New morphological observations on Triassic pterosaurs

Abstract

AbstractSince 1973, about 20 specimens of Triassic pterosaurs have been found in northern Italy, Austria and Greenland, belonging toEudimorphodon, Peteinosaurus, PreondactylusandAustriadactylus. Their age is middle to late Norian andEudimorphodonis the most common genus. The restudy of the specimens shows thatPeteinosauruspresents trimorphodonty in the lower jaw and a fibula unreduced in length, distally expanded and fused to the tibiotarsus above the lateral condyle. Specimen MCSNB 3359 does not show diagnostic features ofPeteinosaurusand is referred to it with doubt, whereas MCSNB 3496 is notEudimorphodonbutPeteinosaurus. Preondactylus, Peteinosaurus, ?PeteinosaurusandDimorphodoncould form a monophyletic group.The tarsus of Triassic pterosaurs consists of two proximal tarsals, which fuse to the tibia during ontogeny, forming a tibiotarsus, and two distal tarsals. The larger of the two proximal tarsals was probably the calcaneum. The lateral condyle of the tibiotarsus is larger or more well formed than the medial one. The shape of the distal tarsals is similar to that of the distal tarsals inDimorphodon. The metatarsals did not spread and the foot was ectaxonic; metacarpal length increases from metacarpal I to IV. This suggests that footprints of Triassic pterosaurs were different fromPteraichnus-like footprints.Some features are unique to Triassic pterosaurs. andAustriadactylushave a multicuspid dentition,Peteinosaurushas cuspules in the distal teeth of the lower jaw andPreondactylushas serrated maxillary teeth. This could be a convergent feature or symplesiomorphic for their clade. andAustriadactylushave very large maxillary teeth below the ascending process of the maxilla. and possiblyPreondactylusdo not have the bundles of elongated caudal zygapophyseal and haemapophyseal processes which are present inPeteinosaurusand in the Jurassic long-tailed pterosaurs.