Complex sentence: Anglerfish typically have at least one long filament sprouting from the middle of the head; termed the "illicium", these are the detached and modified three first spines of the anterior dorsal fin.
Split into simpler sentences: Anglerfish typically have at least one long filament sprouting from the middle of their heads, termed the "illicium." The illicium are the detached and modified first three spines of the anterior dorsal fin.