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Post by araucaria1959 on Nov 3, 2012 12:20:04 GMT -5
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Post by ammocarbsteve on Nov 4, 2012 4:34:19 GMT -5
araucaria1959... Hi and Welcome... Sorry I cant help but maybe Joe & Lucy can, when they can get access to the site...
Uploading... I use the Browse button to find the photo on my pc and when the link appears in the box at the side of it... I dont press anything other that Post Reply... Maybe try that...
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Post by araucaria1959 on Nov 4, 2012 7:56:33 GMT -5
Thanks, I'll try that with the first of the the three pics. araucaria1959 Attachments:
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Post by araucaria1959 on Nov 4, 2012 7:58:20 GMT -5
It worked this time ... here are the other pics: araucaria1959 Attachments:
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Post by araucaria1959 on Nov 4, 2012 8:00:22 GMT -5
Now I understand, I can upload only one pic each time. So here is the last one: araucaria1959 Attachments:
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Post by ammocarbsteve on Nov 6, 2012 11:23:23 GMT -5
Great... Lets hope someone can help you...
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Post by Joe Botting on Nov 6, 2012 20:14:50 GMT -5
Hi Araucaria... although you may be sorry you asked. I'm afraid I'm pretty sure this has nothing to do with Silurian plants. The preservation is wrong (no carbonisation), the environment is wrong (there's very little preserved organically in the Wenlock Limestone, and it's pretty recalcitrant stuff), and the morphology isn't nearly definite enough to suggest Cooksonia to me. What I see is an iron oxide-stained trace that could be one of two things: a remnant of a pyritised burrow, or (perhaps more likely) staining associated with modern plant rootlets that grew into a crack. I've seen a lot of both in the Welsh Borders (grew up collecting the Wenlock/Ludlow of Herefordshire), and it could be either of these... but I really don't think it could be a fossil plant. Wish I could say otherwise.  |
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Post by araucaria1959 on Nov 9, 2012 20:34:14 GMT -5
Hi,
thank you very much for that statement. I'm not really surprised or disappointed, since I had my doubts from the beginning.
When I posted that specimen for thr first time in the fossilforum,
(October 27th), I wrote (among others):
"However, I have my doubts; this time not because of its size (like the one from the Bertie Group), but because of the fully marine setting. Wenlock Limestones in general, and Shadwell Quarry also, are famous for corals and brachiopods - typical for a marine setting (possibly near the shore). Since early Cooksonia were very tiny plants, it seems quite implausible to find them together with corals and brachiopods. That's an unusual taphonomic situation for land (or shoreline) plant fossils"
That is one also one of your arguments too.
Thanks again,
araucaria1959
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Post by araucaria1959 on Nov 10, 2012 13:30:02 GMT -5
Hi, your answer reinforces my doubts about the origin of any pretended (land) plant material from the Wenlock Limestones (e.g., Shadwell Quarry), since missing carbonisation and "wrong environment" applies to all of them. These are exactly the reasons why I started the discussion about this stuff in the fossilforum during October. I also miss primary sources about Cooksonia or related genera from these Limestones or that special quarry, though there are some links where it is pretended that they can be found there, but that's all "outside scientific literature". I show another picture of a dichotomising, non-fertile specimen from the Shadwell Quarry (scale = match = 45 mm). This is the typical material from that location that is often assigned to Cooksonia, though I think it is impossible to assign sterile material of that sort to any genus. What do we have to think about that (more common) material? It is (land) plant at all? I don't see any features defining embryophytes or tracheophytes. But his must not mean something; if there is material of equal size and form from that locality which shows these features, then the lack of these features in my specimen may be due to bad preservation. Does someone know whether it is proved (scientifically) at all, that fragments of land plants in general (or especially Cooksonia do occur in the Wenlock Limestones of Shropshire and Shadwell Quarry, resp.? araucaria1959 Attachments:
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Post by Joe Botting on Nov 16, 2012 1:10:36 GMT -5
Sorry for the delay - been lurgified. First off, I can't find any published records of Cooksonia (or other vascular plant macrofossils) from the Wenlock Limestone, or from Shropshire generally. Of course there are land plants around by the Wenlock (including in Ireland), so it would not be impossible. However, if there were well-known Wenlock plants in the Wenlock Limestone, I somehow think they would have been published...
The new photo is intriguing, in that the general morphology does look Cooksonia-like (in broad terms). There is also a slightly darker outline to the lower branch, which might possibly represent some carbonised material. You can clearly see that the oxidised halo on the upper branch crosses several flakes of rock, however, and is therefore at least a diffusion product into the matrix, rather than the outline of a plant itself. There are some dark brown streaks around the apex of the upper branch, and near the branch point of the axis, which do not really look like primitive plant in my view. These could alternatively be pyritised spicules - I have some branching sponges from Ludlow rocks of Herefordshire with similar preservation. I'm not saying it's a sponge (I really don't think it is), but that it's probably as good an explanataion as plant.
Most worrying is that it appears from the photo to be three-dimensional and sediment-filled (see apex of upper branch). If that's the case, then by far the most likely explanation is a lined burrow, with pyritisation of the lining to give the outline.
This isn't definitive - ideally you'd want a plant specialist like Diane Edwards to have a look, and she'd probably want to see multiple specimens, rather than a photo of one. However, based on what I've seen, I'm personally very sceptical of a plant affinity for these.
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Post by pleecan (Peter Lee) on Nov 16, 2012 13:25:04 GMT -5
Here is cooksonia from Late Silurian Lagerstatte: for comparison  |
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Post by Joe Botting on Nov 16, 2012 18:02:10 GMT -5
Absolutely - no doubts about that one.  |
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Post by araucaria1959 on Nov 21, 2012 15:24:56 GMT -5
Hi,
thank you very much. You confirmed that there is nothing published about land plants in the Wenlock limestones - and that was the reason why I got so many doubts about that material. It is very improbable that there are plant fossils in these wellknown strata when noone mentions them in the scientific literature. There are also other features that differ from typical plant fossils (no compression fossil - 3D preservation; no or minimal carbonisation etc.).
So I agree it's probably some kind of ichnofossil.
araucaria1959
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