Binomial Nomenclature – Naming and Classifying Organisms

Organisms such as animals, plants, fungi and single celled organisms are divided into several groupings that are used by scientists to classify them.  This is known as the taxonomic hierarchy with the largest groupings being known as a Kingdom, Animalia (all animals) for example.  The narrowest definition, putting aside the issue of varieties stated by many plant breeders, is the species.

All organisms have a two-part species name, this is comprised of the genus and then the specific or trivial name, such as the African lion being known as Panthero leo.  In this instance, Panthero relates to the genus to which African lions belong and the trivial or specific name identifying the species is leo.

Extant and Extinct

This two stage species name is referred to as the binomial and the naming of organisms using this methodology is called binomial nomenclature.

The taxonomic hierarchy is a “nested” series with each smaller grouping fitting into a larger grouping in the hierarchy, rather like a set of Russian dolls.  Extinct animals such as dinosaurs are classified using the same scientific methods as extant species (those that are still in existence today).  This is the accepted method of classifying life (although cladistics has added a new dimension or two), the principles of this form of classification were laid down by the Swedish botanist Carolus Linnaeus in the 18th Century.

Organisms should be classified to reflect evolutionary relationships, with each taxon representing organisms that share a common ancestor, very similar to the “Tree of Life” analogy.

Naming Taxa

Formerly, the names of all taxa should be written with a capital letter, except for the species or trivial name, this always begin with a lower case letter.  The species should always be written with the genus to accompany it, even if the genus is reduced to a single letter.  For example, P. leo for our African lion.  To be technically correct all names of genera and species are printed in italics.  If a scientist was preparing a hand-written note then they would underline the genus and the species name.

In formal scientific journals, the name of the scientist(s) person (or people) who first formerly described an organism is sometimes given.  For example, Mammuthus primigenius Blumenbach, indicates that the Woolly Mammoth or Tundra Mammoth as is it sometimes informally known as was named and described by the German scientist Blumenbach.

A Taxonomic Classification of Tyrannosaurus rex

Taxonomic Hierarchy of Tyrannosaurus rex
Category Taxon Contents of Taxon
Kingdom Animalia All animals
Phylum Chordata All vertebrates (plus some minor groups)
Class Reptilia All reptiles
Order Saurischia All lizard-hipped dinosaurs
Sub-Order Theropoda The “beast footed” dinosaurs mainly carnivores
Family Tyrannosauroidea All Tyrannosaurs and close relatives of Tyrannosaurs
Genus Tyrannosaurus The closest relatives of all to Tyrannosaurus rex
Species Tyrannosaurus rex The individual species known as T. rex

Table credit: Everything Dinosaur

Taxonomic Classification

Taxonomic classification is a complicated business, for example in the table above we have not included the Super-Order Dinosauria or subdivided the Tyrannosauroidea, classifying this element as a Super-Family and adding Tyrannosauridae as the smaller family element.  Differences in skull morphology (the shape of the skulls) between currently classified Tyrannosaurus rex specimens may indicate that some of the fossils known as Tyrannosaurus rex, may in the future be assigned to a different species.

For models of Tyrannosaurus rex: Tyrannosaurus rex and Other Models from Papo.

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