Complex sentence: Ten subspecies of the original fifteen survive in the wild; an eleventh subspecies ("C. n. abingdoni") has only a single known living individual, kept in captivity and nicknamed Lonesome George.
Split into simpler sentences: Ten subspecies of the original fifteen survive in the wild. An eleventh subspecies ("C. n. abingdoni") has only a single known living individual, in captivity, nicknamed Lonesome George.