Phaeodarea, or Phaeodaria, is a group of

amoeboid An amoeba (; less commonly spelled ameba or amœba; plural ''am(o)ebas'' or ''am(o)ebae'' ), often called an amoeboid, is a type of cell or unicellular organism with the ability to alter its shape, primarily by extending and retracting pseudopo ...

cercozoa Cercozoa is a phylum of diverse single-celled eukaryotes. They lack shared morphological characteristics at the microscopic level, and are instead defined by molecular phylogenies of rRNA and actin or polyubiquitin. They were the first major eu ...

n organisms. They are traditionally considered

radiolaria The Radiolaria, also called Radiozoa, are protozoa of diameter 0.1–0.2 mm that produce intricate mineral skeletons, typically with a central capsule dividing the cell (biology), cell into the inner and outer portions of endoplasm and Ecto ...

ns, but in molecular trees do not appear to be close relatives of the other groups, and are instead placed among the

Cercozoa Cercozoa is a phylum of diverse single-celled eukaryotes. They lack shared morphological characteristics at the microscopic level, and are instead defined by molecular phylogenies of rRNA and actin or polyubiquitin. They were the first major eu ...

. They are distinguished by the structure of their central capsule and by the presence of a phaeodium, an aggregate of waste particles within the cell. The term "Radiozoa" has been used to refer to radiolaria when Phaeodarea is explicitly excluded. Phaeodarea produce hollow skeletons composed of amorphous

silica Silicon dioxide, also known as silica, is an oxide of silicon with the chemical formula , most commonly found in nature as quartz and in various living organisms. In many parts of the world, silica is the major constituent of sand. Silica is one ...

and organic material, which rarely fossilize. The

endoplasm Endoplasm generally refers to the inner (often granulated), dense part of a cell's cytoplasm. This is opposed to the ectoplasm which is the outer (non-granulated) layer of the cytoplasm, which is typically watery and immediately adjacent to the ...

is divided by a cape with three openings, of which one gives rise to feeding

pseudopod A pseudopod or pseudopodium (plural: pseudopods or pseudopodia) is a temporary arm-like projection of a eukaryotic cell membrane that is emerged in the direction of movement. Filled with cytoplasm, pseudopodia primarily consist of actin filamen ...

s, and the others let through bundles of

microtubule Microtubules are polymers of tubulin that form part of the cytoskeleton and provide structure and shape to eukaryotic cells. Microtubules can be as long as 50 micrometres, as wide as 23 to 27 nm and have an inner diameter between 11 an ...

s that support the

axopod A pseudopod or pseudopodium (plural: pseudopods or pseudopodia) is a temporary arm-like projection of a eukaryotic cell membrane that is emerged in the direction of movement. Filled with cytoplasm, pseudopodia primarily consist of actin filament ...

s. Unlike true radiolarians, there are no cross-bridges between them. They also lack symbiotic

alga Algae (; singular alga ) is an informal term for a large and diverse group of photosynthetic eukaryotic organisms. It is a polyphyletic grouping that includes species from multiple distinct clades. Included organisms range from unicellular mi ...

e, generally living below the

photic zone The photic zone, euphotic zone, epipelagic zone, or sunlight zone is the uppermost layer of a body of water that receives sunlight, allowing phytoplankton to perform photosynthesis. It undergoes a series of physical, chemical, and biological proc ...

, and do not produce any strontium sulphate.

Taxonomy

Phylogeny

Through phylogenetic analyses it has been discovered that Phaeodarea is a

monophyletic In cladistics for a group of organisms, monophyly is the condition of being a clade—that is, a group of taxa composed only of a common ancestor (or more precisely an ancestral population) and all of its lineal descendants. Monophyletic gro ...

clade, but the historical orders and families comprising it aren't. Instead, the clade consists of 11 subclades defined by morphological and phylogenetic values that do not correspond with the traditional orders and families: Despite this, the current taxonomy by

Cavalier-Smith Thomas (Tom) Cavalier-Smith, FRS, FRSC, NERC Professorial Fellow (21 October 1942 – 19 March 2021), was a professor of evolutionary biology in the Department of Zoology, at the University of Oxford. His research has led to discov ...

maintains the original classification of suborders divided between two new orders: #Eodarida, containing phaeodarea with no

skeleton or with a skeleton made of simple radiating spicules. Contains two suborders: Phaeogymnocellina and Phaeocystina. #Opaloconchida, containing phaeodarea with a highly perforated, shell-like opaline silica skeleton. Contains the remaining five suborders: Phaeosphaeria, Phaeocalpia, Phaeogromia, Phaeoconchia and Phaeodendria.

Modern classification

The modern classification is the following, with the subclass containing a total of 2 orders, 7 suborders, 16 families and 39 genera. *Order Eodarida **Suborder Phaeogymnocellina (=

Phaeogymnocellida Phaeogymnocellida is an order of cercozoans in the class Phaeodarea. References External links * Phaeogymnocellidaat the World Register of Marine Spacies (WoRMS) Phaeodaria Cercozoa orders {{Cercozoa-stub ...

) ***Family Phaeosphaeridae – '' Phaeopyla'', '' Phaeodactylis'', '' Phaeosphaera'' ***Family Phaeodinidae – '' Phaeodina'' ***Family Atlanticellidae – '' Gymnocelia'', '' Halocelia'', '' Lobocelia'', '' Miracelia'', '' Planktonetta'' **Suborder Phaeocystina (=

Phaeocystida Phaeocystida, also known as Phaeocystina, is a group of cercozoans in the class Phaeodarea. It was first described by Ernst Haeckel in 1887 and treated traditionally as a suborder, but later was raised to order level until Cavalier-Smith Th ...

) ***Family Aulacanthidae – '' Aulacantha'' ***Family

Astracanthidae ''Astracantha'' is a genus of phaeodaria containing the sole species of plankton ''A. heteracantha''. It was first described by the zoologist Valentin Haecker in 1908. It is the only member of the family Astracanthidae, described by Ernst Haeckel ...

– '' Astracantha'', '' Castanella'', '' Castanissa'' *Order Opaloconchida **Suborder Phaeosphaeria (=

) ***Family Aulosphaeridae – '' Aulosphaera'', '' Aularia'', '' Aulotractus'' ***Family Cannosphaeridae – '' Coelocantha'' ***Family Sagosphaeridae – '' Sagenoarium'', '' Sagenoscena'', '' Sagoscena'' **Suborder Phaeocalpia (=

Phaeocalpida Phaeocalpida is an order of cercozoans in the class Phaeodarea. References * Report on the Radiolaria. E Haeckel, 1887 * Report on the scientific results of the voyage of the HMS Challenger during the years 1873-1876. E Haeckel, Zoology seri ...

) ***Family Castanellidae – ''

Castanea The chestnuts are the deciduous trees and shrubs in the genus ''Castanea'', in the beech family Fagaceae. They are native to temperate regions of the Northern Hemisphere. The name also refers to the edible nut (fruit), nuts they produce. Th ...

'' ***Family Circoporidae – '' Circoporus'', '' Circospathis'', '' Haeckeliana'' ***Family Tuscaroridae – ''

Tuscarora Tuscarora may refer to the following: First nations and Native American people and culture * Tuscarora people **''Federal Power Commission v. Tuscarora Indian Nation'' (1960) * Tuscarora language, an Iroquoian language of the Tuscarora people * ...

'', '' Tuscarilla'', '' Tuscaretta'' ***Family Porospathidae – '' Porospathis'' ***Family Polypyramidae – '' Polypyramis'' **Suborder Phaeogromia (=

Phaeogromida Phaeogromida is an order of cercozoans in the class Phaeodarea. References * Report on the Radiolaria. E Haeckel, 1887 * Report on the scientific results of the voyage of HMS Challenger during the years 1873-1876. E Haeckel, Zoology series, ...

) ***Family Challengeridae – '' Challengeria'', '' Challengeron'' ***Family Medusettiidae – '' Euphysetta'', '' Gazelletta'', '' Medusetta'' ***Family Lirellidae – '' Borgertella'', '' Lirella'' **Suborder Phaeoconchia (= Phaeoconchida) ***Family Concharidae – '' Conchidium'' **Suborder Phaeodendria (=

Phaeodendrida Phaeodendrida is an order of cercozoans in the class Phaeodarea. References * Report on the Radiolaria. E Haeckel, 1887 * Report on the scientific results of the voyage of the HMS Challenger during the years 1873–1876. E Haeckel, Zoology s ...

) ***Family Coelodendridae – '' Coelodendrum'', '' Coelographis''

References

{{Taxonbar, from=Q139462 Cercozoa classes Amoeboids Taxa named by Ernst Haeckel