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Re: Massive answer to the mess of pterosaur mass
As usual, comments inserted.
----- Original Message -----
From: "MICHAEL HABIB" <email@example.com>
Cc: <firstname.lastname@example.org>; <email@example.com>
Sent: Thursday, January 17, 2008 6:17 PM
Subject: Re: Massive answer to the mess of pterosaur mass
By the same token, my mass estimate and Jim's are also not actually so far
off as they might seem, given how much estimate error there can be.
I do think that Jim's estimate is a bit on the low side; he and I have
actually discussed this a bit already, and our disagreement in this regard
is minor in the big scheme of things.
The caveat there is that body weight in long-distance
travelers like albatrosses varies a great deal just within individuals.
Thus, while I get about 200 kg using the average, the estimate can swing a
great deal using a heavily fueled versus skinny set of animals.
Yes. For example, the huge Whooper swan 'Stonker' was known to drop at
times from about 29 pounds down to about 13 or 14 pounds during the flight
from Scotland to Iceland and vice versa.
I do think that the torso may be a bit larger than Jim gives credit for,
though perhaps I'm just reading into his analogy of a large football
player too much.
Might be. I used that as a visual analogy, without intending that too much
be read into it. Expect the distance from notarium socket to acetabulum to
be on the approximate order of 125% of the articular length of the humerus.
While the torso was quite short, my estimates suggest that it should be
quite deep, as well,
Depth scaling is defined by the relationship between the glenoid, dp crest,
and the coracoid flange. The Qsp coracoid flange is preserved. Look at it
and the relationship between the Qn and Qsp dp crests and the Qsp
scapulocoracoid to help scale the depth of the chest after adding in
notarium, sternum, etc. The chest is deep, but it should still look like a
pterosaurian chest, not all that substantially distorted from Qsp, except
more robust by about the same amount that the Qn humerus is more robust than
the Qsp humerus.
and the overall dimensions of the pectoral girdle would be impressive, to
say the least.
The humerus is truly massive; anyone who has seen it on exhibit (or up
close) knows what I mean. That one element would almost fill my thorax
and abdomen (though I grant I'm a small person). The scapulocoracoid
would need to be quite deep, and the flanges quite expanded. The precise
allometry is difficult to calculate, but my rough estimate is that the
football player would have to be a very good sized linebacker at least :)
Add in the huge limbs and giant neck and head, and you have a pretty darn
Agreed. And though the torso is relatively large compared to other
non-azhdarchoid pterosaurs (the azhdarchid torso is roughly about 30% larger
than a similarly spanned anhanguerid), it still gives the impression of
being small relative to the size of the long bones. It's the durned
azhdarchid head and neck that overwhelm me.
I've also started toying with some bone cross-section techniques for
estimating mass, but this is harder than it sounds because we have little
a priori reason to assume a specific safety factor for pterosaurs. It was
probably near that of birds, but we cannot say for certain.
Interestingly, my first swing at that gave me a (admittedly rough) mass of
about 220 kg. The interesting thing there is that the technique would be
expected to give the maximum (ie. heavy fuel load) weight. As such, I
wonder if perhaps Mark's method does the same, and that our estimates are
more congruent than they seem (with 250 or thereabouts being the maximum
fueled mass for a large animal).
I do agree that the animal could carry 250Kg, just point out that it would
not be an optimal loading -- but then, maximum fueled mass never is.
Regardless, the real punchline, I think, is that these large pterosaurs
were not the "ultralights" that is often expected.
You, Mark, Greg Paul, John Conway, and I are in very strong agreement there.
I've been preaching that since 1999. These rascals looked like Arnold
Schwartzenegger on steroids (not that he would ever have taken steroids).
Clearly, they were reasonably heavy animals with plenty of power
generation. This holds whether Qn was a 150 kg animal or a 250 kg one.