ˌ ̷ ̷ ̷ ̷ˈthirēə noun plural
Usage: capitalized
Etymology: New Latin, from prot- + -theria
: a subclass of Mammalia that is coextensive with Monotremata or in some classifications includes both Monotremata and Allotheria and that is represented in the recent fauna solely by the egg-laying platypus and echidnas