Serial changes in the vertebral laminae of Plateosaurus
May 15, 2012
Plateosaurus engelhardti (originally P. trossingensis) SMNS 13200 cervical vertebrae 3-8 in left lateral view. C8 is roughly 15 cm long.
In the recent post on serial variation in sauropod cervicals, I wrote:
Even in ‘adult’ sauropods like the big mounted Apatosaurus and Diplodocus skeletons, the anterior cervicals are less complex than the posterior ones. Compared to posterior cervicals, anterior cervicals tend to have simpler pneumatic fossae and foramina, fewer laminae, and unsplit rather than bifid spines. In all of these things the anterior cervicals are similar to those of juveniles of the same taxa, and to those of adults of more basal taxa. This is also true in prosauropods–in Plateosaurus, the full complement of vertebral laminae is not present until about halfway down the neck.
I was working from memory there and actually understated things a bit. Plateosaurus presacral vertebrae don’t have well-developed spinal laminae, but they do eventually get the four major diapophyseal laminae–the anterior centrodiapophyseal lamina (ACDL), posterior centrodiapophyseal lamina (PCDL), prezygodiapophyseal lamina (PRDL), and postzygodiapophyseal lamina (PODL–please see the lamina tutorial if you need a refresher on these and the other 15 commonly identified laminae). But they aren’t all present halfway down the neck–the ACDL doesn’t really show up until the cervicodorsal transition. The other three kick in sequentially down the neck, as shown in the above image. I think that’s pretty cool, that you get different character states expressed at different points along the neck, in one individual organism, at one time. And possibly also at different times–in sauropods, the anterior cervicals tend to look more ‘juvenile’ or ‘primitive’, even in adult animals, so all of the cervicals go through a juvenile stage, but not all of them grow out of it. I don’t know if there’s a word for that–some kind of serial heterochronotopomorphy or the like–but hopefully someone will enlighten me.
I took the original photo in the collections at the Staatliches Museum für Naturkunde Stuttgart in the spring of 2004. Markus Moser and Rainer Schoch were wonderful hosts during my visit. Mike did all the work of turning the raw photo into a figure, so thanks to him for getting this off my hard drive and out into the world.
Sauropod Vertebra Picture of the Week 
May 15, 2012 at 8:01 am
I have yet to see a convincing argument why this is not P. engelhardti.
May 15, 2012 at 2:51 pm
Heinrich–for all I know, it might be. I confess that the lower-level systematics of prosauropods in general and Plateosaurus in particular are outside my depth. In this case I was following Moser (2003). If there is a better source or a convincing counterargument, please let me know.
May 15, 2012 at 3:00 pm
Hu?
Moser 2003 explicitly states that the Trossingen material is all referable to the type species! In German AND English!
btw, if this is NOT the case, then SMNS 13200 should be P. erlenbergensis – or someone would need to show that Peter Galton was wrong in saying all the cranial material is monospecific.
See http://dinosaurpalaeo.wordpress.com/2011/12/09/plateosaurus-and-taxonomic-nitpicking/
and yes, Plateosaurus species and even genus taxonomy is not something you should want to get mired in ;)
May 15, 2012 at 3:04 pm
See, this kind of thing is why we put the illustrations of our forthcoming papers up on SV-POW! before we submit the manuscripts. Informal pre-submission peer-review FTW!
May 15, 2012 at 3:07 pm
erhm, Mike – when you publish on this, why not have a look at GPIT/RE/7288 as well? I do happen to have very nice CT scans of that neck!
May 15, 2012 at 4:37 pm
Moser 2003 explicitly states that the Trossingen material is all referable to the type species! In German AND English!
Oh, dammit, you’re right. I could explain how I screwed this up, but it’s probably better for everyone if I just fix the post. Thanks for setting me straight!
February 7, 2013 at 6:22 am
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