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Rhizaria
is a heterogeneous assemblage of protists, which includes the
majority of filose and reticulose amoebae and most actinopods,
plus two parasitic lineages and some flagellates. The term
Rhizaria was proposed by Cavalier-Smith (2002), and refers to
the root-like filose and reticulose pseudopodia and/or axopodia
characterizing the majority of the taxa included in it. The
existence of this supergroup is based exclusively on molecular
evidence that accumulated since the demonstration of the close
relationship between euglyphid amoebae and chlorarachniophytes
(Bhattacharya et al. 1995), and their grouping with cercomonad
and thaumatomonad flagellates in SSU rRNA trees (Cavalier-Smith
and Chao 1997). The Rhizaria are also supported by analyses of
actin (Keeling 2001, Nikolaev et al. 2004), polyubiquitin
(Archibald et al. 2003), and RNA polymerase II (Longet et al.
2003) genes. According to the most recent paper (Nikolaev et al.
2004), Rhizaria includes core cercozoans (comprising among
others the Euglyphida, Chlorarachniophyta, Phaeodarea, and
Desmothoracida), some parasites of plants (Phytomyxea) and
animals (Haplosporidia), the Foraminifera, Gromia, and
radiolarians (Acantharea + Polycystinea + Taxopodida).
Figure :
Maximum likelihood phylogeny of Rhizaria inferred from SSU rRNA
gene sequences using the GTR+G+I model of evolution.
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