A Higher Level Classification of All Living Organisms

Abstract

We present a consensus classification of life to embrace the more than 1.6 million species already provided by more than 3,000 taxonomists’ expert opinions in a unified and coherent, hierarchically ranked system known as the Catalogue of Life (CoL). The intent of this collaborative effort is to provide a hierarchical classification serving not only the needs of the CoL’s database providers but also the diverse public-domain user community, most of whom are familiar with the Linnaean conceptual system of ordering taxon relationships. This classification is neither phylogenetic nor evolutionary but instead represents a consensus view that accommodates taxonomic choices and practical compromises among diverse expert opinions, public usages, and conflicting evidence about the boundaries between taxa and the ranks of major taxa, including kingdoms. Certain key issues, some not fully resolved, are addressed in particular. Beyond its immediate use as a management tool for the CoL and ITIS (Integrated Taxonomic Information System), it is immediately valuable as a reference for taxonomic and biodiversity research, as a tool for societal communication, and as a classificatory “backbone” for biodiversity databases, museum collections, libraries, and textbooks. Such a modern comprehensive hierarchy has not previously existed at this level of specificity.

Introduction

Biological classification (taxonomy) aims to simplify and order the immense diversity of life into coherent units called taxa that have widely accepted names and whose members share important properties. It synthesizes information concerning a great variety of characters (e.g., morphological; molecular: genes, metagenome, and metabolome; etho-ecological). There is currently no consensus among the world's taxonomists concerning which classification scheme to use for the overall hierarchy of life, in part because of the confusion resulting from Hennig's [1] redefinition of previous terminology of classification, which has not been universally accepted; the separate goals of cladification and classification [2]; and conflicting or unresolved evidence for phylogenetic relationships. The continuing advances in the use of specialized analytical tools from many different fields and their resulting conclusions and assumptions require regular updates as advances in knowledge are made.

Biological classification can integrate diverse, character-based data in a phylogenetic framework, which allows a broad user community to utilize the disparate knowledge of shared biological properties of taxa. Phylogeny is, therefore, the basis for these biological classifications but there is still strong debate over their accounting for evolutionary divergence or information content other than the branching pattern [3]. Accordingly, classifications have often been labeled either phylogenetic or evolutionary, depending mainly upon whether or not they reject paraphyletic groups [3, 4].

While the type of classification to be used to support further exploration and analysis of any biological scenario may be important, it is not the subject of this paper. The proposed classification does not address detailed phylogenetic questions and, while hierarchical and reflective of phylogeny, is not itself a phylogenetic tree. The aim of this classification is to be a pragmatic means of managing the ever-increasing knowledge of the diversity of life, its relationships, characteristics, and properties. Indeed, the past two decades have witnessed an explosion in biodiversity research and informatics, emphasizing the need for a quality list of accepted scientific names of the more than 1.9 million described living species [5] and for greater consensus on how to classify them at higher taxonomic ranks. Since 2001, Species 2000 and the Integrated Taxonomic Information System (ITIS) have worked with their respective contributors to complete a comprehensive species list, called the Catalogue of Life (CoL). The CoL Annual Checklist (http://www.catalogueoflife.org/annual-checklist/2014/) already contains more than 1.6 million valid or accepted species names provided by more than 140 taxonomic databases involving more than 3,000 taxonomists [6]. More than 82% of the global species databases are provided at the rank of class or below (includes 1.3 million species), and more than 63% are provided at the rank of order or below (includes 1.0 million species). Owing to the heterogeneity in higher level classification among the contributed databases, the CoL managers sought a practical and coherent hierarchical classification that could serve as a framework for data integration. Here we explain the rationale behind the consensus higher level classification that we propose for CoL use.

Our goal, therefore, is to provide a hierarchical classification for the CoL and its contributors that (a) is ranked to encompass ordinal-level taxa to facilitate a seamless import of contributing databases; (b) serves the needs of the diverse public-domain user community, most of whom are familiar with the Linnaean conceptual system of ordering taxon relationships; and (c) is likely to be more or less stable for the next five years. Such a modern comprehensive hierarchy did not previously exist at this level of specificity. In this sense it summarizes overarching aspects of the tree of life, including both paraphyletic and monophyletic groups, both being important in facilitating meaningful communication among scientists and between the scientific community and society.

The most recent higher level classification to this level was published more than 30 years ago, before the advent of modern molecular analysis [7]. Beyond the immediate use for CoL, the hierarchy is valuable as a reference for taxonomic and biodiversity research, as a tool for societal communication, and as a stable classificatory “backbone” for biodiversity databases, museum collections, libraries, and textbooks, to name a few applications.

Approach

When Linnaeus introduced his novel “system of nature” in the mid-18^th century, he recognized three kingdoms of nature: Regnum Vegetabile (plants), Regnum Animale (animals), and Regnum Lapideum (minerals) that has long since been abandoned. However, as is evident from the title of his work, he introduced lower level taxonomic categories (named class, order, genus, and species), each successively nested within higher ranked categories. Linnaeus' system has proven to be robust for more than 250 years (see the comprehensive discussion and suggestions for dealing with potential conflicts in Vences et al. [8]). In modern-day classifications, the starting point for botanical names is Linnaeus’ Species Plantarum [9] and for zoological names it is the tenth edition of the Systema Naturae [10]. Since Linnaeus, the expansion of knowledge and the increase in the number of described species has required an expansion of the number of hierarchical levels (ranks) within the system. The categories of family and phylum (or division) were introduced in the early 19^th century and many intermediate categories have been added since. There is currently little agreement about the general names for categories above that of kingdom; here we use superkingdom rather than empire or domain. In addition, there are three separate codes that govern the assignment and use of scientific names, each with different requirements and terminology and consequences for their classifications. For algae, fungi, and plants (ICN: International Code of Nomenclature for algae, fungi, and plants), the principle of priority does not apply above rank of family; for animals (ICZN: International Code of Zoological Nomenclature), priority does not apply above the family-group ranks; and for prokaryotes other than Cyanobacteria (ICNB: International Code of Nomenclature of Bacteria), only the categories ranked as class and below are covered by the code. A recent paper by the International Committee on Bionomenclature compares terminology among six current nomenclatural codes and makes recommendations for their use in improving communication [11].

In 2005, on behalf of the International Society of Protistologists, Adl et al. [12] presented a nested eukaryote-only cladification that used the names of six supergroups—Amoebozoa, Opisthokonta, Rhizaria, Excavata, Chromalveolata, and Archaeplastida (= Plantae) [13–17]—as the highest ranked eukaryote groups. Their schema was updated in 2012 [18], with Rhizaria and Chromalveolata replaced by SAR plus four small hacrobian groups. Although these taxa are nested, and ranked by a “bulleted” system, Adl et al. avoided the use of Linnaean higher category names (phylum, class, order, family) that would have more usefully denoted rank. Insofar as the nested groups comprise a mix of taxon names based on priority (i.e., according to the year of introduction of the name), many individual genera as well as traditional taxon names (family through class) end up having the same rank in the Adl et al. hierarchy, while at the same time having different suffixes or none at all. The ranks assigned therein often seem to reflect our present partial ignorance of relationships more than careful assessment of relative phenotypic disparity as in Linnaean taxonomy. This is very confusing when these “group names” (genus to kingdom) are used in isolation without regard to phylogenetic relativity. Two of the great benefits of Linnaean-ranked categories and their standardized suffixes are that they instantly relativize taxa that are otherwise unknown to the non-specialist and also indicate the relative degree of phenotypic distinctiveness amongst groups. The overarching higher level classification used by the CoL, therefore, uses the standard formal categories, as it is intended to be simultaneously pragmatic and informative of both evolutionary relatedness and relative phylogenetic subordination. A classification should be biologically well-grounded and widely useful. In its simplicity, it provides less detail about relationships than a complete phylogeny but is still congruent with it [19]. Our classification is not intended to compete with a cladification such as Adl et al.’s—both are valid ways of ordering the living world—but we would argue that their’s is less comprehensible to many in the public-domain user communities.

These actual complexities of phylogenetic history emphasize that classification is a practical human enterprise where compromises must be made [20]. We have therefore named only groups generally considered to have had a monophyletic origin, even though some of them may be paraphyletic (i.e., do not include all descendants of their last common ancestor) and others, e.g., Euglenozoa, Rhizaria, Cercozoa, include subgroups (such as Euglenophyceae, Chlorarachnea, and Paulinella) that evolved by the symbiogenetic merger of two fundamentally different lineages [21], while others have had infusions of genes from elsewhere [22] and therefore do not conform to any purely formal definition of monophyly. We have not adopted the view that one should never accept paraphyletic groups in a classification but rather have evaluated each case of paraphyly on its practicability and usage. In some cases (e.g., classical bryophytes) we accepted the splitting of paraphyletic taxa into holophyletic groups (groups with a monophyletic origin that also include all descendants of their last common ancestor, i.e., clades). In others we retained ancestral (paraphyletic) taxa when it seemed beneficial to do so (e.g., Prokaryota, Protozoa, Crustacea, Sarcopterygii, Reptilia). For practical purposes we treat Proteobacteria and Cyanobacteria as holophyletic phyla even though both exclude their mitochondrial and chloroplast descendants, neither of which is now a bacterium but an evolutionarily chimaeric cell organelle. We have conservatively retained several groups where evidence for paraphyly or holophyly is contradictory, such as Archaea (Archaebacteria).

A panel of experts representing the major taxonomic disciplines was convened to review, revise, and update the existing incomplete CoL hierarchy. These authors consulted more than 200 sources (see S1 Appendix), most of which were from recent taxonomic publications and websites. The product is a current and practical classification that meets the panel’s established goal. In achieving a consensus, the panel was required to make some compromises that may require future revision as the related issues are resolved. While all of these individuals made contributions to the hierarchy, not all necessarily endorse every aspect of it. The CoL classification will undergo review and revision at five-year intervals to consider changes as necessary.

Results and Discussion

We are proposing a two-superkingdom (Prokaryota and Eukaryota), seven-kingdom classification that is a practical extension of Cavalier-Smith’s six-kingdom schema [19]; the latter has been used, for example, in the compendious checklist of marine biota of Chinese seas [23] and in the first comprehensive national inventory of biodiversity for New Zealand [24–26]. For each of these kingdoms we had to exercise our taxonomic judgment and reach a practical compromise among diverse opinions and usages and conflicting evidence about certain phylogenetic questions important for defining the boundaries between and ranks of major taxa, including kingdoms. Our schema includes: the prokaryotic kingdoms Archaea (Archaebacteria) and Bacteria (Eubacteria), and the eukaryotic kingdoms Protozoa, Chromista, Fungi, Plantae, and Animalia. We have retained 14 ranks from superkingdom to order (Table 1). Several key taxonomic issues, some not fully resolved, are discussed below.

Table 1. List of ranks used in the hierarchy with the number of taxa per rank.

Rank	Number of Taxa
Superkingdom	2
Kingdom	7
Subkingdom	11
Infrakingdom	8
Superphylum	6
Phylum	96
Subphylum	60
Infraphylum	4
Superclass	12
Class	351
Subclass	145
Infraclass	23
Superorder	52
Order	1,467

Main ranks are in bold type; unnamed taxa are not counted.

Prokaryota

The higher classification of prokaryotes is still somewhat unsettled. Woese and Fox [27] treated Archaebacteria (Archaea) and Eubacteria (Bacteria) as separate kingdoms. Margulis and Schwartz [28] recognized the superkingdom Prokarya, containing one kingdom Bacteria that included a subkingdom Archaea; Cavalier-Smith also treated Archaebacteria and Eubacteria as prokaryote subkingdoms [19, 29]. Commonly used sources of prokaryote names, such as the List of Prokaryotic Names with Standing in Nomenclature (LPSN) [30] and the Taxonomic Outline of Bacteria and Archaea (TOBA) [31] treat Bacteria and Archaea as separate domains but are silent about the category of kingdom. While these sources list the names of phyla in common use as a service to the user, they are not validly published under the ICNB. We have not placed phylum names in quotation marks as they have but we have so designated a few prokaryote names at lower ranks that are in common use but not (or not yet) valid. As no prokaryote names above the ranks of class are covered by ICNB rules, there is no official higher classification of prokaryotes [32] and any attempt at such is necessarily difficult. We have chosen to adopt the classification in current use by the Catalogue of Life. It is derived from the TOBA and recognizes Bacteria and Archaea as equivalent in rank to the eukaryote kingdoms. We treat them as de facto kingdoms until there is a better resolution of their status. The number of negibacterial “phyla” currently recognized [30] is probably excessive compared with eukaryotes and mainly reflects uncertainty about the true relationships of many small phyla, probably exaggerating the significance of their biological disparity. Greater use of multigene trees rather than over reliance on rRNA gene trees alone may eventually allow further simplification by grouping them into fewer phyla, possibly only about half the present number [28].

Protozoa and Chromista

Unicellular eukaryotes, usually called protists, comprise a polyphyletic group of eukaryotes that do not undergo tissue formation through the process of embryological layering. They include ancestrally unicellular eukaryotes directly descended from bacteria by the origin of the nucleus, endomembrane, cytoskeleton, and mitochondria. Assigning them to separate kingdoms was historically difficult when only light microscopy was available but is now considerably facilitated because of advances in electron microscopy and gene sequencing. Formerly, the unicellular amoeboid group Myxozoa with multicellular spores was included in Protozoa but these protists are now firmly within the animal kingdom, having been proven to be greatly simplified parasitic animals. Yeasts are unicellular fungi that evolved polyphyletically from multicellular filamentous ancestors and are assigned to one of three higher fungal phyla. Microsporidia are highly reduced intracellular parasites traditionally considered to be Protozoa, but they have been known for two decades to be related to Fungi. At one time it was thought microsporidia had evolved from Fungi and therefore were placed in that kingdom [19, 33]. For several years multigene trees were contradictory about whether microsporidia branched within or diverged from Fungi. The latest evidence is that they are most closely related to rozellids [34], which also have been treated either as Fungi or Protozoa. If this recent phylogeny [34] is correct, both should be in the same kingdom. Here we take the view that the best demarcation between Protozoa and Fungi lies immediately before the origin of the chitinous wall around vegetative fungal cells and associated loss of phagotrophy [33]. We therefore include microsporidia and rozellids in Protozoa (vegetatively wall-less, typically phagotrophs) not Fungi (vegetatively walled osmotrophs).

For decades, taxonomists have debated the boundary between Protozoa and Plantae. We accept the view that it should be placed just prior to the evolutionary origin of chloroplasts and that Plantae should comprise all eukaryotes with plastids directly descending from the initially enslaved cyanobacterium, i.e., Viridiplantae (green plants), Rhodophyta (red algae), and Glaucophyta (glaucophyte algae), but exclude those like chromists that got their chloroplasts from plants secondarily by subsequent eukaryote-to-eukaryote lateral transfers. Therefore, all green algae are included in Viridiplantae and Plantae and are excluded from Protozoa. The only photosynthetic Protozoa are Euglenophyceae, which obtained their chloroplasts subsequently from an enslaved green alga [21].

The boundary between Protozoa and Chromista has been more controversial. Chromista was established to include all chromophyte algae (those with chlorophyll c, not b) considered to have evolved by symbiogenetic enslavement of another eukaryote (a red alga) as well as all heterotrophic protists descended from them by loss of photosynthesis or entire plastids [35]. With phylogenetic advances it has become clearer that alveolates (once considered Protozoa) are related to chromistan heterokont algae (and related heterotrophic heterokonts) and more distantly to Rhizaria, the three together forming the major group Harosa (equivalent to SAR). Consequently, Chromista has been greatly expanded to include all Harosa as well as other former protozoa that turned out to be related to haptophytes or cryptophytes. Chromista now includes many groups once treated as Protozoa [19], an expansion followed here. In multigene trees, this expansion is the most difficult part of the entire eukaryote tree to resolve. They sometimes show one or both of Plantae and Chromista as a clade but often their major subgroups are intermingled in contradictory ways [36, 37]. This may be a consequence of the eukaryote-eukaryote chimaeric history of chromists that acquired some genes from red algae or of the very rapid basal radiation of the robust corticate clade (i.e. Plantae plus Chromista). Because of this, some question whether Chromista represents a clade, yet trees are still too poorly resolved to eliminate the likelihood from cell evolutionary considerations that Chromista and Plantae are genuinely distinct sister clades. Evidence that Harosa is a clade is very strong. Evidence that Haptista plus Cryptista are a clade Hacrobia is strong on some trees but questioned by others [37].

Protozoa, like Prokaryota, is certainly a paraphyletic taxon [38]; Animalia, Fungi, Plantae, and Chromista all evolved from it. In our hierarchy Protozoa comprises seven phyla, of which four are probably clades and three paraphyletic. We do not consider it useful in a general classification to subdivide the paraphyletic phyla into numerous smaller ones, often with only a handful of species that most have never heard of, even though a few specialists might favor that despite their constituent subgroups not differing radically in cell structure. For both Protozoa and Chromista we have favored large groups with shared body plans, analogous to extremely diverse animal phyla like Chordata and Arthropoda. The higher proportion of ancestral (paraphyletic) phyla in Protozoa compared with terminal groups like animals and plants is unsurprising because they were the first eukaryotes and they diverged early on but with many fewer associated major changes in body plan than occurred during the much later radiation of bilateral animals. Distinct early diverging protozoan clades can be remarkably similar morphologically and biologically [39].

Fungi

As stated earlier, we take the view that the best demarcation between Protozoa and Fungi lies immediately before the origin of the chitinous wall around vegetative fungal cells and associated loss of phagotrophy. We use an updated version of the higher classification presented in the 10^th Edition of the Dictionary of Fungi [40]. The evolutionarily convergent Oomycetes such as the serious pest Phytophthora, formerly treated as Fungi, belong instead in phylum Pseudofungi of the heterokont Chromista.

Plantae

As with the other kingdoms, Plantae is classified in a variety of ways. Margulis and Schwartz [28] restricted Plantae to land plants (embryophytes or higher plants) and popularized the use of kingdom Protoctista to include lower plants (green, red, and glaucophyte algae) and lower Fungi as well as chromists with classical protozoa. Many now consider such a kingdom too broad and heterogeneous and the associated separation of lower and higher plants in different kingdoms to be undesirable. Now taxonomists almost universally classify lower and higher plants together in the single kingdom Plantae and lower and higher fungi within the single kingdom Fungi. We have adopted this delimitation of Plantae here [19, 35] (for which Archaeplastida [12, 18] is a less familiar recent synonym). The structure of plastid genomes and the derived chloroplast protein-import machinery support a single origin of glaucophytes, red algae, green algae, and embryophytes (land plants). The ancestral embryophyte is thought to have originated from relatives of the Charales (stoneworts) or Coleochaetales (Charophyta). Jeffrey [41] first grouped charophytes and embryophytes as a clade Streptophyta, which was later validated as a superphylum [42] and reduced to phylum by Bremer [43].

Chase and Reveal [44] published a phylogenetic classification of land plants, reasoning that “If the major clades of green algae are recognized as classes, then all land plants, the embryophytes, should be included in a single class, here recognized as Equisetopsida.” This argument, however, overemphasizes cladistic level compared with phenotypic disparity, and is contrary to traditional assignment of phylum (or division) status to the main bryophyte, “pteridophyte” and seed-plant subgroups. This latter treatment was exemplified in the 2008 Annual Checklist of the CoL, which listed three bryophyte phyla, four pteridophyte phyla, and five seed-plant phyla, reflecting the arrangement found in many university textbooks of the late 20^th century and in Margulis and Schwartz’s Five Kingdoms [28]. Here we recognize four embryophyte phyla—three of bryophytes (liverworts, hornworts, and mosses) and a single phylum Tracheophyta for vascular plants—with all species characterized by a diploid phase having xylem and phloem. Bryophyte specialists tend to treat each of the three major bryophyte groups as phyla—Marchantiophyta, Anthocerotophyta, Bryophyta [45, 46]. We have chosen a conservative approach to the higher classification of plants, largely consistent with Mabberley [47] for the embryophyte ranks above class, while using Chase and Reveal [44] and Stevens [48] for the lower ranks.

Animalia (Metazoa)

The numbers of phyla and classes with extant species in kingdom Animalia differ according to molecular and morphological partitioning in phylogenies [49–59] as well as the preferred treatments of specialists of particular traditional phyla and where to “draw the line” between related taxa and how to rank them—the ranking of phylum versus subphylum is sometimes rather subjective. Based on the contributions of taxonomic experts to an outline of higher level classification and survey of taxonomic richness [60, 61], as many as 39 animal phyla might be recognized (more, if Porifera were abandoned as a phylum and constituent major clades given higher rank [62]). Below we discuss some issues encountered in arriving at decisions for our proposed classification, which accepts 34 animal phyla.

(1) Porifera—one phylum or three?

Nielsen [62] argued that ‘The three apparently monophyletic sponge groups Silicea, Calcarea, and Homoscleromorpha do not constitute a monophyletic group, and the “phylum Porifera” thus has to be abandoned.’ More recent studies alternatively support paraphyly [63] or holophyly [58, 64] of sponges. Until the issue is resolved, we will follow the Porifera community [65–67] in retaining one phylum Porifera with four classes.

(2) Status of Myxozoa

Recent work on the vermiform myxozoan Buddenbrockia has demonstrated conclusively that myxozoans are extremely simplified Cnidaria, possibly Medusozoa [68, 69]. We classify Myxozoa as a subphylum of Phylum Cnidaria.

(3) Flatworms—monophyletic or not?

In 1995, Nielsen [70] wrote “The delimitation of the phylum [Platyhelminthes] is not much in question,” but recent molecular analyses, combined with a careful reconsideration of morphology and anatomy, have confused the classification of Platyhelminthes, affecting particularly Acoela, Xenoturbella, and Nemertodermatida. Egger et al. [71] reviewed the evidence, noting the contrast between morphological and phylogenomic data. Whereas the stem-cell system and the mode of replacing epidermal cells unite both Acoela and Rhabditophora and are not found in any other bilaterian lineage, phylogenomic data support a separation of these two groups, a conclusion reached by Philippe et al. [72] based on mitochondrial genes, a phylogenomic data set of 38,330 amino-acid positions, and miRNA complements. We follow Philippe et al. [72] and Tyler and Schilling [73] in uniting Acoela, Xenoturbella, and Nemertodermatida as the deuterostome phylum Xenacoelomorpha. The remaining internal classification of Platyhelminthes is also somewhat problematic. We propose a classification that is based in part on Riutort et al. [74] and Tyler [75].

(4) Phylum Gnathifera or phyla Acanthocephala, Gnathostomulida, Micrognathozoa, and Rotifera?

Until recently, all four of these groups were commonly treated as separate phyla [28, 61, 76–80]. However, numerous recent molecular and morphological analyses nest Acanthocephala within Rotifera [81–86]. A syncytial epidermis links rotifers, Seison and Acanthocephala; Ahlrichs [87, 88] proposed Syndermata for this clade. As revealed by transmission electron microscopy [89] and scanning electron microscopy [90], the jaw apparatus of gnathostomulids and rotifers is remarkably similar. That of Seison is less obviously homologous [91] and the Seisonidea may have diverged from rotifers at an early stage of their evolution. On the other hand, Seison has similar sperm to acanthocephalans and the epidermis of both groups contains bundles of filaments. Limnognathia maerski, representing a new category of organism (Micrognathozoa) from cold fresh waters in Greenland and the Crozet Islands [92, 93], has a remarkable jaw apparatus (the most complicated known among invertebrates) with clear homologies, in both the jaw elements and musculature, with the trophi in Rotifera and the jaws in Gnathostomulida. The jaw apparatus and musculature, as well as molecular analyses, unite these taxa as a clade known as Gnathifera (see [86, 92]). In the analysis by Giribet et al. [94], the issue remained unresolved, as Micrognathozoa appeared independent of Gnathostomulida and Rotifera, with unclear affiliation. Edgecombe et al. [59] and Nielsen [95] retain phylum status for Gnathostomulida, Micrognathozoa, and Rotifera but not Acanthocephala. We treat each of the major gnathiferan groups as a phylum, including Acanthocephala, following Monks and Richardson [79], though some of us think that the number of gnathiferan phyla ought to be substantially reduced when their phylogeny, including ingroup relationships of Rotifera sensu lato, is more firmly established.

(5) The scalidophoran phyla

Adrianov and Malakhov [96] erected phylum Cephalorhyncha for Kinorhyncha, Loricifera, Priapula, and Nematomorpha. The first three of these phyla have in common an eversible snout (introvert) with scalid spines and inner and outer retractor muscles, a similar excretory filter (protonephridium), and similar sense organs, providing strong justification for uniting them in a single clade, the Scalidophora [97]. There is also molecular support, though not unanimity, for a clade of Kinorhyncha, Loricifera, and Priapula, known as Scalidophora. On the other hand, Kinorhyncha has internal and external body segmentation lacking in the other groups. Neuhaus and Higgins [98] noted that conflicting evidence exists for every one of the possible sister-group relationships among these phyla and prefer to keep them separate in a superphylum Scalidophora (which is preferred over Cephalorhyncha, the latter name originally including the Nematomorpha). We recommend separate scalidophoran phyla, though the number might be greatly reduced when the phylogeny becomes clearer.

(6) The chordate subphyla Cephalochordata and Urochordata

Some sequence analyses have questioned the monophyly of Chordata [99, 100]. Nielsen [95] maintains Urochordata (or Tunicata) and Cephalochordata as separate phyla, whereas the group Urochordata is closer to Vertebrata (craniates), in a clade Olfactores, than Cephalochordata. We retain all three groups as traditional chordate subphyla.

Many users of classifications would prefer a stable, unchanging system. Yet classifications are syntheses of biological knowledge, particularly contemporary phylogenetic understanding of taxa, that must be regularly updated in accord with new scientific discoveries. Taxonomy must therefore navigate between the dual perils of ignoring important advances and making premature or unnecessary changes. We seek stability in nomenclature at the species level but at higher levels the concepts and compositions of major taxa, and therefore the scope of well-known names, must inevitably shift as new organisms are discovered and evolutionary affinities are better understood. The fact that we have been able to agree on a practical unified classification shows that taxonomists can broadly agree, despite the diverse experiences, viewpoints, and to some extent, differing philosophies of classification represented on our panel. The present classification (as, indeed, all classifications) should be regarded as interim, and it will inevitably change in certain respects, some hinted at above. However, we suspect that the recent torrent of radical re-evaluations (resulting especially from the application of DNA sequencing and other new techniques) may lessen as time passes. We hope that this unusually comprehensive classification will be widely useful and provide a sound basis for further improvement. A complete proposed classification from superkingdom to order is provided in Table 2 and is available for download at <http://www.catalogueoflife.org/col/>. Below the rank of infrakingdom, we have followed the convention used in the Catalogue of Life and listed taxon names alphabetically. This allows easier searching by those not familiar with the phylogenies of the many taxa therein and provides for easier import and manipulation of data by information systems.

Table 2. Proposed hierarchical classification from superkingdom to order.

SUPERKINGDOM PROKARYOTA

KINGDOM ARCHAEA [= ARCHAEBACTERIA]

Phylum Crenarchaeota

Class “Aigarchaeota”

Order N.N. ("Ca. Caldiarchaeum")

Class “Korarchaeota”

Order N.N. ("Ca. Korarchaeum")

Class “Thaumarchaeota”

Order Cenarchaeales

Class Thermoprotei [= Crenarchaeota]

Order Acidilobales

Order Desulfurococcales

Order Fervidicoccales

Order Sulfolobales

Order Thermoproteales

Phylum Euryarchaeota

Class Archaeoglobi

Order Archaeoglobales

Class Halobacteria

Order Halobacteriales

Class Methanobacteria

Order Methanobacteriales

Class Methanococci

Order Methanococcales

Class “Methanomicrobia”

Order N.N. (Methanocalculus)

Order Methanocellales

Order Methanomicrobiales

Order Methanosarcinales

Class Methanopyri

Order Methanopyrales

Class “Nanohaloarchaea”

Order N.N. (e.g., "Ca. Nanosalinarum")

Class Thermococci

Order Thermococcales

Class Thermoplasmata

Order Thermoplasmatales

KINGDOM BACTERIA [= EUBACTERIA]

SUBKINGDOM NEGIBACTERIA

Phylum Acidobacteria

Class N.N. (Bryobacter)

Class Acidobacteria

Order Acidobacteriales

Class Holophagae

Order Acanthopleuribacterales

Order Holophagales

Phylum Aquificae

Class Aquificae

Order Aquificales

Phylum Armatimonadetes

Class Armatimonadia

Order Armatimonadales

Class Chthonomonadetes

Order Chthonomonadales

Class Fimbriimonadia

Order Fimbriimonadales

Phylum Bacteroidetes

Class Bacteroidia

Order Bacteroidales

Class Cytophagia

Order Cytophagales

Class Flavobacteria

Order Flavobacteriales

Class Sphingobacteriia

Order Sphingobacteriales

Phylum Caldiserica

Class Caldisericia

Order Caldisericales

Phylum Chlamydiae

Class Chlamydiae

Order Chlamydiales

Phylum Chlorobi

Class Chlorobia

Order Chlorobiales

Class Ignavibacteria

Order Ignavibacteriales

Phylum Chrysiogenetes

Class Chrysiogenetes

Order Chrysiogenales

Phylum Cyanobacteria [= Cyanophyta]

Class Cyanophyceae [= Phycobacteria]

Order Chroococcales

Order Nostocales

Order Oscillatoriales

Order Pseudoanabaeniales

Order Synechococcales

Class Gloeobacteria [= Gloeobacterophyceae]

Order Gloeobacterales

Phylum Deferribacteres

Class Deferribacteres

Order Deferribacterales

Phylum Deinococcus-Thermus [= Hadobacteria]

Class Deinococci

Order Deinococcales

Order Thermales

Phylum Dictyoglomi

Class Dictyoglomia

Order Dictyoglomales

Phylum Elusimicrobia

Class Elusimicrobia

Order Elusimicrobiales

Phylum Fibrobacteres

Class Fibrobacteria

Order Fibrobacterales

Phylum Fusobacteria

Class Fusobacteriia

Order Fusobacteriales

Phylum Gemmatimonadetes

Class Gemmatimonadetes

Order Gemmatimonadales

Phylum Lentisphaerae

Class Lentisphaeria

Order Lentisphaerales

Order Victivallales

Class Oligosphaeria

Order Oligosphaerales

Phylum Nitrospira

Class "Nitrospira"

Order "Nitrospirales"

Phylum Planctomycetes

Class Phycisphaerae

Order Phycisphaerales

Class Planctomycea

Order Planctomycetales

Phylum Proteobacteria

Class Alphaproteobacteria

Order N.N. (e.g., Breoghania)

Order Caulobacterales

Order Kiloniellales

Order Kordiimonadales

Order Magnetococcales

Order “Parvularculales”

Order Rhizobiales

Order Rhodobacterales

Order Rhodospirillales

Order Rickettsiales

Order Sneathiellales

Order Sphingomonadales

Class Betaproteobacteria

Order N.N. (Chitinivorax)

Order Burkholderiales

Order Hydrogenophilales

Order Methylophilales

Order Neisseriales

Order Nitrosomonadales

Order "Procabacteriales"

Order Rhodocyclales

Class Deltaproteobacteria

Order N.N. (e.g., Deferrisoma)

Order Bdellovibrionales

Order Desulfarculales

Order Desulfobacterales

Order Desulfovibrionales

Order Desulfurellales

Order Desulfuromonadales

Order Myxococcales

Order Syntrophobacterales

Class Epsilonproteobacteria

Order Campylobacterales

Order Nautiliales

Class Gammaproteobacteria

Order N.N. (e.g., Alkalimonas)

Order Acidithiobacillales

Order Aeromonadales

Order Alteromonadales

Order Cardiobacteriales

Order Chromatiales

Order “Enterobacteriales”

Order Legionellales

Order Methylococcales

Order Oceanospirillales

Order Orbales

Order Pasteurellales

Order Pseudomonadales

Order “Salinisphaerales”

Order Thiotrichales

Order “Vibrionales”

Order Xanthomonadales

Class Zetaproteobacteria

Order Mariprofundales

Phylum Spirochaetae

Class "Spirochaetes"

Order Spirochaetales

Phylum Synergistetes

Class Synergistia

Order Synergistales

Phylum Thermodesulfobacteria

Class Thermodesulfobacteria

Order Thermodesulfobacteriales

Phylum Thermotogae

Class Thermotogae

Order Thermotogales

Phylum Verrucomicrobia

Class Opitutae

Order Opitutales

Order Puniceicoccales

Class Verrucomicrobiae

Order Verrucomicrobiales

SUBKINGDOM POSIBACTERIA

Phylum Actinobacteria

Class Actinobacteria

Order Acidimicrobiales

Order Actinomycetales

Order Bifidobacteriales

Order Coriobacteriales

Order Euzebyales

Order Gaiellales

Order Nitriliruptorales

Order Rubrobacterales

Order Solirubrobacterales

Order Thermoleophilales

Phylum Chloroflexi [= Chlorobacteria]

Class Anaerolineae

Order Anaerolineales

Class Caldilineae

Order Caldilineales

Class Chloroflexia

Order Chloroflexales

Order Herpetosiphonales

Class Dehalococcoidia

Order Dehalococcoidales

Class Ktedonobacteria

Order Ktedonobacterales

Order Thermogemmatisporales

Class Thermomicrobia

Order Sphaerobacterales

Order Thermomicrobiales

Phylum Firmicutes

Class Bacilli

Order Bacillales

Order Lactobacillales

Class Clostridia

Order Clostridiales

Order Halanaerobiales

Order Natranaerobiales

Order Thermoanaerobacterales

Class Erysipelotrichia

Order Erysipelotrichales

Class Negativicutes

Order Selenomonadales

Class Thermolithobacteria

Order Thermolithobacterales

Phylum Tenericutes

Class Mollicutes

Order Acholeplasmatales

Order Anaeroplasmatales

Order Entomoplasmatales

Order Haloplasmatales

Order Mycoplasmatales

SUPERKINGDOM EUKARYOTA

KINGDOM PROTOZOA

SUBKINGDOM EOZOA

INFRAKINGDOM EUGLENOZOA

Phylum Euglenozoa

Subphylum N.N.

Class Diplonemea

Order Diplonemida

Class Kinetoplastea

Order Bodonida

Order Prokinetoplastida

Order Trypanosomatida

Subphylum Euglenoida

Class N.N.

Order Petalomonadida

Order Ploeotiida

Class Euglenophyceae

Order Euglenida

Order Eutreptiida

Class Peranemea

Order Heteronemida

Order Peranemida

Order Rhabdomonadida

Subphylum Symbiontida

Class Postgaardea

Order Postgaardida

INFRAKINGDOM EXCAVATA

Phylum Loukozoa

Subphylum Eolouka

Class Jakobea

Order Jakobida

Class Tsukubea

Order Tsukubamonadida

Subphylum Neolouka

Class Malawimonadea

Order Malawimonadida

Phylum Metamonada

Class Anaeromonadea

Order Oxymonadida

Order Trimastigida

Class Carpomonadea

Order Carpediemonadida

Order Chilomastigida

Order Dysnectida

Class Eopharyngea

Order Diplomonadida

Order Retortamonadida

Class Trichomonadea

Order Cristamonadida

Order Spirotrichonymphida

Order Trichomonadida

Order Tritrichomonadida

Class Trichonymphea

Order Lophomonadida

Order Trichonymphida

Phylum Percolozoa

Subphylum Pharyngomonada

Class Pharyngomonadea

Order Pharyngomonadida

Subphylum Tetramitia

Class Heterolobosea

Order Acrasida

Order Schizopyrenida

Class Lyromonadea

Order Lyromonadida

Class Percolatea

Order Percolomonadida

Order Pseudociliatida

SUBKINGDOM SARCOMASTIGOTA

Phylum Amoebozoa

Subphylum Conosa

Class Archamoebea

Order Mastigamoebida

Order Pelobiontida

Order Rhizomastigida

Class Dictyostelea

Order Dictyostelida

Class Myxogastrea [= Myxomycetes]

Subclass Exosporeae

Order Ceratiomyxida

Subclass Myxogastria

Superorder Columelida

Order Echinosteliida

Order Fuscisporida

Superorder Lucisporida

Order Liceida

Order Trichiida

Class Protostelea

Order Protostelida

Class Variosea

Order Artodiscida

Order Holomastigida

Order Phalansteriida

Order Varipodida

Subphylum Lobosa

Class Discosea

Subclass Flabellinia

Order Dactylopodida

Order Himatismenida

Order Pellitida

Order Stygamoebida

Order Trichosida

Order Vanellida

Subclass Longamoebia

Order Dermamoebida

Order Centramoebida

Order Thecamoebida

Class Tubulinea [= Lobosea]

Order Arcellinida

Order Echinamoebida

Order Euamoebida

Order Leptomyxida

Order Nolandida

Phylum Choanozoa [with Microsporidia, Animalia, and Fungi constitutes "Supergroup Opisthokonta"]

Subphylum Choanofila

Class Choanoflagellatea

Order Acanthoecida

Order Craspedida

Class Corallochytrea

Order Corallochytrida

Class Filasterea

Order Ministeriida

Class Ichthyosporea

Order Dermocystida

Order Eccrinida

Subphylum Paramycia

Class Aphelidea

Order Aphelidida

Class Cristidiscoidea

Order Fonticulida

Order Nucleariida

Class Rozellidea

Order Rozellida

Phylum Microsporidia [with Choanozoa, Animalia, and Fungi constitutes "Supergroup Opisthokonta"]

Class Disporea

Order N.N. (e.g., Nosema)

Class Metchnikovellea

Order Metchnikovellida

Class Minisporea [= Microsporea]

Order Minisporida [= Minisporea]

Class Pleistophorea

Order Pleistophorida

Phylum Sulcozoa

Subphylum Apusozoa

Class Breviatea

Order Breviatida

Class Thecomonadea

Order Apusomonadida

Subphylum Varisulca

Class Diphyllatea

Order Diphylleida

Class Glissodiscea

Order Mantamonadida

Order Planomonadida

Class Hilomonadea

Order Rigifilida

KINGDOM CHROMISTA

SUBKINGDOM HACROBIA

Phylum N.N.

Class Endohelea

Order Heliomonadida

Order Microhelida

Class Picomonadea

Order Picomonadida

Class Telonemea

Order Telonemida

Phylum Cryptista

Subphylum Palpitia

Class Palpitea

Subphylum Rollomonadia

Class Cryptophyceae

Order Cryptomonadales

Order Pyrenomonadales

Order Tetragonidiales

Class Goniomonadea

Order Goniomonadida

Class Leucocryptea

Order Katablepharida

Order Palpitida

Phylum Haptophyta

Class Coccolithophyceae [= Prymnesiophyceae]

Order Coccolithales

Order Coccosphaerales

Order Isochrysidales

Order Phaeocystales

Order Prymnesiales

Order Syracosphaerales

Order Zygodiscales

Class Pavlovophyceae

Order Pavlovales

Phylum Heliozoa

Class Centrohelea

Order Acanthocystida

Order Pterocystida

SUBKINGDOM HAROSA [= "Supergroup SAR"]

INFRAKINGDOM HALVARIA

Superphylum Alveolata

Phylum Ciliophora

Subphylum Intramacronucleata

Class Armophorea

Order Armophorida

Order Clevelandellida

Class Colpodea

Order Bryometopida

Order Bryophryida

Order Bursariomorphida

Order Colpodida

Order Cyrtolophosidida

Order Sorogenida

Class Litostomatea

Subclass Haptoria

Order Cyclotrichiida

Order Haptorida

Order Pleurostomatida

Subclass Trichostomatia

Order Entodiniomorphida

Order Macropodiniida

Order Vestibuliferida

Class Spirotrichea

Subclass Choreotrichia

Order Tintinnida

Subclass Hypotrichia

Order Euplotida

Order Kiitrichida

Subclass Licnophoria

Order Licnophorida

Subclass Oligotrichia

Order Strombidiida

Subclass Protocruziidia

Order Phacodiniida

Order Protocruziida

Subclass Stichotrichia

Order Sporadotrichida

Order Stichotrichida

Order Urostylida

Class Nassophorea

Order Colpodidiida

Order Microthoracida

Order Nassulida

Order Synhymeniida

Class Oligohymenophorea

Subclass Apostomatia

Order Apostomatida

Order Astomatophorida

Order Pilisuctorida

Subclass Astomatia

Order Astomatida

Subclass Hymenostomatia

Order Ophyroglenida

Order Tetrahymenida

Subclass Peniculia

Order Peniculida

Order Urocentrida

Subclass Peritrichia

Order Mobilida

Order Sessilida

Subclass Scuticociliatia

Order Philasterida

Order Pleuronematida

Order Thigmotrichida

Class Phyllopharyngea

Subclass Chonotrichia

Order Cryptogemmida

Order Exogemmiida

Subclass Cyrtophoria

Order Chlamydodontida

Order Dysteriida

Subclass Rhynchodia

Order Hypocomatida

Order Rhynchodida

Subclass Suctoria

Order Endogenida

Order Evaginogenida

Order Exogenida

Class Plagiopylea

Order Odontostomatida

Order Plagiopylida

Class Prostomatea

Order Prorodontida

Order Prostomatida

Subphylum Postciliodesmatophora

Class Heterotrichea

Order Heterotrichida

Class Karyorelictea

Order Loxodida

Order Protoheterotrichida

Order Protostomatida

Phylum Miozoa

Subphylum Myzozoa

Infraphylum Apicomplexa

Superclass Apicomonada

Class Apicomonadea

Order Chromerida

Order Colpodellida

Order Voromonadida

Superclass Sporozoa

Class N.N.

Order Blastogregarinida

Class Coccidiomorphea

Subclass Coccidea

Order Agamococcidida

Order Eimerida

Order Ixorheida

Subclass Coleotrophia

Order Coleotrophiida [= Protococciida]

Subclass Hematozoa

Superorder Aconoidia

Order Nephromycida

Order Piroplasmida

Superorder Haemosporidia

Order Hemosporida

Class Gregarinomorphea

Subclass Cryptogragaria

Order Cryptogregarida (Cryptosporidium)

Subclass Histogregaria

Order Histogregarida

Subclass Orthogregarinia

Order Arthrogarida

Order Vermigregarida

Class Paragregarea

Order Archigregarinida

Order Stenophorida

Order Velocida

Infraphylum Dinozoa

Superclass Dinoflagellata

Class Dinophyceae

Subclass N.N.

Order Actiniscales

Order Blastodinales

Order Coccidinales

Order Dinamoebales

Order Lophodinales

Order Pyrocystales

Order Thoracosphaerales

Subclass Dinophysoidia

Order Dinophysidales

Order Nannoceratopsales

Subclass Gonyaulacoidia

Order Gonyaulacales

Order Gymnodiniales

Subclass Peridinoidia

Order Peridiniales

Order Prorocentrales

Subclass Suessioidia

Order Suessiales

Class Ellobiopsea

Order Ellobiopsida

Class Noctilucea

Order Noctilucida

Class Oxyrrhea

Order Acrocoelida

Order Oxyrrhida

Class Syndinea

Order Rastrimonadida

Order Syndinida

Superclass Perkinsozoa

Class Myzomonadea

Order Algovorida

Class Perkinsea

Order Perkinsida

Order Phagodinida

Subphylum Protalveolata

Class Colponemea

Order Colponemida

Superphylum Heterokonta [= "Supergroup Stramenopiles"]

Phylum Bigyra

Class Bikosea

Order Anoecida

Order Bicoecida

Order Borokida

Order Pseudodendromonadida

Order Rictida

Class Blastocystea

Order Blastocystida

Class Nanomonadea

Order Uniciliatida

Class Opalinea

Order Opalinida

Order Proteromonadida

Class Labyrinthulea

Order Labyrinthulida

Order Thraustochytriida

Class Placididea [= Placidiophyceae]

Order Placidiida

Phylum Ochrophyta [= Heterokontophyta p.p.]

Class Bacillariophyceae [= Diatomeae]

Subclass Bacillariophycidae

Order Achnanthales

Order Bacillariales

Order Cymbellales

Order Dictyoneidales

Order Eunotiales

Order Eupodiscales

Order Lyrellales

Order Mastogloiales

Order Naviculales

Order Rhopalodiales

Order Surirellales

Order Thalassiophysales

Subclass Coscinodiscophycidae

Order Anaulales

Order Arachnoidiscales

Order Asterolamprales

Order Aulacoseirales

Order Biddulphiales

Order Chaetocerotales

Order Chrysanthemodiscales

Order Corethrales

Order Coscinodiscales

Order Cymatosirales

Order Ethmodiscales

Order Hemiaulales

Order Lithodesmiales

Order Melosirales

Order Orthoseirales

Order Paraliales

Order Rhizosoleniales

Order Stictocyclales

Order Stictodiscales

Order Thalassiosirales

Order Triceratiales

Subclass Fragilariophycidae

Order Ardissoneales

Order Climacospheniales

Order Cyclophorales

Order Fragilariales

Order Licmophorales

Order Protoraphidales

Order Rhabdonematales

Order Rhaphoneidales

Order Striatellales

Order Tabellariales

Order Thalassionematales

Order Toxariales

Class Bolidophyceae

Order Parmales [= Bolidomonadales]

Class Chrysomerophyceae

Order Chrysomeridales

Class Chrysophyceae

Order Chloramoebales

Order Chromulinales

Order Chrysosphaerales

Order Heterogloeales

Order Hibberdiales

Order Hydrurales

Order Ochromonadales

Order Paraphysomonadida

Order Synurales

Order Thallochrysidales

Class Eustigmatophyceae

Order Eustigmatales

Class Dictyochophyceae [= Hypogyristea]

Order Dictyochales

Order Olisthodiscales

Order Pedinellales

Order Pelagomonadales

Order Sarcinochrysidales

Class Phaeophyceae

Subclass Dictypophycidae

Order Dictyotales

Order Onslowiales

Order Sphacelariales

Order Syringodermatales

Subclass Discosporangiophycidae

Order Discosporangiales

Subclass Fucophycidae

Order Ascoseirales

Order Asterocladales

Order Desmarestiales

Order Ectocarpales

Order Fucales

Order Laminariales

Order Nemodermatales

Order Phaeosiphoniellales

Order Ralfsiales

Order Scytothamnales

Order Sporochnales

Order Tilopteridales [= Cutleriales]

Subclass Ishigeophycidae

Order Ishigeales

Class Phaeothamniophyceae [= Aurophyceae]

Order Aurearenales

Order Phaeothamniales

Class Picophagophyceae [= Picophagea]

Order Picophagales

Order Synchromales

Class Pinguiophyceae

Order Pinguiochrysidales

Class Raphidophyceae

Order Actinophryida

Order Commatiida

Order Raphidomonadales

Class Schizocladiophyceae

Order Schizocladiales

Class Xanthophyceae

Order Mischococcales

Order Pleurochloridellales

Order Tribonematales

Order Vaucheriales

Phylum Pseudofungi [= Oomycota]

Class Bigyromonadea

Order Developayellida

Class Hyphochytrea

Order Hyphochytriida

Order Pirsoniida

Class Oomycetes

Subclass Eogamia

Order Anisolpidiales

Order Haptoglossales

Order Lagenismatales

Order Olpidiopsidales

Order Rozellopsidales

Subclass Peronosporidae

Order Peronosporales

Order Pythiales

Order Rhipidiales

Subclass Saprolegniidae

Order Albuginales

Order Leptomitales

Order Salilagenidiales

Order Saprolegniales

INFRAKINGDOM RHIZARIA

Phylum Cercozoa

Subphylum Endomyxa

Class Ascetosporea

Order Claustrosporida

Order Haplosporida

Order Paradinida

Order Paramyxida

Class Gromiidea

Order Gromiida

Order Reticulosida

Class Phytomyxea

Order Phagomyxida

Order Plasmodiophorida

Class Vampyrellidea

Order Vampyrellida

Subphylum Monadofilosa

Class Imbricatea

Subclass Placonuda

Order Discocelida

Order Discomonadida

Order Euglyphida

Order Marimonadida

Order Variglissida

Subclass Placoperla

Order Perlofilida

Order Rotosphaerida

Order Spongomonadida

Order Thaumatomonadida

Order Zoelucasida

Class Metromonadea

Order Metopiida

Order Metromonadida

Class Sarcomonadea

Order Cercomonadida

Order Glissomonadida

Order Pansomonadida

Order Pseudosporida

Order Sainouroida

Class Thecofilosea

Subclass Eothecia

Order Cryomonadida

Order Ebriida

Order Matazida

Order Ventricleftida

Subclass Phaeodaria

Order Eodarida

Order Opaloconchida

Subclass Tectosia

Order Tectofilosida

Subphylum Reticulofilosa

Class Chlorarachnea

Order Chlorarachnida

Class Granofilosea

Order Cryptofilida

Order Desmothoracida

Order Leucodictyida

Order Limnofilida

Class Skiomonadea

Order Tremulida

Phylum Retaria

Subphylum Foraminifera

Class Monothalamea

Order Allogromiida

Order Astrorhizida

Order Psamminida

Order Stannomida

Class Globothalamea

Order Carterinida

Order Globeriginida

Order Lagenida

Order Lituolida

Order Lofusiida

Order Robertinida

Order Rotaliida

Order Testulariida

Order Trochamminida

Class Tubothalamea

Order Miliolida

Order Spirillinida

Subphylum Radiozoa

Superclass Polycystinia

Class Polycystinea

Order Collodarida

Order Nassellaria

Order Spumellaria

Superclass Spasmaria

Class Acantharea

Order Arthracanthida

Order Chaunacanthida

Order Holacanthida

Order Symphyacanthida

Class Sticholonchea

Order Taxopodida

KINGDOM FUNGI

SUBKINGDOM DIKARYA [= NEOMYCOTA]

Phylum Ascomycota

Subphylum Pezizomycotina

Class Archaeorhizomycetes

Order Archaeorhizomycetales

Order Lahmiales

Order Triblidiales

Class Arthoniomycetes

Order Arthoniales

Class Dothideomycetes

Subclass N.N.

Order Acrospermales

Order Botryosphaeriales

Order Hysteriales

Order Jahnulales

Order Koralionastetales

Order Patellariales

Order Trypetheliales

Subclass Dothideomycetidae

Order Capnodiales

Order Dothideales

Order Microthyriales

Order Myriangiales

Subclass Meliolomycetidae

Order Meliolales

Subclass Pleosporomycetidae

Order Mytilinidales

Order Pleosporales

Class Eurotiomycetes

Subclass Chaetothyriomycetidae

Order Chaetothyriales

Order Pyrenulales

Order Verrucariales

Subclass Eurotiomycetidae

Order Arachnomycetales

Order Ascosphaerales

Order Coryneliales

Order Eurotiales

Order Onygenales

Subclass Mycocaliciomycetidae

Order Mycocaliciales

Class Laboulbeniomycetes

Order Laboulbeniales

Order Pyxidiophorales

Class Lecanoromycetes

Subclass N.N.

Order Candelariales

Order Umbilicariales

Subclass Acarosporomycetidae

Order Acarosporales

Subclass Lecanoromycetidae

Order Lecanorales

Order Lecideales

Order Peltigerales

Order Rhizocarpales

Order Teloschistales

Subclass Ostropomycetidae

Order Agyriales

Order Baeomycetales

Order Ostropales

Order Pertusariales

Class Leotiomycetes

Order Cyttariales

Order Erysiphales

Order Geoglossales

Order Helotiales

Order Leotiales

Order Mediolariales

Order Rhytismatales

Order Thelebolales

Class Lichinomycetes

Order Eremithallales

Order Lichinales

Class Orbiliomycetes

Order Orbiliales

Class Pezizomycetes

Order Pezizales

Class Sordariomycetes

Subclass N.N.

Order Phyllachorales

Order Trichosphaeriales

Subclass Hypocreomycetidae

Order Coronophorales

Order Hypocreales

Order Melanosporales

Order Microascales

Subclass Sordariomycetidae

Order Boliniales

Order Calosphaeriales

Order Chaetosphaeriales

Order Coniochaetales

Order Diaporthales

Order Ophiostomatales

Order Sordariales

Subclass Spathulosporomycetidae

Order Lulworthiales

Subclass Xylariomycetidae

Order Xylariales

Subphylum Saccharomycotina

Class Saccharomycetes

Order Saccharomycetales

Subphylum Taphrinomycotina

Class Neolectomycetes

Order Neolectales

Class Pneumocystidomycetes

Order Pneumocystidales

Class Schizosaccharomycetes

Order Schizosaccharomycetales

Class Taphrinomycetes

Order Taphrinales

Phylum Basidiomycota

Class Entorrhizomycetes

Order Entorrhizales

Order Wallemiales

Subphylum Agaricomycotina

Class Agaricomycetes

Subclass N.N.

Order Auriculariales

Order Cantharellales

Order Corticiales

Order Gloeophyllales

Order Hymenochaetales

Order Polyporales

Order Russulales

Order Sebacinales

Order Thelephorales

Order Trechisporales

Subclass Agaricomycetidae

Order Agaricales

Order Atheliales

Order Boletales

Subclass Phallomycetidae

Order Geastrales

Order Gomphales

Order Hysterangiales

Order Phallales

Class Dacrymycetes

Order Dacrymycetales

Class Tremellomycetes

Order Cystofilobasidiales

Order Filobasidiales

Order Tremellales

Subphylum Pucciniomycotina

Class Agaricostilbomycetes

Order Agaricostilbales

Order Spiculogloeales

Class Atractiellomycetes

Order Atractiellales

Class Classiculomycetes

Order Classiculales

Class Cryptomycocolacomycetes

Order Cryptomycocolacales

Class Cystobasidiomycetes

Order Cystobasidiales

Order Erythrobasidiales

Order Naohideales

Class Microbotryomycetes

Order Hetrogastridiales

Order Leucosporidiales

Order Microbotryales

Order Sporidiobolales

Class Mixiomycetes

Order Mixiales

Class Pucciniomycetes

Order Helicobasidiales

Order Pachnocybales

Order Platygloeales

Order Pucciniales

Order Septobasidiales

Subphylum Ustilaginomycotina

Class N.N.

Order Malasseziales

Class Exobasidiomycetes

Order Ceraceosorales

Order Doassansiales

Order Entylomatales

Order Exobasidiales

Order Georgefischeriales

Order Microstromatales

Order Tilletiales

Class Ustilaginomycetes

Order Urocystidales

Order Ustilaginales

SUBKINGDOM EOMYCOTA

Phylum Chytridiomycota

Class Blastocladiomycetes [= Allomycetes]

Order Blastocladiales

Class Chytridiomycetes

Order Chytridiales

Order Lobulomycetales

Order Neocallimastigales

Order Olpidiales

Order Rhizophlyctidales

Order Rhizophydiales

Order Spizellomycetales

Class Monoblepharidomycetes

Order Monoblepharidales

Phylum Glomeromycota

Class Glomeromycetes [= Glomomycetes]

Order Archaeosporales

Order Diversisporales

Order Glomerales

Order Paraglomerales

Phylum Zygomycota

Subphylum N.N.

Class N.N.

Order Basidiobolales

Subphylum Entomophthoromycotina

Class N.N.

Order Entomophthorales

Subphylum Kickxellomycotina

Class N.N.

Order Asellariales

Order Dimargaritales

Order Harpellales

Order Kickxellales

Subphylum Mortierellomycotina

Class N.N.

Order Mortierellales

Subphylum Mucoromycotina

Class N.N.

Order Endogonales

Order Mucorales

Subphylum Zoopagomycotina

Class N.N.

Order Zoopagales

KINGDOM PLANTAE

SUBKINGDOM BILIPHYTA

Phylum Glaucophyta

Class Glaucophyceae

Order Glaucocystales

Phylum Rhodophyta

Subphylum Cyanidiophytina

Class Cyanidiophyceae

Order Cyanidiales

Subphylum Eurhodophytina

Class Bangiophyceae

Order Bangiales

Order Goniotrichales

Class Florideophyceae

Subclass N.N.

Order Rhodachlyales

Subclass Ahnfeltiophycidae

Order Ahnfeltiales

Order Pihiellales

Subclass Corallinophycidae

Order Corallinales

Order Rhodogorgonales

Order Sporolithales

Subclass Hildenbrandiophyceae

Order Hildenbrandiales

Subclass Nemaliophycidae

Order Acrochaetiales

Order Balbianiales

Order Balliales

Order Batrachospermales

Order Colaconematales

Order Entwisleiales

Order Nemaliales

Order Palmariales

Order Thoreales

Subclass Rhodymeniophycidae

Order Acrosymphytales

Order Bonnemaisoniales

Order Ceramiales

Order Gelidiales

Order Gigartinales

Order Gracilariales

Order Halymeniales

Order Nemastomatales

Order Peyssonneliales

Order Plocamiales

Order Rhodymeniales

Order Sebdeniales

Subphylum Metarhodophytina

Class Compsopogonophyceae

Order Compsopogonales

Order Erythropeltidales

Order Rhodochaetales

Subphylum Rhodellophytina

Class Porphyridiophyceae

Order Porphyridiales

Class Rhodellophyceae

Order Dixoniellales

Order Glaucosphaerales

Order Rhodellales

Class Stylonematophyceae

Order Rufusiales

Order Stylonematales

SUBKINGDOM VIRIDIPLANTAE

INFRAKINGDOM CHLOROPHYTA

Phylum Chlorophyta

Subphylum Chlorophytina

Class Chlorodendrophyceae

Order Chlorodendrales

Class Chlorophyceae

Order N.N. (e.g., Chlorangiopsidaceae)

Order Chaetopeltidales

Order Chaetophorales

Order Chlamydomonadales [= Volvocales]

Order Oedogoniales

Order Sphaeropleales

Class Pedinophyceae

Order Marsupiomonadales

Order Pedinomonadales

Order Scourfieldiales

Class Trebouxiophyceae

Order Chlorellales

Order Microthamniales

Order Phyllsiphonales

Order Prasiolales

Order Trebouxiales

Class Ulvophyceae

Order Bryopsidales

Order Cladophorales

Order Dasycladales

Order Oltmansiellopsidales

Order Scotinosphaerales

Order Trentepohliales

Order Ulotrichales

Order Ulvales

Subphylum Prasinophytina

Class Mamiellophyceae

Order Dolichomastigales

Order Mamiellales

Order Monomastigales

Class Nephrophyceae [= Nephroselmidophyceae]

Order Nephroselmidales

Class Pyramimonadophyceae

Order Palmophyllales

Order Prasinococcales

Order Pseudoscourfieldiales

Order Pyramimonadales

INFRAKINGDOM STREPTOPHYTA

Superphylum Charophyta

Phylum Charophyta

Class Charophyceae

Order Charales

Class Chlorokybophyceae

Order Chlorokybales

Class Coleochaetophyceae

Order Chaetosphaeridiales

Order Coleochaetales

Class Conjugatophyceae [= Zygnematophyceae]

Order Desmidiales

Order Zygnematales

Class Klebsormidiophyceae

Order Klebsormidiales

Class Mesostigmatophyceae

Order Mesostigmatales

Superphylum Embryophyta

Phylum Anthocerotophyta

Class Anthocerotopsida

Subclass Anthocerotidae

Order Anthocerotales

Subclass Dendrocerotidae

Order Dendrocerotales

Order Phymatocerales

Subclass Notothylatidae

Order Notothyladales

Class Leiosporocerotopsida

Order Leiosporocerotales

Phylum Bryophyta

Class Andreaeobryopsida

Order Andreaeobryales

Class Andreaeopsida

Order Andreaeales

Class Bryopsida

Subclass Bryidae

Order Bartramiales

Order Bryales

Order Hedwigiales

Order Hookeriales

Order Hypnales

Order Hypnodendrales

Order Orthotrichales

Order Ptychomniales

Order Rhizogoniales

Order Splachnales

Subclass Buxbaumiidae

Order Buxbaumiales

Subclass Dicranidae

Order Archidiales

Order Bryoxiphiales

Order Dicranales

Order Grimmiales

Order Pottiales

Order Scouleriales

Subclass Diphysciidae

Order Diphysciales

Subclass Funariidae

Order Encalyptales

Order Funariales

Order Gigaspermales

Subclass Timmidae

Order Timmiales

Class Oedipodiopsida

Order Oedipodiales

Class Polytrichopsida

Order Polytrichales

Class Sphagnopsida

Order Ambuchananiales

Order Sphagnales

Class Takakiopsida

Order Takakiales

Class Tetraphidopsida

Order Tetraphidales

Phylum Marchantiophyta

Class Haplomitriopsida

Order Calobryales

Order Treubiales

Class Jungermanniopsida

Subclass Jungermanniidae

Order Jungermanniales

Order Porellales

Order Ptilidiales

Subclass Metzgeriidae

Order Metzgeriales

Order Pleuroziales

Subclass Pelliidae

Order Fossombroniales

Order Pallaviciniales

Order Pelliales

Class Marchantiopsida

Order Blasiales

Order Lunulariales

Order Marchantiales

Order Neohodgsoniales

Order Sphaerocarpales

Phylum Tracheophyta

Subphylum Lycopodiophytina

Class Lycopodiopsida

Order Isoetales

Order Lycopodiales

Order Selaginellales

Subphylum Polypodiophytina

Class Polypodiopsida

Subclass Equisetidae

Order Equisetales

Subclass Marattiidae

Order Marattiales

Subclass Ophioglossidae [= Psilotidae]

Order Ophioglossales

Order Psilotales

Subclass Polypodiidae

Order Cyatheales

Order Gleicheniales

Order Hymenophyllales

Order Osmundales

Order Polypodiales

Order Salviniales

Order Schizaeales

Subphylum Spermatophytina

Superclass “Angiospermae”

Class Magnoliopsida

Superorder N.N.

Order N.N. (e.g., Icacinaceae)

Superorder Amborellanae

Order Amborellales

Superorder Asteranae

Order Apiales

Order Aquifoliales

Order Asterales

Order Boraginales

Order Bruniales

Order Cornales

Order Dipsacales

Order Ericales

Order Escalloniales

Order Garryales

Order Gentianales

Order Lamiales

Order Paracryphiales

Order Solanales

Superorder Austrobaileyanae

Order Austrobaileyales

Superorder Berberidopsidanae

Order Berberidopsidales

Superorder Buxanae

Order Buxales

Superorder Caryophyllanae

Order Caryophyllales

Superorder Ceratophyllanae

Order Ceratophyllales

Superorder Dillenianae

Order Dilleniales

Superorder Lilianae [= Monocotyledones]

Order Acorales

Order Alismatales

Order Arecales

Order Asparagales

Order Commelinales

Order Dasypogonales

Order Dioscoreales

Order Liliales

Order Pandanales

Order Petrosaviales

Order Poales

Order Zingiberales

Superorder Magnolianae

Order Canellales

Order Chloranthales

Order Laurales

Order Magnoliales

Order Piperales

Superorder Myrothamnanae

Order Gunnerales

Superorder Nymphaeanae

Order Nymphaeales

Superorder Proteanae

Order Proteales

Superorder Ranunculanae

Order Ranunculales

Superorder Rosanae

Order Brassicales

Order Celastrales

Order Crossosomatales

Order Cucurbitales

Order Fabales

Order Fagales

Order Geraniales

Order Huerteales

Order Malpighiales

Order Malvales

Order Myrtales

Order Oxalidales

Order Picramniales

Order Rosales

Order Sapindales

Order Vitales

Order Zygophyllales

Superorder Santalanae

Order Santalales

Superorder Saxifraganae

Order Saxifragales

Superorder Trochodendranae

Order Trochodendrales

Superclass “Gymnospermae”

Class Cycadopsida

Subclass Cycadidae

Order Cycadales

Class Ginkgoopsida

Subclass Ginkgooidae

Order Ginkgoales

Class Gnetopsida

Subclass Gnetidae

Order Gnetales

Class Pinopsida

Subclass Pinidae

Order Pinales

KINGDOM ANIMALIA

SUBKINGDOM N.N.

Phylum Cnidaria

Subphylum Anthozoa

Class Anthozoa

Subclass Hexacorallia

Order Actiniaria

Order Antipatharia

Order Ceriantharia

Order Corallimorpharia

Order Scleractinia

Order Zoantharia [= Zoanthidea]

Subclass Octocorallia

Order Alcyonacea

Order Helioporacea

Order Pennatulacea

Subphylum Medusozoa

Class Cubozoa

Order Carybdeida

Order Chirodropida

Class Hydrozoa

Subclass Hydroidolina

Order Anthoathecata

Order Gonoproxima

Order Leptothecata

Order Siphonophorae

Subclass Trachylina

Order Actinulida

Order Limnomedusae

Order Narcomedusae

Order Trachymedusae

Class Polypodiozoa

Order Polypodiidea

Class Scyphozoa

Order Coronatae

Order Rhizostomeae

Order Semaeostomeae

Class Staurozoa

Order Stauromedusae

Subphylum Myxozoa

Class Malacosporea

Order Malacovalvulida

Class Myxosporea

Order Bivalvulida

Order Multivalvulida

Phylum Ctenophora

Class Nuda

Order Beroida

Class Tentaculata

Order Cambojiida

Order Cestida

Order Cryptolobiferida

Order Cydippida

Order Ganeshida

Order Lobata

Order Platyctenida

Order Thalassocalycida

Phylum Placozoa

Class Placozoa (Trichoplax)

Phylum Porifera

Class Calcarea

Order Baerida

Order Clathrinida

Order Leucosolenida

Order Lithonida

Order Murrayonida

Class Demospongiae

Order Agelasida

Order Astrophorida

Order Chondrosida

Order Dendroceratida

Order Dictyoceratida

Order Hadromerida

Order Halichondrida

Order Haplosclerida

Order Lithistida

Order Poecilosclerida

Order Spirophorida

Order Verongida

Class Hexactinellida

Order Amphidiscosida

Order Aulocalycoida

Order Fieldingida

Order Hexactinosida

Order Lychniscosida

Order Lyssacinosida

Class Homoscleromorpha

Order Homosclerophorida

SUBKINGDOM BILATERIA

INFRAKINGDOM PROTOSTOMIA

Superphylum N.N.

Phylum Chaetognatha

Class Sagittoidea

Order Aphragmophora

Order Phragmophora

Phylum Orthonectida

Order Plasmodigenea

Phylum Rhombozoa

Order Dicyemida

Order Heterocyemida

Superphylum Ecdysozoa

Phylum Arthropoda

Subphylum Chelicerata

Class Arachnida

Superorder N.N.

Order Amblypygi

Order Araneae

Order Opiliones

Order Palpigradi

Order Pseudoscorpiones

Order Ricinulei

Order Schizomida

Order Scorpiones

Order Solifugae

Order Uropygi

Superorder Acariformes

Order Sarcoptiformes

Order Trombidiformes

Superorder Parasitiformes

Order Holothyrida

Order Ixodida

Order Mesostigmata

Order Opilioacarida

Class Merostomata

Order Xiphosura

Class Pycnogonida

Order Pantopoda

Subphylum Crustacea

Class Branchiopoda

Order Anostraca

Order Diplostraca

Order Laevicaudata

Order Notostraca

Class Cephalocarida

Order Brachypoda

Class Malacostraca

Subclass Eumalacostraca

Superorder Eucarida

Order Amphionidacea

Order Decapoda

Order Euphausiacea

Superorder Peracarida

Order Amphipoda

Order Bochusacea

Order Cumacea

Order Isopoda

Order Lophogastrida

Order Mictacea

Order Mysida

Order Spelaeogriphacea

Order Tanaidacea

Order Thermosbaenacea

Superorder Syncarida

Order Anaspidacea

Order Bathynellacea

Subclass Hoplocarida

Order Stomatopoda

Subclass Phyllocarida

Order Leptostraca

Class Maxillopoda

Subclass Branchiura

Order Arguloida

Subclass Copepoda

Infraclass Neocopepoda

Superorder Gymnoplea

Order Calanoida

Superorder Podoplea

Order Cyclopoida

Order Gelyelloida

Order Harpacticoida

Order Misophrioida

Order Monstrilloida

Order Mormonilloida

Order Siphonostomatoida

Infraclass Progymnoplea

Order Platycopioida

Subclass Mystacocarida

Order Mystacocaridida

Subclass Pentastomida

Order Cephalobaenida

Order Porocephalida

Subclass Tantulocarida (e.g., Basipodellidae)

Subclass Thecostraca

Infraclass Ascothoracida

Order Dendrogastrida

Order Laurida

Infraclass Cirripedia

Superorder Acrothoracica

Order Cryptophialida

Order Lithoglyptida

Superorder Rhizocephala

Order Akentrogonida

Order Kentrogonida

Superorder Thoracica

Order Ibliformes

Order Lepadiformes

Order Scalpelliformes

Order Sessilia

Infraclass Facetotecta (Hansenocaris)

Class Ostracoda

Order Halocyprida

Order Myodocopida

Order Paleocopida

Order Platycopida

Order Podocopida

Class Remipedia

Order Nectiopoda

Subphylum Hexapoda

Class Collembola

Order Entomobryomorpha

Order Neelipleona

Order Poduromorpha

Order Symphypleona

Class Diplura

Order N.N. (e.g., Japygidae)

Class Insecta

Subclass Archaeognatha

Order Archaeognatha

Subclass Dicondylia

Order Zygentoma

Subclass Pterygota

Infraclass Neoptera

Superorder Holometabola

Order Coleoptera

Order Diptera

Order Hymenoptera

Order Lepidoptera

Order Mecoptera

Order Siphonaptera

Order Strepsiptera

Order Trichoptera

Superorder Neuropterida

Order Megaloptera

Order Neuroptera

Order Raphidioptera

Superorder Paraneoptera

Order Hemiptera

Order Psocodea

Order Thysanoptera

Superorder Polyneoptera

Order Blattodea

Order Dermaptera

Order Embioptera

Order Grylloblattodea

Order Mantodea

Order Mantophasmatodea

Order Orthoptera

Order Phasmida

Order Plecoptera

Order Zoraptera

Infraclass Palaeoptera

Order Ephemeroptera

Order Odonata

Class Protura

Order Acerentomata

Order Eosentomata

Order Sinentomata

Subphylum Myriapoda

Class Chilopoda

Order Craterostigmomorpha

Order Geophilomorpha

Order Lithobiomorpha

Order Scolopendromorpha

Order Scutigeromorpha

Class Diplopoda

Subclass Chilognatha

Infraclass Helminthomorpha

Superorder N.N.

Order Platydesmida

Order Polyzoniida

Order Siphonocryptida

Order Siphonophorida

Superorder Juliformia

Order Julida

Order Spirobolida

Order Spirostreptida

Superorder Nematophora

Order Callipodida

Order Chordeumatida

Order Stemmiulida

Order Siphoniulida

Superorder Merochaeta

Order Polydesmida

Infraclass Pentazonia

Order Glomerida

Order Glomeridesmida

Order Sphaerotheriida

Subclass Penicillata

Order Polyxenida

Class Pauropoda

Order Hexamerocerata

Order Tetramerocerata

Class Symphyla (e.g., Scolopendrellidae)

Phylum Kinorhyncha

Order Cyclorhagida

Order Homalorhagida

Phylum Loricifera

Order Nanaloricida

Phylum Nematoda

Class Chromadorea

Subclass Chromadoria

Order Chromadorida

Order Desmodorida

Order Desmoscolecida

Order Selachinematida

Subclass Plectia

Superorder Monhysterica

Order Monhysterida

Superorder Plectica

Order Benthimermithida

Order Leptolaimida

Order Plectida

Superorder Rhabditica

Order Diplogasterida

Order Drilonematida

Order Panagrolaimida

Order Rhabditida

Order Spirurida

Superorder Teratocephalica

Order Teratocephalida

Class Dorylaimea

Subclass Bathyodontia

Order Bathyodontida

Order Mermithida

Order Mononchida

Subclass Dorylaimia

Order Dorylaimida

Subclass Trichocephalia

Order Dioctophymatida

Order Marimermithida

Order Muspiceida

Order Trichocephalida

Class Enoplea

Subclass Enoplia

Order Alaimida

Order Enoplida

Order Ironida

Order Rhaptothyreida

Order Trifusiida

Order Tripyloidida

Subclass Oncholaimia

Order Oncholaimida

Subclass Triplonchia

Order Triplonchida

Order Tripylida

Phylum Nematomorpha

Order Gordioidea

Order Nectonematoidea

Phylum Onychophora

Class Udeonycophora

Order Euonycophora

Phylum Priapula [= Priapulida]

Class N.N. (e.g., Priapulidae)

Phylum Tardigrada

Class Eutardigrada

Order Apochela

Order Parachela

Class Heterotardigrada

Order Arthrotardigrada

Order Echiniscoidea

Superphylum Spiralia [= Lophotrochozoa]

Phylum Acanthocephala

Class Archiacanthocephala

Order Apororhynchida

Order Gigantorhynchida

Order Moniliformida

Order Oligacanthorhynchida

Class Eoacanthocephala

Order Gyracanthocephala

Order Neoechinorhynchida

Class Palaeacanthocephala

Order Echinorhynchida

Order Heteramorphida

Order Polymorphida

Class Polyacanthocephala

Order Polyacanthorhynchida

Phylum Annelida

Class N.N.

Order Myzostomida

Class Clitellata

Subclass N.N.

Order Apodadrilida

Subclass Hirudinea

Order Acanthobdellida

Order Arhynchobdellida

Order Rhynchobdellida

Subclass Oligochaeta

Superorder N.N.

Order N.N. (Jennaria)

Order Branchiobdellida

Order Capilloventrida

Order Crassiclitellata

Order Enchytraeida

Order Haplotaxida

Order Lumbriculida

Order Tubificida

Superorder Metagynaphora

Order Moniligastrida

Order Opistophophora

Class Polychaeta

Subclass N.N.

Order N.N. (e.g., Nerillidae)

Subclass Echiura

Order Echiuroinea

Order Heteromyota

Order Xenopneusta

Subclass Errantia

Order Amphinomida

Order Eunicida

Order Phyllodocida

Subclass Sedentaria

Infraclass Canalipalpata

Order Sabellida

Order Spionida

Order Terebellida

Infraclass Scolecida (e.g., Arenicolidae)

Phylum Brachiopoda

Class Craniata

Order Craniida

Class Lingulata

Order Lingulida

Class Rhynchonellata

Order Rhynchonellida

Order Terebratulida

Order Thecideida

Phylum Bryozoa

Class Gymnolaemata

Order Cheilostomata

Order Ctenostomata

Class Phylactolaemata

Order Plumatellida

Class Stenolaemata

Order Cyclostomata

Phylum Cycliophora

Class Eucycliophora

Order Symbiida

Phylum Entoprocta

Order Coloniales

Order Solitaria

Phylum Gastrotricha

Order Chaetonotida

Order Macrodasyida

Phylum Gnathostomulida

Order Bursovaginoidea

Order Filospermoidea

Phylum Micrognathozoa

Class Micrognathozoa

Order Limnognathida

Phylum Mollusca

Class Bivalvia

Subclass Autobranchia

Superorder Heteroconchia

Order Carditida

Order Lucinida

Order Myida

Order Pholadomyida

Order Trigoniida

Order Unionida

Order Veneroida

Superorder Pteriomorphia

Order Arcida

Order Limida

Order Mytilida

Order Ostreida

Order Pectinida

Order Pteriida

Subclass Protobranchia

Order Nuculanida

Order Nuculida

Order Solemyoida

Class Caudofoveata

Order Chaetodermatida

Class Cephalopoda

Subclass Coleoidea

Superorder Decabrachia

Order Sepiida

Order Sepiolida

Order Spirulida

Order Teuthida

Superorder Octobrachia

Order Octopoda

Order Vampyromorphida

Subclass Nautiloidea

Order Nautilida

Class Gastropoda

Subclass Caenogastropoda

Order Littorinimorpha

Order Neogastropoda

Subclass Cocculiniformia (e.g., Cocculinidae)

Subclass Heterobranchia

Order Acochlidioidea

Order Anaspidea

Order Cephalaspidea

Order Gymnosomata

Order Hygrophila

Order Nudibranchia

Order Pleurobranchomorpha

Order Runcinacea

Order Sacoglossa

Order Stylommatophora

Order Systellommatophora

Order Thecosomata

Order Umbraculida

Subclass Neomphalina

Order N.N. (e.g., Neomphalidae)

Subclass Neritimorpha

Order Cycloneritimorpha

Subclass Patellogastropoda

Order N.N. (e.g., Patellidae)

Subclass Vetigastropoda

Order N.N. (e.g., Ataphridae)

Class Monoplacophora

Order Tryblidiida

Class Polyplacophora

Order Chitonida

Order Lepidopleurida

Class Scaphopoda

Order Dentaliida

Order Gadilida

Class Solenogastres

Superorder Aplotegmentaria

Order Cavibelonia

Order Sterrofustia

Superorder Pachytegmentaria

Order Neomeniamorpha

Order Pholidoskepia

Phylum Nemertea

Class Anopla

Order N.N. (e.g., Gorgonorhynchidae)

Class Enopla

Order Monostilifera

Order Polystilifera

Class Paleonemertea (e.g., Carinomidae)

Phylum Phoronida

Class N.N. (e.g., Phoronis)

Phylum Platyhelminthes

Subphylum Catenulidea

Order Catenulida

Subphylum Rhabditophora

Class Macrostomorpha

Order Haplopharyngida

Order Macrostomida

Class Neoophora

Subclass Eulecithophora

Infraclass Adiaphanida

Order Fecampiida

Order Prolecithophora

Order Tricladida

Infraclass Rhabdocoela

Order Dalytyphloplanida

Order Endoaxonemata

Order Kalyptorhynchia

Subclass Neodermata

Infraclass Cestoda

Order Amphilinidea

Order Bothriocephalidea

Order Caryophyllidea

Order Cyclophyllidea

Order Diphyllidea

Order Diphyllobothriidea

Order Gyrocotylidea

Order Lecanicephalidea

Order Litobothridea

Order Proteocephalidea

Order Pseudophyllidea

Order Rhinebothriidea

Order Spathebothriidea

Order Tetrabothriidea

Order Tetraphyllidea

Order Trypanorhyncha

Infraclass Monogenea

Order Capsalidea

Order Chimaericolidea

Order Dactylogyridea

Order Diclybothriidea

Order Gyrodactylidea

Order Mazocraeidea

Order Monocotylidea

Order Montchadskyellidea

Order Polystomatidea

Infraclass Trematoda

Order Aspidogastrida

Order Diplostomida

Order Plagiorchiida

Order Stichocotylida

Class Polycladidea

Order Lecithoepitheliata

Order Polycladida

Subclass Proseriatia

Order Proseriata

Phylum Rotifera

Class Eurotatoria

Subclass Bdelloidea (e.g., Adinetidae)

Subclass Monogonta

Order Collothecaceae

Order Flosculariaceae

Order Ploima

Class Pararotatoria

Order Seisonacea

Phylum Sipuncula

Class Phascolosomatidea

Order Aspidosiphoniformes

Order Phascolosomatiformes

Class Sipunculidea

Order Golfingiiformes

Order Sipunculiformes

INFRAKINGDOM DEUTEROSTOMIA

Phylum Chordata

Subphylum Cephalochordata

Order Amphioxiformes

Subphylum Urochordata

Class Appendicularia

Order Copelata

Class Ascidiacea

Order Enterogona

Order Pleurogona

Class Thaliacea

Order Doliolida

Order Pyrosomida

Order Salpida

Subphylum Vertebrata [= Craniata]

Infraphylum Agnatha

Class Cephalaspidomorphi

Order Petromyzontiformes

Class Myxini

Order Myxiniformes

Infraphylum Gnathostomata

Superclass Actinopterygii

Class Chondrostei

Order Acipenseriformes

Class Cladistei

Order Polypteriformes

Class Holostei

Order Amiiformes

Order Lepisosteiformes

Class Teleostei

Order Acanthuriformes

Order Albuliformes

Order Alepocephaliformes

Order Anabantiformes

Order Anguilliformes

Order Argentiniformes

Order Ateleopodiformes

Order Atheriniformes

Order Aulopiformes

Order Batrachoidiformes

Order Beloniformes

Order Beryciformes

Order Blenniiformes

Order Carangiformes

Order Centrarchiformes

Order Characiformes

Order Cichliformes

Order Cirrhitiformes

Order Clupeiformes

Order Cypriniformes

Order Cyprinodontiformes

Order Elopiformes

Order Ephippiformes

Order Esociformes

Order Gadiformes

Order Galaxiiformes

Order Gobiiformes

Order Gonorynchiformes

Order Gymnotiformes

Order Hidontiformes

Order Holocentriformes

Order Istiophoriformes

Order Kurtiformes

Order Labriformes

Order Lampridiformes

Order Lepidogalaxiiformes

Order Lobotiformes

Order Lophiiformes

Order Mugiliformes

Order Myctophiformes

Order Notacanthiformes

Order Ophidiiformes

Order Osmeriformes

Order Osteoglossiformes

Order Pempheriformes

Order Perciformes

Order Percopsiformes

Order Pholidichthyiformes

Order Pleuronectiformes

Order Polymixiiformes

Order Salmoniformes

Order Scombriformes

Order Siluriformes

Order Spariformes

Order Stomiatiformes

Order Stylephoriformes

Order Synbranchiformes

Order Syngnathiformes

Order Terapontiformes

Order Tetraodontiformes

Order Uranoscopiformes

Order Zeiformes

Superclass Chondrichthyes

Class Elasmobranchii

Order Carcharhiniformes

Order Heterodontiformes

Order Hexanchiformes

Order Lamniformes

Order Myliobatiformes

Order Orectolobiformes

Order Pristiformes

Order Pristiophoriformes

Order Rajiformes

Order Squaliformes

Order Squatiniformes

Order Torpediniformes

Class Holocephali

Order Chimaeriformes

Superclass Sarcopterygii

Class Coelacanthi

Order Coelacanthiformes

Class Dipnoi

Order Ceratodontiformes

Order Lepidosirenoformes

Superclass Tetrapoda

Class Amphibia

Order Anura

Order Caudata

Order Gymnophiona

Class Mammalia

Subclass Prototheria

Order Monotremata

Subclass Theria

Infraclass Eutheria [= Placentalia]

Order Afrosoricida

Order Artiodactyla

Order Carnivora

Order Cetacea

Order Chiroptera

Order Cingulata

Order Dermoptera

Order Erinaceomorpha

Order Hyracoidea

Order Lagomorpha

Order Macroscelidea

Order Perissodactyla

Order Pholidota

Order Pilosa

Order Primates

Order Proboscidea

Order Rodentia

Order Scandentia

Order Sirenia

Order Soricomorpha

Order Tubulidentata

Infraclass Metatheria [= Marsupialia]

Order Dasyuromorphia

Order Didelphimorphia

Order Diprotodontia

Order Microbiotheria

Order Notoryctemorphia

Order Paucituberculata

Order Peramelemorphia

Class Reptilia

Subclass Aves

Infraclass Neognathae

Superorder Galloanseri

Order Anseriformes

Order Galliformes

Superorder Neoaves

Order Accipitriformes

Order Apodiformes

Order Bucerotiformes

Order Caprimulgiformes

Order Cariamiformes

Order Charadriiformes

Order Ciconiiformes

Order Coliiformes

Order Columbiformes

Order Coraciiformes

Order Cuculiformes

Order Eurypygiformes

Order Falconiformes

Order Gaviiformes

Order Gruiformes

Order Leptosomiformes

Order Mesitornithiformes

Order Musophagiformes

Order Opisthocomiformes

Order Otidiformes

Order Passeriformes

Order Pelecaniformes

Order Phaethontiformes

Order Phoenicopteriformes

Order Piciformes

Order Podicipediformes

Order Procellariiformes

Order Psittaciformes

Order Pteroclidiformes

Order Sphenisciformes

Order Strigiformes

Order Suliformes

Order Trogoniformes

Infraclass Paleognathae

Order Apterygiformes

Order Casuariiformes

Order Rheiformes

Order Struthioniformes

Order Tinamiformes

Subclass Crocodylomorpha

Order Crocodylia

Subclass Rhynchocephalia

Order Sphenodontida

Subclass Squamata

Order Anguimorpha

Order Gekkota

Order Inguania

Order Lacertoidea

Order Scincoidea

Order Serpentes

Subclass Testudinata

Order Testudines

Phylum Echinodermata

Subphylum Asterozoa

Class Asteroidea

Order Brisingida

Order Forcipulatida

Order Notomyotida

Order Paxillosida

Order Peripoda

Order Spinulosida

Order Valvatida

Order Velatida

Class Ophiuroidea

Order Euryalida

Order Ophiurida

Subphylum Crinozoa

Class Crinoidea

Order Comatulida

Order Cyrtocrinida

Order Hyocrinida

Order Isocrinida

Subphylum Echinozoa

Class Echinoidea

Subclass Cidaroidea

Order Cidaroida

Subclass Euechinoidea

Infraclass N.N.

Order Echinothurioida

Infraclass Acroechinoidea

Order Aspidodiadematoida

Order Diadematoida

Order Micropygoida

Order Pedinoida

Infraclass Carinacea

Order Arbacioida

Order Camarodonta

Order Salenioida

Order Stomopneustoida

Infraclass Irregularia

Order Cassiduloida

Order Clypeasteroida

Order Echinolampadoida

Order Holasteroida

Order Spatangoida

Class Holothuroidea

Order N.N. (Thyone)

Order Apodida

Order Aspidochirotida

Order Dendrochirotida

Order Elasipodida

Order Molpadida

Phylum Hemichordata

Class Enteropneusta (e.g., Harrimaniidae)

Class Pterobranchia

Subclass Cephalodiscida (Cephalodiscus)

Subclass Graptolithina

Order Rhabdopleurida

Phylum Xenacoelomorpha

Subphylum Acoelomorpha

Class Acoela (e.g., Diopisthoporidae)

Class Nemertodermatida (e.g., Nemertodermatidae)

Subphylum Xenoturbellida

Class N.N. (Xenoturbellidae)

Names below rank of infrakingdom are arranged alphabetically within each parent rank, except for taxa that are not named (N.N.). Brackets indicate synonyms. Quoted names are not validly published but in common use.

Supporting Information

S1 Appendix. List of sources consulted for proposed higher level classification of all living organisms.

(PDF)

S1 Table. Proposed hierarchical classification from superkingdom to order.

(XLSX)

Data Availability

All relevant data are within the paper and its Supporting Information files.

Funding Statement

The authors have no funding or support to report.