Additional embryonic membrane to store nitrogen wastes

Question

Which is the additional embryonic membrane whose purpose is to store nitrogen wastes of the embryo? Is this function existed in placental mammalian embryos?

Answer 1

The allantois is the additional embryonic membrane whose function is to store up excretes of the embryo.

In placental mammals, the allantois is existed however it does not exert that function as the embryonic wastes are composed by the mother’s body via the placenta.