Paucituberculata

Paucituberculata is an order of South American marsupials. Although currently represented only by the eight 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. 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 other South American diprotodont metatherians, specifically the Polydolopimorphia however phylogenetic analyses have found these two groups are not closely related. The order is subdivided into: