Complex sentence: The line consists of many types of animals, usually sold in sets composed of a family of four animals of the same species, or "two-furs" which are two separate toys sold together (but not always of the same species).
Split into simpler sentences: The line consists of many types of animals, usually sold in sets. They are composed of a family of four animals of the same species, or "two-furs," which are two separate toys sold together (but not always of the same species).