|Daughter taxa (time control age-window is: 0-800Ma)|
|Calcidiscus leptoporus subsp. quadriperforatus HOL|
Internal walls define 4-6 pores. Tube 10-15 crystallites high, castellated, higher where it meets internal walls. Tube sometimes double-layered, base open.
|Scyphosphaera apsteinii HOL|
Liths similar to quadriperforatus but larger (3-4 µm), with more pores (8-20) and lacking castellations; single irregular boss near centre of lith.
|Pontosphaera japonica HOL|
Solid, disk-shaped coccolith with several irregular deep depressions; formed of single block of crystalites with sub-vertical c-axes; no outer wall/tube; one or two irregular knobs on long axis.
|Syracolithus sp. type A|
Coccoliths with area inside tube almost filled by concentric walls, distal surface ornamented by 10-15 pyramidal bosses.
|Syracolithus sp. type B|
Liths similar to S. quadriperforatus but more delicate and with open hexagonal mesh fabric.
Liths similar to S. quadriperforatus but walls double layered with open hexagonal mesh fabric.
Distinguishing features: Holococcoliths with tube, open distally and subdivided internally by vertical septae
Farinacci & Howe catalog pages: septate [no catalog entry yet]
Morphology: Coccospheres monomorphic, coccoliths are open tubes with internal septae (walls), extending down to proximal surface. The tube wall shows hexagonal fabric and the crystallites have radial c-axes (birefringent in plan view in LM). The fabric of the septae is not obviously different, but they are non-birefringent in plan view in LM and so the calcite crystallites must have vertical c-axes.
This is a distinctive ultrastructure and although most species have been placed in Syracolithus it is quite different to the other species tradtionally placed in Syracolithus.
Biology & life-cycles: Produced in the haploid phase of Calcidiscaeae (Calcidicus leptoprus ssp. quadriperforatus) and Pontosphaeraceae (
Phylogenetic relations: Young et al. (2003) predicted that holococcolihs with this structure would proved to be closely related, and so produced by the Calcidiscaceae. However, Frada et al. (2009) showed that some of them were produced by the Pontosphaeraceae, and so this holococcolih structure has almost certainly evolved at least twice.
See also: septate ;Search data:
|Metrics||Lith size: 1.8->4µm;|
Last occurrence (top): Extant Data source: Total of range of species in this database
First occurrence (base): at base of Ypresian Stage (0% up, 56Ma, in Thanetian stage). Data source: Total of range of species in this database
Plot of occurrence data:
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