monotrematous
/ˌmɒnə(ʊ)ˈtriːmətəs/ /ˌmɒnə(ʊ)ˈtrɛmətəs/Zoology. Now rare
adjective
= monotreme; resembling the monotremes; (more generally) having a single aperture.
Origin
Mid 19th century; earliest use found in Richard Owen (1804–1892), comparative anatomist and palaeontologist. From Monotremata + -ous.