Duckbill and Monotreme

Duckbill noun - Small densely furred aquatic monotreme of Australia and Tasmania having a broad bill and tail and webbed feet; only species in the family Ornithorhynchidae.

Monotreme and duckbill are semantically related. In some cases you can use "Monotreme" instead a noun "Duckbill".

Monotreme noun - The most primitive mammals comprising the only extant members of the subclass Prototheria.

Duckbill and monotreme are semantically related. Sometimes you can replace term "Duckbill" with "Monotreme", this nouns are similar.