Orientognathus: a long-tailed pterosaur from Liaoning

Orientognathus chaoyangensis is known from a damaged, incomplete skeleton found in Liaoning, northeastern China. It combined a long tail, teeth behind a pointed toothless lower-jaw tip, and a short wing metacarpal relative to the humerus. The original analysis placed it among rhamphorhynchids. The bones are more precisely documented than the age of their particular bed.

Quick facts

A single skeleton from Chaoyang

Lü Junchang and five colleagues named Orientognathus chaoyangensis in 2015. The genus name refers to the east and to a jaw; the species name refers to Chaoyang. Holotype 41HIII-0418 is housed in the Henan Geological Museum in Zhengzhou. It is a damaged and incomplete skeleton, not a series of individuals of different ages.

Parts of the skull and lower jaw, wing bones and hindlimb survived. This is more evidence than an isolated tooth, yet it is no complete outline of the living animal. No skin membrane or body colour was reported for the slab. The shape of a living wing therefore depends in part on comparison with other pterosaurs.

Jaw and limb proportions

The front end of the lower jaw is slightly pointed and toothless, while teeth occur farther back. The approximately contemporary Fenghuangopterus has been compared by jaw and tooth characters, but such comparisons do not identify what this individual ate. No stomach contents or prey remains were described with the holotype.

The fourth wing metacarpal is about 0.38 times the humerus length. It is relatively short compared with some Jurassic forms, including Changchengopterus. The ulna is shorter than the preserved wing-finger phalanges, and the tibia is approximately as long as the femur. The original diagnosis and phylogenetic analysis used this combination of features rather than a single measurement.

An estimated wingspan of about 1.1 m applies to a reconstruction of the one known specimen. A fully extended wing was not measured on the slab, and the size range of adults is unknown. Wingspan alone would not establish body mass or flight speed.

The age and setting of the Tuchengzi beds

The slab came from the Tuchengzi Formation. Its original authors regarded its horizon as probably Late Jurassic. Subsequent uranium–lead dates from other formation levels in western Liaoning indicate deposition across the Jurassic–Cretaceous transition. Those dates do not pin the holotype itself to a particular Tithonian or Berriasian year.

The red beds record a continental setting that included river processes. A flying animal over a river is a possible scene, not a witnessed behaviour or a map of the precise discovery site. The long tail and wing bones identify an animal built for flight, but one skeleton cannot specify its routes, prey-catching method or time of activity.