Open access article with Paul Sereno:

Spinosaurus is not an aquatic dinosaur

Abstract

A predominantly fish-eating diet was envisioned for the sail-backed
theropod dinosaur Spinosaurus aegyptiacus when its elongate jaws with
subconical teeth were unearthed a century ago in Egypt. Recent
discovery of the high-spined tail of that skeleton, however, led to a
bolder conjecture that S. aegyptiacus was the first fully aquatic
dinosaur. The ‘aquatic hypothesis’ posits that S. aegyptiacus was a
slow quadruped on land but a capable pursuit predator in coastal
waters, powered by an expanded tail. We test these functional claims
with skeletal and flesh models of S. aegyptiacus. We assembled a
CT-based skeletal reconstruction based on the fossils, to which we
added internal air and muscle to create a posable flesh model. That
model shows that on land S. aegyptiacus was bipedal and in deep water
was an unstable, slow-surface swimmer (<1 m/s) too buoyant to dive.
Living reptiles with similar spine-supported sails over trunk and tail
are used for display rather than aquatic propulsion, and nearly all
extant secondary swimmers have reduced limbs and fleshy tail flukes.
New fossils also show that Spinosaurus ranged far inland. Two stages
are clarified in the evolution of Spinosaurus, which is best
understood as a semiaquatic bipedal ambush piscivore that frequented
the margins of coastal and inland waterways.
https://elifesciences.org/articles/80092

On Friday, December 16, 2022 at 12:05:46 PM UTC-5, Pandora wrote:
> Open access article with Paul Sereno:

Pardon my asking: does "with" mean that you are one of the co-authors?
Or is it shorthand for "by Paul Sereno and co-authors"?
Feel free not to respond to these questions. I value your privacy highly.

> Spinosaurus is not an aquatic dinosaur
>
> Abstract
>
> A predominantly fish-eating diet was envisioned for the sail-backed
> theropod dinosaur Spinosaurus aegyptiacus when its elongate jaws with
> subconical teeth were unearthed a century ago in Egypt. Recent
> discovery of the high-spined tail of that skeleton, however, led to a
> bolder conjecture that S. aegyptiacus was the first fully aquatic
> dinosaur.

Yes, this is a widely popularized conjecture, but IIRC the popularizations
weren't all so modest about its level of certainty.

>The ‘aquatic hypothesis’ posits that S. aegyptiacus was a
> slow quadruped on land but a capable pursuit predator in coastal
> waters, powered by an expanded tail. We test these functional claims
> with skeletal and flesh models of S. aegyptiacus. We assembled a
> CT-based skeletal reconstruction based on the fossils, to which we
> added internal air and muscle to create a posable flesh model. That
> model shows that on land S. aegyptiacus was bipedal and in deep water
> was an unstable, slow-surface swimmer (<1 m/s) too buoyant to dive.
> Living reptiles with similar spine-supported sails over trunk and tail
> are used for display rather than aquatic propulsion, and nearly all
> extant secondary swimmers have reduced limbs and fleshy tail flukes.

That doesn't seem to be the case with mammals. More about this below.

> New fossils also show that Spinosaurus ranged far inland. Two stages
> are clarified in the evolution of Spinosaurus, which is best
> understood as a semiaquatic bipedal ambush piscivore that frequented
> the margins of coastal and inland waterways.
> https://elifesciences.org/articles/80092

This is a very interesting paper, and its interest is greatly increased for me
because it has a supplement that gives fascinating information about
the refereeing process, showing both editors' and referee's comments,
along with replies by the authors. Thanks for showing it to us, Pandora.

About the mammals: since they lack tails, phocids obviously cannot have tail flukes,
and I don't think their hind legs function the way the flukes of cetaceans do.

A less trivial example: it is not firmly established that the archaeocete *Basilosaurus* had tail flukes.

The abstract carelessly has "swimmers" instead of "aquatic animals," thereby
leaving out semiaquatic swimmers, such as beavers, muskrats, coypus, and freshwater otters.

On the other hand, sea otters qualify as fully aquatic mammals, and they don't have tail flukes.
They very seldom come out on land, and they give birth in the kelp beds.

Long ago, I found another generalization about swimming verterbrates, by Stephen Jay Gould.
In his memorable essay about *Ambulocetus* as the "smoking gun"
[his words] for a transitional animal between terrestrial mammals and
whales, he wrote that while reptiles that swim with their tails move them sideways,
while mammals that swim with their tails move them up and down.

This too has an exception, the otter shrew:

"The powerful tail is flattened and it swims by moving it from side to side.."
-- Collins Guide to the Rare Mammals of the World, by John A. Burton and Bruce Pearson, 1987, p. 34.

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

On Fri, 16 Dec 2022 18:31:00 -0800 (PST), Peter Nyikos
<peter2nyikos@gmail.com> wrote:

>On Friday, December 16, 2022 at 12:05:46 PM UTC-5, Pandora wrote:
>> Open access article with Paul Sereno:
>
>Pardon my asking: does "with" mean that you are one of the co-authors?
>Or is it shorthand for "by Paul Sereno and co-authors"?

I thought I'd let you know a celebrity is throwing his weight into
this discussion, and it's not me. ;-)

Sereno's recognitions include People magazine's 50 Most Beautiful
People (1997), Esquire's 100 Best People in the World (1997).
https://explorer-directory.nationalgeographic.org/paul-c-sereno

On Saturday, December 17, 2022 at 4:56:19 AM UTC-8, Pandora wrote:
> On Fri, 16 Dec 2022 18:31:00 -0800 (PST), Peter Nyikos
> <peter2...@gmail.com> wrote:
>
> >On Friday, December 16, 2022 at 12:05:46 PM UTC-5, Pandora wrote:
> >> Open access article with Paul Sereno:
> >
> >Pardon my asking: does "with" mean that you are one of the co-authors?
> >Or is it shorthand for "by Paul Sereno and co-authors"?
> I thought I'd let you know a celebrity is throwing his weight into
> this discussion, and it's not me. ;-)
>
> Sereno's recognitions include People magazine's 50 Most Beautiful
> People (1997), Esquire's 100 Best People in the World (1997).
> https://explorer-directory.nationalgeographic.org/paul-c-sereno

Nathan Myhrvold displays a lot of diversity himself.

FINALLY made it to Christmas break…. at last, time for another quick dip into my hobbies!

Wow, so based on the reconstructions they have, it sounds like their Spinosaurus would be a bipedal dinosaur who carries its body nearly horizontally! Have there been any other bipeds like that? It seems crazy, all that weight on such relatively short legs!

On 12/18/22 10:06 AM, Sight Reader wrote:
> FINALLY made it to Christmas break…. at last, time for another quick dip into my hobbies!
>
> Wow, so based on the reconstructions they have, it sounds like their Spinosaurus would be a bipedal dinosaur who carries its body nearly horizontally! Have there been any other bipeds like that? It seems crazy, all that weight on such relatively short legs!

Just about any theropod, and notably many of the living ones?

On Sunday, December 18, 2022 at 7:46:48 PM UTC-7, John Harshman wrote:
> On 12/18/22 10:06 AM, Sight Reader wrote:
> > FINALLY made it to Christmas break…. at last, time for another quick dip into my hobbies!
> >
> > Wow, so based on the reconstructions they have, it sounds like their Spinosaurus would be a bipedal dinosaur who carries its body nearly horizontally! Have there been any other bipeds like that? It seems crazy, all that weight on such relatively short legs!
> Just about any theropod, and notably many of the living ones?

Yay, thanks for the reply! Sorry about that stupid “horizontal” part; that’s a pretty embarrassing misstatement (turns very red).

Anyway, what I’m utterly failing to comprehend is the “short legs” part. Even compared to Suchomimus, the hind legs of Spinosaurus are SO short! For a dinosaur that massive, wouldn’t it be difficult to turn or maneuver anywhere but forward? With legs so short, it’s hard for me to picture how they’d get enough horizontal “torque” (if that’s the right word?) needed to change the dinosaur’s direction: I’d think movements of that massive head or tail would generate way more torque than those little legs can handle because they’re horizontally so much farther away from the center of gravity (especially given that the dinosaur’s posture is almost totally horizontal). Another thing I’d think would be a problem is the tiny feet compared to the body size: can those little claws generate enough traction on the ground to propel such an incredible mass abruptly enough for an ambush?

Apologies again if these questions are astoundingly stupid; once again, I’m new at this.

On 12/18/22 10:29 PM, Sight Reader wrote:
> On Sunday, December 18, 2022 at 7:46:48 PM UTC-7, John Harshman wrote:
>> On 12/18/22 10:06 AM, Sight Reader wrote:
>>> FINALLY made it to Christmas break…. at last, time for another quick dip into my hobbies!
>>>
>>> Wow, so based on the reconstructions they have, it sounds like their Spinosaurus would be a bipedal dinosaur who carries its body nearly horizontally! Have there been any other bipeds like that? It seems crazy, all that weight on such relatively short legs!
>> Just about any theropod, and notably many of the living ones?
>
> Yay, thanks for the reply! Sorry about that stupid “horizontal” part; that’s a pretty embarrassing misstatement (turns very red).
>
> Anyway, what I’m utterly failing to comprehend is the “short legs” part. Even compared to Suchomimus, the hind legs of Spinosaurus are SO short! For a dinosaur that massive, wouldn’t it be difficult to turn or maneuver anywhere but forward? With legs so short, it’s hard for me to picture how they’d get enough horizontal “torque” (if that’s the right word?) needed to change the dinosaur’s direction: I’d think movements of that massive head or tail would generate way more torque than those little legs can handle because they’re horizontally so much farther away from the center of gravity (especially given that the dinosaur’s posture is almost totally horizontal). Another thing I’d think would be a problem is the tiny feet compared to the body size: can those little claws generate enough traction on the ground to propel such an incredible mass abruptly enough for an ambush?
>
> Apologies again if these questions are astoundingly stupid; once again, I’m new at this.

Not sure about the rest, but the Sereno et al. paper did conclude that
the center of gravity of the beasty was at its hips.

On Monday, December 19, 2022 at 7:35:38 AM UTC-7, John Harshman wrote:
> Not sure about the rest, but the Sereno et al. paper did conclude that
> the center of gravity of the beasty was at its hips.
Precisely! What I’m trying to say is that turning gigantic dinosaur like that with tiny little legs directly under the center of gravity would be like trying to turn a gigantic 20-ton propeller by trying to grab the hub: the part closest to the center of gravity is the hardest to turn because you have no leverage or “moment arm”, like the long handle on a wrench.

On 12/19/22 6:49 AM, Sight Reader wrote:
> On Monday, December 19, 2022 at 7:35:38 AM UTC-7, John Harshman wrote:
>> Not sure about the rest, but the Sereno et al. paper did conclude that
>> the center of gravity of the beasty was at its hips.
> Precisely! What I’m trying to say is that turning gigantic dinosaur like that with tiny little legs directly under the center of gravity would be like trying to turn a gigantic 20-ton propeller by trying to grab the hub: the part closest to the center of gravity is the hardest to turn because you have no leverage or “moment arm”, like the long handle on a wrench.

Is this not true for all theropods?

Welcome back, Sight Reader! I'm glad you are over your final exams. Did you spend some of your Thanksgiving break
trying to get caught up?

On Monday, December 19, 2022 at 9:49:09 AM UTC-5, thesigh...@gmail.com wrote:
> On Monday, December 19, 2022 at 7:35:38 AM UTC-7, John Harshman wrote:

A little tip: don't delete so much. It's hard to know what "the rest" is when you don't leave
any of your own words in from the earlier post. [Yes, ]we all know how to scroll up, but
that interrupts the rest of the thought.

> > Not sure about the rest, but the Sereno et al. paper did conclude that
> > the center of gravity of the beasty was at its hips.

> Precisely! What I’m trying to say is that turning gigantic dinosaur like that with tiny little legs directly under the center of gravity would be like trying to turn a gigantic 20-ton propeller by trying to grab the hub: the part closest to the center of gravity is the hardest to turn because you have no leverage or “moment arm”, like the long handle on a wrench.

Wait--why do you talk about the tiny little legs being directly under the center of gravity
when they aren't the ones connected to the hips?

As for "hardest to turn": I get the impression from the abominably unhelpful Wikipedia that the gluteus maximus is responsible for raising
the front of the body, and it has plenty of leverage from the attachment at the bottom of the hip.

I do believe that the non-theropod Plateosaurus was a biped that also got down on all fours a lot. Another
non-theropod, Stegosaurus looks like a quadruped that might often have reared up on its much bigger hind legs.

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

On 12/19/22 10:55 AM, Peter Nyikos wrote:
> Welcome back, Sight Reader! I'm glad you are over your final exams. Did you spend some of your Thanksgiving break
> trying to get caught up?
>
> On Monday, December 19, 2022 at 9:49:09 AM UTC-5, thesigh...@gmail.com wrote:
>> On Monday, December 19, 2022 at 7:35:38 AM UTC-7, John Harshman wrote:
>
> A little tip: don't delete so much. It's hard to know what "the rest" is when you don't leave
> any of your own words in from the earlier post. [Yes, ]we all know how to scroll up, but
> that interrupts the rest of the thought.
>
>>> Not sure about the rest, but the Sereno et al. paper did conclude that
>>> the center of gravity of the beasty was at its hips.
>
>> Precisely! What I’m trying to say is that turning gigantic dinosaur like that with tiny little legs directly under the center of gravity would be like trying to turn a gigantic 20-ton propeller by trying to grab the hub: the part closest to the center of gravity is the hardest to turn because you have no leverage or “moment arm”, like the long handle on a wrench.
>
> Wait--why do you talk about the tiny little legs being directly under the center of gravity
> when they aren't the ones connected to the hips?

I believe the ones connected to the hips are in fact what he's talking
about.

> As for "hardest to turn": I get the impression from the abominably unhelpful Wikipedia that the gluteus maximus is responsible for raising
> the front of the body, and it has plenty of leverage from the attachment at the bottom of the hip.

And he's talking about turning left and right.

> I do believe that the non-theropod Plateosaurus was a biped that also got down on all fours a lot. Another
> non-theropod, Stegosaurus looks like a quadruped that might often have reared up on its much bigger hind legs.

And note, both of the descended from obligate bipeds. Whether any
spinosaurs ever got down on all fours is an open question.

Thanks for the corrections, John. I have some comments below.

On Sunday, December 18, 2022 at 9:46:48 PM UTC-5, John Harshman wrote:
> On 12/18/22 10:06 AM, Sight Reader wrote:
> > FINALLY made it to Christmas break…. at last, time for another quick dip into my hobbies!
> >
> > Wow, so based on the reconstructions they have, it sounds like their Spinosaurus would be a bipedal dinosaur who carries its body nearly horizontally! Have there been any other bipeds like that? It seems crazy, all that weight on such relatively short legs!

> Just about any theropod, and notably many of the living ones?

Since there are no living theropods, I take it "ones" refers to "bipeds", specifically birds.
Bipedal mammals, on the other hand, are all exceptions AFAIK.
This includes not only ourselves, but also indris, sifakas and avahis,
all of which are lemurs. I believe tarsiers are another exception.

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

On 12/19/22 1:07 PM, Peter Nyikos wrote:
> Thanks for the corrections, John. I have some comments below.
>
> On Sunday, December 18, 2022 at 9:46:48 PM UTC-5, John Harshman wrote:
>> On 12/18/22 10:06 AM, Sight Reader wrote:
>>> FINALLY made it to Christmas break…. at last, time for another quick dip into my hobbies!
>>>
>>> Wow, so based on the reconstructions they have, it sounds like their Spinosaurus would be a bipedal dinosaur who carries its body nearly horizontally! Have there been any other bipeds like that? It seems crazy, all that weight on such relatively short legs!
>
>> Just about any theropod, and notably many of the living ones?
>
> Since there are no living theropods,

Have you learned nothing from me?

> I take it "ones" refers to "bipeds", specifically birds.
> Bipedal mammals, on the other hand, are all exceptions AFAIK.
> This includes not only ourselves, but also indris, sifakas and avahis,
> all of which are lemurs. I believe tarsiers are another exception.

What about kangaroos? Check out the QANTAS logo.

On Monday, December 19, 2022 at 4:12:36 PM UTC-5, John Harshman wrote:
> On 12/19/22 1:07 PM, Peter Nyikos wrote:
> > Thanks for the corrections, John. I have some comments below.
> >
> > On Sunday, December 18, 2022 at 9:46:48 PM UTC-5, John Harshman wrote:
> >> On 12/18/22 10:06 AM, Sight Reader wrote:
> >>> FINALLY made it to Christmas break…. at last, time for another quick dip into my hobbies!
> >>>
> >>> Wow, so based on the reconstructions they have, it sounds like their Spinosaurus would be a bipedal dinosaur who carries its body nearly horizontally! Have there been any other bipeds like that? It seems crazy, all that weight on such relatively short legs!
> >
> >> Just about any theropod, and notably many of the living ones?
> >
> > Since there are no living theropods,

> Have you learned nothing from me?

I'm sorry, but I refuse to adopt the jargon "birds are dinosaurs."
They are *descended from* what you call "non-avian dinosaurs"
and I call "dinosaurs."

How would you like it if I kept calling you "a unicellular eukaryote,"
just because you are descended from them?

> > I take it "ones" refers to "bipeds", specifically birds.
> > Bipedal mammals, on the other hand, are all exceptions AFAIK.
> > This includes not only ourselves, but also indris, sifakas and avahis,
> > all of which are lemurs. I believe tarsiers are another exception.

> What about kangaroos?

I was thinking in terms of "vertical bipeds," and kangaroos hold
themselves at an angle, which would be closer to horizontal
if it were not for the big fleshy tails. But thanks for the reminder.

Getting back to paleontology: I've often wondered why
the pantodont *Barylambda* is shown with a long thick tail like a kangaroo.
They are the only non-aquatic mammals I can think of with such big thick
tails in proportion to their bodies. [Well, OK, wallabies and other "miniature kangaroos."]

> Check out the QANTAS logo.

Have you learned nothing *about* me? I've been fascinated by
marsupials (also monotremes) since before the age of 12.
As if that weren't enough, my wife grew up in Australia,
and we were married there. We even saw a dead wallaby on the road
on our honeymoon, and my wife stopped the car to get it off the road.

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

Hey guys, thanks a ton for the feedback! Sorry about the snipping… I didn’t want to flood you guys with excess information and didn’t realize that snipping make things inconvenient (feeling embarrassed yet AGAIN). Apparently I only open my mouth to change feet…

Anyways, regarding why I have concerns about this reconstruction of Spinosaurus but not about other theropods, I’m mostly referring to the ratio of stride length to where most of the body mass is.

I’ll give this my best shot. Let’s consider, for example, your average T-rex. Just from eyeballing it, I’d say her front foot would land roughly under her neck. Note that this means that most of her mass would be between that front foot and her center of gravity (presumably over her hip): only her neck and head would be farther away from her center of gravity than where her foot is planted, but with such long legs, she can easily rear up and even move that mass closer to her center of mass. Since her stride length is longer than most of her mass, she could push off of that foot, and the location her foot is planted will have a reasonably long “moment arm” that can amplify the turning force on her center of mass. This would be more like pushing at the END of the 20-ton propeller rather than trying to twist it at its hub: you don’t need nearly as much strength to get it rotating. Now to be clear, I’m not entirely sure how ANY of these theropods turned since their hips don’t seem to let them sprawl their legs out sideways to “cut” like we can: I would guess dinosaurs would require a certain level of “banking” (leaning left or right into a turn) before coming about, but that should be easy enough given sufficiently long legs and I think there are plenty of animals that do that.

Let’s now look at their reconstruction of Spinosaurus. If she puts her foot forward, I’m not even sure her foot makes it to her arms, which means that there is not nearly as much of her mass between her plant foot and her center of gravity: there still remains a LOT of mass outside of where that foot lands, including those big arms, the thick neck, and her even bigger head. Furthermore, she has very little clearance off the ground, so she can’t rear up quasi-erect to come about - she has to hold herself horizontal to avoid bottoming out, thus keeping a significant portion of her mass outside of her stride length (all of this could be SO EASILY described in about 10 words if only I could post a picture… GAH!) Anyways, this is the problem of trying to turn that 20-ton propeller by trying to twist it at its hub - without being able to leverage further out to the “propeller”, I just can’t see how she’s going to maneuver. Now, if she was something of a quadruped, she could plant her arms into the ground - which are much farther away from the center of gravity and can thus exert torque without a ridiculous amount of force, but apparently her arms have no weight bearing function, so I don’t think she can do this unless she grabs a tree or something. As far as my pet theory of “banking” before turning goes, that too would be proportionally more difficult with her short clearance from the ground.

I would finally note that older reconstructions of Spinosaurus - notably the one in Jurassic Park III but there are still quite a few others sitting around - all give her much longer legs than they’re reconstructed. However, these portrayals seem to be getting replaced by the little-leg version, especially those that show her swimming. I have no idea which is right.

Sorry that was so long! I tried my best…

On Monday, December 19, 2022 at 12:26:19 PM UTC-7, John Harshman wrote:
> On 12/19/22 10:55 AM, Peter Nyikos wrote:
> > Welcome back, Sight Reader! I'm glad you are over your final exams. Did you spend some of your Thanksgiving break
> > trying to get caught up?
> >
> > On Monday, December 19, 2022 at 9:49:09 AM UTC-5, thesigh...@gmail.com wrote:
> >> On Monday, December 19, 2022 at 7:35:38 AM UTC-7, John Harshman wrote:
> >
> > A little tip: don't delete so much. It's hard to know what "the rest" is when you don't leave
> > any of your own words in from the earlier post. [Yes, ]we all know how to scroll up, but
> > that interrupts the rest of the thought.
> >
> >>> Not sure about the rest, but the Sereno et al. paper did conclude that
> >>> the center of gravity of the beasty was at its hips.
> >
> >> Precisely! What I’m trying to say is that turning gigantic dinosaur like that with tiny little legs directly under the center of gravity would be like trying to turn a gigantic 20-ton propeller by trying to grab the hub: the part closest to the center of gravity is the hardest to turn because you have no leverage or “moment arm”, like the long handle on a wrench.
> >
> > Wait--why do you talk about the tiny little legs being directly under the center of gravity
> > when they aren't the ones connected to the hips?
> I believe the ones connected to the hips are in fact what he's talking
> about.
> > As for "hardest to turn": I get the impression from the abominably unhelpful Wikipedia that the gluteus maximus is responsible for raising
> > the front of the body, and it has plenty of leverage from the attachment at the bottom of the hip.
> And he's talking about turning left and right.
> > I do believe that the non-theropod Plateosaurus was a biped that also got down on all fours a lot. Another
> > non-theropod, Stegosaurus looks like a quadruped that might often have reared up on its much bigger hind legs.
> And note, both of the descended from obligate bipeds. Whether any
> spinosaurs ever got down on all fours is an open question.

Hey, I thought of a better analogy! Ever try to push open the wrong side of a heavy door?

Try to push open a heavy door near it’s hinges. Much harder, which is why door knobs are on the side OPPOSITE of the hinges. Similarly, once it IS rotating, it’s hard to stop it if you can only push near the hinges.

Same with the Spinosaurus. The hinges are his center of mass. Short legs means she’s stuck exerting force too close to the hinges - her center of mass. Once she does get her body turning, the little legs will have trouble getting enough traction to stop her from over-rotating.

T-rex has longer legs. When she plants HER foot, it’s farther from the center of mass: it’s like planting your hand more towards the middle of the door or even close to the doorknob. Much easier to turn and control the door.

Regarding horizontal versus tilted posture, it’s the same issue. Horizontal posture is like the figure skater spinning with her arms out. If a dinosaur can raise its head and neck, it’s like the figure skater pulling arms in closer to her center of mass: she starts spinning faster.

Did that make sense at all?

On Monday, December 19, 2022 at 12:26:19 PM UTC-7, John Harshman wrote:
> On 12/19/22 10:55 AM, Peter Nyikos wrote:
> > Welcome back, Sight Reader! I'm glad you are over your final exams. Did you spend some of your Thanksgiving break
> > trying to get caught up?
> >
> > On Monday, December 19, 2022 at 9:49:09 AM UTC-5, thesigh...@gmail.com wrote:
> >> On Monday, December 19, 2022 at 7:35:38 AM UTC-7, John Harshman wrote:
> >
> > A little tip: don't delete so much. It's hard to know what "the rest" is when you don't leave
> > any of your own words in from the earlier post. [Yes, ]we all know how to scroll up, but
> > that interrupts the rest of the thought.
> >
> >>> Not sure about the rest, but the Sereno et al. paper did conclude that
> >>> the center of gravity of the beasty was at its hips.
> >
> >> Precisely! What I’m trying to say is that turning gigantic dinosaur like that with tiny little legs directly under the center of gravity would be like trying to turn a gigantic 20-ton propeller by trying to grab the hub: the part closest to the center of gravity is the hardest to turn because you have no leverage or “moment arm”, like the long handle on a wrench.
> >
> > Wait--why do you talk about the tiny little legs being directly under the center of gravity
> > when they aren't the ones connected to the hips?
> I believe the ones connected to the hips are in fact what he's talking
> about.
> > As for "hardest to turn": I get the impression from the abominably unhelpful Wikipedia that the gluteus maximus is responsible for raising
> > the front of the body, and it has plenty of leverage from the attachment at the bottom of the hip.
> And he's talking about turning left and right.
> > I do believe that the non-theropod Plateosaurus was a biped that also got down on all fours a lot. Another
> > non-theropod, Stegosaurus looks like a quadruped that might often have reared up on its much bigger hind legs.
> And note, both of the descended from obligate bipeds. Whether any
> spinosaurs ever got down on all fours is an open question.

On 12/19/22 1:53 PM, Peter Nyikos wrote:
> On Monday, December 19, 2022 at 4:12:36 PM UTC-5, John Harshman wrote:
>> On 12/19/22 1:07 PM, Peter Nyikos wrote:
>>> Thanks for the corrections, John. I have some comments below.
>>>
>>> On Sunday, December 18, 2022 at 9:46:48 PM UTC-5, John Harshman wrote:
>>>> On 12/18/22 10:06 AM, Sight Reader wrote:
>>>>> FINALLY made it to Christmas break…. at last, time for another quick dip into my hobbies!
>>>>>
>>>>> Wow, so based on the reconstructions they have, it sounds like their Spinosaurus would be a bipedal dinosaur who carries its body nearly horizontally! Have there been any other bipeds like that? It seems crazy, all that weight on such relatively short legs!
>>>
>>>> Just about any theropod, and notably many of the living ones?
>>>
>>> Since there are no living theropods,
>
>> Have you learned nothing from me?
>
> I'm sorry, but I refuse to adopt the jargon "birds are dinosaurs."
> They are *descended from* what you call "non-avian dinosaurs"
> and I call "dinosaurs."
>
> How would you like it if I kept calling you "a unicellular eukaryote,"
> just because you are descended from them?

Wrong comparison. How would you like if I kept calling you a mammal,
just because you are descended from them? In your comparison, it's
"unicellular" that's doing the work. I presume you're fine with being a
eukaryote. But of course "unicellular eukaryote" isn't a group.

>>> I take it "ones" refers to "bipeds", specifically birds.
>>> Bipedal mammals, on the other hand, are all exceptions AFAIK.
>>> This includes not only ourselves, but also indris, sifakas and avahis,
>>> all of which are lemurs. I believe tarsiers are another exception.
>
>> What about kangaroos?
>
> I was thinking in terms of "vertical bipeds," and kangaroos hold
> themselves at an angle, which would be closer to horizontal
> if it were not for the big fleshy tails. But thanks for the reminder.

No, it's horizontal precisely because of the big fleshy tail. When
moving fast they are indeed horizontal, balanced over the hind legs.
Like a theropod.

> Getting back to paleontology: I've often wondered why
> the pantodont *Barylambda* is shown with a long thick tail like a kangaroo.
> They are the only non-aquatic mammals I can think of with such big thick
> tails in proportion to their bodies. [Well, OK, wallabies and other "miniature kangaroos."]
>
>
>> Check out the QANTAS logo.
>
> Have you learned nothing *about* me? I've been fascinated by
> marsupials (also monotremes) since before the age of 12.
> As if that weren't enough, my wife grew up in Australia,
> and we were married there. We even saw a dead wallaby on the road
> on our honeymoon, and my wife stopped the car to get it off the road.

So you have no excuse for forgetting about them.

On 12/19/22 2:23 PM, Sight Reader wrote:
> Hey guys, thanks a ton for the feedback! Sorry about the snipping… I didn’t want to flood you guys with excess information and didn’t realize that snipping make things inconvenient (feeling embarrassed yet AGAIN). Apparently I only open my mouth to change feet…
>
> Anyways, regarding why I have concerns about this reconstruction of Spinosaurus but not about other theropods, I’m mostly referring to the ratio of stride length to where most of the body mass is.
>
> I’ll give this my best shot. Let’s consider, for example, your average T-rex. Just from eyeballing it, I’d say her front foot would land roughly under her neck. Note that this means that most of her mass would be between that front foot and her center of gravity (presumably over her hip): only her neck and head would be farther away from her center of gravity than where her foot is planted, but with such long legs, she can easily rear up and even move that mass closer to her center of mass. Since her stride length is longer than most of her mass, she could push off of that foot, and the location her foot is planted will have a reasonably long “moment arm” that can amplify the turning force on her center of mass. This would be more like pushing at the END of the 20-ton propeller rather than trying to twist it at its hub: you don’t need nearly as much strength to get it rotating. Now to be clear, I’m not entirely sure how ANY of these theropods turned since their hips don’t seem to let them sprawl their legs out sideways to “cut” like we can: I would guess dinosaurs would require a certain level of “banking” (leaning left or right into a turn) before coming about, but that should be easy enough given sufficiently long legs and I think there are plenty of animals that do that.
>
> Let’s now look at their reconstruction of Spinosaurus. If she puts her foot forward, I’m not even sure her foot makes it to her arms, which means that there is not nearly as much of her mass between her plant foot and her center of gravity: there still remains a LOT of mass outside of where that foot lands, including those big arms, the thick neck, and her even bigger head. Furthermore, she has very little clearance off the ground, so she can’t rear up quasi-erect to come about - she has to hold herself horizontal to avoid bottoming out, thus keeping a significant portion of her mass outside of her stride length (all of this could be SO EASILY described in about 10 words if only I could post a picture… GAH!) Anyways, this is the problem of trying to turn that 20-ton propeller by trying to twist it at its hub - without being able to leverage further out to the “propeller”, I just can’t see how she’s going to maneuver. Now, if she was something of a quadruped, she could plant her arms into the ground - which are much farther away from the center of gravity and can thus exert torque without a ridiculous amount of force, but apparently her arms have no weight bearing function, so I don’t think she can do this unless she grabs a tree or something. As far as my pet theory of “banking” before turning goes, that too would be proportionally more difficult with her short clearance from the ground.
>
> I would finally note that older reconstructions of Spinosaurus - notably the one in Jurassic Park III but there are still quite a few others sitting around - all give her much longer legs than they’re reconstructed. However, these portrayals seem to be getting replaced by the little-leg version, especially those that show her swimming. I have no idea which is right.
>
> Sorry that was so long! I tried my best…
>
> On Monday, December 19, 2022 at 12:26:19 PM UTC-7, John Harshman wrote:
>> On 12/19/22 10:55 AM, Peter Nyikos wrote:
>>> Welcome back, Sight Reader! I'm glad you are over your final exams. Did you spend some of your Thanksgiving break
>>> trying to get caught up?
>>>
>>> On Monday, December 19, 2022 at 9:49:09 AM UTC-5, thesigh...@gmail.com wrote:
>>>> On Monday, December 19, 2022 at 7:35:38 AM UTC-7, John Harshman wrote:
>>>
>>> A little tip: don't delete so much. It's hard to know what "the rest" is when you don't leave
>>> any of your own words in from the earlier post. [Yes, ]we all know how to scroll up, but
>>> that interrupts the rest of the thought.
>>>
>>>>> Not sure about the rest, but the Sereno et al. paper did conclude that
>>>>> the center of gravity of the beasty was at its hips.
>>>
>>>> Precisely! What I’m trying to say is that turning gigantic dinosaur like that with tiny little legs directly under the center of gravity would be like trying to turn a gigantic 20-ton propeller by trying to grab the hub: the part closest to the center of gravity is the hardest to turn because you have no leverage or “moment arm”, like the long handle on a wrench.
>>>
>>> Wait--why do you talk about the tiny little legs being directly under the center of gravity
>>> when they aren't the ones connected to the hips?
>> I believe the ones connected to the hips are in fact what he's talking
>> about.
>>> As for "hardest to turn": I get the impression from the abominably unhelpful Wikipedia that the gluteus maximus is responsible for raising
>>> the front of the body, and it has plenty of leverage from the attachment at the bottom of the hip.
>> And he's talking about turning left and right.
>>> I do believe that the non-theropod Plateosaurus was a biped that also got down on all fours a lot. Another
>>> non-theropod, Stegosaurus looks like a quadruped that might often have reared up on its much bigger hind legs.
>> And note, both of the descended from obligate bipeds. Whether any
>> spinosaurs ever got down on all fours is an open question.
ßpinosaurus is reconstructed with short legs because that's what the
fossil material looks like. I don't see a way out of that. I would
propose that their feeding strategy didn't require them to turn their
torsos very fast. Perhaps they only lunged straight forward, and any
corection of direction was done with the neck only.

On Monday, December 19, 2022 at 9:26:43 PM UTC-8, John Harshman wrote:
> On 12/19/22 1:53 PM, Peter Nyikos wrote:
> > On Monday, December 19, 2022 at 4:12:36 PM UTC-5, John Harshman wrote:
> >> On 12/19/22 1:07 PM, Peter Nyikos wrote:
> >>> Thanks for the corrections, John. I have some comments below.
> >>>
> >>> On Sunday, December 18, 2022 at 9:46:48 PM UTC-5, John Harshman wrote:
> >>>> On 12/18/22 10:06 AM, Sight Reader wrote:
> >>>>> FINALLY made it to Christmas break…. at last, time for another quick dip into my hobbies!
> >>>>>
> >>>>> Wow, so based on the reconstructions they have, it sounds like their Spinosaurus would be a bipedal dinosaur who carries its body nearly horizontally! Have there been any other bipeds like that? It seems crazy, all that weight on such relatively short legs!
> >>>
> >>>> Just about any theropod, and notably many of the living ones?
> >>>
> >>> Since there are no living theropods,
> >
> >> Have you learned nothing from me?
> >
> > I'm sorry, but I refuse to adopt the jargon "birds are dinosaurs."
> > They are *descended from* what you call "non-avian dinosaurs"
> > and I call "dinosaurs."
> >
> > How would you like it if I kept calling you "a unicellular eukaryote,"
> > just because you are descended from them?
> Wrong comparison. How would you like if I kept calling you a mammal,
> just because you are descended from them? In your comparison, it's
> "unicellular" that's doing the work. I presume you're fine with being a
> eukaryote. But of course "unicellular eukaryote" isn't a group.
> >>> I take it "ones" refers to "bipeds", specifically birds.
> >>> Bipedal mammals, on the other hand, are all exceptions AFAIK.
> >>> This includes not only ourselves, but also indris, sifakas and avahis,
> >>> all of which are lemurs. I believe tarsiers are another exception.
> >
> >> What about kangaroos?
> >
> > I was thinking in terms of "vertical bipeds," and kangaroos hold
> > themselves at an angle, which would be closer to horizontal
> > if it were not for the big fleshy tails. But thanks for the reminder.
> No, it's horizontal precisely because of the big fleshy tail. When
> moving fast they are indeed horizontal, balanced over the hind legs.
> Like a theropod.
> > Getting back to paleontology: I've often wondered why
> > the pantodont *Barylambda* is shown with a long thick tail like a kangaroo.
> > They are the only non-aquatic mammals I can think of with such big thick
> > tails in proportion to their bodies. [Well, OK, wallabies and other "miniature kangaroos."]
> >
> >
> >> Check out the QANTAS logo.
> >
> > Have you learned nothing *about* me? I've been fascinated by
> > marsupials (also monotremes) since before the age of 12.
> > As if that weren't enough, my wife grew up in Australia,
> > and we were married there. We even saw a dead wallaby on the road
> > on our honeymoon, and my wife stopped the car to get it off the road.
> So you have no excuse for forgetting about them.

Credit where credit is due (at least a little credit). Peter's learned at least
two things since he was twelve. He used to bulldog for Feduccia the way he
does now for Behe. Additionally, I think he accepts hippos as the sister group to
whales. Gradual evolution of his worldview; not saltation.

Pandora wrote:

> Open access article with Paul Sereno:
>
> Spinosaurus is not an aquatic dinosaur

Morons see "Aquatic" and think "Sea Monkeys."

There's actually a not very terrible argument favoring an aquatic
spinosaurus. For starters: The sail!

Sails were not the most common feature on dinosaurs, particularly
of later dinosaurs like spinosaurus. However, it would have been
extremely useful for an aquatic animal dependent upon the sun to
provide body heat. As long as the sail stuck out, it could get all the
sun it needed.

"Thermal Regulation."

Baryonyx! Spinosaurus looked like a Baryonyx that had evolved
more, adapted better to an aquatic environment.

The two animals look very much alike, at a glance, and are currently
accepted as related, with the less derived Baryonyx coming first.

Baryonyx is believed to have ate fish. So why would an animal that
didn't have a sail but did eat fish suddenly evolve a sail? Hmm. Maybe
to make it BETTER at eating fish by growing a sail that stuck out of
the water & soaked up the sun and it was mucking about under the
waves, eating fish?

The teeth are also sufficiently different from a T-Rex or even the
much earlier as allosaurus. They look much more similar to other
fish eating animals that inland predators...

-- --

https://jtem.tumblr.com/tagged/Cambridge

On Mon, 19 Dec 2022 21:47:59 -0800 (PST), erik simpson
<eastside.erik@gmail.com> wrote:

>On Monday, December 19, 2022 at 9:26:43 PM UTC-8, John Harshman wrote:
>> On 12/19/22 1:53 PM, Peter Nyikos wrote:
>> > On Monday, December 19, 2022 at 4:12:36 PM UTC-5, John Harshman wrote:
>> >> On 12/19/22 1:07 PM, Peter Nyikos wrote:
>> >>> Thanks for the corrections, John. I have some comments below.
>> >>>
>> >>> On Sunday, December 18, 2022 at 9:46:48 PM UTC-5, John Harshman wrote:
>> >>>> On 12/18/22 10:06 AM, Sight Reader wrote:
>> >>>>> FINALLY made it to Christmas break…. at last, time for another quick dip into my hobbies!
>> >>>>>
>> >>>>> Wow, so based on the reconstructions they have, it sounds like their Spinosaurus would be a bipedal dinosaur who carries its body nearly horizontally! Have there been any other bipeds like that? It seems crazy, all that weight on such relatively short legs!
>> >>>
>> >>>> Just about any theropod, and notably many of the living ones?
>> >>>
>> >>> Since there are no living theropods,
>> >
>> >> Have you learned nothing from me?
>> >
>> > I'm sorry, but I refuse to adopt the jargon "birds are dinosaurs."
>> > They are *descended from* what you call "non-avian dinosaurs"
>> > and I call "dinosaurs."
>> >
>> > How would you like it if I kept calling you "a unicellular eukaryote,"
>> > just because you are descended from them?
>> Wrong comparison. How would you like if I kept calling you a mammal,
>> just because you are descended from them? In your comparison, it's
>> "unicellular" that's doing the work. I presume you're fine with being a
>> eukaryote. But of course "unicellular eukaryote" isn't a group.
>> >>> I take it "ones" refers to "bipeds", specifically birds.
>> >>> Bipedal mammals, on the other hand, are all exceptions AFAIK.
>> >>> This includes not only ourselves, but also indris, sifakas and avahis,
>> >>> all of which are lemurs. I believe tarsiers are another exception.
>> >
>> >> What about kangaroos?
>> >
>> > I was thinking in terms of "vertical bipeds," and kangaroos hold
>> > themselves at an angle, which would be closer to horizontal
>> > if it were not for the big fleshy tails. But thanks for the reminder.
>> No, it's horizontal precisely because of the big fleshy tail. When
>> moving fast they are indeed horizontal, balanced over the hind legs.
>> Like a theropod.
>> > Getting back to paleontology: I've often wondered why
>> > the pantodont *Barylambda* is shown with a long thick tail like a kangaroo.
>> > They are the only non-aquatic mammals I can think of with such big thick
>> > tails in proportion to their bodies. [Well, OK, wallabies and other "miniature kangaroos."]
>> >
>> >
>> >> Check out the QANTAS logo.
>> >
>> > Have you learned nothing *about* me? I've been fascinated by
>> > marsupials (also monotremes) since before the age of 12.
>> > As if that weren't enough, my wife grew up in Australia,
>> > and we were married there. We even saw a dead wallaby on the road
>> > on our honeymoon, and my wife stopped the car to get it off the road.
>> So you have no excuse for forgetting about them.
>
>Credit where credit is due (at least a little credit). Peter's learned at least
>two things since he was twelve. He used to bulldog for Feduccia the way he
>does now for Behe. Additionally, I think he accepts hippos as the sister group to
>whales. Gradual evolution of his worldview; not saltation.

Before giving credit where applicants are likely to default, you might
want to know what they mean by "gradual" more precisely than "not
saltation".

On Tuesday, December 20, 2022 at 6:52:20 AM UTC-8, 69jp...@gmail.com wrote:
> On Mon, 19 Dec 2022 21:47:59 -0800 (PST), erik simpson
> <eastsi...@gmail.com> wrote:
>
> >On Monday, December 19, 2022 at 9:26:43 PM UTC-8, John Harshman wrote:
> >> On 12/19/22 1:53 PM, Peter Nyikos wrote:
> >> > On Monday, December 19, 2022 at 4:12:36 PM UTC-5, John Harshman wrote:
> >> >> On 12/19/22 1:07 PM, Peter Nyikos wrote:
> >> >>> Thanks for the corrections, John. I have some comments below.
> >> >>>
> >> >>> On Sunday, December 18, 2022 at 9:46:48 PM UTC-5, John Harshman wrote:
> >> >>>> On 12/18/22 10:06 AM, Sight Reader wrote:
> >> >>>>> FINALLY made it to Christmas break…. at last, time for another quick dip into my hobbies!
> >> >>>>>
> >> >>>>> Wow, so based on the reconstructions they have, it sounds like their Spinosaurus would be a bipedal dinosaur who carries its body nearly horizontally! Have there been any other bipeds like that? It seems crazy, all that weight on such relatively short legs!
> >> >>>
> >> >>>> Just about any theropod, and notably many of the living ones?
> >> >>>
> >> >>> Since there are no living theropods,
> >> >
> >> >> Have you learned nothing from me?
> >> >
> >> > I'm sorry, but I refuse to adopt the jargon "birds are dinosaurs."
> >> > They are *descended from* what you call "non-avian dinosaurs"
> >> > and I call "dinosaurs."
> >> >
> >> > How would you like it if I kept calling you "a unicellular eukaryote,"
> >> > just because you are descended from them?
> >> Wrong comparison. How would you like if I kept calling you a mammal,
> >> just because you are descended from them? In your comparison, it's
> >> "unicellular" that's doing the work. I presume you're fine with being a
> >> eukaryote. But of course "unicellular eukaryote" isn't a group.
> >> >>> I take it "ones" refers to "bipeds", specifically birds.
> >> >>> Bipedal mammals, on the other hand, are all exceptions AFAIK.
> >> >>> This includes not only ourselves, but also indris, sifakas and avahis,
> >> >>> all of which are lemurs. I believe tarsiers are another exception.
> >> >
> >> >> What about kangaroos?
> >> >
> >> > I was thinking in terms of "vertical bipeds," and kangaroos hold
> >> > themselves at an angle, which would be closer to horizontal
> >> > if it were not for the big fleshy tails. But thanks for the reminder..
> >> No, it's horizontal precisely because of the big fleshy tail. When
> >> moving fast they are indeed horizontal, balanced over the hind legs.
> >> Like a theropod.
> >> > Getting back to paleontology: I've often wondered why
> >> > the pantodont *Barylambda* is shown with a long thick tail like a kangaroo.
> >> > They are the only non-aquatic mammals I can think of with such big thick
> >> > tails in proportion to their bodies. [Well, OK, wallabies and other "miniature kangaroos."]
> >> >
> >> >
> >> >> Check out the QANTAS logo.
> >> >
> >> > Have you learned nothing *about* me? I've been fascinated by
> >> > marsupials (also monotremes) since before the age of 12.
> >> > As if that weren't enough, my wife grew up in Australia,
> >> > and we were married there. We even saw a dead wallaby on the road
> >> > on our honeymoon, and my wife stopped the car to get it off the road..
> >> So you have no excuse for forgetting about them.
> >
> >Credit where credit is due (at least a little credit). Peter's learned at least
> >two things since he was twelve. He used to bulldog for Feduccia the way he
> >does now for Behe. Additionally, I think he accepts hippos as the sister group to
> >whales. Gradual evolution of his worldview; not saltation.
> Before giving credit where applicants are likely to default, you might
> want to know what they mean by "gradual" more precisely than "not
> saltation".

My remarks here don't require or deserve precision or even serious attention.
The words are mine, not Peter's. They simply reflect my amusement at Peter's
reluctance to accept changes to what he learned in his youth.

On Monday, December 19, 2022 at 10:33:54 PM UTC-7, John Harshman wrote:
> On 12/19/22 2:23 PM, Sight Reader wrote:
> > Hey guys, thanks a ton for the feedback! Sorry about the snipping… I didn’t want to flood you guys with excess information and didn’t realize that snipping make things inconvenient (feeling embarrassed yet AGAIN). Apparently I only open my mouth to change feet…
> >
> > Anyways, regarding why I have concerns about this reconstruction of Spinosaurus but not about other theropods, I’m mostly referring to the ratio of stride length to where most of the body mass is.
> >
> > I’ll give this my best shot. Let’s consider, for example, your average T-rex. Just from eyeballing it, I’d say her front foot would land roughly under her neck. Note that this means that most of her mass would be between that front foot and her center of gravity (presumably over her hip): only her neck and head would be farther away from her center of gravity than where her foot is planted, but with such long legs, she can easily rear up and even move that mass closer to her center of mass. Since her stride length is longer than most of her mass, she could push off of that foot, and the location her foot is planted will have a reasonably long “moment arm” that can amplify the turning force on her center of mass. This would be more like pushing at the END of the 20-ton propeller rather than trying to twist it at its hub: you don’t need nearly as much strength to get it rotating. Now to be clear, I’m not entirely sure how ANY of these theropods turned since their hips don’t seem to let them sprawl their legs out sideways to “cut” like we can: I would guess dinosaurs would require a certain level of “banking” (leaning left or right into a turn) before coming about, but that should be easy enough given sufficiently long legs and I think there are plenty of animals that do that.
> >
> > Let’s now look at their reconstruction of Spinosaurus. If she puts her foot forward, I’m not even sure her foot makes it to her arms, which means that there is not nearly as much of her mass between her plant foot and her center of gravity: there still remains a LOT of mass outside of where that foot lands, including those big arms, the thick neck, and her even bigger head. Furthermore, she has very little clearance off the ground, so she can’t rear up quasi-erect to come about - she has to hold herself horizontal to avoid bottoming out, thus keeping a significant portion of her mass outside of her stride length (all of this could be SO EASILY described in about 10 words if only I could post a picture… GAH!) Anyways, this is the problem of trying to turn that 20-ton propeller by trying to twist it at its hub - without being able to leverage further out to the “propeller”, I just can’t see how she’s going to maneuver. Now, if she was something of a quadruped, she could plant her arms into the ground - which are much farther away from the center of gravity and can thus exert torque without a ridiculous amount of force, but apparently her arms have no weight bearing function, so I don’t think she can do this unless she grabs a tree or something. As far as my pet theory of “banking” before turning goes, that too would be proportionally more difficult with her short clearance from the ground.
> >
> > I would finally note that older reconstructions of Spinosaurus - notably the one in Jurassic Park III but there are still quite a few others sitting around - all give her much longer legs than they’re reconstructed. However, these portrayals seem to be getting replaced by the little-leg version, especially those that show her swimming. I have no idea which is right.
> >
> > Sorry that was so long! I tried my best…
> >
> > On Monday, December 19, 2022 at 12:26:19 PM UTC-7, John Harshman wrote:
> >> On 12/19/22 10:55 AM, Peter Nyikos wrote:
> >>> Welcome back, Sight Reader! I'm glad you are over your final exams. Did you spend some of your Thanksgiving break
> >>> trying to get caught up?
> >>>
> >>> On Monday, December 19, 2022 at 9:49:09 AM UTC-5, thesigh...@gmail.com wrote:
> >>>> On Monday, December 19, 2022 at 7:35:38 AM UTC-7, John Harshman wrote:
> >>>
> >>> A little tip: don't delete so much. It's hard to know what "the rest" is when you don't leave
> >>> any of your own words in from the earlier post. [Yes, ]we all know how to scroll up, but
> >>> that interrupts the rest of the thought.
> >>>
> >>>>> Not sure about the rest, but the Sereno et al. paper did conclude that
> >>>>> the center of gravity of the beasty was at its hips.
> >>>
> >>>> Precisely! What I’m trying to say is that turning gigantic dinosaur like that with tiny little legs directly under the center of gravity would be like trying to turn a gigantic 20-ton propeller by trying to grab the hub: the part closest to the center of gravity is the hardest to turn because you have no leverage or “moment arm”, like the long handle on a wrench.
> >>>
> >>> Wait--why do you talk about the tiny little legs being directly under the center of gravity
> >>> when they aren't the ones connected to the hips?
> >> I believe the ones connected to the hips are in fact what he's talking
> >> about.
> >>> As for "hardest to turn": I get the impression from the abominably unhelpful Wikipedia that the gluteus maximus is responsible for raising
> >>> the front of the body, and it has plenty of leverage from the attachment at the bottom of the hip.
> >> And he's talking about turning left and right.
> >>> I do believe that the non-theropod Plateosaurus was a biped that also got down on all fours a lot. Another
> >>> non-theropod, Stegosaurus looks like a quadruped that might often have reared up on its much bigger hind legs.
> >> And note, both of the descended from obligate bipeds. Whether any
> >> spinosaurs ever got down on all fours is an open question.
> ßpinosaurus is reconstructed with short legs because that's what the
> fossil material looks like. I don't see a way out of that. I would
> propose that their feeding strategy didn't require them to turn their
> torsos very fast. Perhaps they only lunged straight forward, and any
> corection of direction was done with the neck only.

I agree. I wonder if those earlier reconstructions with reasonably sized legs were based on incomplete remains? If that’s the case, I wonder which discovery revealed the true leg size.

Anyway, I was also wondering about the lunging forward hypothesis. Seems like not being able to turn very well would be a serious liability - someone is always getting around behind you (“Spino, Spino! Watch your 6!”) Trying to turn by simply redirecting your head would be frustrating because, instead of your body coming about, the rest of you simply rotates back the other way while your tiny feet are trying to keep up (Hey, everyone knows what the girls say about guys with small feet…)

Even if not completely aquatic, maybe hanging around in water habitats plays some sort of role in mitigating this vulnerability? I’m starting to think there’s a certain Murphy’s Law when it comes to interpreting dinosaurs:

“Whatever interpretation makes the MOST sense is almost certainly going to be the one interpretation that can get definitely ruled out…”

On Tue, 20 Dec 2022 08:37:10 -0800 (PST), erik simpson
<eastside.erik@gmail.com> wrote:

>On Tuesday, December 20, 2022 at 6:52:20 AM UTC-8, 69jp...@gmail.com wrote:
>> On Mon, 19 Dec 2022 21:47:59 -0800 (PST), erik simpson
>> <eastsi...@gmail.com> wrote:
>>
>> >On Monday, December 19, 2022 at 9:26:43 PM UTC-8, John Harshman wrote:
>> >> On 12/19/22 1:53 PM, Peter Nyikos wrote:
>> >> > On Monday, December 19, 2022 at 4:12:36 PM UTC-5, John Harshman wrote:
>> >> >> On 12/19/22 1:07 PM, Peter Nyikos wrote:
>> >> >>> Thanks for the corrections, John. I have some comments below.
>> >> >>>
>> >> >>> On Sunday, December 18, 2022 at 9:46:48 PM UTC-5, John Harshman wrote:
>> >> >>>> On 12/18/22 10:06 AM, Sight Reader wrote:
>> >> >>>>> FINALLY made it to Christmas break…. at last, time for another quick dip into my hobbies!
>> >> >>>>>
>> >> >>>>> Wow, so based on the reconstructions they have, it sounds like their Spinosaurus would be a bipedal dinosaur who carries its body nearly horizontally! Have there been any other bipeds like that? It seems crazy, all that weight on such relatively short legs!
>> >> >>>
>> >> >>>> Just about any theropod, and notably many of the living ones?
>> >> >>>
>> >> >>> Since there are no living theropods,
>> >> >
>> >> >> Have you learned nothing from me?
>> >> >
>> >> > I'm sorry, but I refuse to adopt the jargon "birds are dinosaurs."
>> >> > They are *descended from* what you call "non-avian dinosaurs"
>> >> > and I call "dinosaurs."
>> >> >
>> >> > How would you like it if I kept calling you "a unicellular eukaryote,"
>> >> > just because you are descended from them?
>> >> Wrong comparison. How would you like if I kept calling you a mammal,
>> >> just because you are descended from them? In your comparison, it's
>> >> "unicellular" that's doing the work. I presume you're fine with being a
>> >> eukaryote. But of course "unicellular eukaryote" isn't a group.
>> >> >>> I take it "ones" refers to "bipeds", specifically birds.
>> >> >>> Bipedal mammals, on the other hand, are all exceptions AFAIK.
>> >> >>> This includes not only ourselves, but also indris, sifakas and avahis,
>> >> >>> all of which are lemurs. I believe tarsiers are another exception.
>> >> >
>> >> >> What about kangaroos?
>> >> >
>> >> > I was thinking in terms of "vertical bipeds," and kangaroos hold
>> >> > themselves at an angle, which would be closer to horizontal
>> >> > if it were not for the big fleshy tails. But thanks for the reminder.
>> >> No, it's horizontal precisely because of the big fleshy tail. When
>> >> moving fast they are indeed horizontal, balanced over the hind legs.
>> >> Like a theropod.
>> >> > Getting back to paleontology: I've often wondered why
>> >> > the pantodont *Barylambda* is shown with a long thick tail like a kangaroo.
>> >> > They are the only non-aquatic mammals I can think of with such big thick
>> >> > tails in proportion to their bodies. [Well, OK, wallabies and other "miniature kangaroos."]
>> >> >
>> >> >
>> >> >> Check out the QANTAS logo.
>> >> >
>> >> > Have you learned nothing *about* me? I've been fascinated by
>> >> > marsupials (also monotremes) since before the age of 12.
>> >> > As if that weren't enough, my wife grew up in Australia,
>> >> > and we were married there. We even saw a dead wallaby on the road
>> >> > on our honeymoon, and my wife stopped the car to get it off the road.
>> >> So you have no excuse for forgetting about them.
>> >
>> >Credit where credit is due (at least a little credit). Peter's learned at least
>> >two things since he was twelve. He used to bulldog for Feduccia the way he
>> >does now for Behe. Additionally, I think he accepts hippos as the sister group to
>> >whales. Gradual evolution of his worldview; not saltation.
>> Before giving credit where applicants are likely to default, you might
>> want to know what they mean by "gradual" more precisely than "not
>> saltation".
>
>My remarks here don't require or deserve precision or even serious attention.
>The words are mine, not Peter's. They simply reflect my amusement at Peter's
>reluctance to accept changes to what he learned in his youth.

Suit yourself, but whenever someone gives credit to him, I am reminded
of a saying posted behind a store counter:

"In God We Trust. All others pay cash."