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Fwd: Re: DinoMorph Strikes Back!... or does it?
Forwarded from Kent Stevens. DV
Begin forwarded message:
Date: January 3, 2006 4:05:16 PM PST
Subject: Re: DinoMorph Strikes Back!... or does it?
arm posture used by giraffes and okapis). Now, if some sauropods had to
partly disarticulate the cervicals to get the head down far enough to drink
looks like they did so. As long as a joint is not bearing a major load of
body, i. e. a leg joint when on the ground while walking or running, it is
possible for some joints to regularly partly disarticulate in order to
normal function (the premeire example being the wrist of the horse).
Ah, the horse wrist. Some of us remember your admonishments in an earlier
DML posting regarding said horse wrist.
But do you know of an intervertebral joint that can be disarticulated (more
As it seemed to Jeff Wilson and Paul Sereno at an SVP talk, it might appear
that camels can dorsiflect their necks so far they seemingly must
disarticulate. But as Mike Parrish and I have subsequently shown in our
chapter in the
Currie Rogers/Wilson volume, it's simply a camel thing. When flexing their
necks back sufficiently to rub their occipital glands on their shoulders (a
specifically male camel thing apparently) all cervical vertebrae remain
comfortably in articulation. They not only preserve a safe overlap at the
zygapophyses, but as we also show, there are osteological stops that prevent
disarticulation when the postzygapophyses travel posteriorly to the max.
camels can achieve the same degree of dorsal flexion as occurs in the death
Not so with poor sauropods, by the way. Their death pose exceeds
articulation, and thus probably exceeds what they could comfortably achieve in
Sorry, but the juvenile _Camarasaurus_ CM 11338 is probably preserved in a
death pose, unless you believe that they could go around with their necks all
out of articulation.
Going back a decade, at the New York SVP, in the question period after a
talk I delivered with Mike Parrish, you suggested that I verify the DinoMorph
method using a modern analog, such as the giraffe. Well, this last year, as
part of the "Dinosaurs: Ancient Fossils, New Discoveries" exhibit, the AMNH
kindly CT-scanned an entire giraffe neck and I put that digitized morphology
data into DinoMorph, and yes, the virtual giraffe closely replicates the range
of motion observed in living, behaving, giraffes (look at the movie on my
website under AMNH, or better, go to the exhibit and run the software
interactive for yourself) Moreover, I've found the giraffe neck is
braced when laterally flexed to its limit, much as the design in _Diplodocus_
and some other sauropods (for mediolateral flexion, not dorsiflexion, mind).
Thankfully, one simply does not need to postulate sauropods undergoing
disarticulation. The "Eeyore model" of sauropod neck posture, depicted in an
early drawing of a rather dejected _Diplodocus_ in Hatcher, later in an Osborn
and Mook silhouette illustration of _Camarasaurus_ (see the Bozeman SVP
presentation PDF at my site), is pretty much what the bones dictate. Sorry.
Kent said that the dorso-cervicals of AMNH 5761 are fused in a straight
Actually they are fused in a modest upwards kink,
Sigh... please look again... it should be plain to see that the articulation
at the two consecutive centra is indeed straight. This, at least, should not
require an infinite loop of argument. For driving instructions, either go my
and in the "research projects" pulldown, select Camarasaurus, then either 1)
optionally read a bit of the text there, including instructions on three
ways to get a Camarasaurus erect, or 2) just click on the link to the
or 3) just click below and forget reading all the text:
Warm thanks go to Carl Mehling for the hefting and Rick Edwards for the
At the opposite end of things, a number of Camarasaurus and some other
sauropods of course have the necks in a vertical position, with all
in full articulation even though they are at their maximum dorsal
I'd like to see such specimens. Please provide us all with specific
specimen numbers and institutions. For those who have actually studied CM
(either by getting up on a ladder or visiting either Dinosaur National
or the Los Angeles Museum of Natural History casts thereof, which are at eye
level thankfully), it is patently obvious that the poor juvenile in its death
pose is preserved dramatically out of articulation at the zygapophyses!
There's a lot more going on there, including a torsional disarticulation at
base of the neck which much have lead astray at least one paleoartist. The
same is true of a lovely specimen at the Sauriermuseum Aathal, which sure
looks like it's trying to be a "Juraffe", but for the fact that the neck is
twisted axially 90 degrees, which is easily misinterpreted visually as
a 90 degree vertical bend. It becomes obvious only when you note that
cranially the vertebrae are viewed in lateral aspect, while caudally the neck
vertebrae are seen in dorsal aspect; something not obvious to a casual
People forget that because sauopods had so many cervicals that just modest
rotation between any two of them adds up to a lot of total flexion.
We're not forgetting. We also don't forget that there is less angular
flexion per joint permitted by the proportions of the zygapophyseal facets
relative to their centers of rotation in sauropod design, unless of course one
hypothesizes that the vertebrae were routinely capable of disarticulating
everyday neck flexion.
>From giraffes and camels to turkeys (and presumably sauropods) the same
biomechanical principles hold, and seemingly (but the following is not
sufficiently established yet) perhaps the same safety factors apply (e.g. in
amount of overlap). We've simply applied the same safety factors to the
sauropod geometry. Don't blame us that sauropod osteology does not permit
there is no good reason to conclude that such sauropods (and not all
sauropods are like
this) when alive could not raise the neck vertically to high browse or get
maximum view of the landscape.
Yes there is: the cervical vertebral osteology does not permit such extreme
dorsiflexion without disarticulation. Is there an echo in here?
What I am getting at is that an odd view has developed, one that seems to
think that the only way to legitimitely illustrate or mount dinosaur
with the cervicals in perfect neutral osteological articulation. There is no
such law. ...
But what if such illustrations nonetheless depict the vertebrae as
undeflected (based on close examination of the articular facets along the
For instance, examine the _Apatosaurus ajax_ mount at the Yale Peabody
Museum. The neck is mounted in a lovely, gentle sigmoid curve. Looks great.
Now, look carefully at the zygapophyses (take binoculars, or borrow a ladder
Mike Parrish and I did) and you'll see that the zygapophyses appear to be in
neutral position. But before you conclude that this specimen has an
intrinsic swan-like curve to it, just tap on the vertebrae and you'll find a
lot of plaster artfully stained to resemble bone. That is to say, those
vertebrae at the base of the neck where the upturn presents itself were
reconstructed artfully (I use the term "artfully" again, Scott, in the meaning
intend, not merely as suggesting a subjective, aesthetic sense of art). How
that happen? It seems the available fossil material was first attached to a
smoothly curved armature, then the missing pieces were filled in with plaster,
and it just so happens that the way the prezygapophyses were plastered in to
align directly under their associated postzygapophyses, the overall neck
appears to be state of neutral deflection. Sigh.
So, regarding laws, perhaps there should be (if there is not an unwritten
one already) a law stating that if an axial skeleton is formally drawn (or
mounted) for scientific purposes, as depicting OTHER THAN the "perfect neutral
osteological articulation" then said state of deflection should be accurately
and clearly apparent by examination of the articular surfaces. There should
also be documentation, perhaps, suggesting that the artist intends on
depicting the given axial skeleton in a state of deflection out of the neutral
if that is not made sufficiently clear by the intervertebral joint facets.
Such cautions are not needed, of course, with the appendicular skeleton: the
limbs are often drawn as in mid-stride, without the potential of misleading
Since so many colleagues, when referring to silhouette drawing in order to
derive an overall understanding of an extinct animal's bauplan, tacitly assume
that the depiction of the axial skeleton reflects its characteristic
curvature (as is the way skeletons of giraffe, horse, or deer, etc. are
traditionally drawn or mounted), there should indeed be a law. Thanks for