cladotherian

Cladotherians are a group of mammals that includes the monotremes (egg-laying mammals), marsupials (pouched mammals), and placentals (mammals with a placenta). They are characterized by the presence of a cloaca, a single opening through which waste materials, sperm, and eggs are expelled. This feature is a synapomorphy, a shared derived characteristic, that unites these groups. Cladotherians are believed to have diverged from the therapsids, a group of synapsid mammals, during the Permian period. The cladotherian lineage is further divided into two major groups: the metatherians (marsupials and monotremes) and the eutherians (placentals). The metatherians are characterized by the presence of a marsupium, a pouch in which the young develop, while the eutherians are characterized by the presence of a placenta, which allows for more advanced fetal development. The cladotherians are a diverse group of mammals that have adapted to a wide range of environments and ecological niches.