Jianchangnathus

The Middle Jurassic Tiaojishan Formation of Liaoning Province, northeastern China is home to the scaphognathine pterosaur Jiangchangnathus robustus. Jiangchangnathus is known from a single, mostly complete skeleton named in 2012 by Xin Cheng and colleagues in 2012. Its name translates to “robust Jianchang [County] jaw” using the Ancient Greek word for jaw, “gnathos,” and the Latin word for robust, “robustus.” 

The skull is largely complete, although crushed and slightly disarticulated, and measures roughly 14 cm (5.5 inches) long. The snout is triangular in profile, with slightly upturned jaw tips and a low midline ridge. The lower jaws are extremely stout and have jaw tips that were downturned. The upper and lower teeth are widely spaced, stout, and cone-shaped. The upper and lower teeth are directed slightly forward, and would have interlocked with the teeth of the opposite jaw when closed. 

The rest of the skeleton is known from most of the neck vertebrae, a portion of the hip, a few tail vertebrae, and the majority of both wings and legs. In life, its wingspan was about 116 cm (46 inches), but Cheng and colleagues pointed out that the specimen wasn’t an adult at death, so would have been larger when fully grown. Its short hand bones as well as the presence of a long fifth toe show that Jiangchangnathus was a long-tailed pterosaur, even though only seven tail vertebrae are known. 

Cheng and colleagues noted several similarities between Jiangchangnathus and the Upper Jurassic German pterosaur Scaphognathus. Both pterosaurs share a deep tip to the lower jaw, a low midline ridge on the upper surface of the skull, a pear-shaped lower temporal fenestra, widely-spaced teeth, and a boomerang shaped second phalanx of the fifth toe. Traditionally scaphognathines have been characterized by their stout jaws, superficially boat-shaped skulls, widely-spaced teeth, and scalloped jaw margin between teeth and usually also include Sordes, Harpactognathus, and Fenghuangopterus. This group is not always recovered by phylogenetic analyses, with many scaphognathines showing close relationships to other rhamphorhynchids or other pterosaur groups entirely. 

Jiangchangnathus was a carnivore probably focusing on fish, as well as small terrestrial animals. Its stout jaws and teeth suggest it might have been able to focus on larger items than other pterosaurs its size. 

The Middle Jurassic Tiaojishan Formation was deposited in a subtropical forest environment with many lakes and rivers, perfect hunting grounds for Jiangchangnathus. The Tiaojishan has famously produced some of the oldest known feathered dinosaurs – such as the maniraptoran Anchiornis and the heterodontosaur Tianyulong – but also has an increasing number of pterosaur taxa including the wukongopterids, thought to be transitional between early long-tailed forms and the short-tailed pterodactyloids.