Rhizaria
Evolutionary relationships

Rhizaria are part of the SAR supergroup (Stramenopiles, Alveolates, Rhizaria), a grouping that had been presaged in 1993 through a study of mitochondrial morphologies. SAR is currently placed in the Diaphoretickes along with Archaeplastida, Cryptista, Haptista, and several minor clades.

Historically, many rhizarians were considered animals because of their motility and heterotrophy. However, when a simple animal-plant dichotomy was superseded by a recognition of additional kingdoms, taxonomists generally placed amoebae in the kingdom Protista. When scientists began examining the evolutionary relationships among eukaryotes in the 1970s, it became clear that the kingdom Protista was paraphyletic. Rhizaria appear to share a common ancestor with Stramenopiles and Alveolates forming part of the SAR super assemblage. Rhizaria has been supported by molecular phylogenetic studies as a monophyletic group. Biosynthesis of 24-isopropyl cholestane precursors in various rhizaria suggests a relevant ecological role already during the Ediacaran.
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