A vulnerable species is a species basically categorized by the International Union for Conservation of Nature as they are likely to become endangered unless the conditions that are threatening its survival and reproduction improve. An endangered species is a species which has been categorized as very likely to get extinct. by the IUCN. An extinct in the wild species is a species that has been categorized by the International Union for Conservation of Nature as known only by living members kept as a naturalized population outside its historic range due to extensive habitat loss. Living fossil is a taxon that closely resembles organisms otherwise known only from the fossil record.