Complex sentence: The family name is from the Ancient Greek "krypto" ("hidden "), and"branch " ("gill"), which refer to how the members absorb oxygen through capillaries of their side-frills, which function as gills.
Split into simpler sentences: The family name is from the Ancient Greek "krypto" ("hidden "), and"branch " ("gill"). This is a reference to how the members absorb oxygen through capillaries of their side-frills, which function as gills.