Bilateria is an extremely diverse group of animals containing a vast majority of its species, largely due to the enormous amount of arthropods. This article is a list of orders contained within Bilateria separated by phylum. Groups that are not contained within an order are listed separately.
Annelid taxonomy is currently under constant revisions due to the discovery that the class Polychaeta is paraphyletic. As such, a comprehensive list of orders is likely to change depending on what is accepted as valid.
Class Sipuncula
Clade Pleistoannelida
Unplaced groups
Class Craniata
Subphylum Linguliformea
Subphylum Rhynchonelliformea
Class Gymnolaemata
Class Phylactolaemata
Class Stenolaemata
Unplaced groups
Class Eucycliophora
Dicyemida does not contain any established orders but does contain three families: Conocyemidae, Dicyemidae and Kantharellidae
Entoprocta has no orders but is split into four families; Barentsiidae, Pedicellinidae, Loxokalypodidae, and Loxosomatidae
The classes Planctosphaeroidea and Enteropneusta do not contain any orders
Class Pterobranchia
Unplaced groups
Class Cyclorhagida
Class Allomalorhagida
Unplaced groups
Loricifera has no classes and all species are contained within one order
Micrognathozoa has no classes and its single species is placed in one order
Nematode taxonomy is far from fully resolved, and different schemes might be used. For this list, Mike Hodda's Phylum Nematoda: a classification, catalogue and index of valid genera, with a census of valid species classification is used. [1]
Class Enoplea
Class Dorylaimea
Class Chromadorea
Class Hoplonemertea
Class Palaeonemertea
Class Pilidiophora
Onychophora contains no classes and no orders, but is split into two living families; Peripatidae and Peripatopsidae, and 5 extinct genera; Antennacanthopodia , Antennipatus, Helenodora , Succinipatopsis , and Tertiapatus .
Orthonectida contains no classes or orders, but is split into two families; Pelmatosphaeridae and Rhopaluridae
Phoronida contains no classes, orders, or families, but is split into two genera; Phoronis and Phoronopsis
The class Catenulida contains no orders.
Subphylum Rhabditophora
Unplaced groups
Several stem group priapulid genera are not classified within any established orders. The orders listed below are solely crown priapulids.
The group Acanthocephala is traditionally treated as a separate phylum from Rotifera. However, it was found that Acanthocephala are phylogenetically contained within the rotifers, and this list reflects these findings.
Superclass Eurotatoria
Clade Acanthocephala
The class Mesotardigrada contains one species, Thermozodium esakii, which has not been found since its reported discovery in 1937, and its existence is dubious. It is contained within the order Thermozodia.
The subphylum Xenoturbellida does not contain any classes or orders. It's only family is Xenoturbellidae which contains one genus, Xenoturbella.
The class Nemertodermatida does not contain any orders, but does contain two families; Ascopariidae and Nemertodermatidae.
The Apicomplexa are organisms of a large phylum of mainly parasitic alveolates. Most possess a unique form of organelle structure that comprises a type of non-photosynthetic plastid called an apicoplast—with an apical complex membrane. The organelle's apical shape is an adaptation that the apicomplexan applies in penetrating a host cell.
Euglenozoa are a large group of flagellate Discoba. They include a variety of common free-living species, as well as a few important parasites, some of which infect humans. Euglenozoa are represented by four major groups, i.e., Kinetoplastea, Diplonemea, Euglenida, and Symbiontida. Euglenozoa are unicellular, mostly around 15–40 μm (0.00059–0.00157 in) in size, although some euglenids get up to 500 μm (0.020 in) long.
Order is one of the eight major hierarchical taxonomic ranks in Linnaean taxonomy. It is classified between family and class. In biological classification, the order is a taxonomic rank used in the classification of organisms and recognized by the nomenclature codes. An immediately higher rank, superorder, is sometimes added directly above order, with suborder directly beneath order. An order can also be defined as a group of related families.
Lobosa is a taxonomic group of amoebae in the phylum Amoebozoa. Most lobosans possess broad, bluntly rounded pseudopods, although one genus in the group, the recently discovered Sapocribrum, has slender and threadlike (filose) pseudopodia. In current classification schemes, Lobosa is a subphylum, composed mainly of amoebae that have lobose pseudopods but lack cilia or flagella.
Eurotiomycetes is a large class of ascomycetes with cleistothecial ascocarps within the subphylum Pezizomycotina, currently containing around 3810 species according to the Catalogue of Life. It is the third largest lichenized class, with more than 1200 lichen species that are mostly bitunicate in the formation of asci. It contains most of the fungi previously known morphologically as "Plectomycetes".
The Batrachomorpha are a clade containing extant and extinct amphibians that are more closely related to modern amphibians than they are to mammals and reptiles. According to many analyses they include the extinct Temnospondyli; some show that they include the Lepospondyli instead. The name traditionally indicated a more limited group.
Trimeniaceae is a family of flowering plants recognized by most taxonomists, at least for the past several decades. It is a small family of one genus, Trimenia, with eight known species of woody plants, bearing essential oils. The family is subtropical to tropical and found in Southeast Asia, eastern Australia and on several Pacific Islands.
The taxonomy of commonly fossilized invertebrates combines both traditional and modern paleozoological terminology. This article compiles various invertebrate taxa in the fossil record, ranging from protists to arthropods. This includes groups that are significant in paleontological contexts, abundant in the fossil record, or have a high proportion of extinct species. Special notations are explained below:
Opalozoa is a subphylum of heterotrophic protists of the phylum Bigyra, and is the sister group to Sagenista. Opalozoans are non-photosynthetic heterokonts that are ancestrally phagotrophic but many times have evolved to be osmotrophic saprotrophs in the gut of vertebrate animals.
The sarcomonads or class Sarcomonadea are a group of amoeboid biciliate protists in the phylum Cercozoa. They are characterized by a propensity to move through gliding on their posterior cilium or through filopodia, a lack of scales or external theca, a soft cell surface without obvious cortical filamentous or membranous skeleton, two cilia without scales or hairs, tubular mitochondrial cristae, near-spherical extrusomes, and a microbody attached to the nucleus.
Gnathodolus bidens is a species of headstander endemic to the Orinoco and Casiquiare rivers in Venezuela. It is the only member of its genus.
The biological systematics and taxonomy of invertebrates as proposed by Richard C. Brusca and Gary J. Brusca in 2003 is a system of classification of invertebrates, as a way to classify animals without backbones.
The taxonomy of the animals presented by Hutchins et al. in 2003 in Grzimek's Animal Life Encyclopedia is a system of classification which covers all the metazoans, from phyla to orders.
The taxonomy of the vertebrates presented by John Zachary Young in The Life of Vertebrates (1962) is a system of classification with emphasis on this group of animals.
Rhabditophora is a subphylum of flatworms. It includes all parasitic flatworms and most free-living species that were previously grouped in the now obsolete class Turbellaria. Therefore, it contains the majority of the species in the phylum Platyhelminthes, excluding only the catenulids, to which they appear to be the sister group.
Diatoms belong to a large group called the heterokonts, which include both autotrophs such as golden algae and kelp; and heterotrophs such as water moulds. The classification of heterokonts is still unsettled: they may be designated a division, phylum, kingdom, or something intermediate to those. Consequently, diatoms are ranked anywhere from a class, usually called Diatomophyceae or Bacillariophyceae, to a division (=phylum), usually called Bacillariophyta, with corresponding changes in the ranks of their subgroups.
Maldanomorpha is a monophyletic group, or clade, of polychaete worms in the phylum Annelida. Several phylogenetic analyses based on morphological and molecular data have shown that this clade unites the families Arenicolidae and Maldanidae. The two main synapomorphies, morphological characters described to unite both families, are a lecithotrophic larval development and the presence of an uncinus, a hook-like structure with barbs.
Sedentaria is a diverse clade of annelid worms. It is traditionally treated as a subclass of the paraphyletic class Polychaeta, but it is also a monophyletic group uniting several polychaetes and the monophyletic class Clitellata. It is the sister group of Errantia.