Orders in Infraclass Metatheria

Class Mammalia has two subclasses: Subclass Prototheria and Subclass Theria. Subclass Prototheria has only one order, Order Monotremata (monotremes), which has only two extant families. These families are F. Tachyglossidae—echidnas—and F. Ornithorhynchidae—platypuses. The second subclass, Subclass Theria, is made of up of two infraclasss: Infraclass Metatheria, which are all the marsupial mammals and Infraclass Eutheria, which includes all the placental mammals. There are in total 7 orders in Infraclass Metatheria, but in Mammalogy lab we are not including O. Paucituberculata (shrew opossums) and O. Notoryctemorphia (marsupial moles), as we have no available specimens. The orders we are focusing on are O. Diprotodontia, O. Peramelemorphia, O. Didelphimorphia, and O. Dasyuromorphia. These mammalian orders are all found in the Australian zone, with the exception of O. Didelphimorphia, which lives in the Nearctic & Neotropical zones. The seventh order is O. Microbiotheria, which only has a single species that lives in the Neotropical zone. O. Diprotodontia includes the diprotodont and syndactylous marsupials and the other three orders are polyprotodont and didactylous, with the exception of O. Peramelemorphia whose family (F. Peramelidae) are the only marsupials that are both polyprotodont and syndactylous.