Chaos (genus) - Recent Phylogeny

Recent Phylogeny

Until quite recently, the genus Chaos was included, along with all other protists that extend lobose pseudopods or move about by protoplasmic flow, in the phylum Sarcodina. Molecular phylogenies based on the examination of ribosomal DNA, have shown that Sarcodina is a polyphyletic grouping: that some amoeboids shared a more recent common ancestor with members of other phyla than with other Sarcodina. Consequently, the amoeboids of Sarcodina have been distributed among two newly-created supergroups, Rhizaria and Amoebozoa. Chaos and its close relative, Amoeba, are now placed in the latter, within the order Tubulinida: naked amoebas (lacking a test, or shell), either monopodial or possessing somewhat cylindrical pseudopods, with non-adhesive uroid (a region at the posterior of the cell which has a crumpled appearance).

While the monophyly of Amoebozoa has yet to be established, current information confirms the status of Chaos and Amoeba as closely related taxa within the group. However, the same research raises questions about the monophyly of the genus Chaos, since Chaos nobile may be basal to a group containing Chaos carolinensis and at least two species of Amoeba, as illustrated below, following Pawlowski and Burki (2009):