Panarthropoda is a proposed animal clade containing the extant phyla Arthropoda, Tardigrada and Onychophora. Panarthropods also include extinct marine legged worms known as lobopodians ("Lobopodia"), a paraphyletic group where the last common ancestor and basal members (stem-group) of each extant panarthropod phylum are thought to have risen. However the term "Lobopodia" is sometimes expanded to include tardigrades and onychophorans as well.
The opisthokonts are a broad group of eukaryotes, including both the animal and fungus kingdoms. The opisthokonts, previously called the "Fungi/Metazoa group", are generally recognized as a clade. Opisthokonts together with Apusomonadida and Breviata comprise the larger clade Obazoa.
Lophotrochozoa is a clade of protostome animals within the Spiralia. The taxon was established as a monophyletic group based on molecular evidence. The clade includes animals like annelids, molluscs, bryozoans, and brachiopods.
The Apusozoa are a paraphyletic phylum of flagellate eukaryotes. They are usually around 5–20 μm in size, and occur in soils and aquatic habitats, where they feed on bacteria. They are grouped together based on the presence of an organic shell or theca under the dorsal surface of the cell.
Capsaspora is a monotypic genus containing the single species Capsaspora owczarzaki. C. owczarzaki is a single-celled eukaryote that occupies a key phylogenetic position in our understanding of the origin of animal multicellularity, as one of the closest unicellular relatives to animals. It is, together with Ministeria vibrans, a member of the Filasterea clade. This amoeboid protist has been pivotal to unraveling the nature of the unicellular ancestor of animals, which has been proved to be much more complex than previously thought.
Ministeria vibrans is a bacterivorous amoeba with filopodia that was originally described to be suspended by a flagellum-like stalk attached to the substrate. Molecular and experimental work later on demonstrated the stalk is indeed a flagellar apparatus.
Corallochytrium belongs to the class of Corallochytrea within Teretosporea and is a sister group to Ichthyosporea. Corallochytrium limacisporum is the only species of Corallochytrium known so far. It was first discovered and named in the Arabian Sea’s coral lagoons by Kaghu-Kumar in 1987. It was first thought to be a member of the fungi-like thraustochytrids, however, this was later disproven due to Corallochytriums lack of cilia and sagenogenetosome. Little research has been done on the life cycle or morphology. Most research concerning this genus has been done to uncover the evolution of animals and fungi, as Corallochytrium possess both animal and fungal enzymatic trademarks.
Filasterea is a proposed basal Filozoan clade of single-celled ameboid eukaryotes that includes Ministeria and Capsaspora. It is a sister clade to the Choanozoa in which the Choanoflagellatea and Animals appeared, originally proposed by Shalchian-Tabrizi et al. in 2008, based on a phylogenomic analysis with 78 genes. Filasterea was found to be the sister-group to the clade composed of Metazoa and Choanoflagellata within the Opisthokonta, a finding that has been further corroborated with additional, more taxon-rich, phylogenetic analyses.
Holozoa is a clade of organisms that includes animals and their closest single-celled relatives, but excludes fungi and all other organisms. Together they amount to more than 1.5 million species of purely heterotrophic organisms, including around 300 unicellular species. It consists of various subgroups, namely Metazoa and the protists Choanoflagellata, Filasterea, Pluriformea and Ichthyosporea. Along with fungi and some other groups, Holozoa is part of the Opisthokonta, a supergroup of eukaryotes. Choanofila was previously used as the name for a group similar in composition to Holozoa, but its usage is discouraged now because it excludes animals and is therefore paraphyletic.
The Spiralia are a morphologically diverse clade of protostome animals, including within their number the molluscs, annelids, platyhelminths and other taxa. The term Spiralia is applied to those phyla that exhibit canonical spiral cleavage, a pattern of early development found in most members of the Lophotrochozoa.
The Filozoa are a monophyletic grouping within the Opisthokonta. They include animals and their nearest unicellular relatives.
Holomycota or Nucletmycea are a basal Opisthokont clade as sister of the Holozoa. It consists of the Cristidiscoidea and the kingdom Fungi. The position of nucleariids, unicellular free-living phagotrophic amoebae, as the earliest lineage of Holomycota suggests that animals and fungi independently acquired complex multicellularity from a common unicellular ancestor and that the osmotrophic lifestyle was originated later in the divergence of this eukaryotic lineage. Opisthosporidians is a recently proposed taxonomic group that includes aphelids, Microsporidia and Cryptomycota, three groups of endoparasites.
Nephrozoa is a proposed major clade of bilaterian animals. It includes all bilaterians other than Xenacoelomorpha. It contrasts with the Xenambulacraria hypothesis, which instead posits that Xenacoelomorpha is most closely related to Ambulacraria. Which hypothesis is correct is controversial. Authors supporting the Xenambulacraria hypothesis have suggested that the genetic evidence used to support Nephrozoa may be due to systematic error.
Choanozoa is a clade of opisthokont eukaryotes consisting of the choanoflagellates (Choanoflagellatea) and the animals. The sister-group relationship between the choanoflagellates and animals has important implications for the origin of the animals. The clade was identified in 2015 by Graham Budd and Sören Jensen, who used the name Apoikozoa. The 2018 revision of the classification first proposed by the International Society of Protistologists in 2012 recommends the use of the name Choanozoa.
Abeoforma whisleri is a single-celled eukaryote that belongs to the Ichthyosporea, a group of protists closely related to animals.
Pirum gemmata is a unicellular eukaryote that belongs to the Ichthyosporea clade, a group of protists closely related to animals. P. gemmata was isolated from the gut contents of a marine invertebrate, specifically the detritivorous peanut worm Phascolosoma agassizii.
The Scotokaryotes (Cavalier-Smith) is a proposed basal Neokaryote clade as sister of the Diaphoretickes. Basal Scotokaryote groupings are the Metamonads, the Malawimonas and the Podiata. In this phylogeny the Discoba are sometimes seen as paraphyletic and basal Eukaryotes.
Ichthyophonus hoferi is a single-celled protist that occupies a key phylogenetic position to understand the origin of animals. It has chitin cell wall, hyphae, and an amoeboid stage. It is a common parasite of marine and freshwater fishes.
Pluriformea is a proposed sibling clade of the Filozoa, and consists of Syssomonas multiformis and the Corallochytrea. Together with the Ichthyosporea and the Filozoa, they form the Holozoa.
An amoeboflagellate is any eukaryotic organism capable of behaving as an amoeba and as a flagellate at some point during their life cycle. Amoeboflagellates present both pseudopodia and at least one flagellum, often simultaneously.
