Stu Bonk comments 12-22-25

Suprised me,
the images Stu Bonk sent traveled along with his comments!

“I don’t see what you see and I am an amateur 2D animator. For other readers to judge, here is the animation:”

Here they are (if you can’t see them, I can email the screenshots if you’d like):

Thank you, Stu, for providing these images.
This shows an keen interest on your part. Please note the axis of the acetabulum is lateral. The axis of the femora head is medial. Those align. In the animation process the body is one layer. The various leg positions are another layer. Are you saying I was a mm off on the one, but okay on the others?

“I don’t know the ‘actual’ range. What is your precision requirement? This is a crushed fossil. This was the first time on the planet that Sharovipteryx was animated as a biped. The range was set at a little above the prepubis and a little behind it.”

Considering the condition of Sharovipteryx’s fossil, I will give you an exception. I won’t, however, make an exception for any of your animations using pterosaurs as a decent chunk of them are based on taxa with good 3-dimensional remains. Some also have research done into their musculature.

>> Have any done comparisons to lepidosaur musculature? or did they use birds? Or did they use muscle attachment points? If so, how did the prepubis figure into their restorations = best guesses?

“However, your job is not to wonder if I did something wrong, nor to judge based on criteria I was not obligated to, but to repeat what I did and show I did something wrong. In other words: falsify what I did. That’s the scientific method. Be a player, not a spectator. “I’m not convinced” is not a scientific reply.”

3 things:

1. 1. What you describe as not being part of the scientific method is actually a very common practice in science. This is what peer-review is in a lot of cases.
      >> Peer review rarely if ever employs the scientific method. By that I mean have you ever seen or heard of any referee repeating the experiment (= repeating the animation) or observation = requesting the specimen for their own examination. In my experience referees follow their feelings. One said, “you didn’t look at the fossil long enough.’ On another paper the same referee, David Hone, wrote, “you didn’t examine the specimens a second time.” See what I mean? This is reality. This is gatekeeping. You’re going to have to put away your ideals when it comes to paleontologists. Question: have you ever submitted a manuscript and figures for publication? A Yes or No will suffice.

1. 1. You use your reconstructions of pterosaur and supposed pterosaur ancestor locomotion when attempting to falsify the scientific consensus around pterosaur biomechanics and locomotion. This means you have the burden of proof to show that this is actually biomechanically possible.
      >> When showing fossils as they lived and locomoted there is no ‘proof’. Only a hypothesis that then requires confirmation, refutation or modification.

1. 1. By this logic, aren’t you also a spectator when it comes to papers on biomechanics? You haven’t falsified the results from studies on pterosaur biomechanics outside of your beliefs which you haven’t proven to be the case biomechanically.
      >> I presented these arguments in 2011: https://pterosaurheresies.wordpress.com/2011/07/20/seven-problems-with-the-pterosaur-wing-launch-hypothesis/  Please note that when pterosaurs quad launch they do so with wings folded (that makes it tough to use them for thrust and lift as in the competing bird-like launch hypothesis). They do so with wing finger planted on the ground and stretching that tendon so it can snap back when released, like a grasshopper leg. That never happens. Never. Only the free fingers touch the substrate, so no tendon snap.

“Here’s a giant pterosaur running in the manner of Sharovipteryx animated – but using its wings like a fat chicken for thrust and lift – though not enough to fly”

How do you know that type of locomotion would work for an animal that weighs over 300 pounds? Also, considering how heavy the skull is, I doubt Quetz would be able to stably run in that fashion.

>> Doubt is not the scienfic method. Show how Quetz would not be able to stably run in that fashion. How heavy was the skull? What if it was made of something akin to styrafoam or balsa wood? Everything about pterosaurs was extremely thin and supported by needle-like internal struts where necessary. For other readers: animation and other figures are here: https://pterosaurheresies.wordpress.com/2011/07/20/seven-problems-with-the-pterosaur-wing-launch-hypothesis/

“Anhanguera  is much larger and different: it has huge wings that develop lift in a breeze or with thrust.”

My example with Anhanguera applies just as well to any pterosaur you say could run.

>> I say Anhanguera was a poor runner based on having the smallest feet relative to body size of any pterosaur. Worse than all other pterosaurs.

“Also note the extremely small feet on Anhanguera (linked above). Those feet are not made for running. They are vestiges.”

How on earth are the feet vestigial? This is not an aquatic animal nor is it a snake. An animal like Anhanguera will always have to use its feet no matter what. It still needs to nest. When young, they still need to use their feet to move before they can learn how to fly. After landing, they still need to use their feet to take off. Also, I don’t think any of the sediments Anhanguera has been found in are open ocean as the Romualdo Formation is on a shoreline while the Kem Kem Beds are freshwater.

>> Take another look at those feet. They are, if not vestiges, minimized. When young pterosaurs were able to fly shortly after hatching. They had the proportions of an adult only 8x smaller. That is a rule that has not yet been broken based on available data. See: http://www.reptileevolution.com/anhanguera.htm

“Please remember that pterosaur wing membranes are embedded with fibers. Those on Cosesaurus are extremely short and rudimentary. We are lucky to have them. Baby steps.

Pterosaur wing membranes are made up of fibers, yes, but those fibers aren’t the same as the pycnofibers present also on pterosaurs and you depict Cosesaurus with.

>> ‘Those fibers are not the same’ is not an argument. It’s a denial without evidence. Please present data in the form of images from the fossil in Barcelona or your interpretation of photos. To your point, those fibers are shorter, as expected in a transitional taxa. Baby steps = microevolution. Feathers did not appear ready for flight on birds either.

“All reconstructions of mine show the feet placed beneath the center of balance = shoulder joint in pterosaurs, as in birds.”

Henderson, 2024 found the center of gravity/mass on pterosaurs and different groupings of pterosaurs had their center of gravity in different locations with them not always being beneath the shoulder. 4 of the 18 tested pterosaurs had their center of mass directly beneath their shoulder joint: Pteranodon, Nyctosaurus, Anhanguera, and Thalassodromeus. (the paper isn’t open access, but I do have the pdf if you want it)

>> Please provide titles with citations, especially with authors with common last names. I presume you mean “Using your head — cranial steering in pterosaurs”, abstract available on ResearchGate.net. Please note that Henderson is fond of using freehand cartoons for his pterosaurs and gives them deep chord wing membranes attached to the ankles. That gives him no authority to determine center of balance. Please drop Henderson a note and inquire why he employs cartoons in science. And ask his referees and editors why this is permitted and encouraged.

“I note you did not mention that competing quad-launch hypothesis for pterosaurs. It was based on cheating the anatomy of pterosaurs, (SEE LINK ABOVE)”

I’m glad I’m writing this reply late or else I wouldn’t have been able to make this point. A new paper came out a few days back (Ceroula et al., 2025) which I sent you via email when it came out. The paper found that the bending strength index and axial strength index of pterosaur humeri and femurs were in line with both quadrupedal locomotion and the quad launch hypothesis. One thing that the paper found is that the indexes for the humeri and femurs in pterosaurs were similar to many modern quadrupedal animals (e.g. white rhino, water buffalo).

>> Did I read this correctly? Pterosaurs were compared to rhinos and buffalo? In any case, their figure 1 shows a Rhamphorhynchus about to take a drink of water – and a freehand cartoon as well. It is not in the configuration of a bipedal lizard. And they don’t fly!! Please write to the authors demanding more accurate drawings based on specific data.  Here are standing rhamps reconstructed bone-by-bone: http://www.reptileevolution.com/rhamphorhynchus-to-scale.htm  Here is a basal pterosaur, Bergamodactylus. Show me how this pterosaur locomoted quadrupedally: https://www.reptileevolution.com/MPUM6009.htm

“those muscles did not need to be strong enough to push the entire body off the ground. Flapping wings producing thrust and lift helped, as in birds. And to your query, how high is needed? 1cm? 10cm? a meter? Please be precise.”

In hindsight, that was a dumb point to make as you are right, birds don’t need to fully rely on propulsion from their hindlimbs to take off. The better question that I should’ve asked is “how do you know that the wings of pterosaurs could beat fast enough and with enough force to take off in the same manner that birds do?”

>> Which pterosaurs? Which birds? Be specific. Some of both could not fly. Others beat quckly. Others beat slowly. Here’s a hypothesis for Dimorphodon: https://www.reptileevolution.com/dimorphodon.htm  What is impossible in this animation?

“At present you seem to be indicating that pterosaur could not fly in the manner of birds = flapping.”

I only believe that when it comes to taking off from the ground. But when they were flying, they could flap, but they likely flapped less frequently than birds.

>> Be specific. Pick a genus. Then we can talk. I mentioned this on my earlier reply. Try not to be nebulous like this. And try to avoid using the term “I believe”. Better to say ‘my figure 1 shows’.

Source: https://pterosaurheresies.wordpress.com/2025/12/23/stu-bonk-comments-12-22-25/