Invertebrate paleontology

Bryozoan fossils in an Ordovician oil shale from Estonia. Field of view is 15 cm across.

Aviculopecten subcardiformis; an extinct pectenoid from the Logan Formation (Lower Carboniferous) of Wooster, Ohio (external mold).

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+b vmbnParazoa) 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).

Thus modern invertebrate paleontologists deal largely with fossils of this more strictly defined Animal Kingdom (excepting Phylum Chordata), Phylum Chordata being the exclusive focus of vertebrate paleontology. Protist fossils are then the main focus of micropaleontology, while plant fossils are the chief focus paleobotany. Together these four represent the traditional taxonomic divisions of paleontologic study.

Origins and modern evolution of invertebrate paleontology

Main article: History of invertebrate paleozoology

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 roundworms -- 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 protein often infused with tricalcium phosphate), and/or keratin (an even-more complex protein), rather than the vertebrate bone (hydroxyapatite) 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 calcite, chitin, and/or keratin. The most common and often-found macrofossils are the very hard calcareous shells of articulate brachiopods (that is, the everyday "lampshells") and of mollusks (such as the omnipresent clams, snails, mussels and oysters). On the other hand, non-shelly slugs and non-tubiferous worms (for instance, earthworms) have only occasionally been preserved due to their lack of hard parts.

Taxonomy of commonly-fossilized invertebrates

Main article: Taxonomy of commonly fossilized invertebrates

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.
• R. S. Boardman and others (1985). Fossil Invertebrates.
• 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.
• James W. Valentine (2004), On the Origins of Phyla (Chicago: University of Chicago Press). 608 pages. ISBN 0-226-84548-6. A discussion focusing on invertebrates during the Paleozoic era.
• Cyril Walker and David Ward (2002). Smithsonian Handbook of Fossils (London, England: Dorling Kindersley), 320 pages.

See also

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Geological links

Prehistoric periods & events (in geochronological order) Pre-Cambrian time (a.k.a. Cryptozoic) Proterozoic eon ("eon of first life") Paleoproterozoic era Oxygen catastrophe Mesoproterozoic era Neoproterozoic Tonian period Cryogenian period Snowball earth Ediacaran period Ediacaran biota Phanerozoic eon ("eon of well-displayed life") Paleozoic era Cambrian period Cambrian explosion of invertebrates as fossils Burgess shale invertebrates (best fossils of early Paleozoic) Cambrian-Ordovician extinction Ordovician period Ordovician-Silurian extinction Silurian period Devonian period Late Devonian extinction Carboniferous period Mississippian epoch Pennsylvanian epoch Permian period (demise of trilobites, graptolites, rugose corals & sea scorpions) Permian-Triassic extinction Mesozoic era Triassic period Triassic-Jurassic extinction Jurassic period Cretaceous period Cretaceous-Paleogene extinction Cenozoic era Paleogene period, a.k.a. early Tertiary Neogene period, a.k.a. late Tertiary & Quarternary Holocene extinctions Prehistoric oceans, continents & seas Angara continent Baltica continent Fennoscandia continent Gondwana supercontinent Laurasia continent Laurentia continent Laurussia continent Mirovia Ocean Paleo-Tethys Ocean Pangea supercontinent Pannotia supercontinent Panthalassa or Panthalassic Ocean Rodinia supercontinent Tethys Ocean

Fossils & evolution of invertebrates Evolution of invertebrates, etc. Evolutionary history of life Extinction events Fossils of invertebrates, etc. Fossil collecting Fossil parks open to visitors Geologic timescale -- has eras/periods of ancient life Glaciations History of earth Ice ages Index fossils or guide fossils Invertebrate paleontology List of fossil sites -- with link directory List of notable fossils -- includes invertebrate fossil beds List of transitional fossils Living fossil Macrofossils -- includes megafossils Mass extinctions Microfossils -- including microscopic invertebrates Phylogenetic tree of life's evolution Prehistoric animals Pseudofossils -- fossil-like stones and rocks Radiations of invertebrates, etc. Taxonomy of commonly fossilised invertebrates (w/ internal links) Timeline of evolution -- has era/periods of past life Trace fossils -- indirect evidence of past life Areas of scientific inquiry Biochemistry, a.k.a. Organic chemistry Biometrics -- Biology and Statistics Developmental biology and Embryology Earth sciences and Geology Evolutionary biology Evolution, the science of Evolutionary developmental biology ("Evo-devo") Geochemistry or earth chemistry Geochronology and Historical geology History of biology History of evolutionary thought History of geology History of invertebrate paleozoology -- espec. marine invertebrates History of paleontology -- espec. dinosaurs and mammals Malacology -- mollusk shells, etc. Marine biology and Oceanography Micropaleontology -- incl. microscopic invertebrates Natural history and Museums Paleobiology, a subfield of biology Paleoclimatology -- ancient climates Paleoecology -- ancient ecosystems Paleogeography -- ancient lands and seas Paleontologists -- includes paleobiologists Paleontology, a subfield of geology Paleozoology -- the study of all ancient animals Paleozoology: Vertebrates Petrology -- science of rocks & stones Phylogenetics regarding invertebrates Scientific methodology or methods of inquiry Sedimentology and Sedimentary rock Stratigraphy and Rock strata Zoology and its I.C.Z.N. regarding animal taxa

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.