In 1986 Eugen Kessler and Tiberiu Jurcsák named the genus and species Palaeocursornis biharicus for a fossil bone fragment found in the Lower Cretaceous Cornet locality in Bihor County, northwestern Romania. They initially considered the bone to be the distal femur of a ratite, giving it a genus name that translates to “ancient running bird,” with the species name honoring the county.
In 2012, Federico Agnolin and David Varricchio reinterpreted Palaeocursornis and concluded that the fossil was not from a femur or a bird, but was in fact the distal portion of a pterosaur humerus. It shares with pterosaur humeri a deep pneumatic foramen above the distal condyles, only two distal condyles, trochlea with an intertrochlear sulcus, a medially displaced posterior groove, and an ulnar tubercle that separates two concavities on the distal surface of the bone.
Agnolin and Varricchio noted that it seems to be most similar to azhdarchids as Palaeocursornis and azhdarchids share a D-shaped distal humerus, a capitulum with a very deep fossa, and a well-developed and deep trochlear groove.
The fossil itself is extremely small, only about 2.5 cm (1 inch) long, although it would have been about twice as long when complete. Comparison to other azhdarchoids suggests that Palaeocursornis would have a wingspan of only about 75 cm (30 inches), about the same size as a mallard.
Palaeocursornis lived at the very beginning of the Cretaceous Period, about 143 million years ago. At the time, Europe was made up of a number of small- to medium-sized subtropical islands surrounded by lagoons and shallow seas, similar to both Indonesia and the Bahamas. The Cornet locality itself was formed within an ancient limestone cave that was completely filled with sediments and numerous fossil bone fragments in the Early Cretaceous, buried under sediments, and then later exposed at the surface during the Quaternary.
Nothing is known of the diet of Palaeocursornis, but most other azhdarchoids were terrestrial carnivores so it’s likely that it was too. If Palaeocursornis is indeed an azhdarchid, it is both the earliest and smallest known member of that family.
