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Re: Amphicoelias size
Thanks Mark. I have indeed read that post. However, it mainly is dealing with
the proposed dimensions of the vertebrae. I am more concerned with being unable
to replicate Carpenter's work, which as I noted, is due to apparently faulty
assumptions as to the dimensions of *Diplodocus*. If we instead accept Mike
Taylor's estimate of the height at about 2.29 meters, we still get that *A.
fragillimus* was 2.29/.966=2.37 times as long as *D. carnegii* which means an
extrapolated length of over 58 meters, which compares well to Carpenter's
original estimate of 58 meters. However, I get this by assuming *D. carnegii*
was 24.8 meters long; if we instead assume Carpenter's length for the latter
species of 26.25 meters, we get an extrapolated length of just over 62 meters.
Compare this to Mike's length estimate of around 49 meters. So, by my
calculation, we're still off by 9-13 meters from Mike's estimate.
Also, *A. fragillimus* would be (2.37)^3=13.3 times as voluminous, for a
resulting mass estimate of 151.6 tonnes (assuming *D. carnegii* was 11.4
tonnes). Compare this to Mike's reduced mass estimate of 78.5 tonnes. So I'm
still off by over 73 tonnes from Mike's estimate. This is because Mike assumed
Carpenter's original math was right, but, as far as I can tell, it is not. So
we're still talking a sauropod in the 150-250 tonne range, which is still
by at least 50 tonnes than the next biggest sauropod (excluding the problematic
*Bruhathkayosaurus* whose material has now been lost in heavy according to Dr.
Kumar Ayyasami, so it's unlikely we'll ever get a better description, esp.
he apparently has no other photos or drawings of the material) and still around
30 tonnes larger than Carpenter originally estimated.
I should point out that Mike probably underestimates the height of *A.
fragillimus* anyways. If you notice, the neural arch in *A. fragillimus* is a
lot longer than in the scaled up *A. altus* photo--and we are still missing a
good part of the neural arch since the neural cana
of *A. fragillimus* is probably at least
10 cm too short, probably more, for a more probable (IMO) height of 2.39+
meters. That would imply a mass of around 84-85 tonnes using Mike's method
off Carpenter. However, using the real dimensions of *D. carnegii* we would
actually get an implied mass of around 172 tonnes give or take a few kilos.
This is more than double Mike's estimate of 78.5 tonnes for a 2.29 meters
and for the adjusted mass of 84 tonnes for a 2.39 meter dorsal.
Obviously, there are ways to get the numbers down. Greg Paul's original mass of
*D. carnegii* might be too high because he used a density of 0.9 instead of the
more likely 0.8 for the average density of the body and the tail, and 0.6 for
the neck instead of a more likely 0.3. This means we could comfortably reduce
all the mass estimates above by about 10-12%. This still gives us an equally
plausible range of 152-221 tonnes and easily over 60 meters depending on the
exact restored dimensions of the vertebrae, and still indicates an animal the
size of your average Blue Whale and maybe heavier. Whatever, *Amphicoelias* was
----- Original Message ----
From: Mark Witton <Mark.Witton@port.ac.uk>
Sent: Tue, January 11, 2011 4:09:44 AM
Subject: Re: Amphicoelias size
Your comments reminded me of this blogpost, which you may already have seen:
Mike Taylor's closing statement sums it all up nicely:
'Folks â please remember, the punchline is not âAmphicoelias fragillimus only
weighed 78.5 tonnes rather than 122.4 tonnesâ. The punchline is âwhen you
extrapolate the mass of an extinct animal of uncertain affinities from a
132-year-old figure of a partial bone which has not been seen in more than a
century, you need to recognise that the error-bars are massive and anything
resembling certainty is way misplaced.â'
Dr. Mark Witton
y of Portsmouth
Tel: (44)2392 842418
If pterosaurs are your thing, be sure to check out:
- Pterosaur.Net: www.pterosaur.net
- The Pterosaur.Net blog: http://pterosaur-net.blogspot.com/
- My pterosaur artwork: www.flickr.com/photos/markwitton
>>> Zach Armstrong <firstname.lastname@example.org> 10/01/2011 20:44 >>>
Ok, so this has been bugging me for a while, so I decided to see if anyone can
help me out here.
Carpenter (2006) in his review of *Amphicoelias fragillimus* reconstructed a
height of 2.7 meters for the posterior dorsal based off comparisons to *A.
altus*. Now he estimated a length of 58 meters and a mass of 122,400 kg. This
his method for these calculations: "Assuming that the mega-diplodocids are
scaled up versions of Diplodocus, then the volume (hence mass) changes in
proportion to the third power of the linear dimension (Schmidt-Nielsen, 1984).
Thus, if Diplodocus carnegii had a length of 26.25 m and mass of 11,500 kg
(Paul, 1994), then A. fragillimus had a mass of around 122,400 kg, which is
still within the hypothesized maximum mass for a terrestrial animal (Hokkanen,
1986)." Now, the mass follows if we assume that *A. fragillimus* was 58 meters,
and *D. carnegii* was 26.25 meters. This means *A. fragillimus* was
times as big in linear dimensions. This means it should be (2.2)^3=10.648 times
as voluminous and thus presumably that many times more heavier than *D.
carnegii*. So 11,500*10.648=122,452 kg. So that makes sense.
However, where did Carpenter get the length estimate for *A. fragillimus*? He
based it off of *D. carnegii*, as mentioned above and cited the stats for the
latter from Paul (1994). However, Paul (1994) did not list a mass of 11,500 kg
and a length of 26.25 meters for *D. carnegii*. He listed a mass of 11 tonnes
and a length of 24.8 meters. So where did the mass estimates that Carpenter
cited come from? I don't know. Am I missing something here? Maybe someone e
But that's not all. If *A. fragillimus* is supposed to be 2.2 times larger in
linear dimensions, then going backwards from the estimated height of 2.7 meters
estimated for the lone preserved dorsal in *A. fragillimus* means that the
dorsal vertebrae of *D. carnegii* should 2.7/2.2=1.22 meters tall. Now, my
digital copy of Hatcher's (1901) description o
9th dorsal as 94.6 cm tall and the 10th dorsal as 96.6 cm
tall (even the supposed "11th dorsal" was only 105.1 cm tall). So, somehow
Carpenter thought that the comparable dorsal in *D. carngeii* was somewhere
between 25.4 and 27.4 cm taller than it actually was. In fact, Lucas et al.'s
(2006) taxonomic revision lists the 9th dorsal as about 1.2 meters tall for the
"seismosaur" specimen. So Carpenter in essence assumed that an individual
*Diplodocus* with seismosaur-sized vertebrae only massed about 11.5 tonnes and
was 26.25 m long, even though more recent estimates of the seismosaur's size
around 30 tonnes in mass and 30-32 meters in length.
So what happens if we scale off the actual measurements listed for the CMNH 84
*D. carnegii* specimen? Well, assuming the dorsal in *A. fragillimus* was the
10th dorsal, then it was 2.7/0.966=2.79 times larger in linear dimensions than
that *Diplodocus* specimen. If that specimen was indeed 24.8 meters as Paul
(1994) says, than an estimated length for *A. fragillimus* is around 69 meters,
a full 11 meters longer than Carpenter originally estimated. The disparity is
even worse if we assume a 26.25 m *Diplodocus* individual which gives us an
estimated length of around 73 meters.
What about mass? Well, if *A. fragillimus* was 2.79 times larger in linear
dimensions than *D. carnegii*, then it was (2.79)^3=21.7 times more voluminous
and therefore more massive. So, assuming that the CMNH 84 specimen was indeed
11.5 tonnes, then *A. fragillimus* should be 21.7*11.5=249.55 tonnes (!). This
is almost 130 tonnes heavier than estimated by Carpenter, and is larger than
largest Blue Whale spec
have been at least 200 tonnes in mass based off oil yield. Even using Greg
Paul's more precise estimate of 11.4 tonnes listed on his website for the CMNH
*Diplodocus* still gives a mas of over 247 tonnes. I find this mass estimate
nearly 250 tonnes difficult to swallow. Paul uses a density of 0.9 fo
t this should be about 0.8 as indicated
by work done on pneumaticity in sauropods done by Matt Wedel, this would mean
could reduce the mass to be about 88% of of the original mass which reduces it
to 219 tonnes, which is still fairly unbelievable. So, here's the big question:
some major flaw in my reasoning here?
For the record, I think Carpenter's estimated height for *A. fragillimus* is
reasonable. I did a similar scaling technique using GIMP's measuring tools and
got an estimated height of 2.65 meters for the vertebrae based off of *A.
altus*. Using this slightly reduced measurement, you still get a mass estimate
of around 235-237 tonnnes (depending on how many decimal places you want to
truncate) which is still around 110 tonnes heavier than estimated by Carpenter
and is still heavier the heaviest known Blue Whales.
Paul, G.S., 1994, Big sauropods - really, really big sauropods: The Dinosaur
Report, The Dinosaur Society, Fall, p. 12-13.
Lucas, S.G., Spielman, J.A., Rinehart, L.A., Heckert, A.B., Herne, M.C., Hunt,
A.P., Foster, J.R., and Sullivan, R.M. (2006). âTaxonomic status of
Seismosaurus hallorum, a Late Jurassic sauropod dinosaur from New Mexicoâ. In
Foster, J.R., and Lucas, S.G.. Paleontology and Geology of the Upper Morrison
Formation. New Mexico Museum of Natural History and Science (bulletin 36). pp.
149â161. ISSN 1524-4156.
Carpenter, Kenneth. 2006. Biggest of the big: A critical re-evaluation of the
mega-sauropod Amphicoelias fragillimus Cope, 1878. pp. 131-137 in J. Foster
S. G. Lucas (eds.), Paleontology and Geology of the Upper Jurassic Morrison
Formation. New Mexico Museum of
tural History and Science Bulletin 36.
Hatcher, J.B. 1901. Diplodocus (Marsh): its osteology, taxonomy and probable
habits, with a restoration of the skeleton. Memoirs of the Carnegie Museum 1:
1-63 and plates I-XIII.