Paucituberculata
Paucituberculata is an order of South American marsupials. Although currently represented only by the seven living species of shrew opossums, this order was formerly much more diverse, with more than 60 extinct species named from the fossil record, particularly from the late Oligocene to early Miocene epochs. The earliest paucituberculatans date to the late Paleocene (Itaboraian South American land mammal age). The group went through a pronounced decline in the middle Miocene epoch, which resulted in the extinction of all families of this order except for the living Caenolestidae (including Pichipilidae, Palaeothentidae, and Abderitidae). Classification. It is one of  two clades of Ameridelphia, a paraphyletic group; genetic studies have shown these animals to be a sister group to Australidelphia (i.e., Didelphimorphia branched off first). The Paucituberculata were once considered to be closely related to South American polydolopimorph metatherians, however phylogenetic analyses have found this is not true. Subdivision. The order is subdivided into: