Taxonomy of commonly fossilised invertebrates

Although the phylogenetic classification of sub-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 termonology.

So the paleobiologic systematics which follows is not intended to be all-inclusive or completely comprehensive. For practial 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. ^[1]

If a non-vertebrate animal is mentioned below using its common, vernacular, everyday name, the creature is usually a living, present-day invertebrate. But if, on the other hand, 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. ^[2]

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), ^[3] 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 totally -- that is, 100 percent -- extinct are designated with a bracketed dagger/cross [ † ]:

Domain of EUKARYOTA / EUKARYA

(eukaryotes / eukaryans / all cellular organisms bearing a central, organized nucleus with DNA)

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
- but does not include the primal, sub-nuclear, prokaryotic domains of Archaea and Bacteria -- nor the enigmatic domain of Viruses

Sub-domain of OPISTHOKONTA

(opisthokonts / the animal-related kingdoms / the proto-spongal choanoflagellates, proto-fungal microsporidians, true fungi, and true animals

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

Kingdom of ANIMALIA / METAZOA

(metazoans / many-celled true animals / all invertebrates and vertebrates / multi-cellular creatures that grab and ingest their organic food)

comprises most living and deceased species which have ever been recorded by paleontological and life scientists
- excludes all unicellular and fungal opisthokonts

Sub-kingdom of PARAZOA

(parazoans / typically-sessile, basal non-eumetazoans / the most-primitive animals / the simplest, colonial, attached, bottom-dwelling, marine invertebrates)

Phylum Archaeocyatha / Archeocyatha / Archaeocyathida / Archeocyathida / Pleospongia [†]

(cone-shaped archaeocyathids/archeocyathids / cup-shaped archaeocyathans/archeocyathans / reef-building pleosponges / calcareous "ancient-cups")

(includes fossil genera such Archaeocyathus, Cambrocyathus, Atikonia, Tumuliolynthus, Kotuyicyathus, Metaldetes, Ajacicyathus and Paranacyathus)

(Archaeocyatha is sometimes classified as a class of Porifera below)

Phylum Porifera / Nuda / Spongia

(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 ^[4]

(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)

Phylum Placozoa

Sub-kingdom of EUMETAZOA

(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)

Super-phylum of RADIATA

(radiates / non-bilaterian eumetazoans)

Phylum Cnidaria / Coelenterata

(cnidarians / coelenterates)

Class Hydrozoa (hydra or hydroid group)
- Subclass Stromatoporoidea [†] (lime-layered stromatoporoids)
- Subclass Conulata [†] (four-sided, pyramidal conularians)
Class Anthozoa (corals / polyps)
- Subclass Receptaculidea [†] (receptaculites, a.k.a. sunflower corals)
- 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)
  - Order Scleractinia / Hexacoralla [!] (stony corals such as brain coral, Favia, Meandrina, and most living corals)

Super-phylum of LOPHOTROCHOZOA / PROTOSTOMIA # 1

(lophotrochozoan bilaterians, such as flatworms, ribbon worms, lophophorates, and molluscs)

Phylum Bryozoa / Ectoprocta / Polyzoa

(bryozoans / moss animals) -- half of all documented species of Bryozoa are fossils and extinct ^[5]

Class Stenolaemata / Gymnolaemata [!] (mostly marine, calcareous bryozoans)
- Order Cheilostomata [!] (living, rimmed-mouthed moss animals)
- Order Cyclostomata (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)

Phylum Brachiopoda

(lampshells, brachiopods or "brachs," not to be confused with the hard-shelled marine mollusks below) -- 99 percent of all documented species of Brachiopoda are now extinct

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)
    - Suborder Spiriferinida [†] [!] (spiriferid brachs such as Spirifer and Eospirifer)
    - Suborder Atrypida [†] [!] (atrypid brachs such as Atrypa)
  - Order Terebratulida [!] (most living brachiopods; includes fossil Dielasma)
- Class Strophomenata [†] [!] (so-called petrified butterflies)
  - Order Strophomenida [†] [!] (strophomenid brachs)
  - Order Productida [†] [!] (spiny or productid brachs)
    - Suborder Chonetidina [†] [!]
    - Suborder Productidina [†] [!]

Phylum Annelida

(segmented worms such as earthworms and leeches)

Class Polychaeta (marine annelids / polychaetes)
- Order Scolecodonta [!] (mostly chitinous jaws of scolecodonts)

Phylum Mollusca

(molluscs or mollusks, not to be confused with the hard-shelled marine brachiopods above)

Class Monoplacophora (extinct, except for "living fossil" Neopilina)
Class Bivalvia / Pelecypoda (bivalves / pelecypods) -- half of all documented species of Bivalvia are fossils and extinct ^[6]
- Subclass Lamellibranchia [!] (clams, oysters, mussels and scallops)
Class Gastropoda (gastropods / snail group)
- Subclass Prosobranchia (marine snails and conches)
- Subclass Opisthobranchia (sea slugs)
- Subclass Pulmonata (land snails)
Class Cephalopoda (cephalopods) -- 97 percent of all documented species of Cephalopoda are now extinct
- Subclass Nautiloidea (mostly extinct, but includes "living fossil" Nautilus)
  - Order Orthocerida [†] [!] (long, straight-shelled nautiloids)
- Subclass Ammonoidea [†] [!] (generally coiled-shelled ammonoids)
  - Agoniatitic (agoniatites) [†]
  - Goniatitic (goniatites) [†] [!] (ammonoids with simple sutures)
  - Ceratitic (ceratites) [†]
  - Ammonitic [†] [!] (the true ammonites, bearing complex sutures)
- Subclass Coleoidea (includes the living squid, cuttlefish, and octopus)
  - Order Belemnoidea [†] (extinct orthoconic belemnoids)

Super-phylum of ECDYSOZOA / PROTOSTOMIA # 2

(ecdysozoans, such as nematodes, horsehair worms, and molting bilaterians / panarthropods))

Phylum Tardigrada

(panarthropodic water bears)

Phylum Onychophora

(panarthropodic velvet worms, including proto-arthropodic fossils of Arthropleura and Aysheaia)

Phylum Arthropoda

(arthropods; jointed legged creatures with an exoskeleton)

Subphylum Crustacea (crustaceans)
- Class Ostracoda (ostracods)
- Class Malacostraca (true crabs, lobster and most shrimp)
- Class Branchiopoda (brine shrimp)
  - Order Norostraca
- Class Cirripedia(barnacles)
- Class Arachnoidea
Subphylum Trilobitomorpha [†] (extinct trilobite group)
- Class Trilobita [†] (the armored trilobites)
Subphylum Hexapoda
- Class Insecta (insects, best preserved in amber)
Subphylum Chelicerata
- Class Arachnida (spiders, best preserved in amber)
- Class Merostomata ("living fossil" horseshoe crab and extinct eurypterid)
Subphylum Myriapoda
- Class Diplopoda
- Class Chilopoda

Super-phylum of DEUTEROSTOMIA / ENTEROCOELOMATA

(second-mouthed bilaterians called deuterostomians, such as chordates and echinoderms)

Phylum Echinodermata

(echinoderms) -- 72 percent of all documented species of Echinodermata are fossils and extinct ^[7]

Subphylum Crinozoa (sessile echinoderms) -- 91 percent of all documented species of Crinozoa are now extinct
- Class Crinoidea (crinoids / sea lilies) -- See Crinozoa above
Subphylum Blastozoa [†] (extinct blastoids)
- Class Diploporita
- Class Rhombifera
Subphylum Echinozoa (mobile echinoderms) -- 89 percent of all documented species of Echinozoa are now extinct
- Class Echinoidea (echinoids or sea urchins) -- See Echinozoa above
Subphylum Asterozoa
- Class Asteroidea (sea stars / starfish)
- Class Ophiuroidea

Phylum Hemichordata

(hemichordates such as extant acorn worms) -- Less than half of the documented species of Hemichordata are fossils and extinct

Class Graptoloidea [†] (extinct graptolites)
- Order Dendroidea [†]
- Order Graptoloidea [†]
  - Suborder Didymograptina [†]
  - Suborder Diplograptina [†]
  - Suborder Monograptina [†]

Phylum Chordata

(both invertebrate and vertebrate chordates; animals possessing a notochord)

Invertebrate subphyla

Subphylum Urochordata (invertebrate tunicate such as sea squirts)

Subphylum Cephalochordata (invertebrate lancelets)

Subphylum Vertebrata

(vertebrates such as hagfishes, lampreys, conodonts [†], ostracoderms [†], placoderms [†], sharks, ray-finned fishes, lobe-finned fishes, amphibians, reptiles, dinosaurs [†], birds and mammals)