A problem of cartilage

[GSP1954@aol.com]

The more I look into this business of restoring neck posture in sauropods the 
worse it looks in terms of basic feasibility. 

Basically Kent is saying that you can pull any well preserved sauropod neck 
out, as well as a giraffe, presume that the cartilage that spaced out the 
centra is just a few millimeters thick, articulate its neutral posture, and 
assume 
that it accurately records the neutral osteological posture of that 
individual, if not the entire species or genus. It ainât anywhere near that 
that simple. 
And the big problem is that intercentral cartilage.

Iâve been looking at a lot of giraffe necks and wow, are they all over the 
map in terms of morphological and articulation differences. Vertebra 8, the 
first with dorsal ribs, is especially variable, with dramatically differing 
spine 
heights and orientations, as well very different orientations of the 
zygapophyses and anterior centra ball. Compare 8 in fig 6.2 in Kent & Parrish 
to the 
same bone in Fig. 4 in Solounias 1999 J. Zool. Lond. 247: 257. The latter 
neckâs 
neutral osteological posture is definitely subhorizontal. 

At the Smithsonian, since the 60s, ye old skeleton hall (I love it but what 
will they ever do with it in the 21st century?) has had a mounted, large 
juvenile giraffe, maybe 2/3s to 3/4s grown. The neck is mounted erect, like in 
fig. 
6.2 in the Kent & Parrish figure. Iâve long noticed that to get the neck so 
erect the cervical centra are pulled way apart in almost all cases, even when 
the zygapophyses are fully neutral. Inserted between the centra, sort of 
attached to and covering the posterior facet of each centrum, are pads that 
seem 
intended to represent thick cartilage. 

I figured it was time to see how the ossified bones of this specimen 
articulate, so I carefully traced them off a photo at a large scale and 
articulated 
them without the padding. Yikes. The posterior cervicals are pitched up, but 
only a little at about 20 degrees, and the mid and anterior cervicals assume a 
fairly smooth inverted U that leaves C1&2 pitched downwards about 30 degrees, 
and at about the same level as the neck base, or a little below. 

Obviously this neutral bare bone articulation (NBBA) has nothing to do with 
any normal life posture. The only way the get the neck straight and 
subhorizontal (much less subvertical) if it is assumed that little cartilage 
separated 
the centra is to have the all zygapophyses very strongly dorso-flexed, which is 
improbable. It seems that - as those who mounted the skeleton where hinting 
with the intervertebral padding - there is a lot of cartilage in the cervical 
series in growing giraffes. If so it is not possible to restore the neutral 
cervical articulation (NCA, which includes bone and cartilage) in this 
individual 
because the cartilage is gone. 

In the Smithsonian collections is another giraffe neck which, although large, 
may not be fully adult either. It happens to be held together in a straight 
line with all zygapophyses in neutral articulation or very close to it. The 
cervicals are held together by dried out tissues between the centra, cartilage 
or 
joint capsules. If the centra contact one another then the NBBA was 
subhorizontal. But the spacing between the centra suggests they are not in 
contact, 
having being separated by cartilage when alive. If so the NCA would probably be 
another inverted U as per the other immature neck. 

Now it is time to return to the immature Camarasaurus CM 11338, which was 
just a toddler of a few hundred kilograms when the poor thing died a tragically 
premature death circa 145 Myr BP. Kentâs diagram of the neck as preserved 
measures the zygapophyses being dorso-flexed 14.5 to 26 degrees. Add them all 
up 
and the dorso-flexion is 186.5 degrees relative to the NBBA when it comes to 
the 
zags. But the neck over all is dorso-flexed only about 70 degrees over the 11 
cervicals Kent measured. So if the zygapophyses are all lined up fully 
neutral, and the centra remain in close contact, then the neck should be 
depressed 
about 115 degrees relative to the NBBA for the zygapophyses in neutral, and the 
centra closely spaced as preserved. I rearticulated the neck in that manner 
and sure enough it articulates in a strong inverted U with the anterior 
cervicals pointing vertically, about 110 degrees relative to the neck base â 
almost 
identical to the prediction by Kentâs measurements. Again this NBBA has 
nothing 
to do with any normal life posture, and is not even the NCA. 

Kent also provides the centra dorso-flexion figures for the same neck. As he 
notes, they are much less than the zygopophyses deviation from neutral, being 
about 65% less when all measurable joints are added up. So the two systems do 
not match up in the same neck. So much for determining the NBBA in this 
cervical series, its literally impossible because the zags and centra are not 
even 
close to being in neutral articulation at the same time. 

Kent did not try to articulate this neck in a neutral posture. It is becoming 
obvious why.

Again, the only ways to get this neck horizontal requires dorso-flexing each 
set of zygapophyses a lot â about 10 degrees per zag pair â if the centra 
are 
kept closely together. Or, if the zygapophyses are overlapping 100% in full 
neutral, then the centra have to be pulled  apart. 

Itâs the latter which is the only plausible solution. In Bellairs The Life of 
Reptiles it is explained that most reptiles have ball-and-socket centra 
articulations. In most of those there are three layers of cartilage between 
each 
two centra. Each centrumâs articular surface is caped with cartilage. Between 
each pair of centra is the intervertebral disc. Kent has not mentioned this 
basic reptilian feature. 

When CM 11338 died it was a happy go lucky, bouncing baby sauropod, growing 
fast. No two ways about it there was a lot of cartilage between its rapidly 
enlarging centra. How much? We will never exactly know. There is absolutely no 
way to determine this with any confidence. As the carcasse dried out the 
intercentra cartilage dried out and pulled the cervicals together. This jammed 
the 
vertebrae together, over dorso-flexing the zygapophyses beyond what they would 
have been had the neck been in the same pitched upwards pose in life. This is 
why the zags are so extremely overlapped even though all the cervicals are 
actually dorso-flexed just a few degrees relative to the next in the series. 

Now, just a small addition of cartilage between the cervicals results in 
dramatic alterations in the posture of long necks. If the 11338 neck is 
articulated so each zag is fully neutral with 100% overlap and with the centra 
pulled 
apart as much as needed, it is only 10% longer than if the centra are as 
tightly 
articulated as preserved, and the zags are dorso-flexed as much as needed. 
That works out to an average of just 10 mm of cartilage per joint, so just 
small 
changes in intercentra cartilage results in dramatic differences in neck 
posture. This is because just a few differences in the degrees of orientation 
between each cervical add up to a lot over long necks. Because long neck 
posture 
is so hyper sensitive to the thickness of the intercentra cartilage, and 
because it is not possible to even begin to estimate the thickness of the 
intercentra cartilage with anywhere near the needed accuracy, the very concept 
of 
confidently restoring the NCA, much less the NBBA of unfused sauropod necks is 
ruined. It just cannot be done. 

If the intercentra cartilage was just modestly thicker in CM 11338 than 
restored here then the neck would not have been straight when the zags were 
fully 
neutral, it would have been dorso-flexed to a greater or lesser extent. And 
this returns us to the fused posterior cervicals of Camarasaurus 5761. 

Kent is still trying to argue that 5761 cervicals 11 & 12 are fused straight. 
He is not going to win this one. As others who have looked at those very 
photos have commented, the remarkable two vertebrae certainly are not in a 
straight line. I've seen them at the AMNH of course. They are patently visually 
dorso-flexed as preserved, to a measurable 7-8 degrees. One commentator asked 
if 
perhaps they are crushed into that flexion. Cannot be entirely ruled out, but 
the crushing is not severe and there is no objective reason to think the modest 
deformation changed the angulation significantly. I will get around to 
publishing these verts with lines measuring their dorso-flexion along the long 
axes 
of the centra, and their ventral rims to boot. I wonder if Kent will ever do so 
while claiming they are straight, and I challenge he or anyone to insert 
these elements into the old Osborn and Mook Camarasaurus skeletal restoration 
and 
get the same drooped neck without an awkward upwards kink at cervicals 11 & 
12. 

As I noted in the last post, the zygapophyses are ossified into the neutral 
posture. This means that as this old giant fused up its neck base cervicals the 
cartilage between the two had been thick enough to space the cervicals into 
an upwards pitch. This suggests the same was true when camarasaurs were 
juveniles, but it is not possible to be entirely sure. There may or may not 
have been 
ontogenetic changes in neck posture with growth, and if it did change it 
could have gone either more or less erect with maturity. No way to know with 
the 
data on hand. 

Kent seems to assume that if sauropods did not have a sharply pitched up neck 
base that they could or did not elevate the head well above shoulder level. 
But Kentâs own diagrams of bird and camel necks show the head carried well 
above shoulder level even though the posterior cervicals are pitched down a 
little. Getting the head high can be achieved either by a strongly dorso-flexed 
neck 
base, or by a more gradual curve of much or all of the cervical series. 

In a message dated 1/13/06 9:55:37 PM, kent@cs.uoregon.edu writes:

<<4) In the 1999 Science article Mike Parrish and I published, the  
manuscript originally included data for 25% and 75% overlap as well  
as the 50% overlap, but the other estimates were dropped in the  
editing in order to save column inches.  But curiously the height  
results for 25% safety factor were rather similar to those for 50%,  
for reasons that seem to escape GSP:  to raise the head (and NOT  
merely curl the neck into an arc), almost all the dorsiflexion must  
arise at the base of the neck.  The mid neck, and especially the  
cranial few cervical vertebrae must remain STRAIGHT in order to  
maximize the elevation of the head.  So the large number of cervical  
vertebrae don't really enter into how high the head can raise. One  
cannot trivially multiply (say) 5 degrees per joint times 18 joints  
(= 90 degrees) and conclude the neck forms a right angle with respect  
to the trunk of the animal.  What would result is an arc of  
diminishing radius of curvature (because centra length diminishes  
cranially).  Such simple numerology does not yield the desired  
giraffe-like neck, the kind with a sharp kink at the bottom and a  
derrick-like ascent. To get a giraffe-like neck requires specialized  
vertebral morphology at the base of the neck, which informally we  
call "wedge-shaped" or "keystone shaped".  Incidentally, some  
dinosaur illustrations (particularly of camarasaurids and  
brachiosaurids) show both a sharp upturn at the base AND an  
inflection point at mid neck (i.e. an overall sigmoid or reflex  
curve).  In order to create a reflex curve, the cranial portion of  
the neck must be ventriflexed and the caudal part dorsiflexed (if  
they are not already so-disposed in their osteologically neutral  
pose, as in the horse, and the avian neck, for instance).  Trying to  
put a swan-like sigmoid curve in a sauropod neck, one ends up with a  
disappointingly low-amplitude sigmoid curve (unless, of course, one  
disarticulates the vertebrae where necessary to create the desired  
curve).>>

The way to refute this is the look at the quarry map of the type of 
Mamenchisaurus youngi. There simply is no sharp pitch up at the neck base. 
Instead the 
neck describes a gradual curve that arcs the head 5.5 m directly over the 
back. There is somewhat more angulation between each cervical at the neck base 
than anteriorly, but the difference is not dramatic. It is interesting that 
what 
cervical ribs are in place are barely sprung, indicating this was not a 
difficult posture for the neck to adopt in life. This contradicts arguments 
that the 
long overlapping ribs stiffened the neck to near inflexibility. Even if the 
dorso-flexion between each cervical is reduced by about half then the neck 
would still sloop upwards about 45 degrees and the head would be about 5 m over 
shoulder level. This is close to what I did with my skeletal restoration. The 
reason that tall sauropods did not need a sharply pitched up neck base to get 
the head way up there is because they had so many vertebrae in the posterior 
neck, in some cases almost as many as make up the entire neck of a giraffe. The 
sauropods had a lot more to play with, so just a little adds up to a lot. Only 
7 degrees of dorso-flexion each between 7 or so cervo-dorsals and you have 45 
degrees of upward pitch right there, which can be added to by up to another 10 
or more anterior cervicals in the longest necked forms to reach that tasty 
morsel. 

While on M. youngi, more about how weird its skeleton is. The sacral complex 
is extremely wedge shaped apex dorsally, much more so than in other sauropods 
including M. hochuanensis. As a result the tail is pitched strongly upwards 
posteroirly, and the dorsal series - which is nearly straight - slopes 
antero-dorsally about as much as Brachiosaurus. This is exactly the posture 
preserved 
in the quarry, and there is no evidence of distortion. As an artist I recoil at 
what looks like a ridiculous posture, as a scientist I have to go along with 
it because there is no evidence that the arrangement was more normal, and 
straightening it out requires completely decoupling the zygapophyses. Could 
this 
be a sexual thing? Probably not, only one sauropod skeleton out of the many 
collected is known to be like this so it seems the sex ratio would be rather 
skewed. The postural differences between M. hochuanensis and M. youngi are so 
extreme that it seems they are different genera, but bone for bone they are 
quite 
similar so I'm taxonomically torn. 

<<5) Sorry, but I must reiterate that when compositing original  
published illustrations to reconstruct a vertebral series, one needs  
to be mindful of the fact that 1) the vertebrae are sometimes not  
depicted in correct scale within the original document, and 2) some  
bones are crushed and significantly distorted diagenetically.  The  
first issue induces artifactual curvature, leading to the false  
impression of a truffle-hunting, or gopher-hunting sauropod in  
osteologically neutral position.  I hope this red herring doesn't  
keep rearing its ugly head, to mix metaphors.  The second issue,  
attempting to place a distorted vertebrae into close articulation  
with its adjacent vertebrae, is simply silly.  For that reason, I pay  
careful attention to the image scale of each vertebra image, and  
secondly, place any distorted elements with caution, using the  
adjacent vertebrae as an overall guide  (such as I did regarding the  
noted sixth caudal of _Apatosaurus_ CM 3018 from Gilmore, some  
_Dicraeosaurus_ presacrals, and the mid-cervicals of _Diplodocus_ CM  
84 that cause a downturn which Mike Parrish and I checked by  
manipulating casts of the originals, and concluded is due to  
distortion).  The photo-composites, therefore, indeed leave some gaps  
where frank distortions arise in the component vertebrae, so that the  
educated eye can clearly see the distortion for what it is.>>

I'm not entirely sure what is being said here. Since all the 3108 cervicals 
are on the same figure at the same scale and appear to articulate with one 
another it is hard to see how there is a scaling issue. As for deciding what is 
distorted it seems that basically if a cervical does not articulate in a 
straight line Kent assumed to be distorted. That is potential bias in favor of 
a 
desired conclusion, which is one reason I take statement 1 above with some 
salt. 
In any case, if there are cervicals distorted so severe in 3018 that the centra 
have to be grossly disarticulated then the series is useless as a guide for 
restoring NOA in the first place, and one wonders why it is being cited as 
evidence of a hang dog look because such a damaged set of bone cannot be used 
to 
conclude that the taxon carried its head at ground level. In my last post I 
forgot to mention that Ford awhile back got exactly the same downward curve in 
the neck of 3108 that I got completely independently using a somewhat different 
methodology. 


Knowing that it cannot be assumed that all sauropods had little cartilage 
spacing between the centra, letâs relook at the taxa to see what can be done 
with 
them. 

GIRAFFE: I have seen only one neck base that articulates strongly 
dorso-flexed in NBBA, thatâs Kentâs, others are more horizontal if not 
strongly arced 
ventrally. Nor has the neutral life posture been established, nor has the 
neutral life posture (NLP with tendons neither stretched nor relaxed) been 
shown to 
coincide with the NCA. It is interesting that the one technical diagram of a 
walking giraffe, in Gambaryan 1974 How Mammals Run, shows the neck 
subhorizontal. So does the NLP doe coincide with the NBBA in at least some 
giraffes, or is 
the NLP lower than the erect NBBA in Kent's giraffe neck, or was the walking 
giraffe in Gambaryan having a bad day? We do not know. After looking at lots 
of stills and films of wild giraffes determining the typical neck posture, or 
determining if there even is one, has proved most elusive. And at least 
juvenile giraffes demonstrate the critical problem of cartilage spacing making 
it 
impossible to restore the NBBA. So we have no really good modern guide for 
sauropods yet, and may never have. 

CAMARASAURUS: We just saw that juveniles, like those of all growing 
individuals, had a lot of cartilage between the cervicals, but how much is 
unknowable, 
so restoring even the NCA much less the NBBA is not possible. Nor can the 
maximum elevation be reliably restored. It is definitely possible that the 
vertical pose seen in 11338 was achievable in life if the cartilage was 
sufficiently 
thick. Or, maybe it wasnât and the neck is pulled back further than it could 
go in life. That the cervical ribs are not sprung strongly out of place - 
albeit more than in the M. youngi skeleton - place suggests that the neck is 
not 
pulled back into a nonlife position, but this is not definitive either. So 
posing the neck either way is plausible, it is a matter of opinion, not 
science. 

Much more important are the fused posterior cervicals, which are at this time 
the only sauropod cervicals in which there is no need to guess at the 
thickness of the intercentral cartilage (sure would be great to saw these down 
the 
midline and see what the ossified structure looks like in terms of its 
cartilagenous origins - is an intervertebral disc ossified in there?). In this 
one and 
only case in which a sauropod is known to have ossified the intercentral 
cartilage the neckâs NBBA was pitched upwards, not straight or down as Kent 
chronically restores them. If five or 6 other cervo-dorsals had the same pitch 
then 
the NBBA was a strong 35-40 degrees dorsally.  

APATOSAURUS: 3018 is yet another example of a long neck articulating in an 
inverted U when the zags are neutral and the centra are closely spaced. Kent 
says this is distortion. Maybe. More likely it was cartilage spacing. Even 3018 
was not the biggest apatosaur, and it may have still been growing. And sauropod 
dinosaurs were not as well ossified as mammals, they may have retained 
reptilian style intercentra cartilage until the end, except when pathological 
fusion 
occurred as in 5761. Because there is no described cervical series that is 
clearly undistorted it is not possible to reconstruct the NBBA, and lacking 
fused examples it is not possible to restore the NCA of this genus. Nor is it 
possible to reliably estimate the maximum neck elevation because the cartilage 
spacing is unknown. Kentâs estimate that the head could be strongly elevated 
is 
plausible if thick cartilage padding was present. 

While looking at this sauropod, it is interesting that Riggs restored the 
dorsal series of 7163 strongly arched, as I did with 3018, indicating at least 
some Apatosaurus had arced backs. 

DICRAEOSAURUS: The one available neck does not seem to be in NBBA at both the 
zygapophyses and centra consistently. We donât know the cartilage spacing and 
fused cervicals are lacking, so the NCA much less the NLP cannot be restored. 
We do know that it was not possible to elevate the neck strongly in this low 
shouldered form because the neural spines would jam up. 

DIPLODOCUS: The NBBA produced by Kent, myself and Ford (in PreHistTimes) do 
not agree, which is not encouraging. Donât know the cartilage spacing and 
fused 
cervicals are not at hand, so neutral postures are a guess. So is maximum 
elevation, although it was probably much higher than short, low necked 
Dicraeosaurus. 

BAROSAURUS: This should have been able to elevate the head far above shoulder 
level simply because of the sheer length and number of the cervicals, 
combined with the relatively tall shoulders compared to other diplodocids. This 
assumes the head was at an angle of about 30 degrees relative to the shoulders. 
This is why Barosaurus had longer arms, and a less stout tail, already able to 
reach high on all fours it had less to gain from rearing, although it remained 
well adapted for tripodal feeding. 

EUHELOPUS: Although the cervicals are nicely figured in lateral and dorsal 
views they are articulated in series, obscuring the zygapophyses. What is clear 
is that if the figure is accurate then the NBBA places the main cervical 
series pitched up about 30 degress relative to the anterior dorsals, and that 
there 
is significant pitch between 19 & 20 (which is cut off in Kent's straight 
âNBBAâ figure) - BTW it is not necessary for a vertebrae to be wedge shaped 
to 
get pitch up, a parallelogram shape angled antero-dorsally will do the trick. 

The big problem here is the same as always. We have no idea what the 
cartilage spacing was. If it was greater than the spacing preserved in the 
fossil, and 
that is very possible if not probable, then the NCA could have been greater 
than it seems, perhaps much greater. Or maybe not. 

What is clear that even if the zags remain overlapped by a third or so then 
the neck could be elevated far above the shoulders, 45% being not even close to 
being a problem (and that gives about 3/4s of the vertical max reach starting 
from the neck base), and vertical or beyond being definitely possible. And 
this assumes thin intercentral cartilage. If the latter was thick then neck 
elevation was all the easier. There is nothing osteological wise to stop the 
neck 
from being held very high, so Kent's statement that "the osteological 
adaptations used by extant vertebrates to induce neck curvature, and 
specifically to 
elevate the neck, are absent in all the sauropod specimens we have thus far 
examined" is abjectly falsified. Only if all these sauropods had cervical 
articulations that positively barred them from elevating the neck, like 
dicraeosaurs, 
would this be true. 

MAMENCHISAURUS: As nice as all the figures and photos of the cervicals of M. 
youngi are there appears to be some damage in some cases, the zygapophyses are 
ill-defined in others, there are no fused cervicals, and the cartilage is 
long gone, so any attempt to restore NBBA and NCA is pure guess work. Between 
two 
of the best cervicals, 15 & 16, I get 10 degrees of dorso-flexion with 
significant overlap of the zags remaining. That's quite enough to elevate the 
neck 
into the position in the quarry, with the head high over the back. Again it is 
clear that some sauropods did have the osteological adaptations to reach 
extreme heights. 

BRACHIOSAURUS: Because the top half of the neck base is not preserved, and 
because centra facets do not always match up with zags when it comes to NBBA, 
and so forth, the latter cannot be reliably restored. Because getting the neck 
to 45 degrees would require very little dorso-flexion in the numerous 
cervo-dorsals, there is no good reason to conclude brachiosaurs could not reach 
12 m, 
and a vertical 14 m is possible and perhaps probable. 


Looking at the big picture, we have a basic idea of neck base NBBA in only 
one Camarasaurus individual, whose fused verts shows its neck was pitched 
upwards. But exactly how much the rest of the neck base was oriented dorsally 
remains uncertain, and there may have been variation between specimens. It 
seems 
that only one individual sauropod neck, a Euhelopus, is preserved and 
illustrated 
well enough to reasonably determine its entire NBBA, which is elevated about 
30 degrees relative to the anterior dorsals. But NCA and NLP may have been 
even higher if the hydrated cartilage spacing was just modestly thicker than 
the 
spacing preserved in the presumably dried out specimen. Of course there is the 
issue of individual variation. Far from knowing the NBBA and NCA of lots of 
sauropods, the NBBA and NCA proposed to date by Kent are either incorrect, or 
not verified. His conclusions go far beyond what the data actually supports. 
The proposition that many sauropods had drooping NCA that placed their heads in 
a comfortable grazing position is especially dubious at best in some cases, 
and just plain wrong in others. In the end there is no sauropod for which the 
entire neckâs NBBA is known, and because of the cartilage spacing issue it is 
probably not possible to ever determine it for any specimen. Much better 
established is that so far all sauropods with long necks and high shoulders had 
the 
cervical osteology that allowed the neck to elevate to a very steep angle and 
many meters above the shoulders, and probably to vertical if not beyond in the 
longer necked examples, Kent's implications to the contrary not withstanding. 
Even if NBBA or NCA can be determined, it is by no means certain that this 
corresponded with the NLP, or if there really was such a thing as a normal life 
neck posture, in part because it appears that giraffes are happy to carry their 
necks at a variety of angles depending upon circumstances and perhaps sheer 
preference at a given moment. What's a paleoartist to do?  

Kent seems disappointed to now learn that I have not been posing sauropod 
necks in NBBA all these years. Actually its a smart idea; it has never been 
possible to reliably determine NBBA in sauropods, so it has simply not been 
possible to accurately pose the neck in them, we are all guessing including 
Kent 
although he thinks otherwise. I will not attempt to restore any sauropod 
specimen 
with its the neck in the NBBA because doing so would be irresponsible and 
misleading. This situation is very different from the short necked theropods in 
which the NOA is much more readily determined and seems consistent within a 
species. In any case I do not think I have ever claimed to be posing sauropod 
necks in the strict NBBA. In the 1988 Hunteria paper on Brachiosaurus I said 
the 
neck articulated in a gentle S-curve. But the restored skeleton shows a strong 
S-curve with the posterior cervical centra clearly dorso-flexed - just because 
the text says what the neutral posture has been estimated to be does not mean 
the neck has to be posed that way any more than the tail. It's called 
academic-artistic freedom. 

What we know about sauropod NCA is so bad that it by no means can be ruled 
out that in many if not all examples the intercentra cartilage was spaced to 
give the necks those nice S-curves many artists like giving them. If you want 
to 
restore them that way go right ahead. But you don't have to. If you prefer to 
show some or all of them following a U shape that's fine too because the data 
is grossly inadequate to establish otherwise. A strong pitch up of 30-40 
degrees at the 6 or so neck base vertebrae and the anterior neck in a straight 
line? Have fun, knock yourself out, it's as good as anyhting else (except that 
dicraeosaurs could not elevate so far). 

Aside from the inability to determine sauropods cervical NCA, there is 
another reason that it is not good to require that skeletons to be posed that 
way. 
If they are, then artists will automatically tend to illustrate them in that 
manner even though the NcA may be inaccurately restored, and even if correctly 
drawn may not correspond with the normal life poses, which may often be 
significantly higher. It would be like people chronically illustrating giraffes 
with 
horizontal necks because some if not most cervical series articulate 
horizontally. Worse, many scientists will automatically assume that sauropods 
fed low, 
failing to exploit the full vertical reach of the neck. That would not seem to 
be true but it has already been happening. 

It cannot be overemphasized that, contrary to Kentâs opinion, the NBBA, NCA 
and NLP, even if they can be determined, is pretty much irrelevant to restoring 
the minimum or maximum practical vertical feeding range either ventrally or 
dorsally. Many herbivores whose NCA is above horizontal feed at ground level, 
and giraffes whose necksâ NCA are near horizontal can feed with the neck 
vertical. The one thing important to determining how high an animal can feed is 
how 
high the combination of neck length and joint dorso-flexion allows the head to 
reach. Plus adaptations for rearing. Whether NCA is above, below or at 
horizontal has little to do with minimum or maximum vertical reach. The only 
partial 
exception is if the NCA is consistently subvertical, which would be good 
evidence for high browsing. But even that would not be definitive, since even 
giraffes whose NCA is subvertical often feed at shoulder level. 

It is correct that 3-D computer analysis is the best method for restoring 
neck flexibility outside the vertical, midline plane. But when restoring NOA 
and 
maximum elevation 2-D paper articulations are about as good as the computer 
work, as per the Kent & Parrish paper. Due to all the uncertainties that have 
been detailed, all restorations of sauropod neck posture and flexiblity are 
approximations. Biology is just too sloppy when working with long necks in 
which 
just a few degrees of divergence from reality at their many joints will result 
in big differences in the final result. 

Some commentators continue to suggest that sauropods only elevated their 
heads well above shoulder level intermittently to avoid having to have super 
duper 
high blood pressures. Thatâs very unlikely, because as I noted earlier it is 
a bad idea selectively speaking for meters tall, whale sized animals to risk 
miscalculating their intellectual oxygen needs, faint, and flop like a giant 
sack of wet cement onto the ground. Besides, would not work well for habitually 
rearing sauropods. 

Asking why sauropods would have evolved the extreme BPs necessary to feed 
high when plenty of food was available at shoulder height and below is like 
asking why a clade of air-breathing, once terrestrial mammals evolved a marine 
form 
that has extreme respiro-circulatory adaptations in order to dive thousands 
of feet without getting the bends to feed on giant squid, when there is plenty 
to chow down on near the surface much less back on land. It is quite possible, 
but not certain, that even the longest necked sauropods did feed at low and 
medium levels to a greater or lesser extent (although as one person noted a 
Varricchio paper observed the lack of grit wear associated with low browsing on 
Diplodocus teeth, which Kent seems to have ignored in his postings and 
publications). But when herbivore populations were high, and/or drought or the 
like 
reduced floral productivity, sauropods able to tap floral resources (mainly 
conifers whose deep roots and xeric adaptations allow them to weather dry 
conditions) would have had a big selective advantage over shorter statured 
ornithischians. No modern mammal feeds higher than giraffes because what with 
dental 
batteries and big brains they are too big headed to be so long necked. Also, in 
modern floras much of the plant biomass may be more tied up in ground cover 
(especially grasses) than in the Mesozoic. Kent noted that giraffes often feed 
horizontally, which is true. But it is also true that in much of east Africa 
there is a visible browse line at 18 ft., the maximum reach of bull giraffes. 
All 
platable. browse within the reach of a herbivore is important. 
 
Scott is quite right. Only if truly and firmly demonstrated by anatomy would 
restorations of super-long necked sauropods wandering about Mesozoic lands 
with their heads normally barely above ground level, grazing mainly on short 
ferns, be a scientific necessary. It is illogical for such an arrangement to 
evolve as the primary postural and feeding orientation for a long necked animal 
because it would be maladaptive in basic energetic terms, the long neck being 
energetically costly to grow, maintain and breath through. Long necks probably 
did not evolve for cooling since the extra breathing load would increase respi
ratory heat production, and because giant tachymetabolic endotherms do not need 
cooling systems anyway because they are too massive to readily overheat as 
Iâve explained numerous times elsewhere. Only sexual display offers a hint of 
a 
plausible explanation for super-long horizontal necks but even thatâs a real 
stretch if youâll excuse the pun. All the more so since display structures 
tend 
to enhance height to impress potential mates, or intimidate opponents. It 
makes a lot evolutionary sense that sauropod anatomy shows they could elevate 
their long necks by dorso-flexion, and/or rearing.   

As for the tone of this discussion, I noticed that Kent, who is a nice guy, 
in his website and the paper was getting subtle and not so subtle digs in at 
others, including me, as well as making spurious criticisms of the accuracy of 
my technical art work. And I enjoy a good scientific row now and then. More 
importantly, the sauropod work is so defective that I was not going to let it 
slip by without making a fuss about it and the errant review system. And Iâm 
disturbed to see Kent continue to make assertions that have been quite 
thoroughly 
discredited by my and other posts. 

Iâve been wondering what to do with this analysis. Itâs questionable it 
would get through peer review. Politics aside, this is not a study packed full 
of 
precision measurements that comes to an absolute conclusion. Itâs more a 
nature is so sloppy that we donât know what the heck is going on when it 
comes to 
basic aspects sauropod neck posture. Sometimes that's the way nature is.  

And get the cartilage in. 

G Paul