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Post by pleecan (Peter Lee) on Feb 5, 2012 14:15:36 GMT -5
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Post by Joe Botting on Feb 6, 2012 8:36:05 GMT -5
Um... your choids have hexactines. This doesn't deserve a or even a - it deserves something along the lines of this: ;D How can I put this? They ain't meant to be there. Choiids are 'protomonaxonids', and officially are meant to be early demosponges... but the third specimen clearly shows at least three little cross-shaped spicules. They're probably there in the others as well - and we'd need to check, to rule out fortuitous overlying of spicules in the sediment. Isolated hexactines are really not common in the Fezouata, though. This is actually not all that surprising to me, in that I'm writing a series of papers on protomonaxonids, demonstrating that several groups can be traced directly back to some early Cambrian hexactine-bearing sponges (not hexactinellids, incidentally, but that's another story). However, I didn't expect to see any in Choia itself, or its close relatives. Before spotting the spicules, I was actually thinking this might be closer to Hamptonia rather than Choia or Choiaella - based on the Burgess specimens, there really is very little between them, and a juvenile Hamptonia is almost identical to a Choiaella. Hamptoniids I think are the immediate ancestors of choiids, and although I've not seen any hamptoniids with hexactines, it's starting to become more plausible. Based on all that, I suspect this younger species is actually more primitive than the Middle Cambrian ones, and is a basal hamptoniid that has converged onto a choiid morphology. But I reserve the right to change my mind at any time - this is a whole new aspect of sponge history that we're delving into, and each new specimen highlights something new... Assuming it's not a fortuitous overlying of spicules, I'm sure that other specimens will show these spicules as well, and there are numerous examples of this species at the Peabody. So, when I have the chance to write up those sponges, this species is going to be one to look at very closely indeed. Actually, it's probably worth a separate paper. Or maybe mentioning and illustrating in one of the others I'm doing now.... hmm...
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Post by pleecan (Peter Lee) on Feb 6, 2012 9:23:36 GMT -5
Wow Joe! Because I have seen quite a few ... thought these were common stuff.... I have the capabilities of much higher resolutions... these were taken at middle let me know what you would like to see and I can try to zoom in at much higher magnifications.... this is exciting...
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Post by pleecan (Peter Lee) on Feb 6, 2012 21:18:57 GMT -5
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Post by Joe Botting on Feb 7, 2012 7:02:34 GMT -5
Hi Peter, Yes, it may well be a common species - I think there are bedding planes covered with them at certain places. I'm currently begging Lucy to bring a few back, as she's heading out there next month and I think will be going to the area these are from... Being common, though, isn't enough to guarantee that the interesting bits are preserved. Spicules are often very poorly defined in Fezouata sponges - I think they were largely dissolved, whereas the soft tissue was more easily preserved. What you have in yours may be very common - I simply haven't had the chance to find out yet - or it may be just one bed that shows it. It does at least seem to be present in a couple of specimens - I'm sending you an email highlighting the bits of interest. Unfortunately the extra photos are too fuzzy to see anything much, but if you can zoom in and stay sharp on the bits in question we may be able to get somewhere...
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Post by pleecan (Peter Lee) on Feb 7, 2012 8:59:57 GMT -5
Got the email Joe. Thanks... will try to image those areas. PL
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Post by pleecan (Peter Lee) on Feb 7, 2012 20:51:28 GMT -5
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Post by malcolmt on Feb 7, 2012 21:44:26 GMT -5
Nine extension tubes...... amazing .......
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Post by Joe Botting on Feb 7, 2012 22:53:00 GMT -5
Crivvens! (sorry, but I'm so staggered by the non-leaning tower of extensions that I lapsed into Scots there... bad sign) That's seriously impressive... and guess what? It worked. Wow. It really shows the difficulty with interpreting these - the most obvious 'hexactine' actually seems to be randomly overlain rays, but at least some of the others are now clear (there's a very 3D one at the top right of the last image, for example). As far as I'm concerned, it's definitely a hamptoniid/choiid with hexactines. Well done! ;D If you can confirm the same in another specimen, it's job done. I wouldn't want to do a full description without seeing a lot of specimens, but would it be possible to use some of these images in a discussion paper about protomonaxonid relationships? Obviously, fully credited and acknowledged. ps. Myst III: I approve. Did you ever complete it?
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Post by pleecan (Peter Lee) on Feb 8, 2012 5:28:52 GMT -5
Yes Malcolm... 9 sets extension tubes... and it did not tip over Thanks Joe.... The camera is a Sony Nex 5.... with wireless remote shutter release.... The Konica F1.7 50mm was quoted as one of the sharpest lens ever manufactured in the class of Leica.... extreme macro application.... this lens is superior in resolution than Nikon Nikkor F2.8 50mm enlarger lens. The hunt for more hexactine is on.... more tonight. Never completed Myst III Joe... found a better hobby... fossil hunting
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Post by pleecan (Peter Lee) on Feb 8, 2012 6:30:38 GMT -5
For high magnification Calibrated scale : 0.5 mm div Calibrated view: 1mm div for above camera setup with 9 extension tubes + Konica lens.
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Post by pleecan (Peter Lee) on Feb 8, 2012 21:02:14 GMT -5
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Post by pleecan (Peter Lee) on Feb 9, 2012 6:30:43 GMT -5
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Post by pleecan (Peter Lee) on Feb 9, 2012 20:36:51 GMT -5
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Post by pleecan (Peter Lee) on Feb 9, 2012 22:01:59 GMT -5
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