Placental and Ungulate

Placental noun - Mammals having a placenta; all mammals except monotremes and marsupials.

Ungulate and placental are semantically related. In some cases you can replace term "Ungulate" with "Placental", this nouns are similar.

Ungulate noun - Any of a number of mammals with hooves that are superficially similar but not necessarily closely related taxonomically.

Placental and ungulate are semantically related. Sometimes you can use "Placental" instead a noun "Ungulate".