Cercozoa (=Rhizopoda) is a phylum of protists. It was first described in 1998 by Thomas Cavalier-Smith. The phylum Cercozoa belongs to a group called Rhizaria. No specific morphological or behavioral characteristics are observed in its members. This phylum exhibits great diversity. Its members are biciliate and/or amoeboid and generally possess filopodia. Most contain tubular cristae, and cysts are common. Kinetosomes are attached to the nucleus via the cytoskeleton. Microbodies and extrusomes are generally present. This list shows the revisions made to Cavalier-Smith's Cercozoa classification and also shows Adl et al. classifications.
Taxonomy Before the phylum was described, a similar group was named as phylum Rhizopoda instead. In 1997, Rhizopoda was assigned to a superphylum named Neosarcodina that also included another phylum, the Amoebozoa. Here is a scheme from Cavalier-Smith, 1997:
Phylum Rhizopoda Subphylum Phytomyxa Class Phytomyxea Order Phagomyxida Order Plasmodiophorida Subphylum Reticulofilosa Class Chlorarachnea Order Chlorarachnida Class Proteomyxidea Order Pseudosporida Order Leucodictyida Subphylum Monadofilosa Class Sarcomonadea Order Cercomonadida Order Thaumatomonadida Class Filosea Subclass Cristidiscoidia Order Nucleariida Order Fonticulida Order Ministeriida Subclass Cristivesiculatia Order Vampyrellida Subclass Testaceafilosia Order Gromiida Order Euglyphida In Cavalier-Smith, 1998, the phylum was proposed as a replacement for Rhizopoda. It was placed in infrakingdom Sarcomastigota along with the phyla Neomonada, Foraminifera and Amoebozoa. Order Spongomonadida was added to subphylum Monadofilosa and cristidiscoids were transferred to subphylum Choanozoa. The classification was this:
Phylum Cercozoa Subphylum Phytomyxa Class Phytomyxea Order Phagomyxida Order Plasmodiophorida Subphylum Reticulofilosa Class Chlorarachnea Order Chlorarachnida Class Proteomyxidea Order Pseudosporida Order Leucodictyida Subphylum Monadofilosa Order Spongomonadida Class Sarcomonadea Order Cercomonadida Order Thaumatomonadida Class Filosea Subclass Cristivesiculatia Order Vampyrellida Subclass Testaceafilosia Order Gromiida Order Euglyphida In Cavalier-Smith, 2000, a new monotypic class Spongomonadea was named for the order Spongomonadida. Spongomonadea was placed in subphylum Reticulofilosa. Order Cryomonadida was added to class Sarcomonadea. Class Athalamea was used for the families Biomyxidae and Gymnophryidae in subphylum Reticulofilosa. Class Ramicristea was used in subphylum Monadofilosa and included the orders Heliomonadida and Commatiida:
Phylum Cercozoa Subphylum Phytomyxa Class Phytomyxea Order Phagomyxida Order Plasmodiophorida Subphylum Reticulofilosa Class Chlorarachnea Order Chlorarachnida Class Proteomyxidea Order Pseudosporida Order Leucodictyida Class Spongomonadea Order Spongomonadida Class Athalamea Subphylum Monadofilosa Class Sarcomonadea Order Cercomonadida Order Thaumatomonadida Order Cryomonadida Class Filosea Subclass Cristivesiculatia Order Vampyrellida Subclass Testaceafilosia Order Gromiida Order Euglyphida Class Ramicristea Order Heliomonadida Order Commatiida In Cavalier-Smith, 2002, a new subphylum named Endomyxa was introduced to contain the new class Ascetosporea and the class Phytomyxea in the phylum Cercozoa. Ascetosporea contained the orders Haplosporida and Paramyxida. Subclass Testaceafilosia was ranked as a class Testaceafilosea. Phylum Cercozoa was placed in a new infrakingdom named Rhizaria along with the phyla Apusozoa, Retaria and Heliozoa:
Phylum Cercozoa Subphylum Reticulofilosa Class Chlorarachnea Order Chlorarachnida Class Proteomyxidea Order Pseudosporida Order Leucodictyida Class Spongomonadea Order Spongomonadida Class Athalamea Subphylum Monadofilosa Class Sarcomonadea Order Cercomonadida Order Thaumatomonadida Order Cryomonadida Class Filosea Order Vampyrellida Class Testaceafilosea Order Gromiida Order Euglyphida Class Ramicristea Order Heliomonadida Order Commatiida Subphylum Endomyxa Class Phytomyxea Order Phagomyxida Order Plasmodiophorida Class Ascetosporea Order Haplosporida Order Paramyxida In Cavalier-Smith and Chao, 2003, the subphyla Reticulofilosa and Monadofilosa were ranked as superclasses in a new subphylum Filosa. Order Heliomonadida was transferred to class Proteomyxidea, a new order Reticulosida was created to include the only family Gymnophryidae, now also containing family Biomyxidae members. A new order Metopiida was assigned to class Sarcomonadea. A new class named Thecofilosea was created to contain the order Cryomonadida and the new order Tectofilosida. A new class named Imbricatea was created to contain the orders Thaumatomonadida and Euglyphida. A new order Claustrosporida was assigned to class Ascetosporea. A new class named Gromiidea contained the only order Gromiida. Order Commatiida was not listed, and order Vampyrellida was assigned kingdom Protozoa incertae sedis.
Phylum Cercozoa Subphylum Filosa Superclass Reticulofilosa Class Chlorarachnea Order Chlorarachnida Class Spongomonadea Order Spongomonadida Class Proteomyxidea Order Pseudosporida Order Leucodictyida Order Heliomonadida Order Reticulosida Superclass Monadofilosa Class Sarcomonadea Order Metopiida Order Cercomonadida Class Thecofilosea Order Tectofilosida Order Cryomonadida Class Imbricatea Order Thaumatomonadida Order Euglyphida Subphylum Endomyxa Class Phytomyxea Order Phagomyxida Order Plasmodiophorida Class Ascetosporea Order Haplosporida Order Paramyxida Order Claustrosporida Class Gromiidea Order Gromiida In Bass and Cavalier-Smith, 2004, a new order Metromonadida was placed as superclass Monadofilosa incertae sedis. Order Metopiida was removed from class Sarcomonadea and placed subphylum Filosa incertae sedis instead. Class Spongomonadea was transferred to superclass Monadofilosa:
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