Duckbill and Egg-laying mammal

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.

Egg-laying mammal and duckbill are semantically related. In some cases you can use "Egg-laying mammal" instead a noun "Duckbill".

Egg-laying mammal noun - The most primitive mammals comprising the only extant members of the subclass Prototheria.

Duckbill and egg-laying mammal are semantically related. Sometimes you can replace term "Duckbill" with "Egg-laying mammal", this terms are similar.