Of course we don’t mean “fossil expert” when we use the phrase “pterosaur expert,” for this is not a paleontology blog but a cryptozoology blog. In regard to the ropen of Papua New Guinea, I think that Paul Nation and Garth Guessman are the most experienced explorers who have searched for living pterosaurs in that part of the world. But others have made great contributions.
I quote from Whitcomb’s Pterosaur Eyewitness blog, in particular the post titled, “Experts on Living Pterosaurs.” By the way, although Whitcomb does not have as much experience exploring remote areas of the world, he may have more access to eyewitnesses around the world than any other cryptozoologist, in regard to sightings of what seem to be modern pterosaurs, even though his interviews are mostly by emails.
About Paul Nation
Paul was instrumental in helping organize the two ropen expedition of 2004, both of which were searches on Umboi. He was unable to go along that year but had his own expedition with Jacob Kepas, late in 2006, deep in the mainland of Papua New Guinea. That expedition resulted in one daylight sighting of a giant indava by Kepas and several nighttime indava-light sightings by Nation. The video footage recorded by Nation in 2006, showing two glowing objects near the top of a ridge near Tawa Village, was found to be strange: not any camp fires or airplane lights or flash lights or meteors any other commonplace explanation.
About Garth Guessman
Guessman’s knowledge of Rhamphorhynchoid pterosaur fossils allowed him to notice an important clue . . . [Guessman and Woetzel] learned that the native traditions describe the ropen‘s tail as being stiff, never moving except near where it connects to the body. Guessman recognized that this relates to the stiffening extension rods of Rhamphorhynchoid vertebrae: all but a few vertebrae are locked into stiffness; the few that are flexible are near where the pterosaur’s tail connects to the body.
Others have made contributions, over the years, including Professor Peter Beach, James Blume, Jacob Kepas, and Phillip O’Donnell.
On the southern coast of Umboi Island, Papua New Guinea, a bay shelters Opai Beach, the same beach where 
