Darwinopterus + egg = awesome

Many of you may have seen this already, but a new paper is out with what can only be described as a female pterosaur. This is big news, while there have been suggestions in the literature (most notably about Pteranodon) about some specimens representing males or females, this is one rather more convincing than many for the simple reason that there is an egg associated with it. That it is another Darwinopterus and a great specimen too, only adds to the interest.

The egg, sadly, lacks any trace of an embryo (though this is perhaps not surprising as obviously the egg was only about to be laid, not about to hatch) but has all the characteristics of pterosaur eggs and is the right size and shape. It also lies between the legs of the female and just behind the pelvis. That it is not in the body is not a major issue – a similar situation is commonly seen with icthyosaurs for example where decomposition leads to bloating of the body and forces out anything large and solid like a late term embryo or as in this case, and egg that’s ready to be laid.

Oddly enough the real interest in the paper lies in the head of the animal. The egg clearly points to this being a female but the head has no trace of a crest, despite other specimens of Darwinopterus having one (as you can see here for example). The strong suggestion therefore is that Darwinopterus is sexually dimorphic with males having crests and females none. The authors make a pretty good case, though a hatful of other specimens with other consistent differences in something approaching a 50:50 split would be better still.

One note of warning I would add though, is not to take this too far. Such extrapolation is fine for Darwinopterus, but I’d be very wary of taking the same basic criterion and applying it to other pterosaurs. Just as a quick example, many antelope and bovids have horns in males and females, and some can be nearly identical between the two, and in reindeer the females have antlers for parts of the year when males have none, while in most deer of course only males present antlers. I suspect it’s a matter of days before we see the first crested pterosaur specimen = male (or no crest = female) blog posts or media reports but this would be, for me, a very big assumption too far. A great start yes, but not even the end of the beginning for pterosaur dimoprhism.

Special thanks to Lu Jungchang for these special photos.

8 Responses to “Darwinopterus + egg = awesome”

  1. 1 Jim Kirkland 22/01/2011 at 4:52 pm

    Over 10 years ago we collected an egg of unique microstructure in the Upper Jurassic Mygatt-Moore Quarry (Morrison mudhole/marsh-pond) in western Colorado that was in association with the densest accumulation of Mymoorapelta bones. This has always suggested to me we had an ankylosaur egg aborted on the death of the animal. I have always wished someone had followed up on it. The egg is in the collections of the Museum of Western Colorado.

  2. 2 Ragna Redelstorff 23/01/2011 at 3:52 pm

    Hey Dave,

    that’s a great post! Thank you!

    I was wondering, if the soft-shelled egg is preserved (exceptionally), why is there no other soft tissue preserved? Or are the yellow-orange stains within the body cavity and along some bones as well as at the right foot, soft tissues? It is hard to tell from just looking at photos. These stains seem to resemble the colour and texture inside the egg, which may not be surprising, as they would be similar tissues. But then, what struck me when looking at the close-up of the egg is, what is that ridge running from the edge of the egg closest to the body towards the pelvis? It seems like the egg does not have a closed shape but is open at that side and instead is connected to the pelvis through a canal. What is that “canal”? I don’t recall having seen that in connection with eggs. But again, I might be wrong about that canal as I haven’t looked at the actual specimen.
    Just a wild guess: Could the “egg” shape be a sack made of the more decay-resistant abdominal or coelom wall and filled with decayed tissue goo of the animal’s body cavity that has been pushed out through the orifice for the same reason as the authors suggested for the egg? In that case, the “canal” would actually be part of the coelom wall… I have never heard of anything like that to be honest but some experiments on that may be interesting. Also,in order to find out what shape this “tissue sack” would most likely form (roundish, would be my guess).
    Please don’t get me wrong, I think it’s a fantastic specimen and I am sure the authors have had the same doubts and checked them already and could make my doubts vanish into thin air. Fascinating topic altogether! I hope to see more of that specimen soon! Maybe including some UV light analysis, SEM work, CT-scans etc??? 🙂

    • 3 David Hone 23/01/2011 at 5:50 pm

      Bearing in mind that I don’t know much about eggs or taphonomy and have only read the paper and not seen the specimen or spoken to the authors….

      First off, there’s not much that can be done for UV without Helmut Tischlinger and as noted in previous post comments, there’s not really any proper facility to CT stuff in China, and I doubt there’d be an option to sample stuff for SEM analysis.

      As for the main question about soft tissue, the don’t mention or describe any in the paper and I agree there appears to be some around the feet. Pterosaur soft tissue really is pretty rare and while the egg is soft, it will still have some kind of calcerous shell and while I don’t *know* I would guess that this might have a slightly higher preservation potential that most of the wings etc.

      I would though be very surprised if the internal organs had prolapsed and survived and when the wings and claws did not, or for that matter very large amounts of other tissues. Though I agree that you’d really want to check the microstructre of the egg shell for absolute confirmation. I should add that the authors do also discuss why they think this is an egg in a bit more detail in the supplementary data.

  3. 4 Ragna Redelstorff 23/01/2011 at 10:01 pm

    Right, I forgot about it being in China. That fact most probably decreases further studies to normal microscopy – which may still be good enough in terms of soft tissues.

    The question is, are these stains really soft tissues? How much got lost due to preparation? I think Dave Unwin mentioned he documented the preparation process so there might be more photographic evidence.
    Another question is, if that calcareous shell is preserved, why not more recalcitrant tissues such as your mentioned wings and especially claws.
    I agree with you on the internal organs, IF there’s nothing else preserved it is rather unlikely that these labile tissues have. Still, that structure I called “canal” is quite striking and its ridge seems to continue along the egg.
    Anyway, as you said, more microscopic work on the egg and the soft tissues would be interesting.

    I know it’s not exactly your field of work but nevertheless interesting enough for discussion!

    • 5 David Hone 23/01/2011 at 10:35 pm

      I definately wonder about the claws specifically and also to a lesser degree the actinofibrils of the wing. Where are they? Still, all manner of odd things are possible – maybe they had rotted before bloat pushed the egg out? Unlikely but possible.

      No idea what the ‘canal’ is. I’d be very interested to know more about that especially. Good point.

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