Duck-billed platypus and Monotreme

Duck-billed platypus 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 duck-billed platypus are semantically related. In some cases you can use "Monotreme" instead a noun phrase "Duck-billed platypus".

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

Duck-billed platypus and monotreme are semantically related. Sometimes you can replace phrase "Duck-billed platypus" with "Monotreme", this terms are similar.