Nannotax3 - ntax_cenozoic - Pleurochrysidaceae

Citation: Pleurochrysidaceae Fresnel & Billard, 1991

Taxonomic discussion: At one time species were assigned to either Cricosphaera or Pleurochrysis on the basis of their life-cycles. Following revisions of Jordan et al. (1993) the family is now monogeneric.

Distinguishing features:
Parent taxon (Coccolithales): 2N: Mostly placolith heterococcoliths with V-unit forming the distal shield; R-unit the proximal shield. Non-motile
N: Form holococcoliths formed of single block, or non-calcifying
This taxon: 2N: cells motile, bearing narrow-rimmed placoliths, with obviously interlocking V and R units, open central areas. Neritic. N: non-calcifying.

Coccoliths are formed of two cycles of tightly interlocked anvil-shaped crystal-units. V-unit forms distal shield and tube. R-unit forms proximal shield and small element on inside of tube (Marsh 1999). Central area open. Coccoliths with this structure have been termed cricoliths. Coccospheres large with numerous liths, monomorphic.

These species are neritic and easily isolated and maintained in culture., hence taxonomy is based on cultures. Diploid phase is motile and heterococcolith-bearing, haploid phase is non-calcifying, flagellate or benthic.
Key references: Gayral & Fresnel (1983) - life-cycle; van der Wal et al. (1983) - cytology; Fresnel & Billard (1991) - species overview; Marsh (1999) - coccolith ultrastructure.

This family was included in the Coccolithales by Young & Bown (1997) since the rim structure appears to be a simplified version of that of the Coccolithaceae. This is supported by the detailed analysis of coccolith structure of Marsh (1999) and molecular genetic data, (Edvardsen et al., 2000; Fujiwara et al., 2001; Sáez et al. 2004)

Geological Range:
Last occurrence (top): Extant. Data source: Total of range of species in this database
First occurrence (base): at top of No known fossil record modern (100% up, 0Ma, in "Holocene" stage). Data source: Total of range of species in this database

References:

Edvardsen, B., Eikrem, W., Green, J. C., Andersen, R. A., Moon-Van Der Staay, S. Y. & Medlin, L. K. (2000). Phylogenetic reconstructions of the Haptophyta inferred from 18S ribosomal DNA sequences and available morphological data. Phycologia. 39: 19-35. gs

Fresnel, J. & Billard, C. (1991). Pleurochrysis placolithoides sp. nov. (Prymnesiophiceae), a new marine coccolithophorid with remarks on the status of cricolith-bearing species. British Phycological Journal. 26: 67-80. gs V O

Fujiwara, S., Tsuzuki, M., Kawachi, M., Minaka, N. & Inouye, I. (2001). Molecular phylogeny of the haptophyta based on the rbcL gene and sequence variation in the spacer region of the RUBISCO operon. Journal of Phycology. 37: 121-129. gs

Gayral, P. & Fresnel, J. (1983b). Description, sexualité et cycle de développment d'une nouvelle coccolithophoracée (Prymnesiophyceae): Pleurochrysis pseudoroscoffensis sp. nov. Protistologica. 19(2): 245-261. gs V O

Jordan, R. W., Kleijne, A. & Heimdal, B. R. (1993). Proposed changes to the classification system of coccolithophorids. III. INA Newsletter. 15(1): 18-22. gs V O

Marsh, M. E. (1999). Coccolith crystals of Pleurochrysis carterae: Crystallographic faces, organisation and development. Protoplasma. 207: 54-66. gs

Sáez, A. G., Probert, I., Young, J. R., Edvardsen, B., Wenche, E. & Medlin, L. K. (2004). A review of the phylogeny of the Haptophyta. In, Thierstein, H. R. & Young, J. R. (eds) Coccolithophores - from molecular processes to global impact. Springer, Berlin 251-270. gs V O

van der Wal, P., de Jong, E. W., Westbroek, P., de Bruijn, W. C. & Mulder-Stapel, A. A. (1983b). Ultrastructural polysaccharide localization in calcifying and naked cells of the coccolithophorid Emiliania huxleyi. Protoplasma. 118: 157-168. gs

Young, J. R. & Bown, P. R. (1997a). Cenozoic calcareous nannoplankton classification. Journal of Nannoplankton Research. 19(1): 36-47. gs V O

Daughter taxa (time control age-window is: 0-800Ma)					Granddaughter taxa
				Chrysotila Coccoliths elliptical narrow-rimmed placoliths with complex rim structure, open central area	Chrysotila carterae Chrysotila dentata Chrysotila gayraliae Chrysotila la-hague Chrysotila placolithoides Chrysotila roscoffensis Chrysotila scherffelii Chrysotila stipitata Chrysotila sp.

Pleurochrysidaceae

References:

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