Echimyidae (spiny rats, tree rats and the coypu) is the most diverse family of extant South American hystricognath rodents (caviomorphs). Today, they live in tropical forests (Amazonian, coastal and Andean forests), occasionally in more open xeric habitats in the Cerrado and Caatinga of northern South America, and open areas across the southern portion of the continent (Myocastor). The Quaternary fossil record of this family remains poorly studied. Here, we describe the fossil echimyids found in karst deposits from southern Tocantins, northern Brazil. The analyzed specimens are assigned to Thrichomys sp., Makalata cf. didelphoides and Proechimys sp. This is the first time that a fossil of Makalata is reported. The Pleistocene record of echimyids from this area is represented by fragmentary remains, which hinders their determination at specific levels. The data reported here contributes to the understanding of the ancient diversity of rodents of this region, evidenced until now in other groups, such as the artiodactyls, cingulates, carnivores, marsupials, and squamate reptiles.

This work presents a new specimen of Pampatheriidae, which consists of a skull without the rostrum. The fossil comes from an outcrop along the Chuí Creek, Santa Vitória do Palmar Municipality, Rio Grande do Sul State (RS), Brazil. It was found in a sedimentary layer of the Lagoon System III, of 40 cm thickness and consisting predominantly of fine sand and up to 20-25% silt and clay, together with other vertebrate and invertebrate fossils, some of which are related to the mammalian taxa of the Late Pleistocene of the Pampean Region of Buenos Aires Province, Argentina, of Lujanian age. The comparison of the material with the Quaternary Brazilian pampatheres from the Lagoa Santa region, Minas Gerais; Jacobina, Bahia; and Rio Madeira, Rondônia; as well as with those from Uruguay and Argentina, permits the assignment of the specimen to Pampatherium humboldtii (Lund). The specimen represents the first cranial material of this species described from RS, as up until now P. humboldtii was represented mainly by isolated osteoderms. In addition, a preliminary revision of the Pampatheriidae material from the P.W. Lund Collection is presented.