
Taxonomy:
Farinacci & Howe catalog pages: Chiastozygaceae *
Distinguishing features:
Parent taxon (Eiffellithales): Murolith coccoliths with an upper/outer cycle of clockwise-imbricate V-units and a lower/inner cycle of R-units.
This taxon: Typical Eiffelithales - rim with well outer/upper clockwise-imbricate V-units and lower/inner R-units. Central area open or spanned by disjunct cross or bar supporting a spine.
Morphology:
The family is long-ranging (Late Triassic-early Eocene) and in the Mesozoic is largely represented by relatively simply-constructed coccoliths in which iterative homology appears to have been common. Apart from a few distinctive forms, many species (often small) differ in very subtle ways and many species names are poorly constrained and applied in different senses by different authors.
: murolith, |
Lith size: 0->0µm; |
Geological Range:
Last occurrence (top): at top of NP9 zone (100% up, 55.9Ma, in Ypresian stage). Data source: Total of ranges of the species in this database
First occurrence (base): within NT2b subzone (194.83-218.41Ma, base in Norian stage). Data source: Total of ranges of species in this database
Plot of occurrence data:
Bown, P. R. (1998b). Triassic. In, Bown, P. R. (ed.) Calcareous Nannofossil Biostratigraphy. British Micropalaeontological Society Publication Series . 29-33. gs 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 Reinhardt, P. (1965). Neue Familien für fossile Kalkflagellaten (Coccolithophoriden, Coccolithineen). Monatsberichte der Deutschen Akademie der Wissenschaften zu Berlin. 7: 30-40. gs Rood, A. P., Hay, W. W. & Barnard, T. (1973). Electron microscope studies of Lower and Middle Jurassic coccoliths. Eclogae Geologicae Helvetiae. 66: 365-382. gs OReferences:
Chiastozygaceae compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 12-11-2024
Short stable page link: https://mikrotax.org/Nannotax3/index.php?id=10245 Go to Archive.is to create a permanent copy of this page - citation notes |
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