Sauropods of 2008: Dongyangosaurus

January 19, 2009

So, 2008 has come and gone. Was it a good year for sauropods? In terms of new taxa, it wasn’t amazing, but it wasn’t too bad, and (as we’ll see in this and a few following posts) some of the taxa involved had pretty interesting vertebrae. For the record, the taxa named in 2008 were Dongyangosaurus sinensiset al., 2008, Eomamenchisaurus yuanmouensiset al., 2008, Qingxiusaurus youjiangensis Mo et al., 2008, Muyelensaurus pecheni Calvo et al., 2008 (labelled 2007, but actually 2008), Uberabatitan riberoi Salgado & Carvalho, 2008 (previously covered here on SV-POW!), Dixiatitan binglingi You et al., 2008, Pitekunsaurus macayai Filippi & Garrido, 2008, Tastavinsaurus sanzi Canudo et al., 2008 (previously mentioned here), and Malarguesaurus florenciae González Riga et al., 2008 (labelled 2009, but actually 2008). Hold on – that’s 9 new taxa. Wow. I’m not going to look at these taxa in any particular order, nor will I be covering all of them (and if there are any I’ve missed, please let us know).

We start with one of my favourites: Dongyangosaurus from the Fangyan Formation of Dongyang, Zheijiang Province, China. A (probable) non-titanosaurian titanosauriform, its partial skeleton includes beautifully preserved vertebrae (Lü et al. 2008).

plate 1) -- Donyangosaurus dorsals

Le et al. (2008: plate 1) -- Donyangosaurus dorsals

The dorsals [shown here, Plate I from Lü et al. (2008)] are neat. The neural spines are described as bifurcate, which I assume means that they are V-shaped at their apices as they are in, say, Camarasaurus or Opisthocoelicaudia: unfortunately this is neither clearly described nor figured in the paper. Prominent spinodiapophyseal laminae (spdls) extend obliquely up the sides of the neural spines, but what’s really odd is that there are deep hollows dorsal and/or posterodorsal to the spdls: these hollows house small subsidiary laminae. The presence of these ‘hollows with subsidiary laminae’ is unique to Dongyangosaurus. At least some of the dorsals also possess – in addition to anterior and posterior centroparapophyseal laminae and paradiapophyseal laminae – subsidiary laminae ventral to the diapophysis and posterior to the parapophysis.

What’s the deal here? Are those cavities on the sides of the neural spines pneumatic? We’d need detailed information on the bone texture here to test this hypothesis. And why all the extra little laminae? Given that laminae seem to help partition air sacs, the presence of small subsidiary laminae hint at the possibility that Dongyangosaurus went nuts (in pneumatic terms), growing lots of extra pneumatic structures in and around the neural arch.

The two preserved caudal vertebrae [shown below, Plate II from Lü et al. (2008)] also reveal some interesting strangeness. The caudal centra are taller than they are wide, and are amphicoelous (concave at both ends). The bases of the postzygapophyses (in an area bound anteriorly by the spinodiapophyseal lamina and ventrally by the postzygodiapophyseal lamina) are perforated by three small fossae, all of which presumably invade the base (at least) of the postzygapophysis. Again, this is unique and used as a diagnostic character for the taxon.

dongyanosaurus_caudals_lu_et_al_2008

And – that’s it. Another one next time.

Reference

Lü, J., Azuma, Y., Chen, R., Zheng, W. & Jin, X. 2008. A new titanosauriform sauropod from the Early Late Cretaceous of Dongyang, Zhejiang Province. Acta Geologica Sinica 82, 225-235.

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14 Responses to “Sauropods of 2008: Dongyangosaurus

  1. Nathan Myers Says:

    I’m a bit gobsmacked by the remark, “Given that laminae seem to help partition air sacs…”. No argument about the implication above, but do we know any reason why laminae would need help being partitioned? My interpretation is that laminae are bits of necessary bone structure that (therefore) ultimately fended off the incursion of opposing air sacs. Sure, they indicate the boundaries of the air sacs, but the statement seems to invert the roles of bone and air sac from “bone exists where necessary, air sac where not” to something indicating a direct, positive function of air sacs.

    Have I missed something fundamental and/or interesting?

    Getting back to the implication, “subsidiary laminae hint [at] lots of extra pneumatic structures … around the neural arch”, you seem to be saying that the laminae actually do suggest air sacs external to the bone, of unknown, presumably positive function. Am I reading this right?

  2. Graham King Says:

    Given the variable and contingent nature of pneumatisation (discussed previously in SV-POW), I am wondering how stable and reliable as a diagnostic character such features may be. In the absence (I presume?) of multiple specimens of a newly-labelled taxon being available to compare, might the features noted be peculiar to that individual specimen?

    Of course, you may well know good reasons to discount my cavilling. I just wondered!

  3. Mike Taylor Says:

    Ah, you guys are asking such good questions.

    Someone ought to take one of these on as their dissertation.

  4. Brad McFeeters Says:

    If 2008 with ten species wasn’t amazing, which years were?

    Does “actually” published still refer to whenever the print edition of a journal reaches libraries? I know everyone had the .pdf of the Malarguesaurus description in 2008… but everyone had the .pdf of the initial Futalognkosaurus description in 2007 (are you sure you’re not confusing the second paper on Futalognkosaurus with the brief one naming it?). Daxiatitan was never mentioned online until 2009, how do we know it was truly named in 2008?

  5. Nathan Myers Says:

    Brad: Darren did find himself amazed once he totted up last year’s list, if his “Wow.” is any indication. Brits have this understatement thing, you know, and they are obliged to work it hard, even (or particularly) when their very best readers are on the Continent or overseas.


  6. Platycoelous actually means one end is flat and the other is concave. Amphicoelous would be both ends concave.

    But keep the new taxon comments coming! If there’s one group of dinosaurs I can’t keep straight, it’s all the new Chinese and South American sauropods.

  7. Darren Naish Says:

    Hi all, thanks for comments.

    — Nathan noted my vague statement ‘Given that laminae seem to help partition air sacs…’, and wondered what I was getting at. Maybe what I should have said was ‘Given that laminae seem to form the boundaries to air sacs…’. The apparently opportunistic and sometimes asymmetrical distribution of air sacs indicates that they encroach into the bone when mechanical (and developmental?) constraints allow it: in other words, they ‘eat’ into the bone so long as this doesn’t interfere with the integrity of the bone, or with muscle attachment (data on birds indicates that it isn’t the air sac itself that resorbs the bone, but the osteoclasts that are transported by the blood vessels that surround the air sac). I mostly took this hypothesis from Witmer’s work on cranial pneumaticity in archosaurs. He referred to air sacs as ‘opportunistic pneumatizing machines, resorbing as much bone as possible within the constraints imposed by local biomechanical loading regimes’ (Witmer 1997, p. 64). I did not mean to imply that the laminae grow first and that the air sacs then have to sit constrained within (though this is probably true in part – oh crap, we know nothing).

    — On the ‘subsidiary laminae [that] hint [at] lots of extra pneumatic structures … around the neural arch’, my interpretation is that Dongyanosaurus had more air sacs on the lateral surfaces of its neural spine than was usual. We’ve known for a long time that sauropods had air sacs on the lateral sides of the neural spines, but there’s usually a cavity for one or two big air sacs, plus smaller, shallower fossae within indicating a few subsidiary ones. It looks like Dongyanosaurus had several, clearly partitioned air sacs in this region, which is weird. As I said, we need more information to be sure that these cavities are pneumatic (e.g., we need to see evidence for pneumatic tracts). Anyone have any idea what’s going on here?

    — Graham said: ‘Given the variable and contingent nature of pneumatisation (discussed previously in SV-POW), I am wondering how stable and reliable as a diagnostic character such features may be’. Damn good point. Indeed, given the opportunism and hence variability of pneumaticity, individuals within a given species might be variable as goes the details. However – at the moment we don’t have any other (described) sauropods that have the weirdy dorsal neural spine and caudal postzyg characters of Dongyanosaurus, so these features still stand as diagnostic features.

    — Brad asked about publication dates: as you know, the ICZN still mandates that ‘publication date’ refers to the actual, physical appearance of the document, and not to digital publication (though an amendment [published in Zootaxa] was proposed in 2008). This is really annoying when the actual publication date is later than the planned date printed on the journal, meaning that you require ‘special knowledge’ to confirm that a given paper really was published when the journal says it was. We all know of cases where, say, an issue of JVP or Canadian Journal of Earth Sciences dated one year actually appeared the next, the result being that some people cite (say) 1993 (because that’s what it says on the cover), while others cite 1994 (this being the ‘actual’ publication date). I cite the ‘cover date’ unless I specifically know otherwise (this means I’m inconsistent – but what else am I meant to do?). On the cases here, I am reliably informed that, despite existing in pdf form in 2007, the Muyelensaurus paper only appeared in paper form in 2008. You are right about Futalognkosaurus: I’d forgotten that its brief naming appeared in 2007, so have removed it from the text. And, while the Malarguesaurus says ‘2009’ at the top, I personally had my hands on a printed issue in 2008. As for Dixiatitan: you’re right, at the moment I lack ‘special knowledge’ and am assuming that the given date is correct… but this could be wrong.

    — On numbers of new taxa: I recall 2006 being the year when 12 new sauropods were named. If 2008 had exceeded that, I might have been ‘amazed’. My recollection (prior to counting) was that 2008 was an ‘ok year’, but when I realised that there were 10 taxa (now 9, due to removal of Futalognkosaurus)… well, clearly 2008 was actually pretty good.

    — Mickey: amphicoelous vs platycoelous, oops. Thanks for correction.

  8. Brad McFeeters Says:

    Thanks for confirming that about the new Cretaceous Research, it’s been a while since I’ve seen that journal in physical format.

    12 generally accepted sauropod species in 2006, but up to 17 if you count the ones named by Malkani (at least, the internet tells me those are from 2006). Any plans to discuss those mysterious “balochisaurids” and “pakisaurids” on SV-POW some day?

  9. Nathan Myers Says:

    Thanks, Darren, for the voluble reply.

    This must have been happening for centuries. I’m surprised we don’t already have a convention that looks like (e.g.)

    Malarguesaurus florenciae González Riga et al., 2008 (“2009″)

    About the laminae: wouldn’t it be more precise, then, to say they “seem to mark the boundaries” between air sacs? In particular, can’t air sacs end up eating away the entire lamina, perhaps leaving nothing? As for the laminae marking presumed surface sacs: can that be bone that has grown up into a gap where sacs meet, or must the sacs have whittled away surface bone, leaving the laminae? (I suppose these questions are really about what has been observed in analogous structures in living creatures.)

    About Graham’s question: I understand that the sacs themselves are highly variable. Are the fossae also variable in more or less related specimens?


  10. [...] in the ‘sauropods of 2008’ series. In the previous entry we looked at Chinese titanosauriform Dongyanosaurus sinensis. Now for something completely [...]


  11. [...] 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 taxon: Malarguesaurus [...]

  12. David Marjanović Says:

    The Transactions of the Royal Society of Edinburgh has a convention on fake publication dates. On top of the description of Westlothiana (you know, the little Early Carboniferous beastie described as an amniote or almost an amniote, when it’s actually the basalmost amphibian…), it says:

    Transactions of the Royal Society of Edinburgh: Earth Sciences, 84, 383–412, 1994 (for 1993)

  13. David Marjanović Says:

    (I mean the longer description, not the extended abstract from 1990 which actually called it the first amniote.)


  14. [...] ribs, chevrons, and material from the pelvis and hindlimbs (we’ve previously mentioned it here, and figured some of it here). Evidently, only the hindquarters of the animal were preserved. But [...]


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