Hasandong Boreopterid

In 2020 Park Jin-Young and colleagues described an isolated pterosaur wing finger phalanx as a probable boreopterid. The remains were found in rocks of the Lower Cretaceous Hasandong Formation on Dae Island, off the southern coast of South Korea.

The bone is thought to represent the proximal portion of the second phalanx off the left wing finger. It’s approximately 20 cm (8 inches) long, but would have been roughly double that length when complete. Park and colleagues compared the articular surface of the bone to a number of other pterosaurs, and found it was most similar to dsungaripterids and boreopterids. 

The team considered a dsungaripterid affinity unlikely however, as this bone has relatively thin cortical bone, unlike many dsungaripterids. The phalanx is quite similar in size and shape to the boreopterid Zhenyuanopterus, but differs in fine details. Without more remains, it’s impossible to know if those differences were individual variation, or of taxonomic importance. Nothing else is known of the skeleton of this Korean pterosaur, but comparison to Zhenyuanopterus suggests a wingspan of about 4.3 m (14 feet).

Boreopterids had extremely long and narrow jaws lined with dozens of needle-shaped teeth directed vertically, rather than to the side as in most ctenochasmatids; another family with numerous needle-shaped teeth. One species of boreopterid, Zhenyuanopterus also had a low sagittal crest on the upper surface of the rear part of its snout. Boreopterids are thought to have been predators of fish or small invertebrates, using their teeth to puncture or trap prey. At Pteros, we have used Zhenyuanopterus as a model to reconstruct the Korean animal. 

Although it’s only known from a fragment, this is the first record of a boreopterid outside of China’s Liaoning Formation, and the first from sediments deposited by rivers. This expands the geographic and habitat range of boreopterids, but does not greatly expand the temporal range, as the Hasandong Formation was deposited at roughly the same time as the Yixian.