Fossil Classification
Most fossil hunters identify fossils based on the system devised in 1758 by Swedish-born biologist Carolus Linnaeus. Linnaeus proposed a species should have two names; the first being the genus (a group of similar species) and the second being unique to the species itself. From about 1780, use of this system applied to fossils as well as living or extinct species; however many professional palaeontologists choose the cladistics method of identification. No matter the system used, the main fossil classification groups in order include kingdom, phylum (animals)/division (plants), class, order, family, genus and species.
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Taxonomy
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Linnaeus' binomial nomenclature (giving two names as a unique identification) now encompasses all living things. The science of classification of organisms, living or extinct, is called taxonomy.
The levels of identification for a fossil are vast. While amateur palaeontologists find the description 'trilobite' sufficient for a specimen, others may want a more accurate identification. Studying a species' differences and similarities enables you to determine what group classification to assign an organism such as its kingdom, phylum, class, order, family, genus and species.
Group Classifications
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Classifications are based on the Linnaean system where each organism is uniquely identified by combining its genus and species names. Depending on the similarities and evolutionary relationships, species group into genera, families, orders, classes, phyla and kingdoms.
The species group comprises similar individual organisms that interbreed and produce offspring; however with fossils, inconclusive evidence of reproductive isolation is not certain. The definition of a species is based on morphological (form and structure of an organism) criteria, and the chemical analysis of the organisms' shells (hard parts).
Genus refers to closely related species, such as brachiopods. Lingula is one of the genus names for the shellfish called brachiopods (lampshells). Individual species include Lingula gredneri, L. anatine, L. cornea and several others. Genus and species names are usually printed in italics, while names of groups, such as classes or orders, are not.
Genera forms together into major groups of similar organisms called families. Family names always end in "ae".
Families group together into orders. Order names begin with a capital and usually (but not always) end in an "a".
Groups of orders form classes--the basis for most fossil research. The phylum Mollusca contains four classes: gastropoda, cephalopods, pelecypoda and scaphopoda.
Groups of classes form into plyla (plural of phylum). Some of the most common phyla include arthropoda (insects), platyhelminthes (tapeworms), chordata (fishes, retile, birds, mammals), mollusca (snails), and porifera (sponges).
Phyla group together to form kingdoms--the topmost group. Depending on what source you use, this group consists of seven kingdoms including bacteria, crenarchaeota, euryarchaeota, protoctista, plantae, fungi and animalia.
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Cladistics
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A different method of grouping organisms, living or extinct, has gradually taken root over the Linnaean version, especially among professional biologists, palaeontologists and life scientists. The cladostic method of phylogenetic systematics, devised by the German biologist Willi Henning, uses the features of an organism as identification.
In the Linnaean system, the traits used to classify an organism are often a matter of discussion or opinion. In cladistics, these features are specifically identified as synapomorphies or unique derived characters. Since these unique characters appear only once, the organisms' descendants all share the same distinctive trait. Organisms containing the same unique features form a group called a clade. Subsequently, all members of a clade descended from the same common ancestor.
Cladograms
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Cladograms objectively establish an organisms' common origin. As individual characteristics form, clades split up into subclades. This creates a family tree structure called cladograms. This branching system shows where additional characteristics (groups) appear, and the evolutionary relationship between groups and organisms. Cladograms are less prone to opinion and errors than the Linnaean version; however, for everyday purposes, the Linnaean system is still in use.
Origin of Names
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Usually, scientific names of fossils derive from the Latin or another ancient language. The terms are international and recognized throughout the scientific world, no matter the native language spoken. The meaning of scientific names comes from an organisms' physical characteristics, geographic location when found or the name of the discoverer. Scientific names are occasionally cumbersome, so nicknames are given; for example, the 'Dudley bug', a species of trilobite called Calymene blumenbachi, derived its nickname from the region in England where the fossil species is particularly common.
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References
Resources
- Photo Credit Trilobite of Morocco - Period Devonian image by santosilva from Fotolia.com
