tqb
Enthusiastic fossilologist
Posts: 111
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Post by tqb on Aug 5, 2014 11:42:57 GMT -5
Just when I thought I'd never find anything new in the Great Limestone of Co. Durham, this peered up at me from a temporarily dry stream bed. Just a humble demosponge of some sort, I expect it's common somewhere else but I've not seen one like it from this area (and there seems to be no mention of Great Limestone sponges anyway). Sp.5(edit) polished surface about 1cm in)
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Post by pleecan (Peter Lee) on Aug 5, 2014 20:43:29 GMT -5
Neat find!
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tqb
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Post by tqb on Aug 6, 2014 5:14:17 GMT -5
Thanks, Peter, a whole new collecting field for me as I've just about run out of local corals!
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Post by Joe Botting on Aug 21, 2014 15:37:13 GMT -5
This is another really good find, Tarquin. I also don't know of any described from the Great Limestone, although of course there's a bit been done on the Carb of Yorkshire and Derbyshire, and you'd expect it to be roughly the same sort of fauna. That seems to be the case, but working out what it is exactly isn't so simple... although at least the lower one seems to be a Haplistion sp. The papers I have to hand are Hinde's nineteenth century stuff, Wolfenden's 1959 description of Haplistion carbonaria and Scheiia castelonense, and Rigby & Mundy's 2000 paper on Derbyshire sponges. It's usually best to start with the most recent stuff, so going by that the lower one is clearly H. carbonaria. The specimen showing a clear surface with traces of spicules could well be the same, but it's very hard to confirm, as R&M didn't provide close-ups of the spicules and seem to have worked only on polished slabs. Based on Hinde's drawings, thought, it could well be a Haplistion of some sort, and possibly matches a thing called H. vermiculatum. That species is discussed here, in the context of some Permian sponges from Spitsbergen, and again, it seems to broadly fit: app.pan.pl/archive/published/app27/app27-085.pdfChecking Wolfenden (because it's never wise to assume that Rigby got things absolutely right), H. carbonaria does seem to be a good interpretation of your beastie - although the detailed spicule structure wasn't preserved in that material, so it's hard to be absolutely sure. The cross-section of the structure, though, is absolutely right. The dimensions also seem to fit very well indeed, which means I'm happy calling that one Haplistion carbonaria (Wolfenden, 1959). The top one, with the better preservation? Probably the same, but annoyingly, I can't be sure. That is, of course, unless the bottom view is the back of the same specimen, in which case you're sorted, and it's a very nice specimen.
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Post by ammocarbsteve on Aug 21, 2014 15:48:02 GMT -5
Tarquin.... Congratulations again.... I'm saying that a LOT to you lately... send me some luck !....
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tqb
Enthusiastic fossilologist
Posts: 111
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Post by tqb on Aug 22, 2014 4:14:15 GMT -5
Thanks, Steve and Joe! Steve - I don't think you need more luck... but pretend you're looking for belemnites Joe - it's all the same specimen, sorry, should have made it clear. It's great to have a definite ID at last on one of these, gives me some sort of firm base for tackling the others from here which don't look the same to me... Sponge systematics make my head spin but I think I'm hooked! I wonder if there's an undiscovered reef nearby? (Weardale and Teesdale) - as well as the sponges, I have several Michelinia ?egertoni, also apparently unrecorded from the Great Limestone. They're all in probable storm deposits.
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tqb
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Post by tqb on Aug 22, 2014 9:41:19 GMT -5
Great Limestone again. The sponges seem to come in two growth forms: cylindrical tubes 2cm across or more and large curved sheets up to about 1cm thick. Here's a typical cylinder - the amount of silicification varies. It's the weathered silica that shows up, otherwise they're nearly invisible. Sp.3
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Post by Joe Botting on Aug 22, 2014 14:55:57 GMT -5
You're doing pretty well already on these sponges... this one is probably a new species. At least, it's one of the hexactinellid-like sponges, and it's got a very strange, extremely simple structure. The normal one is generally called Hyalostelia smithii, but it's not totally clear what exactly that beast truly was. The root tufts that I'm sure you've seen fall into the same name, although it's very dubious whether they all belong to the same species, or whether that species ties in with the sponge body that it's been described as doing... So, going just on what we can see here, it's got apparently regular, thick-rayed hexactines with the rays apparently rather short (otherwise we'd see a lot more sections through them, relative to the number of centres). The spicules are very densely packed together, and there's no obvious expansion of the rays, or other features typical of Stiodermatidae (which Hyalostelia appears to belong to). It's just an extremely basic, dense wall with relatively few small spicules and no fusion of the skeleton. It's unclear whether the sparser area is the central cavity of a vase-shaped sponge, or the inner surface of something more like a shallow bowl, and both types are quite common in the Palaeozoic. I can't see any specialisation of the dermal layer, which rules out a lot of families. Based on all this, it looks closest to something like the Malumispongium, but with much more robust spicules. I think I'd anticipate this being a new genus, once all the details are worked out. Get some more specimens, and you could write this one up.
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tqb
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Post by tqb on Aug 23, 2014 5:08:36 GMT -5
Thanks very much again, Joe, quite exciting! - you did tell me a while ago that there's a good chance of new species every time you collect a Palaeozoic sponge... I really appreciate being given taxonomic pointers for these things, the literature is bewildering for a beginner. I have about twenty specimens of spongy things from this locality so plenty of sectioning material to work with. Here's the other main form - this one is a 5" wide piece of a large shallow bowl, no surface showing, just in section. Sp.4Right angled block: Vertical section:
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tqb
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Post by tqb on Aug 23, 2014 5:09:54 GMT -5
And a closeup of the tangential section of the last one, Sp.4:
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Post by Joe Botting on Aug 23, 2014 15:40:06 GMT -5
The literature can indeed be really confusing, beginner or not. This one, though, is a lot clearer: you can see that the spicules at the outer edge of the thin wall have very inflated, blobby rays. This is a feature of the Stiodermatidae (Brachiospongioidea), including Stioderma and Hyalostelia. Stioderma has parietal gaps through the wall in described species (which yours apparently doesn't), but the spicules seem too inflated for Hyalostelia smithii, at first glance... but I need to check that. That'll get you started, anyway... it's rapidly turning into an interesting fauna.
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tqb
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Post by tqb on Aug 24, 2014 7:30:00 GMT -5
Thanks very much, Joe, thoroughly helpful again! I've looked at Stioderma in Finks (1960) and can see no parietal gaps in any of my specimens. Any hints on how to spot a hexactinellid in section or is it just years of experience? I'm assuming this 6" specimen is the same; there's also a 2" circular section on the opposite side of the rock (about 5" thick) so perhaps it's a large vase shape. I don't really want to section it though, it's a nice bit of sculpture! Sp.7
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tqb
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Post by tqb on Aug 24, 2014 7:31:23 GMT -5
2" section on the back of the previous one, Sp.7:
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Post by Joe Botting on Aug 25, 2014 15:58:19 GMT -5
Thanks very much, Joe, thoroughly helpful again! I've looked at Stioderma in Finks (1960) and can see no parietal gaps in any of my specimens. Any hints on how to spot a hexactinellid in section or is it just years of experience? Hi Tarquin, It's partly experience, but more a question of 3D visualisation. What you're looking for are spicules in the form of three-dimensional crosses with right angles between the rays. The clearest angle of section is so you're seeing a flat cross, but triradiate arrays are quite common too, where they're cut through the centre at 45 degrees. The trick is really distinguishing them from monaxons (easy) and lithistid spicules (which are usually irregularly lumpy and fused together into a solid framework). It's much easier in flattened material on bedding planes, to be honest, but in limestones at least you get the 3D structure of the sponge as well, to make up for it... I'm assuming this 6" specimen is the same; there's also a 2" circular section on the opposite side of the rock (about 5" thick) so perhaps it's a large vase shape. I don't really to section it though, it's a nice bit of sculpture! This is a much harder one, I'm afraid. It doesn't seem to have any spicules (and no sign of hexactines), but rather a network of thick walls. This is therefore likely to be one of the hypercalcified sponges such as the sphinctozoans and agelasids - quite a specialist area, even within sponges! Most of them are chambered, often cylindrical to branching things, but yours, as you say, is an open bowl shape. There are a few things described with a similar sort of structure, such as the problematic Permian Corynospongia of China, but I can't find anything related from the Carb of the UK. It's probably going to take multiple specimens and, yes, sections to get anywhere useful with it, so keep it intact for the moment at least. You can always chop up some grotty fragments when you find them. On the plus side, it probably is another new species... Alternatively, though, it could be that you've had some diagenetic overgrowth of the spicules to produce what looks like a massively hypercalcified skeleton - in which case, we won't be getting very far at all, I'm afraid. Need more material, like I say. The stiodermatid may be a thing called Uralonema, by the way - as suggested, it doesn't really seem to be Hyalostelia. Unfortunately I don't have a copy of the original description, which is an obscure Russian journal from 1929... next time I go back to Nanjing I can have a look for it, though (probably over the winter).
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tqb
Enthusiastic fossilologist
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Post by tqb on Aug 26, 2014 5:04:55 GMT -5
Joe, thanks for yet another wonderfully detailed reply!
I'll start slicing some more specimens, I think I have pieces like the last one but I'm obviously not very good at telling! On the subject of possible diagenetic overgrowth,it's perhaps suggestive that other (calcite) fossils from here (corals and brachiopods mostly) are often silicified but not overgrown. Anyway, more sections - there are quite a few specimens where the preservation is a very indistinct grey or perhaps colourless on black limestone - might be worth trying some peels, I've got the materials but not sure how to photograph them - I'll look it up.
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