Insights into the origin of ‘shrew-like’ oposssums of South America are gained thanks to a new fossil from the Oligocene Salla Beds in Bolivia. The specimen described here consists of a partial rostrum, palate and postcanine teeth, and shows several generalized features (cranial and dental) in the context of the Paucituberculata. On this basis we recognize Evolestes hadrommatos gen. et sp. nov. In order to evaluate the affinities of the new taxon, we performed a phylogenetic analysis including representatives of the Caenolestidae, Pichipilus and allies (not regarded here as caenolestids), Palaeothentidae, and Abderitidae, with three outgroups. Evolestes is the basalmost ‘caenolestoid’, and provides clues to the morphological changes involved in the origin of caenolestids.

The family Thryonomyidae is known from the Eocene up to the present. Today, this group comprises just two closely related species, which are restricted to sub-Saharan Africa. However, various thryonomyids have been recorded in strata of Miocene age, when the group spread out of Africa eastward to southern Asia (Pakistan). A systematic revision and a cladistic analysis shows that 20 species can be referred to this family: Thryonomys swinderianus (Temninck), T. gregorianus (Thomas), Paraphiomys pigotti Andrews, P. occidentalis Lavocat, P. simonsi Wood, P. hopwoodi Lavocat, P. shipmani Denys et Jaeger, P. australis Mein, Pickford et Senut, P. roessneri Mein, Pickford et Senut, P. afarensis Geraads, Paraphiomys sp. nov. from Saudi Arabia López-Antoñanzas et Sen, P. renelavocati sp. nov., Neosciuromys africanus Stromer, Apodecter stromeri Hopwood, Paraulacodus indicus Hinton, Paraulacodus johanesi Jaeger, Michaux et Sabatier, Gaudeamus aegyptius Wood, Epiphiomys coryndoni Lavocat, Kochalia geespei (de Bruijn et Hussain), Paraphiomys sp. nov. from Saudi Arabia, and Paraphiomys orangeus Mein et Pickford. The unresolved basal position of Sacaresia moyaeponsi with respect to Metaphiomys schaubi and the clade comprising the above-cited species, suggest that this taxon should not be allocated to the family Thryonomyidae. A phylogenetic definition of the family Thryonomyidae is proposed as an outcome of the phylogenetic analysis: Epiphiomys corindoni, Thryonomys swinderianus, their most recent common ancestor and all its descendants (node-based taxon). © 2004 The Linnean Society of London, Zoological Journal of the Linnean Society, 2004, 142, 423–444.