Eothenomys fidelis

The individual chinchilla is very large, with an average body length of up to 120mm (slightly smaller in Sichuan), and is the largest individual in the chinchilla genus. The tail length is about 40% of the body length. The fur on the back of the body is dark gray and dense. There is no obvious boundary between the dorsal and ventral fur, and the ventral fur is slightly lighter in color, gray. The rear edge of the palatine bone of the skull is in the shape of a horizontal plate, without forming a longitudinal ridge, and without a pterygoid fossa. The first lower molar has a triangle running through the middle. The first upper molar has 4 angular processes on the inner side and 3 angular processes on the outer side.