On 12/20/22 10:49 AM, Sight Reader wrote:
> 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.
The Wikipedia article on Spinosaurus will provide the references.

> 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…)

You assume here that some animal is a threat to an adult Spinosaurus.
That seems very unlikely. And of course the body doesn't have to come
about. If necessary, the tail could rotate a bit to counter the head
movement. And this is about predation, not self-defense.

I should also point out that the article is about Spinosaurus not being
a swimmer. It says nothing about whether they were aquatic. Hippos spend
most of their time in the water but never swim at all.

> Even if not completely aquatic, maybe hanging around in water
habitats plays some sort of role in mitigating this vulnerability?
You assume that an enormous theropod has any sort of vulnerability,
which I doubt.

> 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 Wednesday, December 21, 2022 at 8:03:32 AM UTC-7, John Harshman wrote:
> On 12/20/22 10:49 AM, Sight Reader wrote:
> > 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.
> The Wikipedia article on Spinosaurus will provide the references.
> > 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…)
> You assume here that some animal is a threat to an adult Spinosaurus.
> That seems very unlikely. And of course the body doesn't have to come
> about. If necessary, the tail could rotate a bit to counter the head
> movement. And this is about predation, not self-defense.
>
Exactly! If it indeed turns out that Spinosaurus was unwieldy - and yet it still DIDN’T MATTER - I think it would bring up a lot of potentially interesting questions about Spinosaurus and its ecology.

Would its inability to maneuver rule out any sort of extended existence on dry land? If it did live in dry habitats, why weren’t territorial challenges from other large land carnivores - or even members of its own species - if maneuvering was a problem? Would this rule out scavenging - which might bring Spinosaurus into contact with other large predators seeking the same corpse - as a lifestyle? If it did have any sort of extended presence on land, how did it capture more cursorial prey? I would think its massive size would make it hard to conceal itself and I have trouble seeing how the little legs could generate the sort of burst of speed needed to ambush such animals.