Binomial classification refers to the fact that each animal is known by two names, the genus name (i.e. Eurypterus) and the species name (i.e. remipes). There can be several species to one genus; the genus name can be used alone to refer to all species in the genus, but a species name is not used without the genus name. When written down they are both italicised, but only the genus is capitalised.

As well as belonging to a genus and species, each organism also belongs to a family, order, class and phylum, as part of what is known as Linnaean hierarchy. This names are always capitalised, but not italicised. Eurypterids are an order (Eurypterida) belonging to the class Chelicerata of the phylum Arthropoda. As well as these taxonomic levels an organism may be assigned to a number of subdivisions, such as a suborder or superfamily. Each rank seeks to unite organisms that share certain characters and are presumably closer related to each other. For example, eurypterids in the family Eurypteridae are more closely related to each other than they are to those of the family Dolichopteridae, however both these families are in the superfamily Eurypteroidea and are more closely related to each other than they are to eurypterids of the superfamily Mixopteroidea. You can see the basic layout of this hierarchy as presented in the taxonomic list below.

 

Phylum

Class

Order

Suborder

 

Superfamily

 

Family

 

Subfamily

Genus

 

species

 

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