A small number of

dinoflagellate The Dinoflagellates (), also called Dinophytes, are a monophyletic group of single-celled eukaryotes constituting the phylum Dinoflagellata and are usually considered protists. Dinoflagellates are mostly marine plankton, but they are also commo ...

s contain an internal skeleton. One of the best known species is perhaps ''Actiniscus pentasterias'', in which each cell contains a pair of siliceous five-armed stars surrounding the nucleus. This species was originally described by Ehrenberg. Although the description is incomplete and without illustrations, Ehrenberg described the skeletal elements but mentioned that the living cell was colorless and non-motile. Ehrenberg subsequently diagrammed the silicified skeletal elements (pentasters) from geological deposits in various parts of the world. These can be found as

microfossils A microfossil is a fossil that is generally between 0.001 mm and 1 mm in size, the visual study of which requires the use of light or electron microscopy. A fossil which can be studied with the naked eye or low-powered magnification, ...

. Pentasters were studied from the Cenozoic South Pacific by Dumitrică http://deepseadrilling.org/21/volume/dsdp21_25.pdf Tappan gave a survey of dinoflagellates with internal skeletons. This included the first detailed description of the pentasters in ''Actiniscus pentasterias'', based on scanning electron microscopy. The ultrastructure of ''Actiniscus pentasterias'' was investigated.Hansen, G. 1993. Light and Electron Microscopical Observations of the Dinoflagellate Actiniscus pentasterias (Dinophyceae). Journal of Phycology. 29, 486-499 (1 993)

References

{{reflist, 2 Dinoflagellate biology