Sauropods of 2008: Eomamenchisaurus

February 9, 2009

Thanks to all for congrats regarding the baby news. Will this mean a short-term break from blogging? In part, yes, but luckily I’ve had the opportunity lately to prepare quite a lot of stuff in advance, so fear ye not oh fans of SV-POW! and Tet Zoo. And to demonstrate that point: welcome to another article in the ‘sauropods of 2008’ series. In the previous entry we looked at the Chinese titanosauriform Dongyangosaurus sinensis. Now for something completely different…

fig. 11) -- Yuanmosaurus reconstruction

Lu et al. (2006: fig. 11) -- Yuanmousaurus reconstruction

Potentially one of the most interesting of recently named sauropods is Eomamenchisaurus yuanmouensiset al., 2008 from the Middle Jurassic Zhanghe Formation of Yuanmou County, Yunnan Province, China. Yuanmou is already known in the world of sauropod research for yielding Yuanmousaurus [reconstruction above, from Lü et al. (2006)], a possible relative of Euhelopus named in 2006. The only known Eomamenchisaurus specimen consists of dorsal and sacral vertebrae, a partial pelvis, and hindlimb elements: unfortunately, however, the material isn’t fantastic and at least some of the diagnostic characters identified for the taxon are not entirely convincing and mostly look like widespread, primitive features. In the dorsal vertebrae, for example, the absence of pneumatic foramina is listed as a diagnostic feature, but if this animal really is a member of Mamenchisauridae as claimed, then absence of foramina doesn’t work as an autapomophy because other members of the group (e.g., Mamenchisaurus hochuanesis) are also reported to lack foramina on their dorsal centra (as are many other non-neosauropodan sauropods). Pneumatic foramina are indeed absent in Eomamenchisaurus, but note from the image below that pneumatic fossae are present (actually… I assume those lateral cavities are pneumatic fossae, but have just realised that they might not be. Let me know what you think). As is – I hope – well known by now, we’ve found it useful to distinguish ‘pneumatic foramina’ from ‘pneumatic fossae’: gone are the days when all pneumatic holes or cavities could simply be referred to as ‘pleurocoels’ or ‘pneumatopores’.

In the image shown here [from Plate II of Lü et al. (2008)], the ninth and tenth dorsals are shown in (A) ventral and (B) lateral views. See below for discussion. Note the pneumatic fossae. Scale bar = 10 cm.

eomamenchisaurus_lu_et_al_2008

As indicated by its name, Lü et al. regarded Eomamenchisaurus as an early relative of the famously long-necked mamenchisaurid Mamenchisaurus. Are there any characters that support this assignment? There are, but they aren’t very convincing either: three concern the anatomy and degree of fusion in the sacrals, and that’s always a problematic area because sacral fusion varies with age and, in some taxa, with sex. The fusion of two posterior dorsals (probably the ninth and tenth) is used as a fourth character. According to Lü et al., this fusion is also present in M. hochuanensis, M. youngi and in Chuanjiesaurus anaensis. The last taxon listed there was regarded by Lü et al. as a mamenchisaurid, but the original description provides little information and Upchurch et al. (2004) treated this form as Sauropoda incertae sedis, and only provisionally valid. It is entirely coincidental that Matt is also dealing with vertebral fusions at the moment – I hope I’m not treading on his toes by writing all this, apologies if I am.

A full evaluation of Eomamenchisaurus is needed to further determine its affinities: it might be a mamenchisaurid, but we need more data. In fact it’s worth saying at this point that mamenchisaurids as a whole need a thorough revision: as is widely recognised among sauropod workers, Mamenchisaurus (currently containing seven species) now seems to be a waste-basket genus housing disparate animals that are probably not all close relatives.

References

Lü, J., Li, T., Zhong, S., Ji, Q. & Li, S. 2008. A new mamenchisaurid dinosaur from the Middle Jurassic of Yuanmou, Yunnan Province, China. Acta Geologica Sinica 82, 17-26.

Lü, J., Li, S., Ji, Q., Wang, G., Zhang, J. & Dong, Z. 2006. New eusauropod dinosaur from Yuanmou of Yunnan Province, China. Acta Geologica Sinica 80, 1-10.

Upchurch, P., Barrett, P. M. & Dodson, P. 2004. Sauropoda. In Weishampel, D. B., Dodson, P. & Osmólska, H. (eds) The Dinosauria, Second Edition. University of California Press (Berkeley), pp. 259-322.

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17 Responses to “Sauropods of 2008: Eomamenchisaurus

  1. Matt Wedel Says:

    Matt is also dealing with vertebral fusions at the moment – I hope I’m not treading on his toes by writing all this, apologies if I am.

    No apologies necessary. We’re all bringing the sauropod verts to the masses here. Nice post. FWIW, those look like fossae rather than foramina to me. Since we’re both looking at low-rez black and white pix from a PDF, take that with the customary large sodium chloride crystal.

  2. Darren Naish Says:

    Awesome, thanks big daddy.

  3. David Hone Says:

    Having seen at least *some* Mamenchisaurus material and quite a few papers, there definatley are a number of true specimens that are from a single genus, but a lot of questionable stuff too. Shunosaurus and Omeisaurus are arguably far worse as well with even more specimens of even more varied animals dumped into each of them. Someone has a big job someday.

  4. Leonardo A. Says:

    Off topic comment, sorry.
    Congratulations, Darren!

    I’ve linked this blog to mine, “Geomythologica”.
    Lot of stuff on psychology and dinosaurs …and palaeontologists as well…

    Thanx Matt, Mike and Darren for all those sauropod’s vertebrae!

    Leonardo

  5. Nick Gardner Says:

    Big job in more ways than one, David.

    That aside, there are 7 species of Mamenchisaurus? I had no idea. Not surprised though, hasn’t dinosaur taxonomy always been plagued by frequent waste-basket taxonomic assignments in the past?


    Nick

  6. Nathan Myers Says:

    Over on Christopher’s “Catalogue of Organisms”, last year, there was some discussion of the Latin for “wastebasket”, with obvious taxonomic application. I don’t recall the outcome.

  7. Nathan Myers Says:

    … OK, Google reveals, with ridiculous (not to say embarrassing) ease, http://catalogue-of-organisms.blogspot.com/2008/08/amaurobioidea-rummaging-through.html .

    What kind of world is this, wherein Google identifies Catalogue of Organisms as the definitive word on the opposition of wastebaskets and Latin? Answer: a world of the past, because henceforth Google will point here instead, or, at least, too. “Wastebasket taxon” remains conspicuously absent from Wikipedia, an omission that once rectified would, and no doubt, will deprive these more valuable, nuanced and altogether classier forums of one more drop of precious Google juice. In the meantime, here we are. Welcome, Googlenauts.

  8. Nathan Myers Says:

    (Shhhhh! Don’t give it away!)

  9. Graham King Says:

    David Hone said

    Having seen at least *some* Mamenchisaurus material and quite a few papers, there definatley are a number of true specimens that are from a single genus, but a lot of questionable stuff too. Shunosaurus and Omeisaurus are arguably far worse as well with even more specimens of even more varied animals dumped into each of them. Someone has a big job someday.

    There’s a cartoon somewhere* of a doting sauropod mum looking over her nestful of hatchlings wonderfully-varied in form and musing “Hmm, darlings, I think I’ll name you ‘Mamenchi’… and you ‘Omei’… and you ‘Shuno’… and you (etc)…”

    (* okay, it only exists in my head).


  10. […] Upon closer inspection, however, Panphagia shows characters that hint at much larger things to come. Its teeth are long and sharp, particularly near the front of the jaw, but also sport the coarse serrations seen in later plant-eaters. Its name, meaning “Everything Eater,” reflects Martinez and Alcober’s suggestion that it was an omnivore, descended from carnivorous ancestors but capable of supplementing its diet with plant matter as well. Several features of its teeth, skull, and skeleton ally it to the Sauropodomorpha, that great clade of long-necked herbivorous dinosaurs that would, some 75 million years later, give rise to familiar giants like Apatosaurus and Brachiosaurus (as well as a whole panoply of less-well-known but equally fascinating megaherbivores). […]


  11. […] Here’s another article in my ‘sauropods of 2008’ series. Previous entries have looked at Eomamenchisaurus and Dongyangosaurus, both of which are Asian. This time round we look at a new South American […]


  12. […] up for tails. For previous instalments in the Sauropods of 2008 series please see the articles on Eomamenchisaurus, Dongyangosaurus, and […]

  13. Fabrizio Says:

    Hello, i love your works about sauropoda. I’ve a question: what would be the “only” valid Mamenchisaurus species? Thank you for answering
    And please sorry my imperfect english

  14. Mike Taylor Says:

    Hi, Fabrizio, thanks for your kind words. I’m afraid I have no very strong opinions on which species of Mamenchisaurus are valid, as the only material I’ve seen for myself is all of M. hochuanensis (and even that was casts). I will say that I am confident that not all the species can be considered congeneric (based on differences in figured dorsal vertebrae) but I don’t remember the details and I doubt I’ll ever get a chance to see all the relevant material.

  15. Fabrizio Says:

    Thanks. Well i’ll wait until mamenchisaurus taxonomy became more clear… this means mamenchisaurus could be even a wastebasket taxon, something like a chinese titanosaurus. It’s the sauropod i like most


  16. […] caudals are pretty common in sauropods (see here), and fused dorsals turn up a lot (see discussion here), and the fusion of the atlas to the axis is not unheard of (see here and here), fusion of the […]


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