[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]
that paper of ours
Hi folks,
I am
exhausted from a long week of media frenzy and only get the daily digest
version of this list, so please be patient with my slow replies. I
want to reply to everyone's comments, because this is a great forum to
talk about issues like this. I wish more researchers would talk
about their published papers on this list, because it is the perfect
opportunity to exchange ideas with people who know lots of stuff.
And it's a fun topic!
Please: Read the paper and the news and views. Also read the
supplementary information, it is critical. Then check out the
website at:
http://tam.cornell.edu/students/garcia/.trex_www/naturepaper.html
Reporters have all had access to this site, which was prepared with the
goal of minimizing misinterpretation of our research. So if you see
a report and wonder what we really said, check this webpage.
Careful reporters took a look, and it shows in their work.
The same should apply to listmembers, I hope.
Here goes:
==================================
From:
"Thomas R. Holtz, Jr." <tholtz@geol.umd.edu>
To: "dinosaur" <dinosaur@usc.edu>
Subject: New Nature paper on Tyrannosaur Locomotion
Message-ID:
<NDBBIAJHGJBHMGNKDFAHGEJCEGAA.tholtz@geol.umd.edu>
MIME-Version: 1.0
Content-Type: text/plain;
charset="iso-8859-1"
Content-Transfer-Encoding: 7bit
Yes, Tim Williams found me out...
In this week's Nature:
JOHN R. HUTCHINSON and MARIANO GARCIA (2002). _Tyrannosaurus_ was
not a
fast runner. Nature 415: 1018 - 1021
and the News & Views:
ANDREW A. BIEWENER (2002). Walking with tyrannosaurs. Nature 415:
972-973.
In brief, Hutchinson & Garcia model various hindlimb paramaters
(limb
lengths, segment weights, muscle fibre lengths, and more) from
various
specimens (MOR 555, a _T. rex_; a small tyrannosaur from the Field
Museum; a
_Coelophysis_; a modern alligator; a modern chicken). They
attempted to
calculate (for various body positions) the value T, the percent of the
body
mass represented by leg muscles per leg required to allow the animal to
run.
"Running" in this case was set at Froude number (Fr) = 2.5,
based on
observations of modern animals and on biomechanical
theory.
A correction: We made a distinction between "fast
running" (45 mph, Froude 16) and running (theoretically, with lots
of slop, Froude 1 or more).
The magnitude of the ground reaction force at mid-stance was 2.5 times
body weight (is 2.5-4 times body weight during fast running regardless of
size, etc.); the Froude # was not 2.5.
(The Froude
number is a dimensionless descriptor of speed. For their
model
they calculate Fr = (velocity)^2/(hip height x g). An ostrich
running at
12 m/s is doing Fr = 16; in biomechanical theory, Fr = 1 represents
the
walk/run transition).
Most of their estimates for the adult _T. rex_ found values of T which
were
unreasonably high (each leg's muscle mass being 30-50% of the organism!)
for
nearly all the different postures for the Big Guy they tried. The
other
specimens they looked at had lower values: T = 20 for the young
leggy
tyrannosaur, down to T = 4.7 or so for the chicken.
The basic conclusion: big _T. rex_ specimens did not have sufficient
muscle
mass to be able to produce a fast run. However, they point at that
at a
fast walk (presumably close to but not exceeding Fr = 1), MOR 555
would
still be moving at 5 m/s (that is, 11 mph).
A side note: other big theropods and big non-theropod dinosaurs would
be
suffering from the same set backs (and arguably worse with broad
stumpy
feet), so this does not invalidate _T. rex_ as a _Triceratops_ or
_Anatotitan_ chaser.
Checking this against the recent Day et al. (2002) Middle Jurassic
trackway,
their critter (estimated to be 1.93 m tall and moving at an
estimated
maximum speed of 8 m/s) seems to be moving at a Froude number of
3.8. This
is faster than the walk-run transition (theoretically at Fr = 1).
Now an
1.93 m hip height theropod is big: comparable to _Dryptosaurus_ or a
smidge
under the UUVP 6000 specimen of _Allosaurus_: Greg Paul estimates
that
latter specimen at 1.32 tonnes. So *if* the size and speed
estimates of the
MJ theropod are correct, then one tonne theropods could run, at
least
slowly.
Perhaps. Do note that the speed estimate equations are based on
lots of different biomechanical equations (read up on work by Alexander,
Jayes, and others since 1976) and data from a wide assortment of living
animals. Bakker's NPR blurb seemed to say that they are simple
equations. They are not. They are based on a lot of
underlying theory and assumptions. Speed estimates are often off by
a factor of 2.
Very, very
interesting stuff. It will be even more interesting to see
this
model tested against other, smaller theropods and other dinosaurs.
I would
be interested in seeing how other young tyrannosaurs and
ornithomimosaurs
fare in this model.
We model a quite small tyrannosaur (FMNH PR 2211 I think), which should
be the same as an ornithomimosaur I'd expect; about twice as good at
running as an adult Tyrannosaurus.
We also model a human, which (like a chicken) has about 2x the muscle
mass needed for fast running.
The model is a first step in a long series of modeling and experimental
studies that I'm undertaking. I am not ashamed to admit that
details about the model might be shown to be wrong by myself or others in
the future. That's science. An important point of the study
is that we need to start using more sophisticated biomechanics in
paleontology. There is a lot more that can be done. People
have been using Alexander's simple models for >25 yrs now; it's time
to move on and do something new. Like other people in the field
such as Gatesy, Carrano, Blob, Henderson, etc., I am trying to develop
new techniques that yield new insights, rather than drone on and on about
the same old data and methods.
Thomas
R. Holtz, Jr.
Vertebrate
Paleontologist
Department of
Geology Director,
Earth, Life & Time Program
University of
Maryland College
Park Scholars
College
Park, MD 20742
http://www.geol.umd.edu/~tholtz/tholtz.htm
http://www.geol.umd.edu/~jmerck/eltsite
Phone: 301-405-4084 Email: tholtz@geol.umd.edu
Fax (Geol):
301-314-9661 Fax
(CPS-ELT): 301-405-0796
[snip]
Date: Wed, 27
Feb 2002 23:54:47 +0100
From: "David Marjanovic" <david.marjanovic@gmx.at>
To: "The Dinosaur Mailing List" <dinosaur@usc.edu>
Subject: Re: New Nature paper on Tyrannosaur Locomotion
Message-ID: <004001c1bfe1$c2585440$b4432fd5@chello.at>
MIME-Version: 1.0
Content-Type: text/plain;
charset="iso-8859-1"
Content-Transfer-Encoding: 7bit
> In brief, Hutchinson & Garcia model various hindlimb paramaters
(limb
> lengths, segment weights, muscle fibre lengths, and more) from
various
> specimens (MOR 555, a _T. rex_; a small tyrannosaur from the Field
Museum;
a
> _Coelophysis_; a modern alligator; a modern chicken). They
attempted to
> calculate (for various body positions) [...]
What about various weight estimates? They used 6 t... did they also try 4
t,
for example? What about, say, the elastic effects of tendons and
cartilage?
This is a subtle point that is easily missed on reading the paper, but we
factor out body mass from the equation, so it doesn't matter much
really. That is confusing, I know, because mass does matter in the
end. It will be explained in more detail in a later
paper.
Soft tissue elasticity is implictly part of the muscle force/area in the
model. Cartilage elasticity has not been shown to matter much at
all for these sort of problems in living animals. It can safely be
ignored.
BTW, 5 and 8 m/s
are 18 and 28.8 km/h, respectively.
Yes.
---
Outgoing mail is certified Virus Free.
Checked by AVG anti-virus system
(http://www.grisoft.com).
Version: 6.0.325 / Virus Database: 182 - Release Date: 19/02/02
Date: Wed, 27 Feb 2002 19:32:26 -0600
From: "Steve Brusatte" <dinoland@lycos.com>
To: dinosaur@usc.edu
Subject: Re: New Nature paper on Tyrannosaur Locomotion
>The basic conclusion: big _T. rex_ specimens did not have sufficient
muscle
>mass to be able to produce a fast run.
Currie seemed very interested at the Burpee Museum this weekend in the
possibility that young members of a _Tyrannosaurus_ "herd" may
have done the majority of the hunting. Speculation, of course, but
he points to the _Albertosaurus_ bone beds in Alberta as evidence that
tyrannosaurids may have been gregarious. He extrapolated these data
to speculate that perhaps the more agile youngsters may have done the
hunting for the older, slower adults.
The model of the juvenile tyrannosaur that we did is consistent with
Currie's idea; they likely had a broader range of locomotor
performance.
Date: Wed, 27
Feb 2002 18:57:43 -0700 (MST)
From: Richard W Travsky <rtravsky@uwyo.edu>
To: dinosaur@usc.edu
Subject: Re: New Nature paper on Tyrannosaur Locomotion
Message-ID:
<Pine.GSO.4.10.10202271852300.25662-100000@asuwlink.uwyo.edu>
MIME-version: 1.0
Content-type: TEXT/PLAIN; charset=US-ASCII
Content-transfer-encoding: 7BIT
On Wed, 27 Feb 2002, Thomas R. Holtz, Jr. wrote:
> Yes, Tim Williams found me out...
>
> In this week's Nature:
> JOHN R. HUTCHINSON and MARIANO GARCIA (2002). _Tyrannosaurus_
was not a
> fast runner. Nature 415: 1018 - 1021
>
> and the News & Views:
> ANDREW A. BIEWENER (2002). Walking with tyrannosaurs. Nature
415: 972-973.
> [...]
ABC News did a feature on this tonight (Wednesday the 27th).
Their web site has a page on this, including a picture of the
chicken
comparision from Hutchinson's computer
simulation.
Minor note, the 3D model shown is part of the newer, more realistic work
I'm doing at Stanford. The model in the Nature paper is as simple as it
needed to be, which was 2D.
http://abcnews.go.com/sections/wnt/DailyNews/t_rex_020227.html
A link for the video of this segment is also on this
page.
Date: Wed, 27 Feb 2002 18:26:09 -0800
From: "Michael de Sosa"
<ofsosa@uclink4.berkeley.edu>
To: "Dinosaur Mailing List" <dinosaur@usc.edu>
Subject: RE: New Nature paper on Tyrannosaur Locomotion
Message-ID:
<ILEGKCHIMGAMCPJCMCNKCEGJCHAA.ofsosa@uclink4.berkeley.edu>
MIME-Version: 1.0
Content-Type: text/plain;
charset="iso-8859-1"
Content-Transfer-Encoding: 7bit
John was on NPR's All Things Considered radio show this evening
talking
about the research. The counter-argument was given by... wait for it...
you
can probably guess... Bob Bakker! No, really!
Mike D.
As is the tiresome case when dealing with luddites and numerophobes,
Bakker brought up the Ye Olde "Bumblebees can't fly"
Myth. This is a misleading approach that is often used to confuse
people about modeling. In 30 seconds I found these 3 pages that
discuss what science really said about the bumblebee:
http://www.maa.org/mathland/mathland_3_31.html
http://www.sciam.com/2001/0601issue/0601dickinson.html
http://www.news.cornell.edu/releases/March00/APS_Wang.hrs.html
Yes, science can be wrong, but that does not mean that science is
always wrong...
Date: Wed, 27
Feb 2002 21:03:05 -0600
From: "Toby White" <mwhite@houston.rr.com>
To: <dinosaur@usc.edu>
Subject: RE: New Nature paper on Tyrannosaur Locomotion
Message-ID: <000001c1c004$7190c600$9b191942@houston.rr.com>
MIME-Version: 1.0
Content-Type: text/plain;
charset="Windows-1252"
Content-Transfer-Encoding: 7bit
An article on this is on the front page of the web version of the
NY
Times (article at
http://www.nytimes.com/2002/02/27/science/27CND-DINO.html.
I've always been a fan of slow theropods, but this seems almost too
slow. One reason for a slower speed would be the amount of
damage
caused by a fall -- a huge risk for a high mass animal, even if the
probability of a fall were small. However, Tyrannosaurus was a
biped.
It had to have enough agility to balance, and to correct its balance
if
the ground shifted. Unless Tyrannosaurus was confined to plains,
it
also had to have *some* ability to go up and down hills. That
should
require more than a minimal amount of dexterity for a digitigrade
biped.
A *really* slow theropod is almost harder to understand than a
rocket
raptor. Then again, maybe grade and terrain really were important
to
dinosaur behavior. [Wild speculation begins here] For
example,
hadrosaurs with hoof-like feet on unequal front and hind legs look
funny
on a plain. On the other hand (or foot) they'd probably be quite
nimble
climbing a slope, particularly outracing a slow biped who was
having
trouble keeping its balance.
--Toby White
The Vertebrate Notes at
http://home.houston.rr.com/vnotes/index.html
and
http://www.dinodata.net
[moving soon!]
I have no disagreement here, except to note that speeds are all
relative. Is 5 or 11 m/s all that slow, really? I think
not! But it's not fast compared to 20 m/s (45mph). Our
point in the paper was that 11 m/s does not make biomechanical sense, and
we have our doubts about even 11 m/s.
Again, the mantra: We Might Be Wrong (every scientist should be
comfortable saying this sentence). But we have accomodated all of
the data and assumptions that we felt we needed to, and came up with our
answer. Science will keep moving on.
Date: Wed, 27
Feb 2002 19:15:31 -0800
From: "Tracy L. Ford" <dino.hunter@cox.net>
To: "Dinonet \(E-mail\)" <dinosaur@usc.edu>
Subject: RE: New Tyrannosaurus paper
Message-ID: <000101c1c006$2e98ff00$6401a8c0@sd.cox.net>
MIME-Version: 1.0
Content-Type: text/plain;
charset="Windows-1252"
Content-Transfer-Encoding: 7bit
I wonder about this, and if they really looked at the
skeletons?
Umm, yes... I spent the last 7 years studying every sauropsid specimen I
could find, living or dead, from the US to Argentina, China, etc.
I've seen practically every tyrannosaur skeleton that exists and spent a
lot of time with it. Intensive anatomical work is the foundation of
this research; check out my recent papers in ZJLS, Paleobiology, and
upcoming J Morph etc. I am not just some engineering guy; I am
trained as a biologist and work hands-on with specimens, Recent and
Mesozoic, on a daily basis.
Fact,
Tyrannosaurs rex's ilia are tightly oppressed, almost to a point
where
the sacral neural spines are crushed, more than any other theropod;
meaning
large muscles. Giganotosaurus doesn't have this. The cnemial crest on
the
tibia is HUGE. If the animal didn't move fast why have such a huge
cnemial
crest?
We accomodated all of these anatomical features in the model. The
"huge" cnemial crest is merely proportional to the animal's
size. It helps create a large knee extensor moment, but our models
show that it was not enough for 20m/s.
A chicken
is not a T. rex. A chicken's body is totally different. The femur
articulation is totally different. The femoral head is nearly at a
right
angle to the tibia in a chicken while in a theropods is nearly
vertical,
I've said this before and should be some where in the archives. Birds
and
dinosaurs walk differently, and differently with their muscles. Did
the
authors just ASSUME birds and theropods walked the same? You can't
assume
they did because the skeletal structure is different. Greg Paul and
Per
Christian have an article in the theropod Gaia volume on the leg movement
in
Tyrannosaurus. Was this article mentioned?
Yes, the articles were mentioned. Read the paper. And I am
more aware than most researchers about the similarities and differences
between chickens and tyrannosaurs. That was all considered in the
paper, and is actually one of the points of the paper. And I have
published long arguments about that point in several papers. It is
a foundation of my work that tyrannosaurs were different from living
animals. So we used a model in order to understand them
better.
I'll have to
wait till next week when I get the article. I doubt the paper
is all that accurate in depicting the behavior of Tyrannosaurus
rex.
We think we did a good job, but anyone is free to disagree with us if
they have evidence that is relevant.
Tracy L.
Ford
P. O. Box 1171
Poway Ca 92074
Date: Wed, 27 Feb 2002 20:12:59 -0700 (MST)
From: Richard W Travsky <rtravsky@uwyo.edu>
To: dinosaur@usc.edu
Subject: RE: New Nature paper on Tyrannosaur Locomotion
Message-ID:
<Pine.GSO.4.10.10202272012250.17648-100000@asuwlink.uwyo.edu>
MIME-version: 1.0
Content-type: TEXT/PLAIN; charset=US-ASCII
Content-transfer-encoding: 7BIT
Ok, so what about other large carnivores?
We have only modeled a few larger things so far., It's part of the plan
for later work, but the clear conclusion is that they had similar limits
on their locomotion, for similar reasons.
Date: Wed, 27
Feb 2002 22:28:20 -0500
From: "Jordan Mallon" <j_mallon@hotmail.com>
To: dinosaur@usc.edu, vrtpaleo@usc.edu
Subject: Big Theropod Running
Message-ID: <F3li5MRaBC3T9cVHK2F0001ac14@hotmail.com>
Mime-Version: 1.0
Content-Type: text/plain; format=flowed
G'day all,
I was wondering...
With all these papers coming to light on the subject of big theropod
speed these days (Farlow's analysis comes to mind, along with those of
Blanco and Mazzetta, R. McNeil Alexander, and Hutchinson and Garcia's
most recent), which of these are considered to be most accurate? I
understand that different approaches have been taken in each case, but
are any one of these studies considered to be better or more valid than
the others?
Just curious.
Jordan Mallon
http://www.geocities.com/paleoportfolio/
BTW: there's a great supplement to Hutchinson and Garcia's latest paper
in Nature here:
http://tam.cornell.edu/students/garcia/.trex_www/naturepaper.html
_________________________________________________________________
Get your FREE download of MSN Explorer at
http://explorer.msn.com/intl.asp.
Thanks. Blanco and Mazzetta's paper lacks enough data to evaluate
their work in any way, so I'm waiting to see data. Farlow's,
Alexander's etc. modeling is wonderfully complementary to our
paper. To my mind, the available biomechanical evidence is in
agreement.
Date: Wed, 27
Feb 2002 22:13:36 -0600
From: "Toby White" <mwhite@houston.rr.com>
To: <dino.hunter@cox.net>, "'Dinonet \(E-mail\)'"
<dinosaur@usc.edu>
Subject: RE: New Tyrannosaurus paper
Message-ID: <000001c1c00e$4bb65440$9b191942@houston.rr.com>
MIME-Version: 1.0
Content-Type: text/plain;
charset="Windows-1252"
Content-Transfer-Encoding: 7bit
Tracy:
Hutchison has gone into the differences in locomotion between birds
and
more basal theropods in huge detail in previous papers. A few are
cited
below. I don't pretend to understand all of it, but its fairly safe
to
assume that this is not a mistake he'd make.
>From the newspaper accounts, it also doesn't look like the
detailed
mechanics have much to do with the result here. Its just a matter of
the
energetics of moving a body of that size over the ground. How
the
pieces fit together won't have much effect on the muscle mass needed
to
do the job.
The mechanics have everything to do with the result; that's
biomechanics. Or if you mean the anatomy, that's in there
too. What was necessary to include was included. What was
irrelevant was excluded. Later models will become more
realistic. We chose to start simple and move from there.
That said, you
may have a point about the ilia. If (big if) I remember
Hutchison's papers well enough, that would mean a big
caudofemoralis.
Having much of the muscle mass for the legs actually reside along
the
hip and base of the tail might allow the dinosaur to cheat a bit on
any
assumption that the leg muscles must be in the
leg.
We considered the caudofemoralis in all of our models; it is
crucial.
The cnemial
crest may be more problematic. I dunno exactly what the
crest was used for in non-avian dinosaurs, but one might suspect that
it
is related to an ability to swing the lower leg through a wide arc
*without* moving the femur so much. That's the way it gets used in,
for
example, loons. Now a real bipedal sprinter might not need
that
mechanism. Its got time in the air to move the tibia, and it's
pumping
the femur up and down for all it's worth in order to get speed at
the
expense of efficiency. The more likely conclusion might be that
the
tyrannosaur was either adapted for long-distance efficiency or to
make
the most of stride length in a fast walk.
The cnemial crest provides a larger moment arm (compared to lacking a
cnemial crest) for the knee extensors ("quadriceps").
Large moment arms are good for producing large moments about joints, but
not so good for producing high joint velocities.
Date: Thu, 28
Feb 2002 00:20:24 EST
From: MariusRomanus@aol.com
To: dinosaur@usc.edu
Subject: Re: New Nature paper on Tyrannosaur Locomotion
Message-ID: <47.18f0b558.29af1818@aol.com>
MIME-Version: 1.0
Content-Type: multipart/alternative;
boundary="part1_47.18f0b558.29af1818_boundary"
Ok..... This is really
interesting.... BUT... we are doing the math based on the wrong
assumptions again. Here, we are saying that theropods ran like birds and
mammals. They ran like neither. They ran like theropods. Why is this fact
usually shoved under the carpet and the couch moved over
it?
It is not. We say nothing of the sort in the paper. I don't
know why I keep hearing comments like this. People are deeply
misunderstanding what we do in the paper. Please read it
carefully.
Never
mind that we are talking about a combination of crocodilian hips coupled
with an avian lower leg that no longer exists in modern animals, but you
have a huge ilium that gives great leverage. You have the crocodilian
pull of the tail.... The get up and go bit..... This pulls it off its
mark and gets it going. The caudofemoralis... it's huge in tyrannosaurs.
It's tiny in birds. Bird locomotion is thus all in the knees. And
mammals? Mammals have both the knee as well as the lumbar. The
â??arch-range of motion' of the femur is increased by the lumbar region
as it acts as a sort of spring. The shoulder region in mammals also acts
as their spring. This â??arch-range of motion' is rare in bird femurs
most of the time in the first place, and never seen aided by a moving
lumbar region because their dorsal vertabrae are fused. We all know this.
In birds, their spring is in the cnemial tendons. Only when the pectoral
region grows larger to help power the flight muscles do we see the
increased lower limbs in birds and this is most likely because of weight.
With all the weight forwards the body in birds, they needed to move the
gut back to displace some weight. This spreading of both the
distal symphysis of the ischia and pubis, as well as flare in the ilium
in a lateral manner of birds, put the femur at a disadvantage
mechanically. So, the only way birds could make up for this was to select
for moving the motion of the femur that was once a prime mover of the
rear limb to the knee. They did this by elongating the tibia as well as
the metatarsal elements. In this way it helped also to balance the animal
as well by being able to keep its feet further forward when standing...
I'm going offf on a tangent....... Someone smack me...
Smack. None of these criticisms matter much for the paper. It
is not so complicated that these things would matter, but it is
complicated enough that their general importance is captured in the
mathematics.
So
anyway, non-avian theropods use the entire leg...... They use
their femur to make up for the difference. Their caudofemoralis. Leg
length.... Foot prints.... Everything shows this. Yes, the study
definitely showed that they walked fast.... Tyrannosaurs were speed
walkers... Works for me... BUT... they still could also take off from the
ground as well... They still had a "ballistic phase". It's all
the knee cartilage and tendon spring. In birds, its the cnemial
tendons. In theropods, you have the cnemial tendons and lots of cartilage
as well. And by the way, crocodilians are slow??? I guess the footage of
"galloping" crocodiles must be more of that Lucasfilm movie
magic....
Again, we know this. Read the paper. Knee cartilage? I
don't know of a study that shows that it is a major part of elastic
energy storage.
We are very aware of galloping crocs. However, what we modeled, as
you'll see if you read the paper, is bipedal running in an
alligator. They do not do that, to my knowledge, and our model
shows part of the explanation: wimpy leg muscles.
Face
it... Bumble bees would not have been able to fly if we had not seen them
do so. That made the people go back over and over to get their math right
so they didn't have to say "I did the math and they can't do
it."
Again, just because science can be wrong doesn't mean that it is wrong
when you don't like the results. Hypotheses are tested and either
fail or prevail. We're comfortable with either outcome, as long as
science is done.
It's
like a friend of mine says... How about the vaulted palate in birds? In
most animals, we would have thought anything without a secondary palate
was an ectotherm. But, birds do not have in most cases anything like a
secondary palate. So, if we had only theropods, a lack of the secondary
palate would have been proof positive that they were cold blooded. It
would have been wrong, yet proof positive.
Things work like this..... As I see it, if we do not have an example
these days to go by, and we cannot make it work with clever math, then,
it ain't so...... You know, even when we still cannot figure out how in
the hell whales can dive so deep...... And we are only now starting to
maybe figure how tuna swim so fast. All the math says they cannot swim as
fast as they do.... If they were extinct, that case would have been
closed. To make this even funnier, here we are comparing theropods to
animals that look nothing like them and drawing conclusions for them
based on the math we use on these animals that look nothing like them.
Ok...... Sure..... Yeah.... crocs that are alive today look so much like
theropods.... Yup... that is soooooo true. ::rolling eyes:: And
chickens...... closer to theropods, but still greatly changed. I mean
face it.... Chickens are built for chicken sized lives.... Not
theropods..... as in mega theropods. Chicken femurs articulate with the
tibia different then tyrannosaur femurs.... Chicken femurs move in the
vertical. Theropod femurs more more in the horizontal. The locomotion is
completely different in the two animals. Tyrannosaurus are very close in
build to ornithomimids. I mean, they look the same but have more robust
bones. Maybe those are the animals we should be comparing tyrannosaurs
too???? Paul's 1988 book comes to mind.
This is all missing the point of the research. Anatomy matters a
lot, but so does physics. The best we can do is try to evaluate
their importance using scientific methods.
After
reading the paper, (I'll send it to anyone who doesn't want to wait
for their issue to arrive at the house) as far as I can tell, this
study left out the elasticity of cartilage and tendons. I look at it this
way... A friend pointed out to me that whales could not swim without
their skin. If it did not bounce back, all their energy would be lost at
a huge rate. The skin is very tight.. made up of a web stock of
connective tissue. When the whale makes a tail stroke, its power is not
lost. It bounces back and is saved. This is one way that an animal that
huge with the metabolic make-up of the average cow can swim so damn fast.
Birds use their tendons and cartilage like whales use their skin. It's
like a pogo stick effect. They tighten the tendons and sort of bounce.
It's more of a falling forwards and just holding themselves from falling
over. Bounce.... bounce...... bounce.... If this is not put into
calculations correctly, you are completely lost. You loose all your
energy at a very fast rate, and ya blame it on the lack of muscles. :-)
Poor math is always there to help people prove that an animal cannot do
what it does 24 hours a day.
I don't have time to mull over rhetorical arguments like this. If a
revised model shows that any factors that we did or did not consider in
the model falsify our results, then fine. That's
science. But for now, we feel that the models adequately capture
the mechanics of locomotion. We study animal biomechanics
extensively, and biomechanists who know the animals and the mechanics
tend to agree with our results. We may all be wrong, but at least
we made our arguments explicit and testable. I see no hypothesis
testing in your comments above; just smokescreens.
My
conclusion:
Fr = (velocity)^2/(hip height x g)..... As far as I am concerned,
the formula is really no good for theropods. It is again, based on
mammals with their lumbar region moving and birds with motion mostly from
the knee. Theropods need to be measured as living animals to see if they
actually fit the formula. I mean, most of the mammals as well as birds
that run go from the knee down. Theropods do not in any way fit this.
They are femur and knee. And what about measuring how the caudofemoralis
fits in, as well as how the femur works without the flaring of the ilia?
And what about how the muscles of the pubic bone fit in as well? In
birds, they are separated distally, and are thus no good for moving the
femur at all. But in theropods like the rex? Talk about having a nuclear
generator. All of these things have to be added in. Tail muscles....
Iliac muscles... Pubic muscles... All going to the femur. Then in comes
the flexed knee. The monsterous cnemial crest on the tibia. The flexible
ankle. Then comes in the bouncy tendons as well as cartilage.
Show that the formula is wrong in a paper, and it would be an interesting
contribution. Part of what we do in the paper is treat theropods as
living animals; we do not force them into a strict bird, crocodile, or
other model.
Looks
like I'm going to have to break out the Ouija board and ask Capt. Howdy
for the location of a _Tyrannosaurus rex_ trackway that will show it's
stride and maybe even its speed. In my humble opinion, that's the
best we can hope for.
Kris
I agree. Trackways will always be an important source of data that
should be compared to other independent lines of evidence to see what
hypotheses hold up best.
===========================================
John R Hutchinson
NSF Postdoctoral Research Fellow
Stanford University
Durand 209, BME
Stanford, CA 94305-4038
(650) 736-0804 lab
(415) 871-6437 cell
(650) 725-1587 fax
===========================================