The word “ropen” does not have the same meaning across all languages that have that word. In English, it is beginning to mean something like this: “a flying cryptid usually associated with Papua New Guinea and described like a giant Rhamphorhynchoid pterosaur.”
On Umboi Island, “ropen” often refers to the glow that flies horizontally between the highest mountains or from Mount Bel to a reef or from a reef to Mount Bel. The glow itself lasts for only about six seconds at a time. The stories about the flying creature seem to never die. Eyewitness accounts strongly suggest the ropen is a real animal, usually but not always nocturnal, that has a long tail, no feathers, and a wingspan much larger than any eagle or fruit bat. Some of the Umboi Island eyewitnesses who have been interviewed by American cryptozoologists are Gideon Koro, Wesley Koro, Mesa Augustin, Jonah Jim, and Mark Kau, among many others.
But in other parts of Papua New Guinea, in villages using other languages, “ropen” may mean something else. In one village near Wau (on the mainland), the word for a large or giant nocturnal flying creature that glows brightly—that is called “seklo-bali.” In that village, the word “ropen” is used for common birds. This is important to understand for anyone who becomes involved in cryptozoology.
So how should we investigate reports of apparent living pterosaurs? Concentrate on the description given by an eyewitness, not so much on the word uses to label the flying creature that was observed.
When investigating ghost lights, like the Marfa Lights of Texas, concentrate on details of descriptions in particular sightings, rather than on words used by the eyewitness to label what was seen.