Santamartamys rufodorsalis (Allen, 1899) is a rodent commonly called the red-crested tree rat. It is a medium-sized arboreal rat with soft, long pelage, and a crest of long hair on the crown between the ears. The dorsum is a deep rufous, and the sides, including the head and nose, are a paler yellowish orange. It is endemic to the Sierra Nevada de Santa Marta mountain range in the Caribbean region of Colombia. Known only from 2 museum specimens and 1 photographic record from 3 localities of Colombia, it may be one of the rarest rodents in South America. Globally, it is considered “Critically Endangered” by the International Union for Conservation of Nature.