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EspañolINVERTEBRATE PALEONTOLOGY
'Invertebrate paleontology' (also spelled 'Invertebrate palaeontology') is sometimes described as 'Invertebrate paleozoology' and/or 'Invertebrate paleobiology'.
Whether it is considered to be a subfield of paleontology, paleozoology, and/or paleobiology, this discipline is the scientific study of 'prehistoric invertebrates' by analyzing 'invertebrate fossils' in the geologic record.
By ''invertebrates'' are meant the ''non-vertebrate'' creatures of the kingdom Animalia (or Metazoa) in the biotic domain of Eukaryota. By phyletic definition, these many-celled, ''sub-vertebrate'' animals lack a vertebral column, spinal column, vertebrae, backbone, or long, full-length notochord -- in contrast, of course, to the vertebrates in the one phylum of Chordata.
Relatedly, invertebrates have never had a cartilaginous and/or boney internal skeleton, with its skeletal supports, gill slits, ribs and jaws. Finally, throughout geologic time, invertebrates have remained non-craniate creatures; that is, they never developed a cranium, nerve-chord brain, skull, or hard protective braincase.
In the many decades since Jean-Baptiste de Lamarck, a pioneering biologist and evolutionist, first conceptualized and coined the category "Invertebrata" (between 1793 and 1801) and the term "Biology" (in 1802), zoology has come to recognize that the ''non-vertebrate'' category is not a scientifically-valid, monophyletic taxon. Evolutionary biology and developmental biology (a.k.a. "evo-devo") now consider the term "Invertebrata" to be both polyphyletic and paraphyletic. Nevertheless, most earth science departments continue to employ this term; and paleontologists find it both useful and practical in evaluating 'fossil invertebrates' and -- consequently -- 'invertebrate evolution'.
However, there is one contemporary caveat: Paleobiologists and microbiologists in the 21st century no longer classify one-celled "animal-like" microbes ''either'' as invertebrates ''or'' as animals.
For example, the commonly-fossilized foraminifera ("forams") and radiolarians -- zooplankton both formerly grouped under either an animal phylum or animal sub-kingdom called Protozoa ("first animals") -- are now placed in the kingdom or super-kingdom Protista or Protoctista (and thus called protists or protoctists), or -- still more recently -- are placed within the multiple non-animal kingdoms of the domain Eukaryota (the organic domain which comprises the mostly-unicellular, nuclei-bearing eukaryotes). [1]
This radical rearrangement of the branches of the phylogenetic tree of life has resulted from the ''latest'' findings in genetics, cladistics, and molecular biology. [2]
{This section has been moved to the new article History of invertebrate paleozoology due to size constraints}
{This section has ''also'' been moved to the new article History of invertebrate paleozoology due to limitations on size}
When it comes to the fossil record, ''soft-''bodied and ''minuscule'' invertebrates -- such as hydras, jellies, flatworms, hairworms, nematodes, ribbon worms, rotifers and earthworms -- are infrequently fossilized. As a result, paleontologists and other fossil hunters must often rely on trace fossils, microfossils, or chemofossil residue when scouting for these prehistoric creatures.
''Hard-''bodied and ''large'' invertebrates are much-more commonly preserved; typically as sizeable macrofossils. These invertebrates are more frequently preserved because their hard parts -- for example, shell, armor, plates, tests, exoskeleton, jaws or teeth -- are composed of silica (silicon dioxide), calcite or aragonite (both forms of calcium carbonate), chitin (a proteinaceous tricalcium phosphate), and/or keratin (an even-more complex protein), rather than the vertebrate bone (tricalcium phosphate) or cartilage of fishes and land-dwelling tetrapods.
The chitinous jaws of annelids (such as the marine scolecodonts) are sometimes preserved as fossils; while many arthropods and inarticulate brachiopods have easily-fossilized hard parts of chitin and/or keratin. The most common and often-found macrofossils are the very hard calcareous shells of articulate lampshells (that is, the everyday "brachs") and of mollusks (such as the omnipresent clams, snails, mussels and oysters). On the other hand, demosponges (for instance, horny sponges) and hyalosponges (for instance, glass sponges) have occasionally been preserved due to their siliceous or glassy composition.
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. [3]
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. [4]
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), [5] 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, 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 invertebrates)
===Phylum Archaeocyatha / Archeocyathida / Archeocyatha [†]===
(extinct archaeocyathans / archaeocyathids / archeocyathids / archeocyathans / calcareous "ancient-cups" / cone-shaped pleosponges)
(includes fossil genera such ''Archaeocyathus'',
''Cambrocyathus'', ''Atikonia'', ''Metaldetes'', and ''Ajacicyathus'')
(phylum might be reclassified as a class of Porifera below)
===Phylum Porifera / Nuda===
(the true sponges, today mostly silicareous) -- ''half'' of all documented species of Porifera are fossils ''and'' extinct [6]
★ Class Demospongea (most living sponges; e.g., the silicareous horny sponges, bath sponges, fossil Lithistids)
★ Class Hexactinellida / Hyalospongiae (silicareous, deep-sea glass sponges and fossil ''Dictyonina'')
★ Class Calcarea / Calcisongiae (calcareous sponges such as extinct Pharetronids)
★ Class Stromatoporata [†] (calcareous stromatoporates)
==Sub-kingdom of EUMETAZOA
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 [7]
★ 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 [8]
★
★ 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 [9]
★ 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)
★ 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)
1. Correspondingly, the one-celled "plant-like" organisms -- a group of mostly simple algae once known as Protophyta ("first plants") -- are now ''also'' placed among the protists and/or the non-plant eukaryotes. So too are the "plant-like" fungi, which have been discovered to be far-more "animal-like" (genetically speaking) than the early naturalists would have ever suspected.
2. For the new locus of the multi-celled animals in the "tree of life", see especially the tree diagrams on pp. 45, 78 and 555 of Joel Cracraft and Michael J. Donaghue, editors (2004) of ''Assembling the Tree of Life'' (Oxford, England: Oxford University Press ), 592 pages. ISBN 0195172345. And for even ''less technical'' and ''superbly-illustrated'' evolutionary trees, see ''The Variety of Life: A Survey and a Celebration of All the Creatures That Have Ever Lived'' by Colin Tudge (20002), an easy-to-read 704-page book also published by the Oxford University Press. ISBN 0198604262.
3. For superb anatomical illustrations and much-more comprehensive information, the aspiring paleozoologist should scan ''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 obstruse. Incidentally, ''revised'' volumes have been recently published regarding the sponges/archaeocyatha (2004, ISBN 08137 31313) and the brachiopods (2006, ISBN 0813731356).
4. 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).
5. 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.).
6. 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.
7. For bryozoans and brachiopods, the same footnote as above.
8. For bivalves and cephalopods (both mollusks), see the above notation.
9. For the echinoderms, see the above footnote regarding W. E. Easton, 1960, ''Invertebrate Paleontology'', and other sources.
Although these books are ''not'' footnoted in this article, the following are well-illustrated, well-organized -- and often well-worn -- guides to invertebrate (and sometimes other) fossils:
★ Paolo Arduini (1987), ''Simon and Schuster's Guide to Fossils'' (Old Tappan, New Jersey: Fireside), 320 pages. ISBN 0671631322.
★ James R. Beerbower (1968). ''Search for the Past: An Introduction to Paleontology'' (Englewood Cliffs, New Jersey: Prentice-Hall), 512 pages.
★ British Museum of Natural History (1969). ''British Palaeozoic Fossils'' (London, England: British Museum of Natural History).
★ Euan N. K. Clarkson (1998). ''Invertebrate Palaeontology and Evolution'' (London, England: Allen and Unwin), 468 pages. ISBN 9780632052387.
★ Peter Doyle (1996), ''Understanding Fossils: An Introduction to Invertebrate Paleontology'' (Hoboken, New Jersey: John Wiley & Sons), 426 pages. ISBN 0471963518.
★ Carroll Lane Fenton and Mildred Adams Fenton (1958); updated by Patricia Vickers Rich and Thomas Hewitt Rich (1997). ''The Fossil Book: A Record of Prehistoric Life'' (Garden City, New York: Doubleday and Courier Dover Publishing), from 482 to 760 pages. ISBN 0486293718.
★ W. R. Hamilton and others (1974). ''A Guide to Minerals, Rocks and Fossils'' (London, England: Hamlyn Publishing Group Ltd.), 320 pages.
★ W. B. Harland (1967). ''The Fossil Record'' (London, England: Geological Society of London), 827 pages.
★ V. Lehmann and G. Hillmer (1983). ''Fossil Invertebrates'' (Cambridge, England: Cambridge University Press).
★ Harold L. Levin (1998), ''Ancient Invertebrates and Their Living Relatives'' (Boston: Prentice-Hall), 358 pages. ISBN 9780137489558.
★ William H. Matthews III (1962). ''Fossils: An Introduction to Prehistoric Life'' (New York: Barnes and Noble), 337 pages.
★ Helmut Mayr (1992). ''A Guide to Fossils'' (New York: Longman, Harlow).
★ Raymond C. Moore and others (1952). ''Invertebrate Fossils'' (New York: McGraw-Hill), 776 pages. ISBN 00704302.
★ J. W. Murray, editor (1985). ''Atlas of Invertebrate Macrofossils'' (Princeton: Princeton University Press), 256 pages.
★ Douglas Palmer (2004), ''Fossils'' (London, England: Dorling Kindersley).
★ Frank H. T. Rhodes and others (1962). ''Fossils: A Guide to Prehistoric Life'' (New York: Golden Nature Guide), 242 pages.
★ Henry Woodburn Shimer and Robert Rakes Shrock (1944/1983). ''Index Fossils of North America'' (Cambridge, Massachusetts: Massachusetts Institute of Technology Press), 837 pages.
★ Robert Rakes Shrock and W. H. Twenhofel (1953). ''Invertebrate Paleontology'' (New York: McGraw-Hill).
★ Ronald Singer (2000), ''Encyclopedia of Paleontology'' (London, England: Routledge), 1,467 pages. ISBN 1884964966.
★ Ida Thompson (1982/2004). ''National Audubon Society Field Guide to North American Fossils'' (New York: Alfred A. Knopf), 846 pages.
★ Cyril Walker and David Ward (2002). ''Smithsonian Handbook of Fossils'' (London, England: Dorling Kindersley), 320 pages.
{|align-left
★ A colorful, illustrated taxonomy of extinct ''and'' living invertebrate Metazoa by the University of California Museum of Paleontology.
★ The invertebrate fossil record illustrated colorfully for Metazoa provided by the U.C. Museum of Paleontology.
★ Educational and colorful introduction to the three domains of the Tree of Life -- as well as to the topic of "Understanding Evolution" -- sponsored by the U.C. Museum of Paleontology.
★ An introduction to fossils by The Paleontology Portal, a project of four American institutions funded by the National Science Foundation.
★ The introduction to ''invertebrate'' fossils provided by The Paleontology Portal.
★ Thousands of online pictures of invertebrate fossils. sponsored by the Peabody Museum at Yale University.
★ The taxonomy of the Metazoa Kingdom of animals provided by The Tree of Life Project.
★ Home site of the many volumes of the ''Treatise on Invertebrate Paleontology'', a site sponsored by both The Paleontological Institute at the University of Kansas and the Geological Society of America.
Whether it is considered to be a subfield of paleontology, paleozoology, and/or paleobiology, this discipline is the scientific study of 'prehistoric invertebrates' by analyzing 'invertebrate fossils' in the geologic record.
By ''invertebrates'' are meant the ''non-vertebrate'' creatures of the kingdom Animalia (or Metazoa) in the biotic domain of Eukaryota. By phyletic definition, these many-celled, ''sub-vertebrate'' animals lack a vertebral column, spinal column, vertebrae, backbone, or long, full-length notochord -- in contrast, of course, to the vertebrates in the one phylum of Chordata.
Relatedly, invertebrates have never had a cartilaginous and/or boney internal skeleton, with its skeletal supports, gill slits, ribs and jaws. Finally, throughout geologic time, invertebrates have remained non-craniate creatures; that is, they never developed a cranium, nerve-chord brain, skull, or hard protective braincase.
Invertebrate terminology in science
In the many decades since Jean-Baptiste de Lamarck, a pioneering biologist and evolutionist, first conceptualized and coined the category "Invertebrata" (between 1793 and 1801) and the term "Biology" (in 1802), zoology has come to recognize that the ''non-vertebrate'' category is not a scientifically-valid, monophyletic taxon. Evolutionary biology and developmental biology (a.k.a. "evo-devo") now consider the term "Invertebrata" to be both polyphyletic and paraphyletic. Nevertheless, most earth science departments continue to employ this term; and paleontologists find it both useful and practical in evaluating 'fossil invertebrates' and -- consequently -- 'invertebrate evolution'.
However, there is one contemporary caveat: Paleobiologists and microbiologists in the 21st century no longer classify one-celled "animal-like" microbes ''either'' as invertebrates ''or'' as animals.
For example, the commonly-fossilized foraminifera ("forams") and radiolarians -- zooplankton both formerly grouped under either an animal phylum or animal sub-kingdom called Protozoa ("first animals") -- are now placed in the kingdom or super-kingdom Protista or Protoctista (and thus called protists or protoctists), or -- still more recently -- are placed within the multiple non-animal kingdoms of the domain Eukaryota (the organic domain which comprises the mostly-unicellular, nuclei-bearing eukaryotes). [1]
This radical rearrangement of the branches of the phylogenetic tree of life has resulted from the ''latest'' findings in genetics, cladistics, and molecular biology. [2]
Origins of invertebrate paleontology
{This section has been moved to the new article History of invertebrate paleozoology due to size constraints}
Modern evolution of invertebrate paleontology
{This section has ''also'' been moved to the new article History of invertebrate paleozoology due to limitations on size}
Invertebrate fossilization
When it comes to the fossil record, ''soft-''bodied and ''minuscule'' invertebrates -- such as hydras, jellies, flatworms, hairworms, nematodes, ribbon worms, rotifers and earthworms -- are infrequently fossilized. As a result, paleontologists and other fossil hunters must often rely on trace fossils, microfossils, or chemofossil residue when scouting for these prehistoric creatures.
''Hard-''bodied and ''large'' invertebrates are much-more commonly preserved; typically as sizeable macrofossils. These invertebrates are more frequently preserved because their hard parts -- for example, shell, armor, plates, tests, exoskeleton, jaws or teeth -- are composed of silica (silicon dioxide), calcite or aragonite (both forms of calcium carbonate), chitin (a proteinaceous tricalcium phosphate), and/or keratin (an even-more complex protein), rather than the vertebrate bone (tricalcium phosphate) or cartilage of fishes and land-dwelling tetrapods.
The chitinous jaws of annelids (such as the marine scolecodonts) are sometimes preserved as fossils; while many arthropods and inarticulate brachiopods have easily-fossilized hard parts of chitin and/or keratin. The most common and often-found macrofossils are the very hard calcareous shells of articulate lampshells (that is, the everyday "brachs") and of mollusks (such as the omnipresent clams, snails, mussels and oysters). On the other hand, demosponges (for instance, horny sponges) and hyalosponges (for instance, glass sponges) have occasionally been preserved due to their siliceous or glassy composition.
Taxonomy of commonly-fossilized 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. [3]
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. [4]
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), [5] 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, 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 invertebrates)
===Phylum Archaeocyatha / Archeocyathida / Archeocyatha [†]===
(extinct archaeocyathans / archaeocyathids / archeocyathids / archeocyathans / calcareous "ancient-cups" / cone-shaped pleosponges)
(includes fossil genera such ''Archaeocyathus'',
''Cambrocyathus'', ''Atikonia'', ''Metaldetes'', and ''Ajacicyathus'')
(phylum might be reclassified as a class of Porifera below)
===Phylum Porifera / Nuda===
(the true sponges, today mostly silicareous) -- ''half'' of all documented species of Porifera are fossils ''and'' extinct [6]
★ Class Demospongea (most living sponges; e.g., the silicareous horny sponges, bath sponges, fossil Lithistids)
★ Class Hexactinellida / Hyalospongiae (silicareous, deep-sea glass sponges and fossil ''Dictyonina'')
★ Class Calcarea / Calcisongiae (calcareous sponges such as extinct Pharetronids)
★ Class Stromatoporata [†] (calcareous stromatoporates)
==Sub-kingdom of EUMETAZOA
(eumetazoans / typically-mobile, multicellular 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 [7]
★ 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 [8]
★
★ 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 [9]
★ 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)
Footnotes
1. Correspondingly, the one-celled "plant-like" organisms -- a group of mostly simple algae once known as Protophyta ("first plants") -- are now ''also'' placed among the protists and/or the non-plant eukaryotes. So too are the "plant-like" fungi, which have been discovered to be far-more "animal-like" (genetically speaking) than the early naturalists would have ever suspected.
2. For the new locus of the multi-celled animals in the "tree of life", see especially the tree diagrams on pp. 45, 78 and 555 of Joel Cracraft and Michael J. Donaghue, editors (2004) of ''Assembling the Tree of Life'' (Oxford, England: Oxford University Press ), 592 pages. ISBN 0195172345. And for even ''less technical'' and ''superbly-illustrated'' evolutionary trees, see ''The Variety of Life: A Survey and a Celebration of All the Creatures That Have Ever Lived'' by Colin Tudge (20002), an easy-to-read 704-page book also published by the Oxford University Press. ISBN 0198604262.
3. For superb anatomical illustrations and much-more comprehensive information, the aspiring paleozoologist should scan ''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 obstruse. Incidentally, ''revised'' volumes have been recently published regarding the sponges/archaeocyatha (2004, ISBN 08137 31313) and the brachiopods (2006, ISBN 0813731356).
4. 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).
5. 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.).
6. 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.
7. For bryozoans and brachiopods, the same footnote as above.
8. For bivalves and cephalopods (both mollusks), see the above notation.
9. For the echinoderms, see the above footnote regarding W. E. Easton, 1960, ''Invertebrate Paleontology'', and other sources.
Further reading
Although these books are ''not'' footnoted in this article, the following are well-illustrated, well-organized -- and often well-worn -- guides to invertebrate (and sometimes other) fossils:
★ Paolo Arduini (1987), ''Simon and Schuster's Guide to Fossils'' (Old Tappan, New Jersey: Fireside), 320 pages. ISBN 0671631322.
★ James R. Beerbower (1968). ''Search for the Past: An Introduction to Paleontology'' (Englewood Cliffs, New Jersey: Prentice-Hall), 512 pages.
★ British Museum of Natural History (1969). ''British Palaeozoic Fossils'' (London, England: British Museum of Natural History).
★ Euan N. K. Clarkson (1998). ''Invertebrate Palaeontology and Evolution'' (London, England: Allen and Unwin), 468 pages. ISBN 9780632052387.
★ Peter Doyle (1996), ''Understanding Fossils: An Introduction to Invertebrate Paleontology'' (Hoboken, New Jersey: John Wiley & Sons), 426 pages. ISBN 0471963518.
★ Carroll Lane Fenton and Mildred Adams Fenton (1958); updated by Patricia Vickers Rich and Thomas Hewitt Rich (1997). ''The Fossil Book: A Record of Prehistoric Life'' (Garden City, New York: Doubleday and Courier Dover Publishing), from 482 to 760 pages. ISBN 0486293718.
★ W. R. Hamilton and others (1974). ''A Guide to Minerals, Rocks and Fossils'' (London, England: Hamlyn Publishing Group Ltd.), 320 pages.
★ W. B. Harland (1967). ''The Fossil Record'' (London, England: Geological Society of London), 827 pages.
★ V. Lehmann and G. Hillmer (1983). ''Fossil Invertebrates'' (Cambridge, England: Cambridge University Press).
★ Harold L. Levin (1998), ''Ancient Invertebrates and Their Living Relatives'' (Boston: Prentice-Hall), 358 pages. ISBN 9780137489558.
★ William H. Matthews III (1962). ''Fossils: An Introduction to Prehistoric Life'' (New York: Barnes and Noble), 337 pages.
★ Helmut Mayr (1992). ''A Guide to Fossils'' (New York: Longman, Harlow).
★ Raymond C. Moore and others (1952). ''Invertebrate Fossils'' (New York: McGraw-Hill), 776 pages. ISBN 00704302.
★ J. W. Murray, editor (1985). ''Atlas of Invertebrate Macrofossils'' (Princeton: Princeton University Press), 256 pages.
★ Douglas Palmer (2004), ''Fossils'' (London, England: Dorling Kindersley).
★ Frank H. T. Rhodes and others (1962). ''Fossils: A Guide to Prehistoric Life'' (New York: Golden Nature Guide), 242 pages.
★ Henry Woodburn Shimer and Robert Rakes Shrock (1944/1983). ''Index Fossils of North America'' (Cambridge, Massachusetts: Massachusetts Institute of Technology Press), 837 pages.
★ Robert Rakes Shrock and W. H. Twenhofel (1953). ''Invertebrate Paleontology'' (New York: McGraw-Hill).
★ Ronald Singer (2000), ''Encyclopedia of Paleontology'' (London, England: Routledge), 1,467 pages. ISBN 1884964966.
★ Ida Thompson (1982/2004). ''National Audubon Society Field Guide to North American Fossils'' (New York: Alfred A. Knopf), 846 pages.
★ Cyril Walker and David Ward (2002). ''Smithsonian Handbook of Fossils'' (London, England: Dorling Kindersley), 320 pages.
See also
{|align-left
External links
★ A colorful, illustrated taxonomy of extinct ''and'' living invertebrate Metazoa by the University of California Museum of Paleontology.
★ The invertebrate fossil record illustrated colorfully for Metazoa provided by the U.C. Museum of Paleontology.
★ Educational and colorful introduction to the three domains of the Tree of Life -- as well as to the topic of "Understanding Evolution" -- sponsored by the U.C. Museum of Paleontology.
★ An introduction to fossils by The Paleontology Portal, a project of four American institutions funded by the National Science Foundation.
★ The introduction to ''invertebrate'' fossils provided by The Paleontology Portal.
★ Thousands of online pictures of invertebrate fossils. sponsored by the Peabody Museum at Yale University.
★ The taxonomy of the Metazoa Kingdom of animals provided by The Tree of Life Project.
★ Home site of the many volumes of the ''Treatise on Invertebrate Paleontology'', a site sponsored by both The Paleontological Institute at the University of Kansas and the Geological Society of America.
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