These countries are: The United States of America, Mexico, Colombia, Ecuador, Peru, Venezuela, Brazil, Democratic Republic of Congo, South Africa, Madagascar, India, Malaysia, Indonesia, Philippines, Papua New Guinea, China and Australia. Fore detailed information please compare, e.g.: https://www.biodiversitya-z.org/content/megadiverse-countries or https://www.worldatlas.com/articles/ecologically-megadiverse-countries-of-the-world.html or  https://en.wikipedia.org/wiki/Megadiverse_countries (last visit: 2021-06-03).