The Lower Cretaceous Yixian Formation is home to the ctenochasmatid pterosaur Cathayopterus grabaui, named in 2006 by Xiaolin Wang and Zhonghe Zhou. The name means “China wing,” using the word “Cathay,” an archaic alternative name for China in many European languages, ultimately derived from the Khitan people of northern China.
Cathayopterus is only known from a single partially preserved skull, seen in dorsal view. It is extremely long and narrow, measuring about 28 cm (11 inches) in length, but only about 5 cm (2 inches) wide at its widest point. The snout makes up the majority of the skull, and was lined with dozens of long, needle-like teeth. These teeth were oriented to the side rather than vertically, interlocking with the teeth from the opposite jaw, forming a sieve. Unlike many ctenochasmatids, the tips of the jaw do not have a spoon-shaped expansion. Nothing else is known of the skeleton, but comparison to close relatives suggests a wingspan of about 170 cm (5.5 feet).
Ctenochasmatids are known from Upper Jurassic to Lower Cretaceous rocks from all over the world. They are part of a larger lineage known as the archaeopterodactyloids, the earliest major group of short-tailed pterosaurs known in the fossil record. Wang and Zhou noted that Cathayopterus can be differentiated from other ctenochasmatids by details of the toothrow and the size and shape of the nasoantorbital fenestra, a window in the snout housing the nostril and a large facial sinus. Ctenochasmatids like Cathayopterus used their teeth to filter small animals out of mud or water.
The Yixian Formation was deposited approximately 125 million years ago and records the ecosystem in great detail. It’s made up of lake and river deposits of an ancient temperate forest. The Yixian Formation is famous for its feathered dinosaurs, but also preserves a large number of pterosaur species.