Prejanopterus curvirostris is known from Lower Cretaceous rocks of the Leza Formation in La Rioja Province, Spain. Several partial specimens were first discovered in the 1980s, excavated in the 1990s, and finally named and described in 2010 by Carolina Fuentes Vidarte and Manuel Meijide Calvo. The genus name refers to the nearby town of Préjano, and the species refers to the apparent leftward curve of the snout.
The specimens are disarticulated and fragmentary, but represent at least five individuals. Prejanopterus is represented by portions of the skull, mandibles, most of the wing, the pelvis, and most of the hindlimbs.
The snout was extremely long, low, and narrow without any crests. There was a groove on the palate, as well as grooves on each side of the snout. These three grooves made the snout resemble the trilobed Mitsubishi logo in cross-section. There are at least 20 widely-spaced tooth positions on each side of the upper jaw. The teeth were stout cones, and each tooth socket appears to be raised slightly above the oral margin on a small, bony pedestal. Most amazingly, the two individuals with preserved snouts seem to show that the upper jaw gently curved to the left.
The lower jaws are only seen from the bottom, so nothing is known about the lower teeth. Interestingly, the lower jaws appear to be straight without the leftward curvature seen in the upper jaws, looking like a very skinny ‘V.’ When originally described, its wingspan was estimated to be over 4 meters (14 feet) using a method comparing femur size to wingspan.
A follow-up study by Xabier Pereda-Superbiola and colleagues in 2012 redescribed the material, and cast doubts on some details in the original description. They note that the most complete snout is broken into three fragments, and the leftward curvature in both specimens is probably postmortem distortion. They also note that by simply measuring the bones of the wings, it’s clear that the five specimens had wingspans between 1.5 and 2 meters (5 and 6.5 feet).
Fuentes Vidarte and Meijide Calvo did not assign Prejanopterus to any family, noting that they could not narrow down its relations beyond membership in Pterodactyloidea. The pterodactyloid lineage includes the short-tailed pterosaurs first emerging in the Late Jurassic and dominating Cretaceous skies. Pereda-Superbiola and colleagues conducted a phylogenetic analysis and found that it was part of the archaeopterodactyloid lineage, close to the suspension-feeding ctenochasmatids and gallodactylids. In his 2013 book, Mark Witton regarded Prejanopterus as a lonchodectid, noting that they had similar teeth in sockets set on bony pedestals. Lonchodectids are poorly known pterosaurs that have uncertain relationships within the pterodactyloids.
Prejanopterus is known from rocks formed in a lake more than 140 million years ago. At the time, the Iberian Peninsula was a large island between the newly formed Atlantic Ocean to the west and the Tethys Ocean to the east. The long and narrow snout with widely spaced teeth suggests that Prejanopterus may have probed tight spaces for small animals, or possibly scavenged carcasses. If the leftward curvature is actually real and not the result of postmortem distortion, Prejanopterus surely had an extremely strange and specialized feeding or social behavior the likes of which we can hardly imagine.