Temporal range: Neoproterozoic - Recent
|Live Ammonia tepida (Foraminifera)|
This supergroup was proposed by Cavalier-Smith in 2002. It has many species. They vary considerably in form, but for the most part they are amoeba-like with pseudopods. Many produce shells or skeletons, which may be quite complex in structure. They make up the vast majority of protozoan fossils. Nearly all have mitochondria with folds.
Groups[change | change source]
There are three main groups of Rhizaria:
- Cercozoa – Various amoebae and flagellates, usually with pseudopods and common in soil
- Foraminifera – Amoeboids with reticulose pseudopods, common as marine benthos
- Radiolaria – Amoeboids with skeletons, common as marine plankton
Evolutionary relationship[change | change source]
Rhizaria is part of the bikont clade, which also comprises the Archaeplastida, the Chromalveolata, the Excavata, and some smaller, groups. As bikonts, they all descend from a heterotrophic eukaryote with two flagella.
Historically, many rhizarians were considered animals, with their movement and heterotrophy as justification. However, when the five-kingdom system took prevalence over the animal-plant dichotomy, the rhizarians were put into the kingdom Protista. Then, after Carl Woese published his three-domain system, taxonomists turned their attention to the eukaryote domain. The protists are paraphyletic, so needed to be split into monophyletic clades. After much debate, which continues to this day, Rhizaria emerged as one of those monophyletic groups.
References[change | change source]
- Christopher Taylor (2004). "Rhizaria".
- Nikolaev S.I.; et al. (2004). "The twilight of Heliozoa and rise of Rhizaria, an emerging supergroup of amoeboid eukaryotes". Proc. Natl. Acad. Sci. U.S.A. 101 (21): 8066–71. doi:10.1073/pnas.0308602101. PMC 419558. PMID 15148395.
- Brown; et al. (2012). "Aggregative multicellularity evolved independently in the Eukaryotic Supergroup Rhizaria".
- Cavalier-Smith, Thomas (2002). "The phagotrophic origin of eukaryotes and phylogenetic classification of Protozoa". International Journal of Systematic and Evolutionary Microbiology. 52 (2): 297–354. ISSN 1466-5026. PMID 11931142. Retrieved 2007-06-08.
- Moreira D.; et al. (2007). "Global eukaryote phylogeny: combined small- and large-subunit ribosomal DNA trees support monophyly of Rhizaria, Retaria and Excavata". Mol. Phylogenet. Evol. 44 (1): 255–66. doi:10.1016/j.ympev.2006.11.001. PMID 17174576.