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Tropeognathus landfall by paleopeter Tropeognathus landfall by paleopeter

Tropeognathus. Species: T. mesembrinus, T. robustus. 

Meaning of name: Keel jaw.

Brazil, Early Cretaceous. 

Classification: Pterosauria, Pterodactyloidea, Ornithocheiroidea. 

Wingspan: 6.2m. 

Lifestyle: Piscivore. 

I have updated Tropeognathus to illustrate the Propatagium (membrane in front of the arm) attached to the first finger, enclosing a forwards pointing Pteroid bone & webbed hands, after a conversation with the Palaeontologist David Martill who I was privileged to meet at a paleo convention on the Isle of Wight.
David wasn’t advocating a forward pointing Pteroid but that the Propatagium would have been strong enough to attach to the hand & there is evidence of webbed fingers in some species.  I think it’s probable that species that regularly took off from water would have webbed fingers & if the Propatagium was attached to the hand this would have worked like a paddle to aid take-off as well as the aerodynamic advantages.

Early Rhamphorhynchidae had long tails & neutral stability. Then the Pterodactyloids lost their tails, generally elongated their necks & enlarged their skulls & to crown it all evolved a large crest on top of that. Many retained their heavy teeth with no attempt to evolve a lightweight keratinous beak & many had such large jaws they could fill their little stomachs with one good mouthful & sunbathe for the rest of the day! These changes & how they affect their flight characteristics haven’t been clearly explained. Swept forward wings would stabilize them but aren’t efficient at low speeds. Upward sloped legs, feet & Uropatagium would stabilize in flight but produce a great deal of negative lift. As it isn’t in the nature of nature to be inefficient then perhaps there is another explanation for their excessively front heavy posture. I suspect that palaeontologists have overestimated the stiffness of pterosaurs’ necks, if they could pull their heads back over their shoulders that would efficiently overcome the stability problem. After 160 million years of evolution even an elephant could evolve flight & yet we are supposed to believe that many Mesozoic reptiles were handicapped with stiff necks i.e. Sauropods, Plesiosaurs & Pterosaurs & never managed to overcome these setbacks. That is why I was tempted to draw a pterosaur with an enlarged Propatagium in an attempt to solve this problem.




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December 1, 2013
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