Trinomys yonenagae (Rocha, 1995), Yonenaga's Atlantic spiny-rat, is a small caviomorph rodent locally known as “rabo-de-facho” (Portuguese) due to its setiform hairs and long penciled tail. It is endemic to the sand dune field of the arid Brazilian Caatinga, on the west side of the Middle São Francisco River, from Barra to Pilão Arcado (Bahia, Brazil). The long hind feet, the fossorial and colonial habits, and the inflated tympanic bullae are cited as adaptations to the hot and sandy habitat. One of 10 species in the genus, it is listed as “Endangered” by the International Union for Conservation of Nature and Natural Resources because it is found only at a single location of less than 5,000 km² and its habitat continues to decline due to the extraction of sand.