Classification: ntax_non_cocco -> Dinophytes -> Silicifying dinoflagellates -> Actiniscus
Sister taxa: Actiniscus

Distinguishing features: Dinoflagellate with siliceous internal skeleton formed of two star-like bodies

Daughter taxa (time control age-window is: 0-800Ma)
Actiniscus pentasterias
Skeletal bodies are 5-rayed with concavo-convex shape and a sculpted surface


Citation: Actiniscus Ehrenberg 1843
Rank: Genus
Type species: Actiniscus pentasterias (Ehrenberg) Ehrenberg 1843
Taxonomic discussion: According to Algaebase 36 species have been described in Actiniscus, predominantly by Ehrenberg. Of these they regard the following as 'currently accepted' Actiniscus pentasterias is thus the only accepted modern marine species, although the other names do appear in some taxonomic lists. This is confirmed by a web and PDF search, the only name being used for modern marine Actiniscus is A. pentasterias
Locker & Martini (1986 DSDP 90) is useful initial reference for the literature on fossil actiniscids.

Catalog entries: Actiniscus

Distinguishing features: Dinoflagellate with siliceous internal skeleton formed of two star-like bodies

Morphology: Slightly compressed biflagellated cells of medium-sized (30-70 µm) with a slightly displaced cingulum and well-developed sulcus giving the cells an appearence of Gymnodinium Stein. Differs from Gymnodinium by the presence of siliceous internal skeleton composed of 2 equal parts composed of a ring from which 5 (4-8) star-like arms radiate. No chloroplasts, nucleus enclosed in the internal skeleton. Marine plankton, of worldwide distribution [description by M. Elbrachter on Algaebase].

Geological Range:
Last occurrence (top): Extant Data source: Total of range of species in this database
First occurrence (base): within No known fossil record modern (0.00-0.00Ma, base in "Holocene" stage). Data source: Total of range of species in this database


Ehrenberg, C. G. (1843). Über die verbreitung des jetzt wirkenden kleinsten organischen lebens in Asien, Australien und Afrika und über die vorherrschende bildung auch des oolithkalkes der Juraformation aus kleinen polythalamischen thieren. Bericht uber die zu Bekanntmachung geeigneten Verhandlungen der Koniglichen Preussische Akademie der Wissenschaften zu Berlin. 100-106. gs

Locker, S. & Martini, E. (1986). Ebridians and actiniscidians from the southwest Pacific. Initial Reports of the Deep Sea Drilling Project. 90: 941-951. gs V O


Actiniscus compiled by Jeremy R. Young viewed: 20-6-2021

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Comments (3)

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Ines Galovic (Zagreb, Croatia)

Please see the records from Miocene to Holocene in the following article: Orr W.N. and Conley S. (1976): Siliceous dinoflagellates in the northeast Pacific rim. Micropaleontology 22/1, 92-99.

Ines Galovic (Croatia)
I found A. stella (Ehrenberg,1840)Ehrenberg, 1854, in middle Miocene i.e. Sarmatian (Croatia) and A. pentasterias from Karpatian (Austria) to Recent (Adriatic).
Ines Galovic (Croatia)
It looks like more to A. stella (Ehr.)Ehrenberg than A. pentasterias (Ehrenberg)Ehrenberg.
Jeremy Young (UCL, UK)
In the modern plankton it is generally accepted that there is only one species, A. pentasterias and these are quite typical specimens.
Ines Galovic (Croatia)
I'm sending a SEM and LM figures of fossil and recent A. pentasterias that differs from your images. I'm sorry for bad scan. Unfortunately, AlgaeBase are not complete and missing lot of species, descriptions, references and their synonyms from Paratethyan and Adriatic Sea. (invalid-image)
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