Eutherian and Flying lemur

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

Flying lemur and eutherian are semantically related. In some cases you can replace phrase "Flying lemur" with "Eutherian", this terms are similar.

Flying lemur noun - Arboreal nocturnal mammal of southeast Asia and the Philippines resembling a lemur and having a fold of skin on each side from neck to tail that is used for long gliding leaps.

Eutherian and flying lemur are semantically related. You can use "Eutherian" instead a noun phrase "Flying lemur".