Were pterosaurs bipedal?

[Oxyaena]

Nyikos recently mentioned to me that there was a "consensus" among
paleontologists that pterosaurs were bipedal. I hadn't heard of that
claim until he brought it up, and it seems pretty wild. Given that it's
Nyikos it could be just be typical Nyikosian hyperbole, but I'm still
inclined to see if the claim has any merit.

First, let's start off by engaging in comparative anatomy. Bats have a
superficially similar wing structure to pterosaurs, and most definitely
*aren't* bipedal. The forearms are too specialized, and fragile, to
allow for the bat to engage in bipedal locomotion, and the overall
morphology of any species of bat is more in line with a species that's
capable of powered flight but is quadrupedal on the ground, as bats use
their wings as supports during locomotion when on the ground, similar to
how pterosaurs presumably did so.

Bottom line is, is that the overall body structure of pterosaurs doesn't
lend any credence to the idea they were bipedal when on the ground, and
a cursory look at the morphology and locomotory habits of bats suggests
likewise.
--
"There is only one good, knowledge, and one evil, ignorance." -
Socrates, as recorded by Diogenes Laertius

"Is God willing to prevent evil, but not able? Then he is not
omnipotent. Is he able, but not willing? Then he is malevolent. Is he
both able and willing? Then whence cometh evil? Is he neither able nor
willing? Then why call him God?" - Epicurus

[John Harshman]

On 8/18/18 6:05 AM, Oxyaena wrote:
> Nyikos recently mentioned to me that there was a "consensus" among
> paleontologists that pterosaurs were bipedal. I hadn't heard of that
> claim until he brought it up, and it seems pretty wild. Given that it's
> Nyikos it could be just be typical Nyikosian hyperbole, but I'm still
> inclined to see if the claim has any merit.

This was the claim of Kevin Padian, who stuck with it for many years and
convinced a fair number of people. But the data showed otherwise, so it
faded.

> First, let's start off by engaging in comparative anatomy. Bats have a
> superficially similar wing structure to pterosaurs, and most definitely
> *aren't* bipedal. The forearms are too specialized, and fragile, to
> allow for the bat to engage in bipedal locomotion, and the overall
> morphology of any species of bat is more in line with a species that's
> capable of powered flight but is quadrupedal on the ground, as bats use
> their wings as supports during locomotion when on the ground, similar to
> how pterosaurs presumably did so.
>
> Bottom line is, is that the overall body structure of pterosaurs doesn't
> lend any credence to the idea they were bipedal when on the ground, and
> a cursory look at the morphology and locomotory habits of bats suggests
> likewise.

You should inform Padian that his efforts were silly from the start, then.

[Peter Nyikos]

On Saturday, August 18, 2018 at 9:05:06 AM UTC-4, Oxyaena wrote:

> Nyikos recently mentioned to me that there was a "consensus" among
> paleontologists that pterosaurs were bipedal.

Wrong. I wrote that Carroll (1988) made it seem as though
this had been the consensus. But I knew very well that it was
not a consensus in the way mature adults use the word. John Ostrom
had unequivocally stated in a collection of research articles
that birds were the only bipedal fliers, and specifically said
that pterosaurs were quadrupedal.

Back in the late 90's, the distinguished dinosaur paleontologist Tom
Holtz was a regular in talk.origins, and he voiced somewhat of a preference
for pterosaurs having been bipedal. With all the respect someone of his
stature deserved, I wrote,

For what it's worth, John Ostrom disagrees with you.

and then I quoted Ostrom, giving a full reference. Tom's reply began,
"I am aware of my mild disagreement with John..."

> I hadn't heard of that
> claim until he brought it up, and it seems pretty wild. Given that it's
> Nyikos it could be just be typical Nyikosian hyperbole, but I'm still
> inclined to see if the claim has any merit.

You sure are milking your faulty memory for all it's worth. :-)


<snip preaching to the choir>


Peter Nyikos
Professor, Department of Mathematics -- standard disclaimer--
University of South Carolina
http://people.math.sc.edu

[Oxyaena]

On 8/20/2018 9:58 PM, Peter Nyikos wrote:
> On Saturday, August 18, 2018 at 9:05:06 AM UTC-4, Oxyaena wrote:
>
>> Nyikos recently mentioned to me that there was a "consensus" among
>> paleontologists that pterosaurs were bipedal.
>
> Wrong. I wrote that Carroll (1988) made it seem as though
> this had been the consensus. But I knew very well that it was

> not a consensus in the way mature adults use the word. [snip]

Contrast this with:

"That's the ideal. The reality includes such things as Padian's
benighted idea that pterosaurs were all bipeds. Reading what Carroll
wrote about it, one would get the impression that this was also
part of the 'consensus'. Yet one look at those tiny pelvises, and
the angles that the femurs' heads made with them in some species, should
have
made it clear how few expertly informed people went into this 'consensus'."

You made no indication in this little paragraph of yours that I just
reposted that you believed it was anything other than the scientific
consensus at the time. In short, you're a two-faced liar.

>
> Back in the late 90's, the distinguished dinosaur paleontologist Tom
> Holtz was a regular in talk.origins, and he voiced somewhat of a preference
> for pterosaurs having been bipedal. With all the respect someone of his
> stature deserved, I wrote,
>
> For what it's worth, John Ostrom disagrees with you.
>
> and then I quoted Ostrom, giving a full reference. Tom's reply began,
> "I am aware of my mild disagreement with John..."

And this engagement with a long-gone poster is relevant how exactly?

>
>> I hadn't heard of that
>> claim until he brought it up, and it seems pretty wild. Given that it's
>> Nyikos it could be just be typical Nyikosian hyperbole, but I'm still
>> inclined to see if the claim has any merit.
>
> You sure are milking your faulty memory for all it's worth. :-)

Glad to see you're still insulting me.

>
>
> <snip preaching to the choir>
>
>
> Peter Nyikos
> Professor, Department of Mathematics -- standard disclaimer--
> University of South Carolina
> http://people.math.sc.edu
>
>

--
"Get your facts first, and then you can distort them as much as you
please." - Mark Twain

[Oxyaena]

On 8/18/2018 11:49 AM, John Harshman wrote:
> On 8/18/18 6:05 AM, Oxyaena wrote:
>> Nyikos recently mentioned to me that there was a "consensus" among
>> paleontologists that pterosaurs were bipedal. I hadn't heard of that
>> claim until he brought it up, and it seems pretty wild. Given that
>> it's Nyikos it could be just be typical Nyikosian hyperbole, but I'm
>> still inclined to see if the claim has any merit.
>
> This was the claim of Kevin Padian, who stuck with it for many years and
> convinced a fair number of people. But the data showed otherwise, so it
> faded.

As it should be. Nyikos only brought it up to show why he thought that
the scientific consensus is faulty and shouldn't be relied upon, he'll
likely play word games and accuse me of lying of course. The evidence
showed otherwise, the paradigm shifted, this is how science works.
Padian's assertions were proven to be incorrect, end of story. Science
isn't dogmatic in nature, science is constantly shifting to accommodate
new evidence, old hypotheses and theories get thrown out or revised when
new evidence comes in that shines new light on a subject, for decades
after Darwin published his *Origin* the scientific paradigm was that
while evolution existed and natural selection existed as well, it only
played a minor role in it, with most scientists believing that some
other mechanism was in play for evolution, with most preferring either
orthogenesis or Neo-Lamarkism as their pet theories, with the
geneticists later favoring mutationism as well.

It took the Modern Synthesis to show why they were wrong. A big problem
that Darwin never managed to fully explain was the origin of variation,
and natural selection didn't explain it, they saw that Neo-Lamarkism
did. With the rediscovery of Gregor Mendel's work on heredity, they
realized that there was an explanation that perfectly matched with
natural selection for the origins of variation, and the rest was history.

The scientific consensus is only as good as the evidence at hand, and
will inevitably change when new evidence comes to light, but that
doesn't mean the consensus is wrong. Linnaean taxonomy has been
repeatedly shown to be an out-dated form of systematic classification,
with cladistics doing a far better job. Nyikos has never gave a
convincing answer as to why Linnaean taxonomy is better than cladistics,
and one can easily pierce through the veil to discover that the only
reason Nyikos favors Linnaean taxonomy is because of nostalgia.

>
>> First, let's start off by engaging in comparative anatomy. Bats have a
>> superficially similar wing structure to pterosaurs, and most
>> definitely *aren't* bipedal. The forearms are too specialized, and
>> fragile, to allow for the bat to engage in bipedal locomotion, and the
>> overall morphology of any species of bat is more in line with a
>> species that's capable of powered flight but is quadrupedal on the
>> ground, as bats use their wings as supports during locomotion when on
>> the ground, similar to how pterosaurs presumably did so.
>>
>> Bottom line is, is that the overall body structure of pterosaurs
>> doesn't lend any credence to the idea they were bipedal when on the
>> ground, and a cursory look at the morphology and locomotory habits of
>> bats suggests likewise.
>
> You should inform Padian that his efforts were silly from the start, then.

Why is it that you put a passive-aggressive remark here? What point does
that bring to the discussion? You're a hypocrite, John, like Nyikos. You
don't like people snarking at each other on your precious cladistics
threads, but when it comes to regular paleontology you take the
opportunity to snark at me with pleasure.

[Peter Nyikos]

On Saturday, August 18, 2018 at 9:05:06 AM UTC-4, Oxyaena wrote:

.... a comparison with bats, but such comparisons are of limited value
due to major differences in anatomy.

> First, let's start off by engaging in comparative anatomy. Bats have a
> superficially similar wing structure to pterosaurs, and most definitely
> *aren't* bipedal. The forearms are too specialized, and fragile, to
> allow for the bat to engage in bipedal locomotion,

Forearms = wings. I don't see where fragility comes into play.

> and the overall
> morphology of any species of bat is more in line with a species that's
> capable of powered flight but is quadrupedal on the ground, as bats use
> their wings as supports during locomotion when on the ground, similar to
> how pterosaurs presumably did so.

On the ground the bat is almost helpless, and can only creep
along on all fours pushing its body forward on its stomach.
Pterosaurs could certainly move more confidently on the ground
than bats. They could lift their body off the ground, at least,
and walk in a semi-erect manner on four legs.

-- Peter Wellnhofer, _The Illustrated Encyclopedia of Pterosaurs_,
Translated from the German by Michael Robinson. Crescent Books,
1991, p. 157

> Bottom line is, is that the overall body structure of pterosaurs doesn't
> lend any credence to the idea they were bipedal when on the ground, and
> a cursory look at the morphology and locomotory habits of bats suggests
> likewise.

Yes, but comparison with bats is especially risky because bats use all
but one digit (the pollex) for the wing structure, while pterosaurs
only one. This leaves the other digits of the manus free for other
purposes. So besides the difference in legs to which Wellnhofer alludes,
this too and makes walking on the ground easier, though hardly as
simple as for birds or wingless quadrupeds.


Peter Nyikos
Professor, Dept. of Mathematics -- standard disclaimer--

[Oxyaena]

On 8/22/2018 7:16 AM, Peter Nyikos wrote:
> On Saturday, August 18, 2018 at 9:05:06 AM UTC-4, Oxyaena wrote:

So you finally decided to actually reply to the on-topic portion of my
post instead of dismissing it as mere "preaching to the choir"? Why not
say so?

>
>> First, let's start off by engaging in comparative anatomy. Bats have a
>> superficially similar wing structure to pterosaurs, and most definitely
>> *aren't* bipedal. The forearms are too specialized, and fragile, to
>> allow for the bat to engage in bipedal locomotion,
>
> Forearms = wings. I don't see where fragility comes into play.
>

Bats are notorious for their unreliable fossilization ratio to other
mammals *because* of the fragility of their bones, and I suspect that's
a big reason why they're "almost helpless" on the ground.

>> and the overall
>> morphology of any species of bat is more in line with a species that's
>> capable of powered flight but is quadrupedal on the ground, as bats use
>> their wings as supports during locomotion when on the ground, similar to
>> how pterosaurs presumably did so.
>
> On the ground the bat is almost helpless, and can only creep
> along on all fours pushing its body forward on its stomach.
> Pterosaurs could certainly move more confidently on the ground
> than bats. They could lift their body off the ground, at least,
> and walk in a semi-erect manner on four legs.
>
> -- Peter Wellnhofer, _The Illustrated Encyclopedia of Pterosaurs_,
> Translated from the German by Michael Robinson. Crescent Books,
> 1991, p. 157
>
>
>> Bottom line is, is that the overall body structure of pterosaurs doesn't
>> lend any credence to the idea they were bipedal when on the ground, and
>> a cursory look at the morphology and locomotory habits of bats suggests
>> likewise.
>
> Yes, but comparison with bats is especially risky because bats use all
> but one digit (the pollex) for the wing structure, while pterosaurs
> only one. This leaves the other digits of the manus free for other
> purposes. So besides the difference in legs to which Wellnhofer alludes,
> this too and makes walking on the ground easier, though hardly as
> simple as for birds or wingless quadrupeds.

What other clade of vertebrates uses their entire forearm as a wing,
without using feathers and with using extended skin flaps on their
forearms for wings? Bats are really the only flying vertebrates today,
or for all of the Cenozoic, that are truly comparable in terms of
morphology to pterosaurs, since birds use a whole different anatomical
system to attain and maintain powered flight. Flying mechanics is a
different matter, and I suspect that birds are closer to pterosaurs than
bats in that regard, but I use bats instead of birds because bats, like
pterosaurs, are quadrupedal when on the ground whereas birds are bipedal.

>
>
> Peter Nyikos
> Professor, Dept. of Mathematics -- standard disclaimer--
> University of South Carolina
> http://people.math.sc.edu
>

--
"Get your facts first, and then you can distort them as much as you
please." - Mark Twain

"Humanity is a race of cowards, and I am not only marching in that
procession, but carrying a banner." - Mark Twain

[Peter Nyikos]

Not without a lot more details of pterosaur anatomy. Here is a start on
that which may be of special interest to you as an orthithologist.
A distinguished researcher and author on pterosaurs contrasted them with birds:

The pelvic muscles work in such a way that the bird is
suspended over its hind legs as in a seesaw, and the legs
swinging forwards and backwards. Thus the femur has to
be articulated in the hip socket in such a way that it can
be moved in this vertical plane parallel with the longitudinal
axis of the body. In birds this is possible because the articular
head of the femur is set almost at a right angle inwards from
the bone shaft, and the sideways oriented hip socket is covered
by a bony protuberance. Thus the weight taken by the hind legs
is absorbed at the top.

-- Peter Wellnhofer, _The Illustrated Encyclopedia of Pterosaurs_,
Translated from the German by Michael Robinson. Crescent Books,

1991, p. 155

On the next page we get the contrast with pterosaurs:

The hip sockets in the pelvis are not only oriented sideways,
but also somewhat upward and backwards. There is no rim above
the hip socket to support the femur. The articular head of the
femur is never at right angles, as in birds, but in the best case
bent at 120 degrees to the bone shaft, usually at 130 to 160
degrees. If the femur of a pterosaur is placed in the hip socket
of the pelvis, the bone is splayed out and cannot be moved
into a vertical position. [31]

[31] Wellnhofer, P. and Vahldiek, B.-W., 1986. "Ein Flugsauter-Rest
aus dem Posidonienschiefer (Unter-Toarcian) von Schadelah bei
Braunschweig." Palaeontologische Zeitschrift, 60:329-340, Stuttgart.

Wellnhofer, P. 1988. "Terrestrial Locomotion in Pterosaurs." Historical
Biology, 1:3-16.


Note the dates. Perhaps Carroll (1988) was unaware of the first footnoted
reference and published before seeing the second. Do you know whether
Padian ever tried to rebut Wellnhofer?


Peter Nyikos
Professor of Mathematics -- standard disclaimer--

[Peter Nyikos]

On Wednesday, August 22, 2018 at 6:25:29 AM UTC-4, Oxyaena wrote:
> On 8/20/2018 9:58 PM, Peter Nyikos wrote:
> > On Saturday, August 18, 2018 at 9:05:06 AM UTC-4, Oxyaena wrote:
> >
> >> Nyikos recently mentioned to me that there was a "consensus" among
> >> paleontologists that pterosaurs were bipedal.
> >
> > Wrong. I wrote that Carroll (1988) made it seem as though
> > this had been the consensus. But I knew very well that it was
> > not a consensus in the way mature adults use the word. [snip]
>
> Contrast this with:

...something that includes comments about the femur, supported
in detail by me a few minutes ago:

> "That's the ideal. The reality includes such things as Padian's
> benighted idea that pterosaurs were all bipeds. Reading what Carroll
> wrote about it, one would get the impression that this was also
> part of the 'consensus'. Yet one look at those tiny pelvises, and
> the angles that the femurs' heads made with them in some species, should
> have
> made it clear how few expertly informed people went into this 'consensus'."

Note the scare quotes by me. I was referring to the informal use
of the word "consensus" which is almost ubiquitous among BADs,
whereby a hypothesis which 20 specialists argue in detail for,
and 2 argue in detail against (while the other 99+% of biologists
either don't comment on it or know too little about it to make
a really informed judgment), counts as a "consensus".

I think a mature adult would not use the word "consensus" in this way.
Your mileage, and that of Harshman and Simpson and Safir, may vary.

> You made no indication in this little paragraph of yours that I just
> reposted that you believed it was anything other than the scientific
> consensus at the time.

You missed what the scare quotes were all about.

> >
> > Back in the late 90's, the distinguished dinosaur paleontologist Tom
> > Holtz was a regular in talk.origins, and he voiced somewhat of a preference
> > for pterosaurs having been bipedal. With all the respect someone of his
> > stature deserved, I wrote,
> >
> > For what it's worth, John Ostrom disagrees with you.
> >
> > and then I quoted Ostrom, giving a full reference. Tom's reply began,
> > "I am aware of my mild disagreement with John..."
>
> And this engagement with a long-gone poster is relevant how exactly?

Ostrom was one exception to the "consensus". Wellnhofer was another.
There may have been more.


And maybe Carroll didn't intend to create the impression
that there was a "consensus" [note the scare quotes again],
but his comments about Padian's hypothesis were supportive.

Peter Nyikos
Professor of Mathematics -- standard disclaimer--
Univ. of South Carolina
http://people.math.sc.edu

[John Harshman]

I don't. You might look up Padians papers on this subject to see his
arguments. I only vaguely remember them. Anyway, pterosaur trackways are
pretty conclusive.

[Oxyaena]

On 8/22/2018 8:02 AM, Peter Nyikos wrote:
> On Wednesday, August 22, 2018 at 6:25:29 AM UTC-4, Oxyaena wrote:
>> On 8/20/2018 9:58 PM, Peter Nyikos wrote:
>>> On Saturday, August 18, 2018 at 9:05:06 AM UTC-4, Oxyaena wrote:
>>>
>>>> Nyikos recently mentioned to me that there was a "consensus" among
>>>> paleontologists that pterosaurs were bipedal.
>>>
>>> Wrong. I wrote that Carroll (1988) made it seem as though
>>> this had been the consensus. But I knew very well that it was
>>> not a consensus in the way mature adults use the word. [snip]
>>
>> Contrast this with:
>

[snip]

>
>> "That's the ideal. The reality includes such things as Padian's
>> benighted idea that pterosaurs were all bipeds. Reading what Carroll
>> wrote about it, one would get the impression that this was also
>> part of the 'consensus'. Yet one look at those tiny pelvises, and
>> the angles that the femurs' heads made with them in some species, should
>> have
>> made it clear how few expertly informed people went into this 'consensus'."
>
> Note the scare quotes by me. I was referring to the informal use
> of the word "consensus" which is almost ubiquitous among BADs,
> whereby a hypothesis which 20 specialists argue in detail for,
> and 2 argue in detail against (while the other 99+% of biologists
> either don't comment on it or know too little about it to make
> a really informed judgment), counts as a "consensus".

Then it's not a "consensus", Nyikos. There's no need to make a formal
distinction between an "informal" definition of consensus and a "formal"
definition of consensus, it's a distinction without a difference. Every
person I know uses the word consensus to mean "something everyone is in
agreement with, or has reached agreement on", and the definition Carrol
offered matches that definition. It isn't that there was an "informal"
meaning of consensus, it's simply that he was WRONG about there being a
consensus.

>
> I think a mature adult would not use the word "consensus" in this way.

I do, because the definition's the damn same thing, there's nothing
"informal" about this usage of the word "consensus", Carrol was WRONG
about there being a consensus, but his usage of the word "consensus" met
the definition of "consensus", so there was nothing "informal" about it.

>
>
>> You made no indication in this little paragraph of yours that I just
>> reposted that you believed it was anything other than the scientific
>> consensus at the time.
>
> You missed what the scare quotes were all about.

You offered the piece on pterosaurs as a rebuttal of sorts to my point
that the consensus matters, so in the original context of what you
wrote, no, you didn't give any indication that you thought it was
anything other than the consensus at the time. Something many people
have pointed out is that you need to clarify your positions better,
something you adamantly *refuse* to do. Why?

>
>>>
>>> Back in the late 90's, the distinguished dinosaur paleontologist Tom
>>> Holtz was a regular in talk.origins, and he voiced somewhat of a preference
>>> for pterosaurs having been bipedal. With all the respect someone of his
>>> stature deserved, I wrote,
>>>
>>> For what it's worth, John Ostrom disagrees with you.
>>>
>>> and then I quoted Ostrom, giving a full reference. Tom's reply began,
>>> "I am aware of my mild disagreement with John..."
>>
>> And this engagement with a long-gone poster is relevant how exactly?
>
> Ostrom was one exception to the "consensus". Wellnhofer was another.
> There may have been more.

There were probably plenty more, in terms of pterosaur specialists there
was no consensus that pterosaurs were bipedal, so Carroll was wrong.

>
>
> And maybe Carroll didn't intend to create the impression
> that there was a "consensus" [note the scare quotes again],
> but his comments about Padian's hypothesis were supportive.
>

Which indicates that Carroll knew almost nothing about pterosaur
morphology, nothing more, nothing less. If he believed that claptrap
he's obviously *not* a pterosaur specialist. I`m a professional
paleontologist (no more information than that, sorry) and I've never
heard of this seemingly minor hiccup of Carroll's, then again I`m not a
pterosaur specialist.

> Peter Nyikos
> Professor of Mathematics -- standard disclaimer--
> Univ. of South Carolina
> http://people.math.sc.edu
>

--
"Get your facts first, and then you can distort them as much as you
please." - Mark Twain

[Peter Nyikos]

On Wednesday, August 22, 2018 at 9:45:55 AM UTC-4, John Harshman wrote:
> On 8/22/18 4:45 AM, Peter Nyikos wrote:
> > On Saturday, August 18, 2018 at 11:49:41 AM UTC-4, John Harshman wrote:
> >> On 8/18/18 6:05 AM, Oxyaena wrote:
> >
> >>> Bottom line is, is that the overall body structure of pterosaurs doesn't
> >>> lend any credence to the idea they were bipedal when on the ground, and
> >>> a cursory look at the morphology and locomotory habits of bats suggests
> >>> likewise.
> >>
> >> You should inform Padian that his efforts were silly from the start, then.
> >
> > Not without a lot more details of pterosaur anatomy. Here is a start on
> > that which may be of special interest to you as an orthithologist.

Then again, maybe not.

How about some comments on what I quoted from Wellnhofer? Are you
too specialized in the direction of systematics to comment on such
anatomical details?

> Anyway, pterosaur trackways are
> pretty conclusive.

Not as conclusive as you might think. I've heard about trackways
of pterosaurs "walking on their hands," although the conventional
wisdom is that they were in water that partly supported their weight.


But the people who designed a traveling exhibit that came to
the South Carolina State Museum a few years ago didn't go along
with that. The display included a full-sized Pteranodon dummy
on dry land, standing on its manuses, the wing folded with the
phalanges pointing almost straight up, while its hind legs dangled
in the air.


It reminded me of a science fiction novel by Poul Anderson
(I forget the title) which featured an intelligent race of
such pterosaur analogues that evolved on a low-gravity planet.
One picture showed one of them at a bar, grasping a drink
with its right pes while standing on its manuses.

Peter Nyikos
Professor of Mathematics -- standard disclaimer--

U. of South Carolina at Columbia
http://people.math.sc.edu

[Peter Nyikos]

On Wednesday, August 22, 2018 at 7:25:47 AM UTC-4, Oxyaena wrote:
> On 8/22/2018 7:16 AM, Peter Nyikos wrote:
> > On Saturday, August 18, 2018 at 9:05:06 AM UTC-4, Oxyaena wrote:

> >> First, let's start off by engaging in comparative anatomy. Bats have a
> >> superficially similar wing structure to pterosaurs, and most definitely
> >> *aren't* bipedal. The forearms are too specialized, and fragile, to
> >> allow for the bat to engage in bipedal locomotion,
> >
> > Forearms = wings. I don't see where fragility comes into play.
> >
>
> Bats are notorious for their unreliable fossilization ratio to other
> mammals *because* of the fragility of their bones, and I suspect that's
> a big reason why they're "almost helpless" on the ground.

I fail to see the relevance to bipedalism, which presumably would
be on the hind legs. Anyway, this is another relevant difference between
bats and pterosaurs: the flimsiness of the wing bones in bats is
in contrast to the robustness of the ones of pterosaurs. The latter
were able to "do pushups" using their three free fingers and
strong humerus and forearm bones.

Also, see what I wrote to Harshman earlier this evening
about pterosaurs "walking on their hands."

At some point we need to get away from analogies, what with the
meager clades of that sort at our disposal, and get down to
reasoning about anatomical details like the ones I posted in
reply to Harshman.


The rest of your post was about more analogies, and about flight,
which is getting away from quadrupedalism v. bipedalism and
deserves a separate thread of its own.


Peter Nyikos
Professor, Department of Mathematics -- standard disclaimer--

University of South Carolina
http://people.math.sc.edu

PS There was one clade of Triassic reptiles that might actually
have "flown on hindwings" -- wings that were to hind legs
as pterosaur wings were to the forelegs. *Podopteryx* [now given
a different name I can't recall right now] was one of them.
Based on fragmentary remains, it was depicted in Bakker's
1975 "Dinosaur Renaissance" cover article of Scientific American
as a colugo with the head of a pterosaur, but that reconstruction
has been discredited.

[John Harshman]

What does "the direction of systematics" have to do with it? Isn't
comparative anatomy a feature of systematics?

I just have nothing much to say about what you quoted. What were you
hoping for?

>> Anyway, pterosaur trackways are
>> pretty conclusive.
>
> Not as conclusive as you might think. I've heard about trackways
> of pterosaurs "walking on their hands," although the conventional
> wisdom is that they were in water that partly supported their weight.

Whose conventional wisdom? Azhdarchids were clearly terrestrial
predators, and there are tracks.

> But the people who designed a traveling exhibit that came to
> the South Carolina State Museum a few years ago didn't go along
> with that. The display included a full-sized Pteranodon dummy
> on dry land, standing on its manuses, the wing folded with the
> phalanges pointing almost straight up, while its hind legs dangled
> in the air.

That's bizarre. I wonder what support they thought they had for that model.

> It reminded me of a science fiction novel by Poul Anderson
> (I forget the title) which featured an intelligent race of
> such pterosaur analogues that evolved on a low-gravity planet.
> One picture showed one of them at a bar, grasping a drink
> with its right pes while standing on its manuses.

You're talking about the Ythri. They appear in a number of stories about
the Polesotechnic League, its breakup, and the early days of the Terran
Empire.

[Peter Nyikos]

I wasn't talking about comparative anatomy, I was talking about
anatomical clues as to "gait" which includes "bipedal on manuses,
bipedal on the two pes, quadrupedal crawling, and quadrupedal creeping
when on level ground ("belly crawl", as in bats stranded on level ground).

> I just have nothing much to say about what you quoted. What were you
> hoping for?

Opinion as to how strong an argument for quadrupedalism crawling
that Wellnhofer has given via the anatomical details he provided.

> >> Anyway, pterosaur trackways are
> >> pretty conclusive.
> >
> > Not as conclusive as you might think. I've heard about trackways
> > of pterosaurs "walking on their hands," although the conventional
> > wisdom is that they were in water that partly supported their weight.
>
> Whose conventional wisdom? Azhdarchids were clearly terrestrial
> predators, and there are tracks.

I think you misinterpreted "walking on their hands". I was referring
to the sort of thing the dummy mentioned below might have done,
had it been rigged up to move around:

> > But the people who designed a traveling exhibit that came to
> > the South Carolina State Museum a few years ago didn't go along
> > with that. The display included a full-sized Pteranodon dummy
> > on dry land, standing on its manuses, the wing folded with the
> > phalanges pointing almost straight up, while its hind legs dangled
> > in the air.
>
> That's bizarre. I wonder what support they thought they had for that model.

Hence my concern that you misinterpreted what I wrote.

> > It reminded me of a science fiction novel by Poul Anderson
> > (I forget the title) which featured an intelligent race of
> > such pterosaur analogues that evolved on a low-gravity planet.
> > One picture showed one of them at a bar, grasping a drink
> > with its right pes while standing on its manuses.
>
> You're talking about the Ythri. They appear in a number of stories about
> the Polesotechnic League, its breakup, and the early days of the Terran
> Empire.

Thanks for that reference. Our libraries are very skimpy with SF that
goes back more than a decade or two, but I'll look for it.


Peter Nyikos
Professor, Department of Math. -- standard disclaimer --

U. of South Carolina at Columbia

http://www.math.sc.edu/~nyikos/

[Oxyaena]

On 8/22/2018 10:00 PM, Peter Nyikos wrote:
> On Wednesday, August 22, 2018 at 7:25:47 AM UTC-4, Oxyaena wrote:
>> On 8/22/2018 7:16 AM, Peter Nyikos wrote:
>>> On Saturday, August 18, 2018 at 9:05:06 AM UTC-4, Oxyaena wrote:
>
>>>> First, let's start off by engaging in comparative anatomy. Bats have a
>>>> superficially similar wing structure to pterosaurs, and most definitely
>>>> *aren't* bipedal. The forearms are too specialized, and fragile, to
>>>> allow for the bat to engage in bipedal locomotion,
>>>
>>> Forearms = wings. I don't see where fragility comes into play.
>>>
>>
>> Bats are notorious for their unreliable fossilization ratio to other
>> mammals *because* of the fragility of their bones, and I suspect that's
>> a big reason why they're "almost helpless" on the ground.
>
> I fail to see the relevance to bipedalism, which presumably would
> be on the hind legs. Anyway, this is another relevant difference between
> bats and pterosaurs: the flimsiness of the wing bones in bats is
> in contrast to the robustness of the ones of pterosaurs. The latter
> were able to "do pushups" using their three free fingers and
> strong humerus and forearm bones.
>
> Also, see what I wrote to Harshman earlier this evening
> about pterosaurs "walking on their hands."

The tracks still clearly indicate that pterosaurs were quadrupeds while
on the ground, even if part of their weight was supported by water.
Pterosaurs show none of the anatomical traits associated with
bipedalism, such as a repositioning of the pelvis to accommodate two
erect legs that now have the duty of supporting body weight rather than
using all four limbs to support body weight.

The rest of the thread was justifying my usage of bats as a suitable
analogy for pterosaurs, and why birds aren't as suitable for analogical
purposes.

>
>
> Peter Nyikos
> Professor, Department of Mathematics -- standard disclaimer--
> University of South Carolina
> http://people.math.sc.edu
>
> PS There was one clade of Triassic reptiles that might actually
> have "flown on hindwings" -- wings that were to hind legs
> as pterosaur wings were to the forelegs. *Podopteryx* [now given
> a different name I can't recall right now] was one of them.
> Based on fragmentary remains, it was depicted in Bakker's
> 1975 "Dinosaur Renaissance" cover article of Scientific American
> as a colugo with the head of a pterosaur, but that reconstruction
> has been discredited.
>

Yes, the simiosaurs or "monkey lizards". I've read all about them.