The modern system of classification started in the 18^th century with Linnaeus. Carl Linné (Linnaeus), a Swede, set out to give every living thing, plant and animal a scientific name. The names are all in Latin because that was the international language at the time; all educated men used Latin in official correspondence. Linnaeus’ system involved giving each life form a double-barrelled name, called a Linnaean binomial. The first name is the genus, or generic name and the second is the species. Thus the domestic dog is Canis familiaris, and the wolf is Canis lupus. This example also demonstrates the other great advantage of this system which is that similar types of animals share the same generic name and thus it gives some idea of the relationships between animals.

Victorian scientists must have been very tidy, or at least very organised, because they were obsessed with finding order in the Natural World. They looked at the plants and animals and divided them up into hierarchical groups so that they were more manageable. They wanted to be able to place every living thing into its “natural order” in the world. As a result of this way of thinking they were also very keen on the “natural progression” of life from “lower” to “higher” forms.

The groups into which living things are placed are nested so that each large group will contain several smaller groups. Each group can also be subdivided or combined so that we can have the prefixes sub or super etc.

Phylum

An organisation called the International Commission for Zoological Nomenclature (ICZN) regulates the rules governing this system. When a new fossil species is named a type specimen or holotype must be designated. These are the specimens to which all finds are compared to determine if the new fossil belongs to an existing species. If a new find is named and then later discovered to belong to a previously named species the newer name is termed a junior synonym and declared invalid. Older names (senior synonyms) have historical priority. Probably the most famous example is Brontosaurus (1879) as a junior synonym of Apatosaurus (1877).

Before we go any further it is probably best to note that the only natural groups in nature are those of biological species. Biological species are defined as lifeforms which mate together to produce fertile offspring. The offspring of a horse and a donkey is a mule and it is sterile. All other divisions such as families and orders are artificial and merely for our convenience. It is also important to note that biological species can only be accurately defined in living animals (and even then it can be tricky); fossil species are not necessarily the same as biological species, they might be but we can never know.

The division of living things into the higher taxa is based on similarity. For fossil animals we have only the bones to go on but comparison of the bones of fossil animals to those of living ones can give us extra clues, for example if we find the bones of a fossil bird we can assume that in life it had feathers.

The idea of grouping animals on the basis of similarity is that this will tell us something about how they are related. This will lead us to the construction of a phylogeny or “tree of life” and they ways in which we do this are called phylogenetic systems.

If the use of classification is to determine relationships between taxa then at some stage each taxon related to another must share a common ancestor somewhere along the line. Thus in admitting relationships of varying degrees between different animals we are acknowledging that evolution must have taken place. So before we go any further in looking at systematics and methods we should probably take a detour into evolutionary terms and mechanisms.

Information provided by: http://carbon.cudenver.edu