Taxonomy of commonly fossilised invertebrates
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Although the phylogenetic classification of non-vertebrate animals (both extinct and extant) remains a work-in-progress, the following taxonomy attempts to be useful by combining both traditional (old) and new (21st-century) paleozoological terminology.
The paleobiologic systematics which follows is not intended to be all-inclusive or completely comprehensive. For practical reasons and relevancy, the below classification and annotations emphasize invertebrates that (a) are popularly collected as fossils and/or (b) no longer continue alive on this planet. Therefore, as a result, some phyla, classes, and orders of invertebrates are not listed.
If a non-vertebrate animal is mentioned below using its common, or vernacular name, the creature is usually a living, present-day invertebrate. But if a non-vertebrate is cited below by its scientific, taxonomic genus (in italics), then it is typically an extinct invertebrate, known only from the fossil record.
Invertebrate clades that are (a) very important as fossils (for example, ostracods frequently used as index fossils), and/or (b) very abundant as fossils (for example, crinoids easily found in crinoidal limestone), are highlighted with a bracketed exclamation mark [ ! ].
Invertebrate groups that (a) are now substantially extinct, and/or (b) contain a large proportion of extinct species, are followed by a dashed notation [ – such as this ]. But invertebrate clades which are now completely extinct are designated with a bracketed dagger [ † ]:
- comprises most of the species of life which have been documented by biologists and paleontologists as either living or deceased
- includes a wide variety of single-celled protists, all algae, most plankton, most molds, the green plants, and all animal-related kingdoms
Sub-domain of OpisthokontaEdit
- comprises most life forms documented as either living or deceased
- excludes many molds, all one-celled protists (or protoctists), all algae, and all green plants
Phylum Archaeocyatha / Archeocyatha / Archaeocyathida / Archeocyathida / Pleospongia [†]Edit
(includes fossil genera such Archaeocyathus, Cambrocyathus, Atikonia, Tumuliolynthus, Kotuyicyathus, Metaldetes, Ajacicyathus and Paranacyathus)
(quintessential true sponges / marine, colonial, pore-bearing animals / organized collar-flagellates / poriferans; today mostly siliceous) – half of all documented species of Porifera are fossils and extinct 
(Porifera may eventually be broken up into separate phyla)
- Sub-phylum Calcarea / Calcispongiae (primitive calcareous poriferans such as yellow lemon sponge, sphinctozoans, pharetronids, Scypha, Leucetta, Gravestockia, Grantia, Astraeospongium, Clathrina, Lelapia, Rhaphidonema, and Girtyocoelia)
- Class Calcinea
- Class Calcaronea
- Class Stromatoporoidea / Stromatoporata / Stromatoporida / Spongliomorphida [†] (lime-layered stromatoporoids / reef-building stromatoporates / button-shaped stromatoporids / disc-shaped spongliomorphids; e.g., Stromatopora, Aulacera, Stromatactis, Actinostroma, Discophyllum, Parallelopora and Amphipora)
- Class Heteractinida [†] (Paleozoic calcitic heteractinids such as Eiffelia)
- Sub-phylum Silicea / Silicospongia (siliceous poriferans)
- Class Demospongea / Demospongiae (most living sponges hardened by opaline silica or spongin; for instance, horny sponge, bath sponge, stove-pipe sponge, yellow boring sponge, carnivorous sponge, bristle sponge, chaetids, lithistids, Astroclera, Ceractinomorpha, Clionoides, Hindia, Ventriculites, Laosoiadia, Clionolithes, Tetractinella, and Astylospongia)
- Class Hexactinellida / Hyalospongiae / Sclerospongiae (siliceous, deep-sea glass sponges, e.g. glassy-latticed Venus flower basket, bird's nest sponge, cloud sponge, Hexactinella, Hydroceras, Dictyonina, Brachiospongia, Titusvillea, and Rhizopoterion)
(eumetazoans / true metazoans / typically mobile, multicellular animals)
(Eumetazoa contains most of the living and deceased species of recorded life, including most invertebrates (alive and extinct), as well as all vertebrate animals)
Phylum Cnidaria / CoelenterataEdit
- Class Hydrozoa (hydra or hydroid group)
- Class Anthozoa (corals / polyps)
- Subclass Octocorallia / Alcyonaria (soft corals and sea pens)
- Subclass Zoantharia [!] (sea anemones and most extant corals)
- Order Rugosa / Tetracoralla [†] [!] (wrinkled, horn-shaped tetracorals such as Petoskey coral, Caninia and Heliophyllum)
- Order Tabulata / Schizocoralla [†] [!] (tabulate corals, for instance, Favosites and Aulopora)
- Order Scleractinia / Hexacoralla [!] (stony corals such as brain coral, Favia, Meandrina, and most living corals)
Super-phylum of Lophotrochozoa / Protostomia # 1Edit
- Class Stenolaemata / Gymnolaemata [!] (mostly marine, calcareous bryozoans)
- Order Cheilostomata [!] (living, rimmed-mouthed moss animals)
- Order Cyclostomatida (uncontracted, round-mouthed bryozoans including fossil Stomatopora)
- Order Cystoporata [†] (extinct, minor group of moss animals)
- Order Trepostomata [†] [!] (changed-mouthed bryozoans such as extinct Constellaria and Monticulipora)
- Order Cryptostomata [†] [!] (round hidden-mouthed bryozoans such as Archimedes, Fenestrellina and Rhombopora)
- Order Ctenostomata [†] (uncommon, comb-mouthed bryozoans)
- Order Phylactolaemata (living, fresh-water bryozoans)
- Subphylum Linguliformea (inarticulate atremates, such as "living fossil" Lingula) – but mostly extinct
- Subphylum Craniiformea (inarticulate neotremates, such as extant Crania) – but mostly extinct
- Subphylum Rhynchonelliformea [!] (articulate brachiopods with hinged valves; includes most extinct and living brachs)
- Class Rhynchonellata [!]
- Order Orthida [†] [!] (orthid brachs such as fossil Orthis)
- Order Pentamerida [†] (pentamerid brachs such as Conchidium)
- Order Rhynchonellida [!] (rhynchonellid brachs such as fossils Rhynchotrema and Rhynchonella)
- Order Spiriferida [†] [!] (spiriferid brachs)
- Order Terebratulida [!] (most living brachiopods; includes fossil Dielasma)
- Class Strophomenata [†] [!] (so-called petrified butterflies)
- Class Rhynchonellata [!]
- Class Polychaeta (marine annelids / polychaetes)
- Class Monoplacophora (extinct, except for "living fossil" Neopilina)
- Class Bivalvia / Pelecypoda (bivalves / pelecypods) – half of all documented species of Bivalvia are fossils and extinct 
- Class Gastropoda (gastropods / snail group)
- Class Cephalopoda (cephalopods) – 97 percent of all documented species of Cephalopoda are now extinct
- Subclass Nautiloidea (mostly extinct, but includes "living fossil" Nautilus)
- Subclass Ammonoidea [†] [!] (generally coiled-shelled ammonoids)
- Subclass Coleoidea (includes the living squid, cuttlefish, and octopus)
Super-phylum of Ecdysozoa / Protostomia # 2Edit
(panarthropodic water bears)
(panarthropodic velvet worms, including proto-arthropodic fossils of Arthropleura and Aysheaia)
- Subphylum Crustacea (crustaceans)
- Subphylum Trilobitomorpha [†] (extinct trilobite group)
- Class Trilobita [†] (the armored trilobites)
- Subphylum Hexapoda
- Subphylum Chelicerata
- Subphylum Myriapoda
Super-phylum of Deuterostomia / EnterocoelomataEdit
(echinoderms) – 72 percent of all documented species of Echinodermata are fossils and extinct 
- Subphylum Crinozoa (sessile echinoderms) – 91 percent of all documented species of Crinozoa are now extinct
- Subphylum Blastozoa [†] (extinct blastoids)
- Subphylum Echinozoa (mobile echinoderms) – 89 percent of all documented species of Echinozoa are now extinct
- Subphylum Asterozoa
(hemichordates such as extant acorn worms) – Less than half of the documented species of Hemichordata are fossils and extinct
- Class Graptoloidea [†] (extinct graptolites)
(both invertebrate and vertebrate chordates; animals possessing a notochord)
- Subphylum Urochordata (invertebrate tunicate such as sea squirts)
- Subphylum Cephalochordata (invertebrate lancelets)
- For superb anatomical illustrations and much-more comprehensive information, see Volume E (Archaeocyatha / Porifera) through Volume V (Graptolithina), published 1953 to 2006 (and continuing), of the Treatise on Invertebrate Paleontology, long-edited by Raymond C. Moore and Roger L. Kaesler (Boulder, Colorado: Geological Society of America; and Lawrence, Kansas: University of Kansas Press). But be warned that some terms therein employed – such as supersubphylum – can be unnecessarily wordy or abstruse. Incidentally, revised volumes have been recently published regarding the sponges/archaeocyatha (2004, ISBN 0-8137-3131-3) and the brachiopods (2006, ISBN 0-8137-3135-6).
- The names of genera, orders, classes and phyla have been culled from dozens of sources, both current and decades-old. See the International Code of Zoological Nomenclature (ICZN), as well as Volume 1 and Volume 2 of Grzimek's Animal Life Encyclopedia (Farmington Hills, Michigan: Gale Group), edited by zoologists Michael Hutchin, Dennis A. Thorney and Sean F. Craig (2003).
- For correspondingly ancient ecosystems, see the Treatise on Ecology and Paleoecology, Volume 2: Paleoecology, edited for years by Harry S. Ladd (1957 / 1971), and published by both the Geological Society of America (Boulder, Colorado) and the Waverly Press (Washington, D.C.).
- The rates of extinction for sponges and other phyla are derived from W. H. Easton, 1960, Invertebrate Paleontology (New York: Harper and Brothers) and various modern sources.
- For bryozoans and brachiopods, the same footnote as above.
- For bivalves and cephalopods (both mollusks), see the above notation.
- For the echinoderms, see the above footnote regarding W. E. Easton, 1960, Invertebrate Paleontology, and other sources.