Pterosaur Take-Off from Water

Earlier we talked about various pterosaur takeoff techniques from dry land. Some techniques make sense. Others, like the forelimb launch, are more risky.

Some birds (like shearwaters) have no trouble diving into and flying out of water. Others, like ducks and geese, float upon the surface then take-off whenever they want to. Others, like frigate birds, take quick baths.

If pterosaurs ever landed on the water, were they able to take-off again? And if so, how did they do it? These are good questions for which answers can only come through pure speculation, drawing on physics, analogy and imagination.

Dr. Mike Habib has worked out the problem following the pattern of his forelimb launch from land. There’s an update here. Dr. Mark Witton illustrated the feat. Habib thinks it would take several leaps from the water before enough speed could be attained to generate lift. He reported at pterosaur-net.blogspot, “Anhanguerids probably took multiple hops across the water surface to launch, but our calculations suggest that most of the actual energy expenditure was spent escaping the surface tension.” Unfortunately Witton’s drawings never get to the point of actually extending the wings, leaving the pterosaur flopping about on the surface, wing fingers always down. Not sure how anything can generate sufficient thrust from a standing start and several dunks before flapping. Seems rather awkward at best. And when do the wings actually open?

Pelican Take-off from Water
Do pelicans give us some idea how a pterosaur could have taken off from a standing start while floating on the surface? Click the image to see the YouTube video of a pelican taking off from water. Apparently keeping the wings dry is important. They rise first.

Pelican take-off sequence from water.

Figure 2. Pelican take-off sequence from water. Click to enlarge. Besides flapping, the pelican runs furiously along the surface of the water until sufficient airspeed is attained to rise above the surface. At 5 and 7 the wings are parallel with the water's surface. You can see it takes quite a few flaps and paddles to get this ornithochierid-sized bird off the water and into the air at a steady clip. One big, well-timed, extremely fast flap just won't do it.

Are Pelicans Good Analogs to Pterosaurs?
Let’s put the pterosaur in the water now and see if it could lift its wings and take-off like a pelican. The pelican uses running legs and webbed feet to provide extra thrust during takeoff. The small feet of ornithochierids would not have been as helpful. Even so, the legs probably ran fast, like a basilisk (Jesus lizard) doing what they could. Most of the thrust would have to come from the flapping wings.

 

Pterosaur water launch

Figure 3. Click to enlarge. Ornithocheirid water launch sequence in the pattern of a pelican launch. LIke ducks, geese and pelicans, pterosaur probably floated high in the water. Here the wings rise first and unfold in an unhurried fashion, keeping dry and unencumbered by swirling waters. Then the legs run furiously, like a Jesus lizard, but with such tiny feet, they were not much help in generating forward motion. The huge wings, however, did create great drafts of air, thrusting the pterosaur forward until sufficient airspeed was attained, as in the pelican.

We Will Never Know Certain Aspects of Pterosaur Behaviour
We can only guess. Hopefully we will be able to discard those hypotheses with the longest list of problems.

Look for Mark Witton’s book on pterosaurs coming out (more or less) soon. The pterosaur launch from water illustration will be published there.

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.

4 thoughts on “Pterosaur Take-Off from Water

  1. Dave,

    You were kind enough to ask for permission to use my image in this post, and I asked you not to for what we both agreed were just reasons. You have used it anyway. Please remove this image from the post in keeping with our original agreement.

    I am a little baffled why you feel the need to use this very low resolution version of the image, anyway: you have plenty of your own skeletals you could use for this purpose.

    Mark

      • It’s always helpful to hear how things evolved in disagreements.

        First of all, it’s always good policy in scientific testing to compare apples to apples. In other words, to avoid changing formulas, etc. while trying to duplicate or test results. That’s why I originally was going to publish a side-by-side comparison using Mark’s own images, one reconfigured, one not, to show an alternate launch hypothesis. US copyright law permits such Fair Usage in cases of scientific experiments, teaching, etc. (all non-profit). Even so, I wrote to Mark Witton prior to publication to seek his permission to republish from a web image he created. He declined giving permission (that was a first in my experience) due to the upcoming publication of the image in his book. I acquiesed, not giving another thought to the second image, one which bore little resemblance to the original, but used retouched elements Mark created therein. Mark objected (see above). I acceded to his request immediately, replacing the image in its entireity. So, at every turn I thought I was doing the right thing and was well within the bounds of Fair Usage. Hope this clears things up for all concerned.

        David Peters

  2. Thanks Dave, I appreciate that. Once the image has been published in either my book or the Habib/Cunningham paper on water launch, it’s fair game.

    Also, the lack of finger extension is something of an oversight. I’ll add some to the terminal launch phase for the final version of the illustration: well done for spotting it.

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