Kigahn A guide to extant coccolithophore taxonomy Author: Citations are based on reference standards. You may send this item to up to five recipients. Reviews User-contributed reviews Add a review and share your thoughts with other readers. English View all editions and formats. Preview this item Preview this item. Write a review Rate this item: Find more information about: Please choose whether or not you want other users to be able to see on your profile that this library is a favorite of yours.

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The copyright remains with the authors. Cover illustration: False coloured image of a Pappomonas sp. Back cover: False coloured image of Coronosphaera mediterranea from the S. Atlantic, off Namibia. They are one of the main groups of marine phytoplankton playing key roles in the marine ecosystem as primary producers and in marine biogeochemistry as producers of organic carbon, carbonate and dimethyl sulphide.

In addition they are major sediment formers, key biostratigraphic marker fossils and valuable indicators of palaeoceanographic change. These diverse interests have lead to intensive research on extant coccolithophores over the past decade.

In addition there has been extensive work, especially in Europe and Japan, on coccolithophore communities in the plankton and on fluxes of coccoliths in sediment traps. As a result of this recent research the taxonomy of coccolithophores has advanced significantly over the past decade, i.

So there is a need for a new synthesis, and especially for an identification guide. There is still work to be done, especially formal description of many now well-established informally described species, but coccolithophores are now one of the most comprehensively described, and most reliably identifiable groups of oceanic microplankton.

In consequence they are an ideal group for developing study of the pattern and role of biodiversity in plankton ecology. We hope this identification guide will facilitate such studies, as well as informing palaeontologists studying fossil coccoliths of the nature of the modern biota.

Acknowledgements This work is a synthesis of many years work and the authors have been assisted by many colleagues. Financial and logistic support has been provided by all of our institutions, recognising the fundamental importance of taxonomy in underpinning all biological research. Young et al. Major heterococcolith groups, except Syracosphaerales Holococcoliths [Calyptrosphaeraceae] It is primarily intended to act as an aide memoire to coccolithophorid taxonomy, with brief notes serving as a reminder to the distinguishing features of taxa, extended descriptions can be found in the primary literature.

Terminology The terminology used here essentially follows the Guidelines for Coccolith and Calcareous Nannofossil Terminology of Young et al. An additional glossary of terms for haptophytes is provided by Jordan et al.

The following aspects are worth noting. Coccolithophores produce two very different types of coccoliths: a heterococcoliths, which are formed of a radial array of complex crystal-units. We now know that holococcoliths and heterococcoliths are products of respectively haploid and diploid life-cycle phases and form via very different biomineralisation processes see e. A few structures do not conform to either pattern and so have been termed nannoliths, following palaeontological usage.

Nannoliths are probably formed by different biomineralisation processes, and in some cases possibly not by coccolithophores. We use the terms placolith, murolith and planolith as descriptors of heterococcolith shape, independent of structure.

Each of the heterococcolith types can conveniently be subdivided into a rim and central area. The terms segment, crystal-unit and element form a hierarchy of structural components: Elements are the superficially discrete units observed on the surface of a coccolith. Crystal-units are single crystals and typically are composed of several interconnected but superficially discrete elements.

A segment consists of the different crystal-units that constitute one radially repeated portion of a heterococcolith rim. A basic characteristic of coccoliths is that their morphology and structure is highly variable, with the result that homology is limited. Elaborate specialist terminology would therefore be counter-productive, instead we have tried as far as possible to avoid obscure terms. In particular, following Young et al. Coccolith crystallography and growth Kamptner , Prins and Romein showed that crystallographic orientation was an invaluable key to understanding coccolith ultrastructure and phylogenetic relationships.

These two crystal-unit types originate from a proto-coccolith ring of alternating V-unit and R-unit nuclei. This proto-coccolith ring is formed within the cell, on an organic baseplate scale, as the first phase of coccolith growth.

This basic structure provides a key to interpreting cross-polarised light images and to elucidating relationships, so the structure of coccoliths in these terms is discussed in the family and order descriptions. Within family groups the coccolith structure and crystallography is usually constant, so for specieslevel identification, especially in SEM, it is a feature that can be ignored. However, it should be noted that this crystallographic aspect of the classification means that it is based on variation in rather stable biomineralisation processes and so is much more robust than might appear superficially.

This provides the basis for grouping of the Syracosphaeraceae, Rhabdosphaeraceae, and Calciosoleniaceae into the order Syracosphaerales.


A guide to extant coccolithophore taxonomy

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