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Post by Joe Botting on Nov 12, 2014 7:37:16 GMT -5
Well now... that is very nice indeed. It's also very, very interesting. You'll notice that several of the spicules seem to have pentagonal symmetry rather than being crosses (although crosses exist as well). You'll also notice that the reflections of some facets show continuous cleavage planes that hint at each spicule being a single crystal. That can't happen by replacement of silica by calcite, so far as I know; the process should involve dissolution and cavity-filling, giving a completely different texture. My hunch here is that this is not a hexactinellid at all, but one of the heteractinids - a mysterious groups of very primitive calcareous sponges. However, one of the spicules (the clearest cross) seems to have a ghost of an axial structure that looks like a silicean axial canal; that would suggest I'm barking up completely the wrong tree. It would be really interesting to see a thin section of this for a petrographic study, but that tends to be expensive... still, this is another intriguing addition to the fauna... Well done again.  |
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tqb
Enthusiastic fossilologist
Posts: 111
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Post by tqb on Nov 12, 2014 16:01:40 GMT -5
Thanks very much, Joe, I was confused by the pentagonal ones so that seems very promising - I've just got the paper by Rigby & Church (1993) on Wewokella from the Pennsylvanian which looks a good candidate.
I'll at least do a polished section of this one, perhaps a quick etch would help?
I think I have another specimen too - I did polish a bit but the surface shows very little in normal light.
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Post by Joe Botting on Nov 13, 2014 6:37:35 GMT -5
Thanks very much, Joe, I was confused by the pentagonal ones so that seems very promising - I've just got the paper by Rigby & Church (1993) on Wewokella from the Pennsylvanian which looks a good candidate. I'll at least do a polished section of this one, perhaps a quick etch would help? I think I have another specimen too - I did polish a bit but the surface shows very little in normal light. It certainly fits Wewokellidae in general, but the high number of pentaradiates is very unusual. Many of the others are heptiradiate or triradiate, and most described species seem to be tubular... in other words, a new genus of wewokellid is where this seems to be heading... |
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tqb
Enthusiastic fossilologist
Posts: 111
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Post by tqb on Nov 13, 2014 12:40:51 GMT -5
Thanks, Joe, this is all fascinating - seems that you were right that new sponges just need looking for!
I see also that Wewokella solida is fairly narrow cylindrical/obconical whereas this one seems more like a slice out of a large vase or cone.
Is the Treatise (E, vol 3 (revised) 2004) worth having? - I'd like a quick reference for all this stuff (apart from you!). The size is a bit daunting but if it's reliable I don't mind splashing out...
I already have vol 2 which, as I'm sure you know, is the introductory part but I'd like more pictures!
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Post by Joe Botting on Nov 13, 2014 15:32:46 GMT -5
You've got mail.  |
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tqb
Enthusiastic fossilologist
Posts: 111
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Post by tqb on Nov 13, 2014 16:01:42 GMT -5
So I have, I'm in your debt again! |
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tqb
Enthusiastic fossilologist
Posts: 111
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Post by tqb on Nov 14, 2014 4:41:59 GMT -5
Joe - I replied to your email but it said your inbox here is full... There are an awful lot of sponge taxa.  |
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Post by Joe Botting on Nov 14, 2014 4:59:40 GMT -5
Joe - I replied to your email but it said your inbox here is full... There are an awful lot of sponge taxa.  Aren't there just!! Rigby may have been 40 years out of date when it came to the evolution and higher taxonomy, but he did an incredible piece of work on compiling the information. And don't forget, the Treatise only lists genera, and not species..! I've changed the email here to the one I use nowadays - the other gets clogged with spam every few hours, so I've cast it aside for the past few years. Just away for a few days now, but back early next week. |
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Aren't there just!! Rigby may have been 40 years out of date when it came to the evolution and higher taxonomy, but he did an incredible piece of work on compiling the information. And don't forget, the Treatise only lists genera, and not species..!