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[long]Re: How Did Hadrosaurs (and this thread) Survive?



Ignoring the rest of the message for the moment:
> Of course some hadrosaurs adapted. Edmontosaurus was relatively gracile
and long legged-exactly the assets needed to escape.<
Having been told this again and again, I decided to do some checking on
this. So, I pulled out my trusty copy of The Dinosauria, and flipped to the
hadrosaur section. I found it woefully lacking in postcranial information,
but none the less, I was able to use the information provided therein, along
with supplemental data that I have concerning postcrania (read: accurate
skeletal drawings and photographs). I was able to derive ratios for femur:
tibia, femur: tibia+MtIII, and humerus:radius for 9 hadrosaur genera, from
both Asia and NA, both lambeosaur and hadrosaurine (is that the right
terminology?). Beware, the results may shock you!
Taxa                        F:T   F:T+MtIII   H:R
Corythosaurus:       1.05    .714          1
Kitrosaurus:            1.25    .952          1
Brachylophosaurus: 1.125   .857        .81
Prosaurolophus:      1.23     .89          1.1
Edmontosaurus:       1.29    .92          1.1
Maiasaura:               1        .79          1.06
Parasaurolophus:     1.06    .78           1
Saurolophus:           1.14     .8            1
Tsintosaurus:           1.23     .959        .77
Now, going by the old maxim that longer lower legs in relationship to the
upper legs make for a (theoretically) swifter animal, what is the above data
saying? Well, it appears to be saying that Tsintosaurus, Kitrosaurus,
Edmontosaurus, Prosaurolophus, Brachylophosaurus, and Saurolophus are the
slowest of the hadrosaurs sampled, with ratios between .96 down to .8. But
wait, with the exception of Tsintosaurus, all of those are
hadrosaurids...how does that jive? I thought that Edmontosaurus and
Saurolophus (your two main examples) were the speed demons of the hadrosaur
world, and they basically outran the lambeosaurs when a T. rex approached.
Okay, so, then, who are the (theoretical) fastest animals? Well, it appears
that Corythosaurus would come out on top, followed by Parasaurolophus, and
then Maiasaura, with ratios between .71 and .79. So then the two
(theoretically) quickest animals in this dataset are lambeosaurs (and in a
dataset heavy with hadrosaurids...). How could these animals then be hunted
to extinction, if they appear to be the faster of the two clades (with the
exception of Tsintosaurus)? But wait, there's more!
I took the liberty of doing these ratios for the three predators that we've
been discussing in this topic. The arrangement of the ratios is the same as
above.
Albertosaurus:   1.08    .65
Tarbosaurus:     1.16    .71
T. rex:               1.27    .756
There appears to be a general trend here towards the shortening of the lower
leg, but the ratio still appears to be pretty healthy. But what else appears
in the data? Well, when we look at the ratio of T. rex, and then look at the
ratios of our "speediest" hadrosaurs, we see that Corythosaurus has a
_better_ ratio than Tyrannosaurus, and one equal to that of Tarbosaurus, and
Parasaurolophus is almost equal (within .03) to Tyrannosaurus. So how could
T. rex bring about the extinction of animals that would have been
(theoretically) faster it!? These animals, along with the #3 speedster,
Maiasaura, were surviving alongside the putative Flash Gordon of the
tyrannosaurid world, Albertosaurus, which was no doubt much faster than any
of the top 3. But then we have things like Edmontosaurus, with a ponderous
.92 ratio...and yet we're supposed to buy that it outran the lambeosaurs
that would have been quicker than T. rex, and thus drove them to extinction?
I'm sorry, but the data here just doesn't seem to support your conclusions.
Yes, there are some sources of error here, but at least there's data here as
well (that probably isn't pretty far off), instead of just blindly asserting
that things must be fact because it sounds nice. Still don't agree with what
I'm arguing here? Fine, that is your prerogative, in fact, it wouldn't be
science without disagreement. But if you want to disagree, bring some facts
to back up your claims, don't just dismiss out-of-hand.
Peace,
Rob

Student of Geology
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Northern Arizona University
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