"Prototheria (/\u02CCpro\u028At\u0275\u02C8\u03B8\u026A\u0259ri\u0259/; from Greek \u03C0\u03C1\u03CE\u03C4\u03BF\u03C2, pr\u014Dtos, first, + \u03B8\u03AE\u03C1, th\u0113r, wild animal) is a taxonomic group, or taxon, to which the order Monotremata belongs. It is conventionally ranked as a subclass within the mammals; see Yinotheria \u00A7\u2009History of classification.Most of the animals in this group are extinct. The egg-laying monotremes are known from fossils of the Cretaceous and Cenozoic periods; they are represented today by the platypus and several species of echidna."@en . . .