Fully quadrupedal swimming in plesiosaurs

[Peter Nyikos]

Plesiosaurs are among the few marine vertebrates that do/did not mostly
use their tails to propel themselves through the water. Offhand I cannot
think of any other exceptions besides pinnepeds (seal, sea lions, walruses).

This OP is about an article whose url was posted in sci.anthropology.paleo,
where it was off topic, in another OP. Small wonder, then, that nobody
discussed the central theme of the article. I remedy that defect here.

Muscutt LE, Dyke G, Weymouth GD, Naish D, Palmer C, Ganapathisubramani B. 2017 The four-flipper swimming method of plesiosaurs enabled
efficient and effective locomotion. Proc. R. Soc. B 284: 20170951.
http://dx.doi.org/10.1098/rspb.2017.0951

Abstract

The extinct ocean-going plesiosaurs were unique within vertebrates because
they used two flipper pairs identical in morphology for propulsion.
Although fossils of these Mesozoic marine reptiles have been known for
more than two centuries, the function and dynamics of their tandem-flipper
propulsion system has always been unclear and controversial. We address
this question quantitatively for the first time in this study, reporting a
series of precisely controlled water tank experiments that use reconstructed
plesiosaur flippers scaled from well-preserved fossils.

Our aim was to determine which limb movements would have resulted in the
most efficient and effective propulsion. We show that plesiosaur hind
flippers generated up to 60% more thrust and 40% higher efficiency when
operating in harmony with their forward counterparts, when compared with operating alone,
and the spacing and relative motion between the flippers
was critical in governing these increases.

The results of our analyses show that this phenomenon was probably
present across the whole range of plesiosaur flipper motion and resolves the
centuries-old debate about the propulsion style of these marine reptiles, as
well as indicating why they retained two pairs of flippers for more than 100 million years.


I have put in two paragraph breaks to enhance readability.


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

[Glenn]

So the flippers were like oars...maybe they were supersonic swimmers! Give me a break, Peter. Resolving the debate with water tank experiments??
Where'd they get the plesiosaur?

[Peter Nyikos]

On Monday, September 27, 2021 at 6:56:13 PM UTC-4, Glenn wrote:
> On Monday, September 27, 2021 at 3:11:41 PM UTC-7, Peter Nyikos wrote:

> > Plesiosaurs are among the few marine vertebrates that do/did not mostly
> > use their tails to propel themselves through the water. Offhand I cannot
> > think of any other exceptions besides pinnepeds (seal, sea lions, walruses).

> >
> > This OP is about an article whose url was posted in sci.anthropology.paleo,
> > where it was off topic, in another OP.

The url was the only thing that was posted there in the OP, by Daud Deden.
Why Daud (who used to frequent s.b.p. at least as often as Mario, another s.a.p. regular)
posted it there and not here is something only he can figure out, and hasn't divulged.

It's sort of nice to see you filling in for him here, Glenn. :)

Don't be daft. Sound travels four times as fast in water as in air.
Except perhaps for the X-15, there hasn't been a plane that could
fly that fast -- in air! Only in science fiction can you hear of submarines
breaking the sound barrier while submerged.

> Give me a break, Peter. Resolving the debate with water tank experiments??

Nothing wrong with that. You've heard of wind tunnels to evaluate
aircraft features without having the full airplane to test, haven't you?

I seem to recall them using pterosaur models in wind tunnels to see
just how aerodynamically efficient they are.

> Where'd they get the plesiosaur?

Unfortunately, there are no live animals that could make good models.
Right in the opening paragraph you can read:

"Plesiosaurs were unique because they evolved four
large wing-like flippers almost always identical in size and form;
all other animals that swim using lateral flapping appendages (e.g. turtles and sea lions) use
their forward pair primarily for propulsion and the hind pair for manoeuvring,
and this results in markedly different morphologies [1–3]. Thus, the almost
identical morphology of the fore and hind flippers of plesiosaurs poses the
question of why they adopted such a different approach to all other living
and extinct vertebrates and maintained it for such a long time."

I don't quite get the part about "markedly different morphologies."
To a layman like me, the front and hind flippers of the California sea lion
(of which I saw lots when I lived in Monterey, and also at the Riverbanks Zoo
here in Columbia, SC) don't look all that different to me. Also some
Mesozoic sea turtles, dwarfing even the biggest living one (the leatherback),
also had flippers not so very different in size and shape between front and hind.
On the other hand, the long-necked plesiosaur Elasmosaurus seems to
have somewhat different front and hind paddles.

https://en.wikipedia.org/wiki/Elasmosaurus

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

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

[John Harshman]

On 9/27/21 3:11 PM, Peter Nyikos wrote:
> Plesiosaurs are among the few marine vertebrates that do/did not mostly
> use their tails to propel themselves through the water. Offhand I cannot
> think of any other exceptions besides pinnepeds (seal, sea lions, walruses).

Seahorses and relatives. Various reef fish. Trunkfish, I believe.
Electric fish of various sorts, though I'm not sure any are marine. Rays
and skates. Ocean sunfish. Probably others.

Or did you mean just tetrapods? In which case, the crab-eating frog Rana
cancrivora. Or just amniotes? In which case sea turtles and all
seabirds. Still, plesiosaurs may have a unique mode.

What stroke are we talking about? Simultaneous front and back, left and
right? Some kind of sequence?

[Glenn]

Haven't heard that word "daft" in quite a while. Is that sarcasm as well?

> > Give me a break, Peter. Resolving the debate with water tank experiments??
> Nothing wrong with that. You've heard of wind tunnels to evaluate
> aircraft features without having the full airplane to test, haven't you?

You're backwards. Not all proposed shapes pass wind tunnel tests.
And most wind tunnel tests are done on airplanes with knowledge of past airplanes,
fossils don't come with the whole body, usually with just the bone structure.

>
> I seem to recall them using pterosaur models in wind tunnels to see
> just how aerodynamically efficient they are.
> > Where'd they get the plesiosaur?
> Unfortunately, there are no live animals that could make good models.

That is one problem. But there are live animals that could be used as references, such as the tail of whales.

> Right in the opening paragraph you can read:
>
> "Plesiosaurs were unique because they evolved four
> large wing-like flippers almost always identical in size and form;
> all other animals that swim using lateral flapping appendages (e.g. turtles and sea lions) use
> their forward pair primarily for propulsion and the hind pair for manoeuvring,
> and this results in markedly different morphologies [1–3]. Thus, the almost
> identical morphology of the fore and hind flippers of plesiosaurs poses the
> question of why they adopted such a different approach to all other living
> and extinct vertebrates and maintained it for such a long time."

That makes little sense, that because the flippers are similar means they used them as the only source or main source of propulsion.

>
> I don't quite get the part about "markedly different morphologies."
> To a layman like me, the front and hind flippers of the California sea lion
> (of which I saw lots when I lived in Monterey, and also at the Riverbanks Zoo
> here in Columbia, SC) don't look all that different to me. Also some
> Mesozoic sea turtles, dwarfing even the biggest living one (the leatherback),
> also had flippers not so very different in size and shape between front and hind.
> On the other hand, the long-necked plesiosaur Elasmosaurus seems to
> have somewhat different front and hind paddles.
>

So what? Do you accept the reasoning that because they are similar, they must have been used for propulsion?

I'd suggest that with such a long neck, they'd need to be good at changing direction quickly to catch prey. The tail could provide significant propulsion depending on what was attached to the bones, the flippers well suited for changing trajectories quickly, left-right, up-down.

What I object to though is the claim that the question has been "resolved". More likely what was resolved is the authors getting published.

[Peter Nyikos]

On Monday, September 27, 2021 at 9:55:05 PM UTC-4, John Harshman wrote:
> On 9/27/21 3:11 PM, Peter Nyikos wrote:
> > Plesiosaurs are among the few marine vertebrates that do/did not mostly
> > use their tails to propel themselves through the water. Offhand I cannot
> > think of any other exceptions besides pinnepeds (seal, sea lions, walruses).

When I did the OP, I was about to pack up and leave my office to go home.
Shortly thereafter, I realized that turtles are another clear example.
I didn't say this when I responded to Glenn, because the important thing
was to talk about them, which I did. Did you read that post?

> Seahorses and relatives. Various reef fish. Trunkfish, I believe.
> Electric fish of various sorts, though I'm not sure any are marine. Rays
> and skates. Ocean sunfish. Probably others.

Yup, these critters didn't occur to me. Just like when most people think of "bird,"
they automatically think of flying birds. The Kiwis are a big exception, of course.
[Note the capitalization. New Zealanders are often referred to as "Kiwis," for reasons
that should be obvious to anyone reading this.]

But are you sure that electric eels [eels is a misnomer, but electric sure is not]
do not propel themselves mainly with their tails? What do they propel themselves with?

By the way, the torpedo ray is very much electric, and marine.
It figures in one of Plato's dialogues, "Meno" complete with mention of a shock
which is translated as "electric." This word traces back to the Greek word "elektron"
but the meaning may only go back to Latin.

>
> Or did you mean just tetrapods? In which case, the crab-eating frog Rana
> cancrivora. Or just amniotes? In which case sea turtles and all
> seabirds. Still, plesiosaurs may have a unique mode.

Yes. Australian lungfish have similar pectoral and pelvic fins, which could be called "flippers"
because the fleshy part predominates. However, I suspect they mostly use their
diphycercal tails for swimming.

Back before they were put on the protected list, they were shown in some aquariums.
I saw some at the San Francisco Aquarium when I was 12, and by that time I knew a lot about
their taxonomic significance, and so I took a long, lingering look at them.
Unfortunately, I can no longer recall what their primary swimming mode was.

Try reading the article; you might catch a lot that I missed on a first run-through.
It's in technical language, including prominent use of "Strouhal numbers."
At one point it uses the term "Absolute thrust" but the next word is "coefficient."

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

Univ. of South Carolina in Columbia
http://people.math.sc.edu/nyikos

[John Harshman]

On 9/28/21 6:13 AM, Peter Nyikos wrote:
> On Monday, September 27, 2021 at 9:55:05 PM UTC-4, John Harshman wrote:
>> On 9/27/21 3:11 PM, Peter Nyikos wrote:
>>> Plesiosaurs are among the few marine vertebrates that do/did not mostly
>>> use their tails to propel themselves through the water. Offhand I cannot
>>> think of any other exceptions besides pinnepeds (seal, sea lions, walruses).
>
> When I did the OP, I was about to pack up and leave my office to go home.
> Shortly thereafter, I realized that turtles are another clear example.
> I didn't say this when I responded to Glenn, because the important thing
> was to talk about them, which I did. Did you read that post?

Yes, but I'm happy to let you deal with Glenn all by yourself. Enjoy.

>> Seahorses and relatives. Various reef fish. Trunkfish, I believe.
>> Electric fish of various sorts, though I'm not sure any are marine. Rays
>> and skates. Ocean sunfish. Probably others.
>
> Yup, these critters didn't occur to me. Just like when most people think of "bird,"
> they automatically think of flying birds. The Kiwis are a big exception, of course.
> [Note the capitalization. New Zealanders are often referred to as "Kiwis," for reasons
> that should be obvious to anyone reading this.]
>
> But are you sure that electric eels [eels is a misnomer, but electric sure is not]
> do not propel themselves mainly with their tails? What do they propel themselves with?

Not sure about electric eels, but most electric fish keep their tails
stiff and propel themselves with their dorsal fins.

> By the way, the torpedo ray is very much electric, and marine.
> It figures in one of Plato's dialogues, "Meno" complete with mention of a shock
> which is translated as "electric." This word traces back to the Greek word "elektron"
> but the meaning may only go back to Latin.

I urge you to contain your digressions, if you can.

Don't know what Strouhal numbers are, but the point is clear that left
and right flippers are supposed to work in tandem and there is an
optimal phase difference between front and back flippers, with its exact
value depending on speed, angle of attack, and distance between them.
The difference is never 180 but may be sometimes close to zero.

[Glenn]

On Tuesday, September 28, 2021 at 6:13:45 AM UTC-7, Peter Nyikos wrote:
> On Monday, September 27, 2021 at 9:55:05 PM UTC-4, John Harshman wrote:
> > On 9/27/21 3:11 PM, Peter Nyikos wrote:
> > > Plesiosaurs are among the few marine vertebrates that do/did not mostly
> > > use their tails to propel themselves through the water. Offhand I cannot
> > > think of any other exceptions besides pinnepeds (seal, sea lions, walruses).
> When I did the OP, I was about to pack up and leave my office to go home.
> Shortly thereafter, I realized that turtles are another clear example.
> I didn't say this when I responded to Glenn, because the important thing
> was to talk about them, which I did. Did you read that post?

You are aware that turtles have no tails and essentially no neck?

> > Seahorses and relatives. Various reef fish. Trunkfish, I believe.
> > Electric fish of various sorts, though I'm not sure any are marine. Rays
> > and skates. Ocean sunfish. Probably others.
> Yup, these critters didn't occur to me. Just like when most people think of "bird,"
> they automatically think of flying birds. The Kiwis are a big exception, of course.
> [Note the capitalization. New Zealanders are often referred to as "Kiwis," for reasons
> that should be obvious to anyone reading this.]
>
> But are you sure that electric eels [eels is a misnomer, but electric sure is not]
> do not propel themselves mainly with their tails? What do they propel themselves with?

Eels are "all tail".

>
> By the way, the torpedo ray is very much electric, and marine.
> It figures in one of Plato's dialogues, "Meno" complete with mention of a shock
> which is translated as "electric." This word traces back to the Greek word "elektron"
> but the meaning may only go back to Latin.

This is not helping you support your claim 'Plesiosaurs are among the few marine vertebrates that do/did not mostly
> > > use their tails to propel themselves through the water'.

What kind of numbers would you expect from a fossil skeleton in a water tank experiment?

[Peter Nyikos]

On Tuesday, September 28, 2021 at 9:53:38 AM UTC-4, John Harshman wrote:
> On 9/28/21 6:13 AM, Peter Nyikos wrote:
> > On Monday, September 27, 2021 at 9:55:05 PM UTC-4, John Harshman wrote:
> >> On 9/27/21 3:11 PM, Peter Nyikos wrote:
> >>> Plesiosaurs are among the few marine vertebrates that do/did not mostly
> >>> use their tails to propel themselves through the water. Offhand I cannot
> >>> think of any other exceptions besides pinnepeds (seal, sea lions, walruses).
> >
> > When I did the OP, I was about to pack up and leave my office to go home.
> > Shortly thereafter, I realized that turtles are another clear example.
> > I didn't say this when I responded to Glenn, because the important thing
> > was to talk about them, which I did. Did you read that post?

> Yes, but I'm happy to let you deal with Glenn all by yourself. Enjoy.

What am I supposed to enjoy? Does it include your not commenting on the content of my replies to Glenn?

I loaded the first one down with things of general paleontological
interest [and one that was about the physics of sound].
Isn't there anything you want to discuss about them?

> >> Seahorses and relatives. Various reef fish. Trunkfish, I believe.
> >> Electric fish of various sorts, though I'm not sure any are marine. Rays
> >> and skates. Ocean sunfish. Probably others.
> >
> > Yup, these critters didn't occur to me. Just like when most people think of "bird,"
> > they automatically think of flying birds. The Kiwis are a big exception, of course.
> > [Note the capitalization. New Zealanders are often referred to as "Kiwis," for reasons
> > that should be obvious to anyone reading this.]
> >
> > But are you sure that electric eels [eels is a misnomer, but electric sure is not]
> > do not propel themselves mainly with their tails? What do they propel themselves with?

> Not sure about electric eels, but most electric fish keep their tails
> stiff and propel themselves with their dorsal fins.

*Dorsal* fins? that's a new one on me.

What electric fish did you have in mind? Obviously not the torpedo ray:

> > By the way, the torpedo ray is very much electric, and marine.
> > It figures in one of Plato's dialogues, "Meno" complete with mention of a shock
> > which is translated as "electric." This word traces back to the Greek word "elektron"
> > but the meaning may only go back to Latin.

> I urge you to contain your digressions, if you can.

Your urging is duly noted. This one has no effect on me, because my digression
was a short aside, and it may be relevant to a newsgroup about language in which
Daud Deden is a regular. I thought someone reading this [possibly Daud himself, lurking]
knew more about the history of this particular word.

Don't forget, if it weren't for Daud, I wouldn't have heard about this article on plesiosaurs.

> >> Or did you mean just tetrapods? In which case, the crab-eating frog Rana
> >> cancrivora. Or just amniotes? In which case sea turtles and all
> >> seabirds. Still, plesiosaurs may have a unique mode.
> >
> > Yes. Australian lungfish have similar pectoral and pelvic fins, which could be called "flippers"
> > because the fleshy part predominates. However, I suspect they mostly use their
> > diphycercal tails for swimming.

No ideas on this?

> > Back before they were put on the protected list, they were shown in some aquariums.
> > I saw some at the San Francisco Aquarium when I was 12, and by that time I knew a lot about
> > their taxonomic significance, and so I took a long, lingering look at them.
> > Unfortunately, I can no longer recall what their primary swimming mode was.


> >>> This OP is about an article whose url was posted in sci.anthropology.paleo,
> >>> where it was off topic, in another OP. Small wonder, then, that nobody
> >>> discussed the central theme of the article. I remedy that defect here.
> >>>
> >>> Muscutt LE, Dyke G, Weymouth GD, Naish D, Palmer C, Ganapathisubramani B. 2017 The four-flipper swimming method of plesiosaurs enabled
> >>> efficient and effective locomotion. Proc. R. Soc. B 284: 20170951.
> >>> http://dx.doi.org/10.1098/rspb.2017.0951
> >>>
> >>> Abstract
> >>>
> >>> The extinct ocean-going plesiosaurs were unique within vertebrates because
> >>> they used two flipper pairs identical in morphology for propulsion.
> >>> Although fossils of these Mesozoic marine reptiles have been known for
> >>> more than two centuries, the function and dynamics of their tandem-flipper
> >>> propulsion system has always been unclear and controversial. We address
> >>> this question quantitatively for the first time in this study, reporting a
> >>> series of precisely controlled water tank experiments that use reconstructed
> >>> plesiosaur flippers scaled from well-preserved fossils.
> >>>
> >>> Our aim was to determine which limb movements would have resulted in the
> >>> most efficient and effective propulsion. We show that plesiosaur hind
> >>> flippers generated up to 60% more thrust and 40% higher efficiency when
> >>> operating in harmony with their forward counterparts, when compared with operating alone,

The article talks about percentages a lot more than it does about absolute
numbers. It does not talk about thrust in absolute physics terms like Newtons.

https://www.learncram.com/physics/thrust/#:~:text=The%20SI%20unit%20of%20thrust%20is%20newton.,The%20CGS%20unit%20of%20thrust%20is%20dyne.

> >>> and the spacing and relative motion between the flippers
> >>> was critical in governing these increases.
> >
> >
> >>> The results of our analyses show that this phenomenon was probably
> >>> present across the whole range of plesiosaur flipper motion and resolves the
> >>> centuries-old debate about the propulsion style of these marine reptiles, as
> >>> well as indicating why they retained two pairs of flippers for more than 100 million years.
> >>>
> >>>
> >>> I have put in two paragraph breaks to enhance readability.
> >
> >
> >> What stroke are we talking about? Simultaneous front and back, left and
> >> right? Some kind of sequence?
> >
> > Try reading the article; you might catch a lot that I missed on a first run-through.
> > It's in technical language, including prominent use of "Strouhal numbers."
> > At one point it uses the term "Absolute thrust" but the next word is "coefficient."

> Don't know what Strouhal numbers are, but the point is clear that left
> and right flippers are supposed to work in tandem and there is an
> optimal phase difference between front and back flippers, with its exact
> value depending on speed, angle of attack, and distance between them.
> The difference is never 180 but may be sometimes close to zero.

Thanks. I hope you don't mind a "digression" into ornithology.
Are there studies as to the phase differences between wingbeats and "tail beats"
[retrices moving up, down, or whatever] in birds flying? I've had a chance to
see how there are contributions to flight by retrices through watching pet cockatiels.

Peter Nyikos
Professor, Dept. of Mathematics

Univ. of South Carolina -- standard disclaimer--
http://people.math.sc.edu/nyikos

[John Harshman]

On 9/28/21 11:39 AM, Peter Nyikos wrote:
> On Tuesday, September 28, 2021 at 9:53:38 AM UTC-4, John Harshman wrote:
>> On 9/28/21 6:13 AM, Peter Nyikos wrote:
>>> On Monday, September 27, 2021 at 9:55:05 PM UTC-4, John Harshman wrote:
>>>> On 9/27/21 3:11 PM, Peter Nyikos wrote:
>>>>> Plesiosaurs are among the few marine vertebrates that do/did not mostly
>>>>> use their tails to propel themselves through the water. Offhand I cannot
>>>>> think of any other exceptions besides pinnepeds (seal, sea lions, walruses).
>>>
>>> When I did the OP, I was about to pack up and leave my office to go home.
>>> Shortly thereafter, I realized that turtles are another clear example.
>>> I didn't say this when I responded to Glenn, because the important thing
>>> was to talk about them, which I did. Did you read that post?
>
>> Yes, but I'm happy to let you deal with Glenn all by yourself. Enjoy.
>
> What am I supposed to enjoy? Does it include your not commenting on the content of my replies to Glenn?
>
> I loaded the first one down with things of general paleontological
> interest [and one that was about the physics of sound].
> Isn't there anything you want to discuss about them?

Not with Glenn, to the extent that I don't want to get involved in any
discussion between you and Glenn.

>>>> Seahorses and relatives. Various reef fish. Trunkfish, I believe.
>>>> Electric fish of various sorts, though I'm not sure any are marine. Rays
>>>> and skates. Ocean sunfish. Probably others.
>>>
>>> Yup, these critters didn't occur to me. Just like when most people think of "bird,"
>>> they automatically think of flying birds. The Kiwis are a big exception, of course.
>>> [Note the capitalization. New Zealanders are often referred to as "Kiwis," for reasons
>>> that should be obvious to anyone reading this.]
>>>
>>> But are you sure that electric eels [eels is a misnomer, but electric sure is not]
>>> do not propel themselves mainly with their tails? What do they propel themselves with?
>
>> Not sure about electric eels, but most electric fish keep their tails
>> stiff and propel themselves with their dorsal fins.
>
> *Dorsal* fins? that's a new one on me.
>
> What electric fish did you have in mind? Obviously not the torpedo ray:

Thinking of knife-fish. But I guess it's more the anal fin there. One
point is that there are fish, particularly reef fish, that use pectoral,
dorsal, and/or anal fins for primary propulsion. Good for slow motion,
directional control (backwards swimming especially), and in electric
fish keeping the tail area straight.

>>> By the way, the torpedo ray is very much electric, and marine.
>>> It figures in one of Plato's dialogues, "Meno" complete with mention of a shock
>>> which is translated as "electric." This word traces back to the Greek word "elektron"
>>> but the meaning may only go back to Latin.
>
>> I urge you to contain your digressions, if you can.
>
> Your urging is duly noted. This one has no effect on me, because my digression
> was a short aside, and it may be relevant to a newsgroup about language in which
> Daud Deden is a regular. I thought someone reading this [possibly Daud himself, lurking]
> knew more about the history of this particular word.
>
> Don't forget, if it weren't for Daud, I wouldn't have heard about this article on plesiosaurs.
>
>
>>>> Or did you mean just tetrapods? In which case, the crab-eating frog Rana
>>>> cancrivora. Or just amniotes? In which case sea turtles and all
>>>> seabirds. Still, plesiosaurs may have a unique mode.
>>>
>>> Yes. Australian lungfish have similar pectoral and pelvic fins, which could be called "flippers"
>>> because the fleshy part predominates. However, I suspect they mostly use their
>>> diphycercal tails for swimming.
>
> No ideas on this?

No, but it would not be surprising if you were correct.

Are tails really producing lift in those cockatiels, or are they just
producing drag when the bird wants to slow or change direction? I don't
know of any studies on "tail beats" and know nothing of any such phenomenon.

[John Harshman]

Looks like electric eels also mainly use their anal fins for propulsion,
just like knife-fish. Holding the tail still helps them maintain a
stable electric field, making it easier to sense their surroundings.

[Peter Nyikos]

It's been fun discussing lots of things here, many of them on topic, but I need to
get down to some serious preparation for tomorrow's multivariate calculus courses
after this reply to you, Glenn.

On Tuesday, September 28, 2021 at 12:21:29 PM UTC-4, Glenn wrote:
> On Tuesday, September 28, 2021 at 6:13:45 AM UTC-7, Peter Nyikos wrote:
> > On Monday, September 27, 2021 at 9:55:05 PM UTC-4, John Harshman wrote:
> > > On 9/27/21 3:11 PM, Peter Nyikos wrote:
> > > > Plesiosaurs are among the few marine vertebrates that do/did not mostly
> > > > use their tails to propel themselves through the water. Offhand I cannot
> > > > think of any other exceptions besides pinnepeds (seal, sea lions, walruses).

> > When I did the OP, I was about to pack up and leave my office to go home.
> > Shortly thereafter, I realized that turtles are another clear example.
> > I didn't say this when I responded to Glenn, because the important thing
> > was to talk about them, which I did. Did you read that post?

> You are aware that turtles have no tails and essentially no neck?

I guess you don't know about sidenecked turtles, which may be confined
to southern continents. They have such long necks, they can't withdraw them
into their shells. Instead, they tuck them into the space between the carapace and plastron,
along with their heads.

> > > Seahorses and relatives. Various reef fish. Trunkfish, I believe.
> > > Electric fish of various sorts, though I'm not sure any are marine. Rays
> > > and skates. Ocean sunfish. Probably others.

> > Yup, these critters didn't occur to me. Just like when most people think of "bird,"
> > they automatically think of flying birds. The Kiwis are a big exception, of course.
> > [Note the capitalization. New Zealanders are often referred to as "Kiwis," for reasons
> > that should be obvious to anyone reading this.]
> >
> > But are you sure that electric eels [eels is a misnomer, but electric sure is not]
> > do not propel themselves mainly with their tails? What do they propel themselves with?

> Eels are "all tail".

I don't know of any true eels that are electric; do you?

> > By the way, the torpedo ray is very much electric, and marine.
> > It figures in one of Plato's dialogues, "Meno" complete with mention of a shock
> > which is translated as "electric." This word traces back to the Greek word "elektron"
> > but the meaning may only go back to Latin.

> This is not helping you support your claim 'Plesiosaurs are among the few marine vertebrates that do/did not mostly
> > > > use their tails to propel themselves through the water'.

The first line filled in a gap in Harshman's knowledge. As for the rest, see my
reply to Harshman after he got testy with that same digression.

> > > Or did you mean just tetrapods? In which case, the crab-eating frog Rana
> > > cancrivora. Or just amniotes? In which case sea turtles and all
> > > seabirds. Still, plesiosaurs may have a unique mode.
> > Yes. Australian lungfish have similar pectoral and pelvic fins, which could be called "flippers"
> > because the fleshy part predominates. However, I suspect they mostly use their
> > diphycercal tails for swimming.
> >
> > Back before they were put on the protected list, they were shown in some aquariums.
> > I saw some at the San Francisco Aquarium when I was 12, and by that time I knew a lot about
> > their taxonomic significance, and so I took a long, lingering look at them.
> > Unfortunately, I can no longer recall what their primary swimming mode was.

So far, I couldn't find out anything about their swimming mode online.

For once, Harshman took the hint and did some reading of the article.
You should too:

> What kind of numbers would you expect from a fossil skeleton in a water tank experiment?

They weren't stupid enough to use one, or even a model of one. They modeled the flippers
in the way they described in the article. They used their best guess as to how they may
have looked with flesh on the bones.

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

University of So. Carolina at Columbia
http://people.math.sc.edu/nyikos

[Peter Nyikos]

On Tuesday, September 28, 2021 at 3:02:48 PM UTC-4, John Harshman wrote:

> Looks like electric eels also mainly use their anal fins for propulsion,
> just like knife-fish.

I get the impression from the following scholarly wiki entry that they are generally
thought of by ichthyologists as a kind of knife-fish:
https://en.wikipedia.org/wiki/Gymnotiformes

The opening lines are:

"The Gymnotiformes /dʒɪmˈnɒtɪfɔːrmiːz/ are an order of teleost bony fishes commonly known as the Neotropical or South American knifefish. They have long bodies and swim using undulations of their elongated anal fin. Found almost exclusively in fresh water (the only exceptions are species that occasionally may visit brackish water to feed), these mostly nocturnal fish are capable of producing electric fields for navigation, communication, and, in the case of the electric eel (Electrophorus electricus), attack and defense.[2]

> Holding the tail still helps them maintain a
> stable electric field, making it easier to sense their surroundings.

All this got me to thinking about the lateral line of fishes, and how they might be connected to these other sensors.
There's a great deal of information about these remarkable sensory organs here:
https://en.wikipedia.org/wiki/Lateral_line

There isn't much about electric fields there, but this caught my eye:

"In some species, the receptive organs of the lateral line have been modified to function as electroreceptors, which are organs used to detect electrical impulses, and as such, these systems remain closely linked. Most amphibian larvae and some fully aquatic adult amphibians possess mechanosensitive systems comparable to the lateral line.[1]"

The Wiki entry on electric eels is almost a stub in comparison, without any neurophysiological information
comparable to that of the one on the lateral line, and so the above passage is the only clue I have as
to the connection between the two phenomena.

The one on Gymnotiformes has some paleontology and lots about the evolution of the order, beginning with:

"Gymnotiformes are among the more derived members of Ostariophysi, a lineage of primary freshwater fishes. The only known fossils are from the Miocene about 7 million years ago (Mya) of Bolivia.[21]

"Gymnotiformes has no extant species in Africa. This may be because they did not spread into Africa before South America and Africa split, or it may be that they were out-competed by Mormyridae, which are similar in that they also use electrolocation.[14]

"Gymnotiformes and Mormyridae have developed their electric organs and electrosensory systems (ESSs) through convergent evolution.[22] As Arnegard et al. (2005) and Albert and Crampton (2005) show,[23][24] their last common ancestor was roughly 140 to 208 Mya, and at this time they did not possess ESSs. Each species of Mormyrus (family: Mormyridae) and Gymnotus (family: Gymnotidae) have evolved a completely unique waveform that allows the individual fish to identify between species, genders, individuals and even between mates with better fitness levels.[25] The differences include the direction of the initial phase of the wave (positive or negative, which correlates to the direction of the current through the electrocytes in the electric organ), the amplitude of the wave, the frequency of the wave, and the number of phases of the wave."

It's a pity the group sci.bio.evolution is long defunct. This, and several paragraphs to follow,
give me the impression that this could have been a good topic for it.


Peter Nyikos

[Peter Nyikos]

No, just an indication that I think your joke, which would be fine for talk.origins,
is a bit out of place for a science forum.

> > > Give me a break, Peter. Resolving the debate with water tank experiments??
> > Nothing wrong with that. You've heard of wind tunnels to evaluate
> > aircraft features without having the full airplane to test, haven't you?

> You're backwards.

No, just thinking outside the box.

>Not all proposed shapes pass wind tunnel tests.
> And most wind tunnel tests are done on airplanes with knowledge of past airplanes,

And we have knowledge of living animals, like sea lions allegedly using their
rear flippers for steering rather than generating forward thrust.

It's more believable about the platypus, which doesn't have full fledged flippers, but webbed feet,
and the rear feet are less fully webbed than the front:

"Uniquely among mammals, it propels itself when swimming by an alternate rowing motion of the front feet; although all four feet of the platypus are webbed, the hind feet (which are held against the body) do not assist in propulsion, but are used for steering in combination with the tail.[62]"
https://en.wikipedia.org/wiki/Platypus

As is so often the case in Wikipedia, the illustrations don't match the description [1] : "held against the body"
is contradicted in the photographs. However, I believe the rest of the description, which is corroborated here:

"All other amphibious [2] mammals, including the native Australian water rat [3], kick with their back feet.
Otters also use their body undulations in swimming, and the beaver employs its tail as well as its limbs."
_The Platypus_, by Tom Grant, illustrated by Dominic Fanning, New South Wales University Press, 1984.


[1] Remember a different mismatch about the early ape *Proconsul* between an artist's drawing
and the photographs of the skeleton? You and I had a big clash with an anti-ID fanatic
in talk.origins several years ago that was centered on the mismatch once I added my voice to yours.

[2] As opposed to marine, I suppose. Also, among fresh water mammals, the otter shrew swims
mostly with the help of its powerful tail, which is flattened from side to side, unlike that of other
aquatic/marine mammals (cetaceans, sirenians, beavers...). Stephen Jay Gould was guilty of claiming
that all mammals that are tail-swimmers use up and down motions [4].

[3] A number of rodents made it to Australia millions of years ago by rafting at a time when the continent
was even further from Asia than it is now.

[4] This was in the very essay where he talked about *Ambulocetus* as being "the smoking gun"
of whale ancestry, despite the inconvenient fact that its rear limbs were *longer* than its forelimbs.
The anti-ID zealots here and in talk.origins don't like to be reminded of such on-topic mistakes by fellow zealots
by the likes of us: if there is to be any criticism of Gould, Harshman wants himself and his allies to be the ones to make it.

> fossils don't come with the whole body, usually with just the bone structure.

Of course, but forensic science has progressed to where musculature, etc. can often
be deduced from bone structure.

> >
> > I seem to recall them using pterosaur models in wind tunnels to see
> > just how aerodynamically efficient they are.
> > > Where'd they get the plesiosaur?
> > Unfortunately, there are no live animals that could make good models.

> That is one problem. But there are live animals that could be used as references, such as the tail of whales.

Unfortunately, plesiosaur tails were quite short, and the OP article has them playing

So, no help from whales. Except for showing how off base Gould was: whales have all lost their hind
legs and even their hip bones.

> > Right in the opening paragraph you can read:
> >
> > "Plesiosaurs were unique because they evolved four
> > large wing-like flippers almost always identical in size and form;
> > all other animals that swim using lateral flapping appendages (e.g. turtles and sea lions) use
> > their forward pair primarily for propulsion and the hind pair for manoeuvring,
> > and this results in markedly different morphologies [1–3]. Thus, the almost
> > identical morphology of the fore and hind flippers of plesiosaurs poses the
> > question of why they adopted such a different approach to all other living
> > and extinct vertebrates and maintained it for such a long time."

> That makes little sense, that because the flippers are similar means they used them as the only source or main source of propulsion.

You mean all four of them. Yes.

> > I don't quite get the part about "markedly different morphologies."
> > To a layman like me, the front and hind flippers of the California sea lion
> > (of which I saw lots when I lived in Monterey, and also at the Riverbanks Zoo
> > here in Columbia, SC) don't look all that different to me. Also some
> > Mesozoic sea turtles, dwarfing even the biggest living one (the leatherback),
> > also had flippers not so very different in size and shape between front and hind.
> > On the other hand, the long-necked plesiosaur Elasmosaurus seems to
> > have somewhat different front and hind paddles.
> >
> So what? Do you accept the reasoning that because they are similar, they must have been used for propulsion?

Of course not.

>
> I'd suggest that with such a long neck, they'd need to be good at changing direction quickly to catch prey.

Only about half of the plesiosaurs had long necks. At least one short-necked plesiosaur had a skull three meters
in length, with proportionate jaws and teeth. A great potential character for a "Jaws V" movie that wants
to go in a fresh, unexpected direction.

It must have been the terror of the seas. Just look at the painting in the lower right corner of:
https://en.wikipedia.org/wiki/Kronosaurus

> The tail could provide significant propulsion depending on what was attached to the bones, the flippers well suited for changing trajectories quickly, left-right, up-down.

See above about the almost nonexistent tail. [Also that painting I told you about just now, showing both Kronosaurus
and a hapless long-necked plesiosaur.] You may be thinking of mosasaurs, which came along in the Cretaceous period.
They were like short-necked plesiosaurs up front, but had very long tails.

The prevalent belief is that long-necked plesiosaurs swept their necks rapidly from
side to catch fish from an unexpected direction.

>
> What I object to though is the claim that the question has been "resolved". More likely what was resolved is the authors getting published.

I agree that it is more likely, but I think what they meant was "resolved to the satisfaction of us co-authors."

Or there might be a convention in biology where "resolved" is a code word for "If you don't like our
hypothesis, give evidence for another one. Once your evidence is published, biologists are free
to decide which is the better."

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

Univ. of So. Carolina at Columbia
http://people.math.sc.edu/nyikos

[Glenn]

So explaining about airplane speeds is your way of saying it was out of place here?

> > > > Give me a break, Peter. Resolving the debate with water tank experiments??
> > > Nothing wrong with that. You've heard of wind tunnels to evaluate
> > > aircraft features without having the full airplane to test, haven't you?
>
> > You're backwards.
> No, just thinking outside the box.
> >Not all proposed shapes pass wind tunnel tests.
> > And most wind tunnel tests are done on airplanes with knowledge of past airplanes,
> And we have knowledge of living animals, like sea lions allegedly using their
> rear flippers for steering rather than generating forward thrust.

I don't see any benefit in extrapolating what an extinct animal did by looking at existing animals.

To an extent, perhaps. But the problem with inferences and assumptions is that not everyone will share them and they can't be "resolved".
Apparently the old assumption is that the animal propelled with it's tail, but now supposedly the body is too rigid, and the tail apparently does not serve a use. This sort of consideration can go on forever.

> > >
> > > I seem to recall them using pterosaur models in wind tunnels to see
> > > just how aerodynamically efficient they are.
> > > > Where'd they get the plesiosaur?
> > > Unfortunately, there are no live animals that could make good models.
>
> > That is one problem. But there are live animals that could be used as references, such as the tail of whales.
> Unfortunately, plesiosaur tails were quite short, and the OP article has them playing

So are flippers. Flippers also create drag. On and on and on.

And some had longer tails than others.

>
> It must have been the terror of the seas. Just look at the painting in the lower right corner of:
> https://en.wikipedia.org/wiki/Kronosaurus

Must have been? Nah.

> > The tail could provide significant propulsion depending on what was attached to the bones, the flippers well suited for changing trajectories quickly, left-right, up-down.
> See above about the almost nonexistent tail. [Also that painting I told you about just now, showing both Kronosaurus
> and a hapless long-necked plesiosaur.] You may be thinking of mosasaurs, which came along in the Cretaceous period.
> They were like short-necked plesiosaurs up front, but had very long tails.
>
> The prevalent belief is that long-necked plesiosaurs swept their necks rapidly from
> side to catch fish from an unexpected direction.
> >
> > What I object to though is the claim that the question has been "resolved". More likely what was resolved is the authors getting published.
> I agree that it is more likely, but I think what they meant was "resolved to the satisfaction of us co-authors."
>
> Or there might be a convention in biology where "resolved" is a code word for "If you don't like our
> hypothesis, give evidence for another one. Once your evidence is published, biologists are free
> to decide which is the better."

Seems childish.

[Peter Nyikos]

Note the claim about "first time". If that is true, the article is worth a careful look,
even if it turns out that its methods were flawed.

I don't like the word "scaled," by the way. You can't get reliable results by scaling
things up or down. I hope the authors meant "to the same scale."

> > > > > >
> > > > > > Our aim was to determine which limb movements would have resulted in the
> > > > > > most efficient and effective propulsion. We show that plesiosaur hind
> > > > > > flippers generated up to 60% more thrust and 40% higher efficiency when
> > > > > > operating in harmony with their forward counterparts, when compared with operating alone,
> > > > > > and the spacing and relative motion between the flippers
> > > > > > was critical in governing these increases.
> > > > > >
> > > > > > The results of our analyses show that this phenomenon was probably
> > > > > > present across the whole range of plesiosaur flipper motion and resolves the
> > > > > > centuries-old debate about the propulsion style of these marine reptiles, as
> > > > > > well as indicating why they retained two pairs of flippers for more than 100 million years.
> > > > > >
> > > > > >
> > > > > > I have put in two paragraph breaks to enhance readability.
> > > > > >
> > > > > So the flippers were like oars...maybe they were supersonic swimmers!
> >
> > > > Don't be daft. Sound travels four times as fast in water as in air.
> > > > Except perhaps for the X-15, there hasn't been a plane that could
> > > > fly that fast -- in air! Only in science fiction can you hear of submarines
> > > > breaking the sound barrier while submerged.
> >
> > > Haven't heard that word "daft" in quite a while. Is that sarcasm as well?
> > No, just an indication that I think your joke, which would be fine for talk.origins,
> > is a bit out of place for a science forum.

> So explaining about airplane speeds is your way of saying it was out of place here?

I thought you might appreciate a little actual scientific data. I just happened to come across
the fact that sound travels four times as fast through water (and about 17 times as fast thru
iron) once, and then never again.

> > > > > Give me a break, Peter. Resolving the debate with water tank experiments??

> > > > Nothing wrong with that. You've heard of wind tunnels to evaluate
> > > > aircraft features without having the full airplane to test, haven't you?
> >
> > > You're backwards.

> > No, just thinking outside the box.

> > >Not all proposed shapes pass wind tunnel tests.
> > > And most wind tunnel tests are done on airplanes with knowledge of past airplanes,

> > And we have knowledge of living animals, like sea lions allegedly using their
> > rear flippers for steering rather than generating forward thrust.

> I don't see any benefit in extrapolating what an extinct animal did by looking at existing animals.

If the bone structure and musculature are very similar, why not? We don't extrapolate from past
airplanes either. The tests each serve legitimate purposes.

> > It's more believable about the platypus, which doesn't have full fledged flippers, but webbed feet,
> > and the rear feet are less fully webbed than the front:
> >
> > "Uniquely among mammals, it propels itself when swimming by an alternate rowing motion of the front feet; although all four feet of the platypus are webbed, the hind feet (which are held against the body) do not assist in propulsion, but are used for steering in combination with the tail.[62]"
> > https://en.wikipedia.org/wiki/Platypus
> >
> > As is so often the case in Wikipedia, the illustrations don't match the description [1] : "held against the body"
> > is contradicted in the photographs. However, I believe the rest of the description, which is corroborated here:
> >
> > "All other amphibious [2] mammals, including the native Australian water rat [3], kick with their back feet.
> > Otters also use their body undulations in swimming, and the beaver employs its tail as well as its limbs."
> > _The Platypus_, by Tom Grant, illustrated by Dominic Fanning, New South Wales University Press, 1984.

["footnotes" deleted this time since you had nothing to say about them]

All these differences come into play when trying to find out the swimming modes of extinct animals.
Similarly, scientists don't just throw up their hands in the air about pterosaur flight with the favorite answer
of Mark Isaak to everything where he is at a loss for a good answer to ID and creationist arguments, "We don't know."


They look at how birds fly, they look at how bats fly, they do wind tunnel tests and actual flight tests
of pterosaur models.

> > > fossils don't come with the whole body, usually with just the bone structure.
> > Of course, but forensic science has progressed to where musculature, etc. can often
> > be deduced from bone structure.

> To an extent, perhaps. But the problem with inferences and assumptions is that not everyone will share them and they can't be "resolved".

There's no point in getting bogged down in the shortcomings of the authors of this paper ("resolved")
when it is the truth that we [I hope I can include you] are trying to get at.

> Apparently the old assumption is that the animal propelled with it's tail,

Never elasmosaurus or a number of other plesiosaurs whose tails were stubs. Some plesiosaurs
had longer tails, but I grew up with the conventional wisdom that plesiosaurs used their flippers
while mosasaurs and ichthyosaurs used their tails to propel themselves forward. I've seen
nothing to make me think otherwise; this article certainly doesn't call it into question.

> but now supposedly the body is too rigid, and the tail apparently does not serve a use. This sort of consideration can go on forever.

As in real life, when the preponderance of evidence is on one side, people stop trying to "go on forever" and
are content with one explanation unless something comes along to upset the apple-cart.

In physics and chemistry that seldom happens. In geology and astronomy, a bit more often. In biology, it
depends very much on what the topic is.


Remainder deleted, to be replied to on Monday. I have one reply to Harshman to go before
calling it quits for the weekend.

It looks like, for once, I'll have some ornithology to teach *him*. I suggest you take a look
at it and look for his reaction.

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

University of So. Carolina at Columbia
http://people.math.sc.edu/nyikos

[Peter Nyikos]

On Tuesday, September 28, 2021 at 2:57:27 PM UTC-4, John Harshman wrote:
> On 9/28/21 11:39 AM, Peter Nyikos wrote:
> > On Tuesday, September 28, 2021 at 9:53:38 AM UTC-4, John Harshman wrote:
> >> On 9/28/21 6:13 AM, Peter Nyikos wrote:
> >>> On Monday, September 27, 2021 at 9:55:05 PM UTC-4, John Harshman wrote:
> >>>> On 9/27/21 3:11 PM, Peter Nyikos wrote:
> >>>>> Plesiosaurs are among the few marine vertebrates that do/did not mostly
> >>>>> use their tails to propel themselves through the water. Offhand I cannot
> >>>>> think of any other exceptions besides pinnepeds (seal, sea lions, walruses).
> >>>
> >>> When I did the OP, I was about to pack up and leave my office to go home.
> >>> Shortly thereafter, I realized that turtles are another clear example.
> >>> I didn't say this when I responded to Glenn, because the important thing
> >>> was to talk about them, which I did. Did you read that post?
> >
> >> Yes, but I'm happy to let you deal with Glenn all by yourself. Enjoy.
> >
> > What am I supposed to enjoy? Does it include your not commenting on the content of my replies to Glenn?
> >
> > I loaded the first one down with things of general paleontological
> > interest [and one that was about the physics of sound].
> > Isn't there anything you want to discuss about them?

> Not with Glenn, to the extent that I don't want to get involved in any
> discussion between you and Glenn.

You could do that by deleting everything said by Glenn and only react to what I say.

<snip for focus>

> >> Not sure about electric eels, but most electric fish keep their tails
> >> stiff and propel themselves with their dorsal fins.
> >
> > *Dorsal* fins? that's a new one on me.
> >
> > What electric fish did you have in mind? Obviously not the torpedo ray:

> Thinking of knife-fish. But I guess it's more the anal fin there. One
> point is that there are fish, particularly reef fish, that use pectoral,
> dorsal, and/or anal fins for primary propulsion. Good for slow motion,
> directional control (backwards swimming especially), and in electric
> fish keeping the tail area straight.

I'm getting the hang of terminology: "electric" has primarily to with electrolocation,
and only the minority of the time with stunning others. So the torpedo ray
stands out more than I thought:

> >>> By the way, the torpedo ray is very much electric, and marine.
> >>> It figures in one of Plato's dialogues, "Meno" complete with mention of a shock
> >>> which is translated as "electric." This word traces back to the Greek word "elektron"
> >>> but the meaning may only go back to Latin.
> >
> >> I urge you to contain your digressions, if you can.

It turns out that this "digression" was relevant to this being one of the minority of "stun" cases.


<snip for focus>

> >>> Try reading the article; you might catch a lot that I missed on a first run-through.
> >>> It's in technical language, including prominent use of "Strouhal numbers."
> >>> At one point it uses the term "Absolute thrust" but the next word is "coefficient."
> >
> >> Don't know what Strouhal numbers are, but the point is clear that left
> >> and right flippers are supposed to work in tandem and there is an
> >> optimal phase difference between front and back flippers, with its exact
> >> value depending on speed, angle of attack, and distance between them.
> >> The difference is never 180 but may be sometimes close to zero.
> >
> > Thanks. I hope you don't mind a "digression" into ornithology.
> > Are there studies as to the phase differences between wingbeats and "tail beats"
> > [retrices moving up, down, or whatever] in birds flying? I've had a chance to
> > see how there are contributions to flight by retrices through watching pet cockatiels.

> Are tails really producing lift in those cockatiels, or are they just
> producing drag when the bird wants to slow or change direction? I don't
> know of any studies on "tail beats" and know nothing of any such phenomenon.

I wonder whether others do know of them, because the incident I relate below
did fall under "tail beats."

Context: my wife regularly clipped "the wings" [flight remiges] of our first cockatiel,
and also of the pet cockatiel of a good friend of the family.

Our cockatiel, for reasons we could never find out, kept losing its retrices and
seldom had more than two of normal size at any one time. As a result,
each time its wings had only recently been clipped, it would drop like a rock whenever
it tried to take off. On one memorable occasion, this had near-fatal consequences.

On the other hand, our friend's cockatiel, Misty, always had a very healthy set of retrices.
Once, when we took care of it when our friend was away, Misty took off from its perch on someone's
hand and flew eight feet with hardly any loss of altitude by vigorously pumping its tail up and down.
Yet at that point its wings had just been clipped.

Do you have any correspondents to whom you could pass this on with some hope
of an explanation?


Peter Nyikos

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

University of So. Carolina in Columbia
http://people.math.sc.edu/nyikos

[John Harshman]

No, I don't know anyone who studies tail-based flight. Are you sure the
wings weren't involved and that the lift was actually generated by the
tail? If I had to pick a bird that might have a lift-generating tail,
that wouldn't be my first choice. I don't think your experiment had
adequate controls. Even if the observation is correct, I have strong
doubts that it would ever happen in the wild.

[Glenn]

Bird tails are like airplane tails, flight stabilizers, rudder and elevator. A bird tail would appear to have the ability to change the angle of attack of the body, and subsequently the primary wings, which could be seen as contributing to lift. Wings do not work like rigid airplane wings, and do "pump up and down" but the size of bird tails, along with the position at the back of the bird behind the center of gravity, would preclude any significant thrust or lift by itself, if at all. Basically, such pumping would force the wings to work much harder to maintain level flight, let alone not flying headlong into the ground.

[Glenn]

Apparently, cockatiels and some other birds sometimes move "wag" their tails up and down or side to side in flight because muscles attached work to help the heart in times of distress. Trying to fly with clipped wings may signal that behavior.

[John Harshman]

I am surprised to agree with you twice in a row.

[Glenn]

Get a party hat.

https://en.wikipedia.org/wiki/Ornithopter

[John Harshman]

Now that's my Glenn.

[Glenn]

You're one strange bird.

[Peter Nyikos]

On Saturday, October 2, 2021 at 12:47:06 PM UTC-4, Glenn wrote:
> On Friday, October 1, 2021 at 8:17:21 PM UTC-7, John Harshman wrote:
> > On 10/1/21 7:15 PM, Peter Nyikos wrote:
> > > On Tuesday, September 28, 2021 at 2:57:27 PM UTC-4, John Harshman wrote:
> > >> On 9/28/21 11:39 AM, Peter Nyikos wrote:
> > >>> On Tuesday, September 28, 2021 at 9:53:38 AM UTC-4, John Harshman wrote:
> > >>>> On 9/28/21 6:13 AM, Peter Nyikos wrote:
> > >>>>> On Monday, September 27, 2021 at 9:55:05 PM UTC-4, John Harshman wrote:
> > >>>>>> On 9/27/21 3:11 PM, Peter Nyikos wrote:
> > >>>>>>> Plesiosaurs are among the few marine vertebrates that do/did not mostly
> > >>>>>>> use their tails to propel themselves through the water. Offhand I cannot
> > >>>>>>> think of any other exceptions besides pinnepeds (seal, sea lions, walruses).
> > >>>>>
> > >>>>> When I did the OP, I was about to pack up and leave my office to go home.
> > >>>>> Shortly thereafter, I realized that turtles are another clear example.
> > >>>>> I didn't say this when I responded to Glenn, because the important thing
> > >>>>> was to talk about them, which I did. Did you read that post?
> > >>>
> > >>>> Yes, but I'm happy to let you deal with Glenn all by yourself. Enjoy.
> > >>>
> > >>> What am I supposed to enjoy? Does it include your not commenting on the content of my replies to Glenn?
> > >>>
> > >>> I loaded the first one down with things of general paleontological
> > >>> interest [and one that was about the physics of sound].
> > >>> Isn't there anything you want to discuss about them?
> > >
> > >> Not with Glenn, to the extent that I don't want to get involved in any
> > >> discussion between you and Glenn.
> > >
> > > You could do that by deleting everything said by Glenn and only react to what I say.

Harshman, as usual in such cases, ignored this comment. But see my PS at the end.

John was just babbling nonsense above; most of it was already addressed by me.
Adult birds almost never lose all their flight feathers in the wild, and he could
have made his comments sound less stupid by pointing that out.

You, on the other hand, write quite sensibly below.

> Bird tails are like airplane tails, flight stabilizers, rudder and elevator.

Also flaps and ailerons, although in the latter role it is probably secondary to the wings.
As you probably know, the flaps on an airplane make for good landings. The same goes for the tails of birds.

Which may explain why swifts, who spend most of the time airborne, have such small tails.
They don't need lots of controlled landings each day. I wonder whether a swift has ever been filmed landing.
To cage a swift for more than a few hours should be punishable as cruelty to animals.

>A bird tail would appear to have the ability to change the angle of attack of the body, and subsequently the primary wings, which could be seen as contributing to lift.

There can be no doubt about the tail providing lift. This was one of the main functions attributed to them
in a detailed article about the role of the tail in flight ca. 1999. I've been trying to find a more recent one that
is so comprehensive, but no luck so far.

>Wings do not work like rigid airplane wings, and do "pump up and down"

I wouldn't call that pumping; it doesn't have the same feel as what I saw Misty doing with its tail.

> but the size of bird tails, along with the position at the back of the bird behind the center of gravity, would preclude any significant thrust or lift by itself, if at all. Basically, such pumping would force the wings to work much harder to maintain level flight, let alone not flying headlong into the ground.

In this case, of course, the wings had no such ability. I've forgotten how that article talked about the way
the tail provides lift, but it stands to reason that if the tail is held at a downwards angle, lift would be generated
just as lift is generated by the wings of an airplane because of their downward tilt.

I've even read that it is a huge misconception that the main source of lift in an airplane is the way the streamlining
of the wings is done. The article said that even a perfectly flat wing produces lots of lift when the wings are
angled in the usual way.

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

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

PS I believe John Hashman could have told you a lot of this. But that would spoil
the virtual reality he and Hemidactylus and many others have built around you for over a decade now.
It's a good thing I was absent from this thread as long as I was. He actually "forgot"
about his boycott of you and of my posts where I am replying to you.

[Mark Isaak]

On 9/28/21 6:13 AM, Peter Nyikos wrote:

[snip all but a digression]

> By the way, the torpedo ray is very much electric, and marine.
> It figures in one of Plato's dialogues, "Meno" complete with mention of a shock
> which is translated as "electric." This word traces back to the Greek word "elektron"
> but the meaning may only go back to Latin.

"Torpedo" comes from Latin _torpore_, to be numb, alluding to the fish's
electric jolt. "Electric" comes from Latin _electrum_ and/or Greek
_elektron_, both of which mean "amber"; I don't know which of those two
came first. The modern word, however, went through Modern Latin before
getting its English form.

--
Mark Isaak eciton (at) curioustaxonomy (dot) net
"Omnia disce. Videbis postea nihil esse superfluum."
- Hugh of St. Victor

[Daud Deden]

Another digression: https://www.torqeedo.com/us/en-us/products/outboards/ultralight