Taxonomy of commonly fossilised invertebrates is a complex and evolving field that combines both traditional and modern paleozoologicalterminology. This article provides an overview of various invertebrate taxa found in the fossil record, ranging from protists to arthropods. The taxonomy discussed is not exhaustive, but rather emphasizes invertebrates that are either frequently collected as fossils or are extinct. This includes groups that are significant in paleontological contexts, notably abundant in the fossil record, or have a high proportion of extinct species. For better understanding, special notations used in this context are explained below:
[ ! ]: Indicates clades that are important as fossils or very abundant in the fossil record.
[ – ]: Indicates clades that contain a large proportion of extinct species.
[ † ]: Indicates clades that are completely extinct.
The paleobiologicsystematics that follow are not intended to be comprehensive, rather encompass invertebrates that (a) are popularly collected as fossils and/or (b) extinct. As a result, some groups of invertebrates are not listed.[1]
If an invertebrate animal is mentioned below using its common (vernacular) name, it is an extant (living) taxon, but if it is cited by its scientific genus, then it is typically an extinct invertebrate known only from the fossil record.[2]
Invertebrate clades that are important fossils (e.g. ostracods, frequently used as index fossils), and/or clades that are very abundant as fossils (e.g. crinoids, easily found in crinoidal limestone),[3] are highlighted with a bracketed exclamation mark [ ! ].
Pattersonia ulrichi Rauff, 1894; an Ordovician hexactinellid sponge from near Cincinnati, Ohio.Tetractinella trigonella at MUSE - Science Museum in Trento
Eumetazoa contains most of the living and deceased species of recorded life, including most invertebrates (extinct and extant), as well as all vertebrate animals.
Peltoceras solidum ammonite from the Matmor Formation (Jurassic, Callovian) in the Matmor Formation, Makhtesh Gadol, Israel.Vermetid gastropod Petaloconchus intortus attached to a branch of the coral Cladocora; Pliocene of Cyprus.
Pendeograptus fruticosus graptolites from the Bendigonian Australian Stage (Lower Ordovician) near Bendigo, Victoria, Australia. Two overlapping, three-stiped rhabdosomes.
Hemichordates such as extant acorn worms – Less than half of the documented species of Hemichordata are fossils and extinct.
^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, ISBN0-8137-3131-3) and the brachiopods (2006, ISBN0-8137-3135-6).
^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.
