Axopodorhabdaceae


Classification: Mesozoic -> Podorhabdales -> Axopodorhabdaceae
Sister taxa: Axopodorhabdaceae, Biscutaceae, Calyculaceae, Cretarhabdaceae, Mazaganellaceae, Prediscosphaeraceae, Tubodiscaceae,

Distinguishing features: Regular placoliths; central-area, with cross-bars or perforated plate; often with tall, hollow spines.
Distal shield elements non-imbricate V-units; proximal shield and inner cycle formed from R-units. Rim often appears beaded in LM


Daughter taxa: (blue => in age window 0-800Ma) Granddaughter taxa
central area with 2-8 large openings
Sub-circular, rim broad; central area spanned by a granular bar supporting a broad, tall, hollow, flaring spine.

Elliptical; central area narrow, spanned by a transverse bar.

Elliptical; central area with axial cross and tall spine

Elliptical; central area with diagonal cross or offset crossbars bars, supporting hollow spine

Elliptical; central area spanned by six broad bars delineating six large perforations, including one at each end of the central area. Central hollow spine.

Elliptical; central area spanned by eight bars delineating eight large perforations arranged either side of the long axis.

Elliptical; central area spanned by eight bars that delineate eight large perforations. Central hollow spine.

central area with 1 or 2 cycles of small openings around a large process
Elliptical; central area with one cycle of about 12 perforations and central hollow spine

Elliptical; central area with one or two cycles of perforations and central hollow spine

Elliptical; central area with >12 perforations and central hollow spine

central area filled by perforate plate
Elliptical to subrectangular; central-area with coarsely-perforate net.

Elliptical, narrow rim; central area wide, spanned by multiperforate net, with or without axial cross and spine.

Reniform; central-area net with two to numerous pores

Similar to Cribrosphaerella but with perforations only in centre of central area

cylindrical
Subcircular with very high rim; central-area narrow, with grill.

Taxonomy:

Citation: Axopodorhabdaceae Wind & Wise in Wise & Wind, 1977
Rank: Family
Type species: Axopodorhabdus Wind and Wise in Wise and Wind, 1977.
Notes & discussion: The generic taxonomy of this group is unsatisfactory. Using genera based on number of openings in the central area rather than ultrastructure is liable to be artificial. So far no alternative criterion for grouping has been established, but some of the illogicality could be reduced, in particular it might make sense to combinne Hexapodorhabdus, Octopodorhabdus and Octocyclus into one genus (with 6-8 large openings) and Dodekapodorhabdus, Perissocyclus and Teichorhabdus into another (with mutiple small openings around a well developed process).

Farinacci & Howe catalog pages: Axopodorhabdaceae [no catalog entry yet]

Distinguishing features: Regular placoliths; central-area, with cross-bars or perforated plate; often with tall, hollow spines.
Distal shield elements non-imbricate V-units; proximal shield and inner cycle formed from R-units. Rim often appears beaded in LM


Morphology remarks: Placoliths with two shields and a central-area, spanned by axial cross-bars or granular plates with variable numbers of perforations; the central structure generally supports tall, hollow spines. The distal shield is formed from V-unit elements joined along radial or near-radial sutures that show little or no imbrication. The proximal shield and inner cycle (if present) are formed from R-units. LM image is generally dark, but bright inner-cycles may be visible. The image is characterised by clearly visible shield elements, often giving a 'beaded' appearance around the inner edge of the shields.
The informal term podorhabdid is useful and widely used to described the coccoliths classified together in the Axopodorhabdaceae.

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): in lower part of Pliensbachian Stage (40% up, 187.6Ma, 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

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

GrĂ¼n, W. & Allemann, F. (1975). The Lower Cretaceous of Caravaca (Spain): Berriasian Calcareous Nannoplankton of the Miravetes Section (Subbetic Zone, Prov. of Murcia). Eclogae Geologicae Helvetiae. 68: 147-211. gs

Wise, S. W. & Wind, F. H. (1977). Mesozoic and Cenozoic calcareous nannofossils recovered by DSDP Leg 36 drilling on the Falkland Plateau, south-west Atlantic sector of the Southern Ocean. Initial Reports of the Deep Sea Drilling Project. 36(269-491): -. gs


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Axopodorhabdaceae compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 28-1-2020

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