Well. Raising a holy hullabaloo on the internet pays dividends. Vincent Perrichot, one of the authors on the contested PNAS paper, has sent along another aspect of the mystery fossil:
Having trouble? I've arranged a Formica specimen to model the pose:
In the comments below, Vincent provides his perspective:
Well, sounds that the ant nature of our fossil is getting much controversy here! I understand that the photograph provided in our paper is not very clear, so I'd like to clarify things and try to convince everyone. First of all the photograph you are commenting on was published here and by Wired Science in reverse position. It should be viewed at 180º to give at least a better idea.
I've sent a picture to Alex, which might help if he wants to post it on his blog. Now, the fossil is preserved enrolled and contrary to extant specimens, it is impossible to unroll, which makes its study much more difficult. Plus, anyone having tried to image some amber fossil one day knows that it is very challenging to obtain a good, well-focused, picture. So here I totally agree with one of my co-author Matthias Svojtka that it is very speculative to reject a determination based on a single photograph. Even with the specimen under your steromicroscope you will need time to figure out how this specimen is preserved and what it actually is.
I've been examining and working on thousands of amber arthropods in the last 11 years and my first thought when I discovered this one was: "what the hell is this?". It is only after a careful examination that I was able to see by transparency the antennae, a part of the mandible, and the petiole. So yes, it's actually an ant!! No wing, no elytra... Sorry that the photo is not speaking better by itself. When it's viewed on the correct position, the head is on the top with the right eye small, darkened. The vertically oval structure on the bottom right is the gaster with apex pointing upward, touching and overlying the mouthparts. The petiole appears cylindrical between the gaster and the legs that are mostly folded over the mesosoma and run on the left side of the pic.
Our PNAS article is an overview paper of the amber deposit, thus it was not the purpose to describe the fossils in detail (will come elsewhere) and the space is too limited to justify our determination (otherwise I would have had to do so for each of the 30 arthropods). There are 12-segmented geniculate antennae with a very long scape, mandibles triangular to falcate, with a multi-toothed masticatory margin, a metapleural gland opening, a well-defined (although unusual) petiole, forelegs with a calcar spur... For now I am unable to tell what subfamily it belongs to (except it is not a sphecomyrmine) because too many characters are hidden by the legs and gaster, as preserved. This is why I am currently making a 3D reconstruction using high-resolution X-ray synchrotron imaging. The reconstruction of the specimen has been completed only very recently, which explains why such image was not provided in our paper but only the stereomicroscopic photo. The detailed study will be published elsewhere ASAP and you will understand that I cannot provide this reconstructed image here. Still, the diagnostic features are hidden on this view, so I am now
working on a virtual dissection (e.g., reconstruction of the head alone, of the alitrunk alone. etc...) to access all characters. This is a long work on which I and two colleagues from the synchrotron are working for several months, so be patient and you'll see a true ant! :)
Ok, I see it now. Anyone else?
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Oh jeez, I do. Wow. Having the "newer" specimen as a comparison makes all the difference.
What a great development!
Vincent, thanks for your detailed reply!
I never would have guessed without the Formica model for comparison! Very nice 'clean-up' of the suspected taxonomy fail.
i still don't see it. i see the head, and maybe a jumble of legs...is the gaster detached?
Wow, I stared at the picture for a few seconds still to actually tell it was an ant. Very interesting, and now completely convincing picture!
It took me awhile to figure out what was going on with the gaster, but it looks like the arrangement is something like this:
The petiole is long and cylindrical and appears to attach to the gaster partway down the ventral surface. It's an unusual arrangement, but something similar is seen in the modern genera Technomyrmex and Tapinoma. This ant is biting the tip of the gaster, which is folded forward.
(image from discoverlife.org)
I'm glad to see that my comment and new photo, along with the Formica model of Alex, helped. And yes, the petiole does look like in Technomyrmex, and Dolichoderinae was my best bet until now judging from what is visible. Will need to be confirmed...
OK, this is very good. I see now that the oval was indeed the gaster, but I mistook the flexed anterior edge of the first gastral tergite for the gastral apex! It also makes more sense now knowing that the visible eye is the right one, not the left one as I had assumed.
I agree with Alex that the petiole is reminiscence of either Tapinoma or Technomyrmex. But looking at the gastral apex, it doesn't seems to be Tapinoma or any other Dolichoderinea for that matter other than Technomyrmex given the "unflexed" pygidium. But again, the folding and deformation makes interpretation very tricky from just that photograph.
If this specimen can indeed be assigned to Dolichoderines unambiguously, it is a huge deal given the age of the fossil!
Perrichot, many thanks for making available in advance all these additional information to a bunch of knowledge-hungry myrmecologists.
Voila! After sleeping on it, I see it quite clearly now. It was like one of those [i]trompe l'oeil[/i] effects. I've always had trouble getting those to switch.
So, reason, evidence and study prevail, as it should be in science.
I had a similar thought, James. It reminds me of this optical illusion.
As I recall, one finding from the new AToL dolichoderine paper is that this cylindrical petiolar form seems to have emerged twice, once in Tapinoma and once in Technomyrmex. Perhaps this trait evolves more readily than we'd thought, and this ant is yet another convergent instance.
ok i get it...i thought the bottom was the tip, but now i think i see the petiole. eeeenteresting! i imagine sitting there with the block and being able to turn it around helps with that sort of thing.