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Volant Maniraptors: more pterodactyl-ish than pterosaurs?

December 21, 2011

Microraptor as rendered in Planet Dinosaur. A gliding/soaring, aerial carnivore that kills with the feet, has teeth and a long bony tail, has a crest and barely can take off from the ground. Where have I heard that before...

Historically, and unfortunately still today on most popular culture inaccurate crap, pterosaurs were viewed as exclusively soaring abominations poorly adapted to flapping flight and incapable of taking off from the ground. Add in a rhamphorhynchid fetish and the image of the pterodactyl became that of toothed, long tailed wyverns, often swooping down from the Heavens to carry prey like eagles.

However, in modern times pterosaurs are understood to have been extremely efficient flyers, perhaps the tetrapods most adapted to aerial locomotion that have ever lived, with very complex wings, high metabolisms, catapult style launching. While long tails are turning out to be common among pterodactyloid taxa, their rostrums, toothed or not, are though to have been their weapons, and their feet were plain like those of bears and other plantigrade mammals, playing no role in grasping prey.

However, the traits once associated with pterosaurs have turned out to be common in non-ornithothorace flying dinosaurs:

– Like the classical pterodactyls, these animals were mostly gliders. While I think it’s obvious microraptorines and the like were capable of powered flight, it is very clear that the fact they couldn’t raise their arms much above the back got in the way, forcing these animals to rely mostly on gliding with occasional shallow strokes to stay airborne for longer. Indeed, microraptorines show extensive adaptations to dedicated gliding flight, and Rahonavis, with abnormally long arms, was likely a specialised soarer. By contrast, while pterosaurs were far more efficient at gliding, we’ve now realised that they show a much wider range of flight styles, and were clearly nearly always well adapted to powered flight, just like modern birds.

– The fact that non-ornithothorace maniraptors could not raise their arms much above the back also prevented ground based take-off, meaning that trees and cliffs were necessary as take-off spots. Since always that we’ve known that pterosaurs could raise their arms above the back, but the fact that they could take off quadrupedally like bats further shows that they were capable of ground based take-off, allowing them to colonise terrestrial niches without sacrificing flight.

– Deinonychosaurs had long tails and teeth, just like cartoon and toy pterodactyls. Seeveral species appearently also had crests, although ones made of feathers. True pterosaurs obviously also had teeth, long tails and crest, and in fact some ornithocheiroids and wukongopterids combined the three, so this trait is not unjustified in modern pterosaur iconography.

– The idea that pterosaurs could kill and carry prey eagle style was never taken seriously to begin with, as their feet are plain and barely able to grasp anything, just like those of plantigrade mammals. However, while carrying prey was also impossible for deinonychosaurs as their hallux was vestigial as in most theropods, their iconic killing claws certanly had a role in killing prey (although that exact role has been debated endlessly).

Confuciusornis silhouette by Matthew Martyniuk. As he pointed out, it does look like a classical pterodactyl sillhoutte. Nature's lampshading anyone?


One Comment leave one →
  1. December 22, 2011 5:30 am

    Very interesting observation.

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