University of Bristol

Mike Taylor

Now that the new Wilson and Allain (2015) paper [has redescribed
*Rebbachisaurus*](http://svpow.com/2015/07/08/rebbachisaurus-gets-a-proper-description/),
we can use it to start thinking about some other specimens. Particularly
helpful is [this beautiful rotating
animation](https://umorf.ummp.lsa.umich.edu/wp/gallery/vertebrate-animations/) of
the best dorsal vertebra (here captured at the point of the rotation
where we've viewing it in right anterolateral):

[![rebbachisaur-dorsal-rotation](https://svpow.files.wordpress.com/2015/07/rebbachisaur-dorsal-rotation.png?w=170&h=500){.wp-image-12288
.aligncenter loading="lazy" attachment-id="12288"
permalink="http://svpow.com/2015/07/14/is-xenoposeidon-a-rebbachisaur/rebbachisaur-dorsal-rotation/"
orig-file="https://svpow.files.wordpress.com/2015/07/rebbachisaur-dorsal-rotation.png"
orig-size="289,851" comments-opened="1"
image-meta="{\"aperture\":\"0\",\"credit\":\"\",\"camera\":\"\",\"caption\":\"\",\"created_timestamp\":\"0\",\"copyright\":\"\",\"focal_length\":\"0\",\"iso\":\"0\",\"shutter_speed\":\"0\",\"title\":\"\",\"orientation\":\"0\"}"
image-title="rebbachisaur-dorsal-rotation" image-description=""
image-caption=""
medium-file="https://svpow.files.wordpress.com/2015/07/rebbachisaur-dorsal-rotation.png?w=102"
large-file="https://svpow.files.wordpress.com/2015/07/rebbachisaur-dorsal-rotation.png?w=289"
width="170" height="500"
srcset="https://svpow.files.wordpress.com/2015/07/rebbachisaur-dorsal-rotation.png?w=170 170w, https://svpow.files.wordpress.com/2015/07/rebbachisaur-dorsal-rotation.png?w=51 51w, https://svpow.files.wordpress.com/2015/07/rebbachisaur-dorsal-rotation.png 289w"
sizes="(max-width: 170px) 100vw, 170px"}](https://svpow.files.wordpress.com/2015/07/rebbachisaur-dorsal-rotation.png)

As [I briefly discussed on
Twitter](https://twitter.com/MikeTaylor/status/618775840093028352),
seeing this made me think of my baby,
*[Xenoposeidon](http://svpow.com/papers-by-sv-powsketeers/xenoposeidon-week/)*.
Now that specimen, [beautiful though it
is](http://svpow.com/2014/06/27/xenoposeidon-in-glorious-3d/), preserves
only the lower one third of the vertebra. But there are some clear
commonalities, and they're clearer if you look at the animation.

[![Xenoposeidon-TNF](https://svpow.files.wordpress.com/2011/10/xenoposeidon-tnf.jpeg?w=480&h=412){.aligncenter
.size-full .wp-image-4627 loading="lazy" attachment-id="4627"
permalink="http://svpow.com/2011/10/31/xenoposeidon-in-all-its-glory/xenoposeidon-tnf/"
orig-file="https://svpow.files.wordpress.com/2011/10/xenoposeidon-tnf.jpeg"
orig-size="4773,4095" comments-opened="1"
image-meta="{\"aperture\":\"0\",\"credit\":\"\",\"camera\":\"\",\"caption\":\"\",\"created_timestamp\":\"0\",\"copyright\":\"\",\"focal_length\":\"0\",\"iso\":\"0\",\"shutter_speed\":\"0\",\"title\":\"\"}"
image-title="Xenoposeidon-TNF" image-description="" image-caption=""
medium-file="https://svpow.files.wordpress.com/2011/10/xenoposeidon-tnf.jpeg?w=300"
large-file="https://svpow.files.wordpress.com/2011/10/xenoposeidon-tnf.jpeg?w=1024"
width="480" height="412"
srcset="https://svpow.files.wordpress.com/2011/10/xenoposeidon-tnf.jpeg?w=480&h=412 480w, https://svpow.files.wordpress.com/2011/10/xenoposeidon-tnf.jpeg?w=960&h=824 960w, https://svpow.files.wordpress.com/2011/10/xenoposeidon-tnf.jpeg?w=150&h=129 150w, https://svpow.files.wordpress.com/2011/10/xenoposeidon-tnf.jpeg?w=300&h=257 300w, https://svpow.files.wordpress.com/2011/10/xenoposeidon-tnf.jpeg?w=768&h=659 768w"
sizes="(max-width: 480px) 100vw, 480px"}](https://svpow.files.wordpress.com/2011/10/xenoposeidon-tnf.jpeg)

Most obviously, there are laminae running up and down the anterior and
posterior margins of the lateral face of Xeno's neural arch, and those
same laminae seem to exist in *Rebbachisaurus*. We didn't name these
laminae in the Xeno paper, but if they're the same thing as in
*Rebbachisaurus*, then they're ACPLs and PCDL --- anterior
centroparapophyseal and posterior centodiapophyseal laminae.

If that's right, then we misinterpreted the site of the parapophysis in
*Xenoposeidon*. We (Taylor and Naish 2007) thought it was at the
cross-shaped junction of laminae near the anterodorsalmost preserved
part of the vertebra. In *Rebbachisaurus*, this cross exists, but it's
merely where the CPRL (centroprezygapophyseal lamina) intersects the
ACPL.

But there's more. In *Xenoposeidon*, the base of the CPRL (if
that's what it is) forms a "V" shape with an accessory lamina that
proceeds posterodorsally from the same origin. (This is one of the
features that's apparent on the more damaged right side of Xeno as well
as the nicer left side.) That lamina also seems to exist in
*Rebbachisaurus* --- but with the whole vertebra to consider, we can see
that it's not an accessory lamina, but a perfectly well-behaved CPOL
(centropostzygapophseal lamina).

So if Xeno is indeed a rebbachisaurid, then the two branches of the "V"
go to support the pre- and postzygs, and the laminae running up
the anterior and posterior margins of the centrum support the
parapophyses and diapophyses respectively. There are actually *two*
crosses on each side of the neural arch: one at the intersection of CPRL
and ACPL, the other at the intersection of CPOL and PCDL; but in the
Xeno specimen, the posterior cross is lost, having been just above where
the break occurs at the top of the neural arch.

Here's what I mean:

[![reconstructed-as-rebbachisaur](https://svpow.files.wordpress.com/2015/07/reconstructed-as-rebbachisaur.jpeg?w=480&h=776){.aligncenter
.size-full .wp-image-12292 loading="lazy" attachment-id="12292"
permalink="http://svpow.com/2015/07/14/is-xenoposeidon-a-rebbachisaur/reconstructed-as-rebbachisaur/"
orig-file="https://svpow.files.wordpress.com/2015/07/reconstructed-as-rebbachisaur.jpeg"
orig-size="2238,3619" comments-opened="1"
image-meta="{\"aperture\":\"0\",\"credit\":\"\",\"camera\":\"\",\"caption\":\"\",\"created_timestamp\":\"0\",\"copyright\":\"\",\"focal_length\":\"0\",\"iso\":\"0\",\"shutter_speed\":\"0\",\"title\":\"\",\"orientation\":\"0\"}"
image-title="reconstructed-as-rebbachisaur" image-description=""
image-caption=""
medium-file="https://svpow.files.wordpress.com/2015/07/reconstructed-as-rebbachisaur.jpeg?w=186"
large-file="https://svpow.files.wordpress.com/2015/07/reconstructed-as-rebbachisaur.jpeg?w=633"
width="480" height="776"
srcset="https://svpow.files.wordpress.com/2015/07/reconstructed-as-rebbachisaur.jpeg?w=480&h=776 480w, https://svpow.files.wordpress.com/2015/07/reconstructed-as-rebbachisaur.jpeg?w=960&h=1552 960w, https://svpow.files.wordpress.com/2015/07/reconstructed-as-rebbachisaur.jpeg?w=93&h=150 93w, https://svpow.files.wordpress.com/2015/07/reconstructed-as-rebbachisaur.jpeg?w=186&h=300 186w, https://svpow.files.wordpress.com/2015/07/reconstructed-as-rebbachisaur.jpeg?w=768&h=1242 768w, https://svpow.files.wordpress.com/2015/07/reconstructed-as-rebbachisaur.jpeg?w=633&h=1024 633w"
sizes="(max-width: 480px) 100vw, 480px"}](https://svpow.files.wordpress.com/2015/07/reconstructed-as-rebbachisaur.jpeg)

In case it's not clear, the grey lines are an (extremely crude)
reconstruction, the blue lines label the important laminae, and the red
circles highlight the two crosses.

Hmm. The more I look at this, the more convincing I find it.

But there's more! The anterior aspect of the *Rebbachisaurus* vertebra
also bears a notable resemblance to what we see in Xeno, with a pair or
arched laminae forming a vaulted roof to the neural canal.

 

[![rebbachisaur-dorsal-rotation2](https://svpow.files.wordpress.com/2015/07/rebbachisaur-dorsal-rotation2.png?w=327&h=418){.aligncenter
.size-full .wp-image-12293 loading="lazy" attachment-id="12293"
permalink="http://svpow.com/2015/07/14/is-xenoposeidon-a-rebbachisaur/rebbachisaur-dorsal-rotation2/"
orig-file="https://svpow.files.wordpress.com/2015/07/rebbachisaur-dorsal-rotation2.png"
orig-size="327,418" comments-opened="1"
image-meta="{\"aperture\":\"0\",\"credit\":\"\",\"camera\":\"\",\"caption\":\"\",\"created_timestamp\":\"0\",\"copyright\":\"\",\"focal_length\":\"0\",\"iso\":\"0\",\"shutter_speed\":\"0\",\"title\":\"\",\"orientation\":\"0\"}"
image-title="rebbachisaur-dorsal-rotation2" image-description=""
image-caption=""
medium-file="https://svpow.files.wordpress.com/2015/07/rebbachisaur-dorsal-rotation2.png?w=235"
large-file="https://svpow.files.wordpress.com/2015/07/rebbachisaur-dorsal-rotation2.png?w=327"
width="327" height="418"
srcset="https://svpow.files.wordpress.com/2015/07/rebbachisaur-dorsal-rotation2.png 327w, https://svpow.files.wordpress.com/2015/07/rebbachisaur-dorsal-rotation2.png?w=117&h=150 117w, https://svpow.files.wordpress.com/2015/07/rebbachisaur-dorsal-rotation2.png?w=235&h=300 235w"
sizes="(max-width: 327px) 100vw, 327px"}](https://svpow.files.wordpress.com/2015/07/rebbachisaur-dorsal-rotation2.png)

[Jeff Wilson spotted the same
thing](https://twitter.com/MikeTaylor/status/618775840093028352) in a
sequence of comments on my tweets, saying:

> That's not a bad call---the infrazygapophyseal region of that vert is
> elongate, and there is a nice CPRF and those closely positioned TPRLs
> could mean that prz's are close to one another or even conjoined. It's
> tantalizing, but not much to go on. Would be nice to prep out CPRF &
> work out laminae on lat sfc.

Jeff is right that more preparation would help to figure this out.

Not that everything about the *Rebbachisaurus* dorsal is Xeno-ish. Most
notably, the lateral foramen is nothing like that of Xeno, being an
uninspiringly dull and simple oval rather than the much more
elegant foramen-within-a-fossa arrangement that we see in Xeno. But
there are other points of commonality, too, such as the flat stretch of
bone above the fossa and the way the posterior margin of the neural
arch reaches the posterior margin of the centrum.

All in all --- while there is *plenty* of work yet to do --- I am
increasingly inclined to think that the evidence we currently have
suggests *Xenoposeidon* is a rebbachisaurid. If that's right, it would
be quite an exciting result. It would be the earliest known
rebbachisaur, and the only named one from the UK. (Mannion 2009
described, but did not name, a rebbachisaurid scapula from Wessex
formation of the Wealden). Could Mannion's scapula be *Xenoposeidon*?
Unlikely, as it's 10 million years more recent. But it could be a close
relative.

Exciting times!

# References

- Mannion, Philip D. 2009. A rebbachisaurid sauropod from the Lower
  Cretaceous of the Isle of Wight, England. *Cretaceous Research*
  **30**:521-526.
  [doi:10.1016/j.cretres.2008.09.005](http://dx.doi.org/10.1016/j.cretres.2008.09.005)
- [Taylor, Michael P. and Darren Naish. 2007. An unusual new neosauropod
  dinosaur from the Lower Cretaceous Hastings Beds Group of East Sussex,
  England. *Palaeontology* **50(6)**:1547-1564.
  doi:10.1111/j.1475-4983.2007.00728.x](http://www.miketaylor.org.uk/dino/pubs/taylor-and-naish2007/TaylorNaish2007-xenoposeidon.pdf)
- Wilson, Jeffrey A., and Ronan Allain. 2015. Osteology
  of *[Rebbachisaurus]{.il} garasbae* Lavocat, 1954, a diplodocoid
  (Dinosauria, Sauropoda) from the early Late Cretaceous--aged Kem Kem
  beds of southeastern Morocco. *Journal of Vertebrate
  Paleontology* **35(4)**:e1000701.
  [doi:10.1080/02724634.2014.1000701](http://dx.doi.org/10.1080/02724634.2014.1000701)

 


A rebbachisaurid sauropod from the Lower Cretaceous of the Isle of Wight, England

Now that the new Wilson and Allain (2015) paper has redescribed

 Rebbachisaurus

, we can use it to start thinking about some other specimens.

Is Xenoposeidon a rebbachisaur?

Sauropod guru Jeff Wilson [is on
Twitter](https://twitter.com/diapophysis), as of a couple of weeks ago.
In [one of his earliest
tweets](https://twitter.com/diapophysis/status/432903153910943745), he
showed the world this gorgeous photo of a *Rebbachisaurus* dorsal:

::: {#attachment_9867 .wp-caption .aligncenter shortcode="caption" style="width: 490px"}
[![Jeff Wilson (left) and Ronan Allain (right), with dorsal vertebra of
Rebbachisaurus.](https://svpow.files.wordpress.com/2014/02/bgh7h_eceaamqjn.jpg?w=480&h=721){.size-full
.wp-image-9867 aria-describedby="caption-attachment-9867" loading="lazy"
attachment-id="9867"
permalink="http://svpow.com/2014/02/27/rebbachisaurus-description-incoming/bgh7h_eceaamqjn/"
orig-file="https://svpow.files.wordpress.com/2014/02/bgh7h_eceaamqjn.jpg"
orig-size="998,1500" comments-opened="1"
image-meta="{\"aperture\":\"0\",\"credit\":\"\",\"camera\":\"\",\"caption\":\"\",\"created_timestamp\":\"0\",\"copyright\":\"\",\"focal_length\":\"0\",\"iso\":\"0\",\"shutter_speed\":\"0\",\"title\":\"\"}"
image-title="BgH7H_eCEAAmqjn" image-description=""
image-caption="Jeff Wilson (left) and Ronan Allain (right), with dorsal vertebra of Rebbachisaurus.
"
medium-file="https://svpow.files.wordpress.com/2014/02/bgh7h_eceaamqjn.jpg?w=200"
large-file="https://svpow.files.wordpress.com/2014/02/bgh7h_eceaamqjn.jpg?w=681"
width="480" height="721"
srcset="https://svpow.files.wordpress.com/2014/02/bgh7h_eceaamqjn.jpg?w=480&h=721 480w, https://svpow.files.wordpress.com/2014/02/bgh7h_eceaamqjn.jpg?w=960&h=1442 960w, https://svpow.files.wordpress.com/2014/02/bgh7h_eceaamqjn.jpg?w=100&h=150 100w, https://svpow.files.wordpress.com/2014/02/bgh7h_eceaamqjn.jpg?w=200&h=300 200w, https://svpow.files.wordpress.com/2014/02/bgh7h_eceaamqjn.jpg?w=768&h=1154 768w"
sizes="(max-width: 480px) 100vw, 480px"}](http://svpow.files.wordpress.com/2014/02/bgh7h_eceaamqjn.jpg)

Jeff Wilson (left) and Ronan Allain (right), with dorsal vertebra of
*Rebbachisaurus*. Photograph by MNHN photographer, Copyright © Muséum
National d'Histoire Natural.
:::

I'm pretty certain this is the dorsal vertebra that's been on exhibition
in Paris for some time, and which is part of the holotype of
*Rebbachisaurus garasbae*, which is in turn the type specimen of
*Rebbachisaurus* and so of Rebbachisauridae as a whole. In which case
it's pretty darned important as defining a major group of sauropods.

This specimen was initially described, very briefly and without
illustrations, by Lavocat (1954). The species (though a different
specimen) was given a slightly better treatment by Russell (1996), as
part of a larger work on isolated dinosaur bones. Russell included some
line-drawings of the material (his figures 29-31), of which the pick is
definitely this one of the bottom part of a dorsal vertebra:

::: {#attachment_9868 .wp-caption .aligncenter shortcode="caption" style="width: 490px"}
[![xx](https://svpow.files.wordpress.com/2014/02/rebbachisaurus-russell-1996.jpg?w=480&h=576){.size-full
.wp-image-9868 aria-describedby="caption-attachment-9868" loading="lazy"
attachment-id="9868"
permalink="http://svpow.com/2014/02/27/rebbachisaurus-description-incoming/rebbachisaurus-russell-1996/"
orig-file="https://svpow.files.wordpress.com/2014/02/rebbachisaurus-russell-1996.jpg"
orig-size="1504,1805" comments-opened="1"
image-meta="{\"aperture\":\"0\",\"credit\":\"\",\"camera\":\"\",\"caption\":\"\",\"created_timestamp\":\"0\",\"copyright\":\"\",\"focal_length\":\"0\",\"iso\":\"0\",\"shutter_speed\":\"0\",\"title\":\"\"}"
image-title="Rebbachisaurus Russell 1996" image-description=""
image-caption="xx
"
medium-file="https://svpow.files.wordpress.com/2014/02/rebbachisaurus-russell-1996.jpg?w=250"
large-file="https://svpow.files.wordpress.com/2014/02/rebbachisaurus-russell-1996.jpg?w=853"
width="480" height="576"
srcset="https://svpow.files.wordpress.com/2014/02/rebbachisaurus-russell-1996.jpg?w=480&h=576 480w, https://svpow.files.wordpress.com/2014/02/rebbachisaurus-russell-1996.jpg?w=960&h=1152 960w, https://svpow.files.wordpress.com/2014/02/rebbachisaurus-russell-1996.jpg?w=125&h=150 125w, https://svpow.files.wordpress.com/2014/02/rebbachisaurus-russell-1996.jpg?w=250&h=300 250w, https://svpow.files.wordpress.com/2014/02/rebbachisaurus-russell-1996.jpg?w=768&h=922 768w, https://svpow.files.wordpress.com/2014/02/rebbachisaurus-russell-1996.jpg?w=853&h=1024 853w"
sizes="(max-width: 480px) 100vw, 480px"}](http://svpow.files.wordpress.com/2014/02/rebbachisaurus-russell-1996.jpg)

*Rebbachisaurus garasbae*, NMC 50844, anterior dorsal vertebra in (a)
right lateral, (b) anterior, (c) left lateral and (d) posterior aspect.
From Russell (1996:figure 30).
:::

As noted by Russell (p388), this vertebra is similar, but not identical,
to the one in Wilson's photo. Russell says of his specimen that "the
greater length of the centrum relative to the height and width of the
intercentral articulations and less steeply projecting transverse
processes imply that the vertebra occupied a more anterior position in
the column."

Will *Rebbachisaurus* ever get the detailed treatment that such gorgeous
material deserves? Yes! here's another tweet from Jeff:

::: {.embed-twitter}
> Rebbachisaurus is submitted; Ronan and I start work next Summer on
> Nigersaurus remains housed in Paris and Chicago.
>
> --- Jeff Wilson Mantilla (@diapophysis) [February 11,
> 2014](https://twitter.com/diapophysis/status/433278653829357568?ref_src=twsrc%5Etfw)
:::

Fantastic to think that Rebbachisaurus is in the works, and
*Nigersaurus* to follow! Happy days!

# References

- Lavocat, R. 1954. Sur les Dinosauriens du continental intercalaire des
 Kem-Kem de la Daoura. \[On the dinosaurs of the Continental
 Intercalaire of the Kem Kem of the Daoura\].*Comptes Rendus* 19th
 Intenational Geological Congress 1952 (1):65-68. \[[English
 translation](http://www.paleoglot.org/files/Lavocat_54.pdf)\]
- Russell, D.A. (1996). Isolated dinosaur bones from the Middle
 Cretaceous of the Tafilalt, Morocco. *Museum Natl. d'Histoire Nat.
 (Paris) Bull*. Ser. 4 18 (Section C, Nos. 2-3), 349-402.

Sauropod guru Jeff Wilson is on Twitter, as of a couple of weeks ago.

Messaggi di Rogue Scholar

Is Xenoposeidon a rebbachisaur?

Rebbachisaurus description incoming!