According to Official Guinness Records,
The largest cave-dwelling bat is Bulmer’s fruit bat (Aproteles bulmerae), native to Papua New Guinea. Adult females have a wingspan of around 1 m (3 ft 3 in), and weigh approximately 600 g (21 oz). It was known to science only from 9,000-year-old fossils until 1977, when some modern-day preserved specimens were unexpectedly uncovered in a museum. Living specimens were later discovered in a huge cave within western Papua’s Hindenburg mountain range.
For a complete list of Unknown date records, please visit Unknown date Guinness Records in Papua New Guinea.