Hovering pterosaurs?

Hovering pterosaurs?
Well, maybe, maybe not… but let’s explore the concept. I’ve animated the possibility  (Figs. 1, 2). Let’s look for problems.

Click to animate. Hovering pterosaur in fast motion.

Figure 1. Click to animate. Hovering pterosaur in fast motion. Perhaps animated not nearly as fast as necessary, here restricted by GIF animation standards. This animation has been reduced to 3 frames at 558 dpi width. The scale bar at 72 dpi is actual size, so this pterosaur is actual size here.

Hovering tiny pterosaur, BMNH 42736, provided with a much larger sternal complex than other tiny pterosaurs.

Figure 1. Click to animate and enlarge. Hovering tiny pterosaur, BMNH 42736 in slow motion (15 frames in the cycle). Here we see either the take-off or the landing phase, with most of the thrust of the wing elevating the pterosaur above the substrate. The hind limbs are foreshortened because they are extended toward and away from the viewer. As in hovering birds and bats, thrust/lift is generated throughout the flapping cycle.

Take-off
Perhaps all pterosaurs were able to hover only briefly, especially at take-off and landing. A vertical take-off would have facilitated lift-off from water, if floating prior to flying.

Landing
Hovering would also have facilitated accurate landings on small runways, like branches, by rapidly reducing forward airspeed by “raising the nose,” presenting the maximum area for drag and rotating the thrust component downward.

Rotation to the minimum drag flight configuration
From the hovering mode, simply dropping or extending the skull anteriorly, especially in long-necked forms, would have rotated the pterosaur to the traditional flight configuration, reducing drag to a minimum and rotating the thrust vector to the horizontal to maximize airspeed.

Tiny vs. giant
Perhaps certain tiny pterosaurs with a large sternal complex, like BMNH 42736, would have found hovering easier due to their tiny size. We can only image a giant pterosaur hovering at present. Perhaps it is unlikely or impossible, as in large birds.

The ability to hover must be considered the acme of flight in vertebrates, requiring the most sensitive and energetic sort of morphology and metabolism. We know that pterosaur wings were imbued with nerves and blood vessels, so there would have been a constant stream of instructions and feedback traveling back and forth to the brain.

Sternal complex variations
The sternum in birds differs greatly, from the giant sternum in hummingbirds, to the much smaller one in ostriches. Similarly, in pterosaurs the sternal complex varies greatly, from the giant broad one in Dendrorhynchoides to the rather tiny ones in Dorygnathus. This may have something to do with hovering and vertical take-off.  Not sure. Makes sense.

Flight membrane
This hypothesis and model is shown with the narrow-chord wing membrane found in all known pterosaurs that preserve the wing membrane. A narrower wing membrane can flap more quickly due to less drag.

I really don’t see any problems having tiny pterosaurs hover — especially during take-off and landing — and thus for only short periods of time. Perhaps the best of them had the deepest or largest sternal complex. Perhaps these could hover for longer periods of time.

Notably, the vampire pterosaur, Jeholopterus, had a very small sternal complex. So, given this hypothesis, it is unlikely that it hovered the way Dendrorhynchoides and other anurognathids could have. Instead, Jeholopterus more likely landed with a thud.

As always, I encourage readers to see specimens, make observations and come to your own conclusions. Test. Test. And test again.

Evidence and support in the form of nexus, pdf and jpeg files will be sent to all who request additional data.

2 thoughts on “Hovering pterosaurs?

  1. Are pterosaur shoulder joints capable of the figure of 8 motion hummingbirds use to turn but the up and downstroke into a lifting stroke? It needs the shoulder joint to be able to rotate 180 degrees.

  2. I’m not proposing that any pterosaur can do all the time what a hummingbird does all the time. I am simply rotating the axis of thrust for take-off and landing, where groundspeed is near zero for a short amount of time. The flight stroke remains the same as in horizontal flight. The subtleties will have to be figured out with uncrushed specimens, difficult to find and determine in tiny Solnhofen pterosaurs.

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