Pterosaurs Were NOT Birds, Especially Floating in Water

The posture of floating pterosaurs: Ecological implications for inhabiting marine and freshwater habitats

Authors:

David WE Hone and Donald M Henderson

Abstract:

The highly pneumatic skeleton of the extinct flying pterosaurs suggests that they would float high up on open water, but in a posture rather different to that of birds. However, the exact posture of the body and head remains unknown and would be critical for an ocean going pterosaur forced onto the waters’ surface or animals that alighted to feed. Using computational methods with recent models and body mass estimates for four pterosaur genera – Dimorphodon, Rhamphorhynchus, Pteranodon and Dsungaripterus we show that the floating posture of pterodactyloid pterosaurs led to the head, neck and body being horizontal with the ventral 1/4 to 1/3 being immersed, and the external nares being almost at, or potentially partially below, the waterline that could have left them vulnerable to drowning. The floatation methods were verified using a model of a Canada goose (Branta canadensis) that is able to successfully replicate the expected orientation and depth of immersion of the bird. While there is convincing evidence for a number of pterosaurs foraging in marine and freshwater environments, these results suggest many did not regularly rest on the surface of the water and if immersed would need to take off again rapidly. The high numbers of fossils of juvenile pterosaurs compared to the terrestrial Mesozoic dinosaurs suggests that this may be linked to their poor ability in water.