Phylogenetic Revision of the Order Entactinaria—Paleozoic Relict Radiolaria (Rhizaria, SAR)

Entactinaria, an order of Radiolaria, are defined by a specific skeletal structure called “initial spicular system (ISS)”. The oldest entactinarians appeared in the Ordovician period, and the extant species are thought to have survived until today. However, the morphological observation revealed tha...

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Bibliographic Details
Published in:Protist 2020-02, Vol.171 (1), p.125712-125712, Article 125712
Main Authors: Nakamura, Yasuhide, Sandin, Miguel M., Suzuki, Noritoshi, Tuji, Akihiro, Not, Fabrice
Format: Article
Language:English
Subjects:
Cercozoa
Entactinaria
Environmental Sciences
Orosphaeridae
Phaeodaria
Phylogeny
Rhizaria
Rhizaria - classification
RNA, Ribosomal, 18S - genetics
RNA, Ribosomal, 28S - genetics
Species Specificity
unicellular zooplankton
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Summary:Entactinaria, an order of Radiolaria, are defined by a specific skeletal structure called “initial spicular system (ISS)”. The oldest entactinarians appeared in the Ordovician period, and the extant species are thought to have survived until today. However, the morphological observation revealed that the ISSs of entactinarian families are highly variable, and the validity of this characteristic is questionable. This is supported by the results of 18S and 28S rRNA molecular phylogenetic analysis that suggested the polyphyly of the four families analyzed in this study. Orosphaeridae, Rhizosphaeridae, Hexalonchidae and Hexastylidae should be excluded from the order Entactinaria. Considering the present results and the diversity in the ISS, it is also possible that “living entactinarians” are polyphyletic.
ISSN:1434-4610
1618-0941
DOI:10.1016/j.protis.2019.125712