Whenever the common names of turtles occur in the professional or hobbyist literature they are invariably accompanied by their scientific name. These scientific names are important because they are directly linked to one or more "type" or reference specimens that are stored in major museum collections and are standard throughout the world. The identity of a turtle can be confirmed because it can be compared directly to type specimens or their published descriptions.

However, the scientific name fulfills a more important function than just being a label. The name gives, or should give, scientific information about the likely "kin" and/or evolutionary relationships between the named species and other species. In this sense a scientific name is not fixed but is a hypothesis based on the available facts. Like all scientific hypotheses it is subject to testing, and may be changed when new evidence appears or an error is detected. While hobbyists and lay readers may find periodic name changes frustrating, they actually represent improvements in our knowledge and understanding of the species in question.

Take the desert tortoise, known to many of us as Gopherus agassizii. Gopherus is a uniquely North American genus consisting of tortoises that are structurally adapted to a burrowing and digging lifestyle. Three other species of gopher tortoise are alive today - the Texas tortoise (berlandieri), the Mexican Bolson tortoise (flavomarginatus), and the Florida gopher tortoise (polyphemus). Over the years, experts in the field came to realize that the genus Gopherus includes two sorts of tortoise, separable on the basis of differences in their bone and shell structure. The desert and Texas tortoises fall in one group and the gopher and Bolson tortoise in the other. In 1982, John Bramble suggested that these differences were great enough to warrant recognition of two separate genera and proposed the genus Scaptochelys (from the Greek meaning digger-tortoise) that would include the desert and Texas tortoises.

However, when the Texas and desert tortoises were first described in the nineteenth century they had been given the genus name Xerobates (from the Greek xero meaning "dry" and bates meaning "one who walks or haunts"). Under the rules used in assigning scientific names Xerobates took priority over Scaptochelys because it had been used first. So, the "new" name of the Texas tortoise became Xerobates berlandieri and the desert tortoise becameXerobates agassizii. The Florida gopher tortoise and the closely related Mexican Bolson tortoise remained in the genus Gopherus. However, not all authorities accept the new genus (it took 100 years or so before even Gopherus was widely recognized as valid!). This confusion explains why the desert tortoise is sometimes listed as Gopherus (Xerobates) agassizii, a technically "untidy" moniker because it suggests that Xerobates is a sub-genus of Gopherus and not a separate genus. No doubt this will be clarified in the future when more is known about these tortoises.

Scientific names consist of the genus (generic name) followed by a specific or species name. Occasionally a third name is added to designate so-called sub-species, populations of the species with distinct characteristics. For more precision, the scientific name is often followed by the name of the person who first assigned the name and description. For example, the desert tortoise may be referred to as Xerobates agassizii Cooper. If the scientific name has undergone changes since the original description, then the describer's name is placed in parenthesis. For example, if the desert tortoise is in the genus Gopherus then the name becomes Gopherus agassizii (Cooper) because Cooper designated it as Xerobates in his original description.

Scientific names are often Latinized forms of the name of a person connected with the discovery of the plant or animal, or may describe some quality, such as coloration, size, or habitat. Here are explanations and background to the names of the four North American tortoises.