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Sauropod necks, revisited...




>From the desk of Kent Stevens:
 
Drs. Taylor, Naish and Wedel: Your paper provides an opportunity for those 
interested in sauropods to re-visit the last decade of work on sauropod neck 
posture, and through future exchanges I believe some assumptions and 
conclusions will withstand scrutiny, and others will be revised. While I will 
indeed respond, I did not jump in reactively and immediately. 
 
Instead, as I get time, I am compiling additional resources, explanations, 
demonstrations, and new 2D and 3D illustrations that hopefully address many of 
the concerns you, Darren, and Matt raise. But I very much believe the story 
should stay focussed on the majestic megaherbivores themselves; blogs posting 
playful taunts and snarky admonishments about "good biology", etc. tend to draw 
attention away from the sauropods and towards ourselves, our egos, and who's 
right and who's wrong. In any science, some published ideas are outright wrong, 
others are outright right, but both of those cases are relatively rare. 
 
Most proposed ideas, unfortunately, are right only conditionally, and their 
application requires caution and care. A relevant example is the care needed in 
selecting modern analogs for sauropod necks. Some very useful work on this 
seems to have been forgotten or ignored by recent authors, such as the 1999 
work by Matt Wedel & R. Kent Sanders (that both complemented and complimented 
the Stevens & Parrish 1999 study). Wedel & Sanders made compelling arguments 
for avian models (specifically _Struthio camelius_) for soft tissue 
reconstructions and importantly, inferring the limits on cervical joint 
mobility in sauropods. 
 
But rabbit necks? With their playtspondylous amphiarthroidial joints, flat 
central articular surfaces separated by thick fibrocartilaginous disks, and 
absence of a central synovium, rabbits are an unlikely model for the strongly 
opisthocoelous, synovial capsules containing tight-fitting, congruous articular 
condyle-cotyle pairs characteristic of sauropod cervicals. The role of the 
zygapophyses in limiting range of motion has more empirical support than one 
might expect from reading Taylor et al., despite one those authors, Matt, 
having worked with radiologist R. Kent Sanders, M.D., to independently examine 
the proposal by myself and Mike Parrish. I'll get back to this in detail. 
 
There's also more to say about osteological stops in limiting lateral flexion 
in some diplodocids but not others, and regarding replicating giraffe neck 
flexibility using digital models. Lots to discuss, but that requires some new 
effort to prepare, not knee-jerk reactivity. Overall, some conclusions about 
sauropod neck osteology, pose, and flexibility are much better established and 
supported empirically than a reading of the recent Mike Taylor et al. paper 
might suggest, and I'll point those out. 
 
Skeletal reconstructions have revised the slope of the back of the diplodocids, 
and this work changes head height out on the end of the boom, without requiring 
any hypothesis that these animals went around in a state of dorsiflexion. Given 
I had no awareness of the manuscript, nor any opportunity to contribute in the 
peer review process, I'll now have to spend some effort correcting numerous 
misattributions and trivializations of the work that coauthor Mike Parrish and 
I started in the late 1990's but which certainly did not stop with "Walking 
with Dinosaurs". 
 
But engaging in the written equivalent of competitive scent-marking does not 
appeal particularly. Instead, I've started to work towards a revision of my 
on-line resources, which will precipitate further peer- reviewed publication 
submissions, but I've other projects that are competing for my attention this 
summer. I'd suggest that those of us who have interest in reaching a common 
understanding of sauropod paleobiology to meet in Bristol this fall and 
exchange ideas with ale, if not synovial, lubrication. 
 
Kent