Yellow-footed tortoise

The yellow-footed tortoise (Chelonoidis denticulatus), also known as the Brazilian giant tortoise, is a species of tortoise in the family Testudinidae and is closely related to the red-footed tortoise (C. carbonarius). It is found in the Amazon Basin of South America. The species name has often been misspelled as denticulata, an error introduced in the 1980s when Chelonoidis was elevated to genus and mistakenly treated as feminine, an error recognized and fixed in 2017.

With an average length of 40 cm (15.75 in) and the largest known specimen at 94 cm (37 in), this is the sixth-largest tortoise species on Earth, after the Galapagos tortoise, the Aldabra tortoise, the African spurred tortoise (Geochelone sulcata, typical size 76 cm (30 in)), the leopard tortoise (Stigmochelys pardalis), and the Asian forest tortoise (Manouria emys), typical size 60 cm (23.6 in)).

The yellow-footed tortoise is also called the yellow-foot or yellow-legged tortoise, the Brazilian giant tortoise, or South American forest tortoise, as well as local names such as jabuti-tinga^{[what language is this?]}, jabuti^{[what language is this?]}, morrocoy^{[what language is this?]}, woyamou^{[what language is this?]} or wayamo^{[what language is this?]}, or some variation of jabuta^{[what language is this?]}. Many of the local names are shared with the similar red-footed tortoise.

Originally, Carl Linnaeus assigned all turtles and tortoises to the genus Testudo and described this species as Testudo denticulata in 1766. Soon the term Testudo was only being used for tortoises as opposed to all chelonians, with tortoises defined by completely terrestrial behaviors, heavy shells, and elephant-like limbs with nails but no visible toes. The species got several other names, as well, for several reasons such as difficulty in distinguishing it from the red-footed, confusion over locations, researchers thinking they had discovered a new species in collections or in the field, etc.

Leopold Fitzinger created the genus Geochelone for medium-to-large tortoises that did not come from the Mediterranean area (which remained Testudo), or have other special characteristics such as the hinged shells of the genus Kinixys. Fitzinger further used the term Chelonoidis as a subgenus to categorize Geochelone from South America. Neither term was widely used until they were resurrected by researchers such as Williams in 1960.

Researchers such as Roger Bour and Charles Crumly separated Geochelone into different genera based largely on their skulls. They created or re-established several genera: Aldabrachelys, Astrochelys, Cylindraspis, Indotestudo, Manouria, and Chelonoidis. The debate is on-going over the definitions and validity of some of these genera. Chelonoidis is primarily defined as being from South America, lacking a nuchal scute (the marginal scute located over the neck) and a large, undivided supracaudal (the scute or scutes directly over the tail).

Chelonoidis is made up of two very different-looking groups: the C. carbonarius group with the yellow-footed and red-footed tortoises; and the C. chilensis group with the Galapagos tortoises (C. niger), and the Chaco tortoise (C. chilensis). The taxonomic and evolutionary relationship of these two groups is poorly understood.

Yellow-footed tortoises are a large species – fifth-largest overall and third-largest mainland species, after the Aldabra giant tortoise (Aldabrachelys gigantea), Galapagos giant tortoise (Chelonoidis niger), African spurred tortoise, and Asian forest tortoise. Typical sizes average 40 cm (15.75 in), but much larger specimens are common. The largest known specimen is a female that was 94 cm (37 in) long. They closely resemble the red-footed tortoise, and can sometimes be difficult to tell apart, especially as a preserved specimen, which led to quite a bit of confusion over the names and ranges.