With a nod to Mike Habib, there are (at least) three tetrapods that can walk on water, each in their own way.
1. The famous Basilisk, otherwise known as the Jesus Christ lizard.
2. The Stormy Petrel, which actually just flies or glides (with a nice headwind) so close to the water that it dips its toes in.
3. The western Grebe, which, like the basilisk, actually gets up and runs on water (Fig. 3). Looks strenuous. Ends in a cool dip. Hope these guys get lucky because it is a mating ritual designed to show their skills. The wings are semi deployed and do not provide lift during this excursion, but this is not a flightless bird.
Another video of grebes from the BBS here.
Using the same technique (rapid leg movements) here is another video of yet another grebe ritual, performed belly to belly, largely out of the water.
These odd birds also have an unusual way of walking on the beach seen here in video (Fig. 4).
Western Grebes, like Jesus lizards, move their feet incredibly rapidly to remain above the water. I haven’t seen such rapid foot movements in large birds that actually takeoff from the water. I have searched for video of grebes taking off to no avail.
Addendum: January 4
Here is a video of the largest bird that can fly, the Kori bustard. The thing you may not be able to see unless you stop and start the video several times is the frantic kicking of the hindlimbs during the strenuous high angle take-off and acceleration to normal flight speed. It is reminiscent of the toe touches we’ve already seen pelicans do during takeoff, but there’s no water around. It’s just residual frantic leg movements timed with wing beats. So, is the pelican gaining speed with every toe touch on the water, or is it just more of the same frantic leg movement before the “landing gear” are finally stowed away at cruising speed?
Finally, an image of a duck spanking the water on its first downstroke (Fig. 5) and using the recoil to propel it into the sky. I’m sure the feet are also moving like crazy, but are they moving together, as in a leap, or are they running? It happens so fast, it’s all a blur.
All of these are instructive with regard to pterosaurs and their ability to take off from a floating configuration.
The grebe shows that an apparently top-heavy tetrapod can still get about on two legs and take-off from the water.
The duck shows that laterally extended wings can spank the water and contribute to a quick take-off.
The petrel shows that a headwind can provide enough airspeed to achieve flight at a very low to no groundspeed.
The basilisk shows a non-webbed foot moving rapidly in a sprawling configuration can achieve no-wind takeoff speeds. Pterosaurs had webs. All of these expand the possibilities for pterosaurs.
We’ll be taking a look at pterosaur thighs in the near future. [Rated P-G. ]
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.