Placentalia
/ˌplas(ə)nˈteɪlɪə/Zoology
noun
With singular concord: a division of mammals comprising those in which the females develop a placenta, equivalent to the infraclass Eutheria. Treated as plural: placental mammals collectively; eutherians, as distinguished from marsupials and monotremes.
Origin
Mid 19th century; earliest use found in William T. Brande (1788–1866), chemist. From scientific Latin Placentalia, use as group name of neuter plural of placentalis, adjective.