Rigifilida is a

clade In biology, a clade (), also known as a Monophyly, monophyletic group or natural group, is a group of organisms that is composed of a common ancestor and all of its descendants. Clades are the fundamental unit of cladistics, a modern approach t ...

of non-

ciliate The ciliates are a group of alveolates characterized by the presence of hair-like organelles called cilia, which are identical in structure to flagellum, eukaryotic flagella, but are in general shorter and present in much larger numbers, with a ...

phagotrophic

eukaryote The eukaryotes ( ) constitute the Domain (biology), domain of Eukaryota or Eukarya, organisms whose Cell (biology), cells have a membrane-bound cell nucleus, nucleus. All animals, plants, Fungus, fungi, seaweeds, and many unicellular organisms ...

s. It consists of two

genera Genus (; : genera ) is a taxonomic rank above species and below family as used in the biological classification of living and fossil organisms as well as viruses. In binomial nomenclature, the genus name forms the first part of the binomial s ...

: '' Micronuclearia'' and '' Rigifila''.

Characteristics

Cells of rigifilids are covered with either a single or a double-layered submembrane pellicular lamina that makes them rigid in consistence. Slender branching

filopodia Filopodia (: filopodium) are slender cytoplasmic projections that extend beyond the leading edge of lamellipodia in migrating cells. Within the lamellipodium, actin ribs are known as ''microspikes'', and when they extend beyond the lamellipod ...

emanate from a ventral aperture of the cell and are employed to collect

bacteria Bacteria (; : bacterium) are ubiquitous, mostly free-living organisms often consisting of one Cell (biology), biological cell. They constitute a large domain (biology), domain of Prokaryote, prokaryotic microorganisms. Typically a few micr ...

upon which they feed and to attach the organism to the substratum. Around this aperture, the pellicle is reflexed around forming a peristomial collar. Other notable features are flat and irregular shaped mitocondrial cristae, a single dorsal nucleus and the lack of

centriole In cell biology a centriole is a cylindrical organelle composed mainly of a protein called tubulin. Centrioles are found in most eukaryotic cells, but are not present in conifers ( Pinophyta), flowering plants ( angiosperms) and most fungi, an ...

s and

cilia The cilium (: cilia; ; in Medieval Latin and in anatomy, ''cilium'') is a short hair-like membrane protrusion from many types of eukaryotic cell. (Cilia are absent in bacteria and archaea.) The cilium has the shape of a slender threadlike proj ...

Phylogeny

Taxonomy

Rigifilida is currently placed in

CRuMs CRuMs is a clade of microbial eukaryotes, whose name is an acronym of the following constituent groups: i) Diphylleids, ii) rigifilids and iii) mantamonads as sister of the Amorphea. A new CRuMs order Glissandrida was proposed in 2025 to pla ...

. *Order Rigifilida Cavalier-Smith 2012 icronucleariida Cavalier-Smith 2008** Family Rigifilidae Yabuki & Cavalier-Smith 2012 *** Genus '' Rigifila'' Yabuki & Cavalier-Smith 2012 **** Species '' Rigifila ramosa'' Yabuki & Cavalier-Smith 2012 ** Family Micronucleariidae Cavalier-Smith 2008 *** Genus '' Micronuclearia'' Mikrjukov & Mylnikov 2001 **** Species '' Micronuclearia podoventralis'' Mikrjukov & Mylnikov 2001

References

{{Eukaryote-stub CRuMs orders Eukaryote stubs