TqB Posted January 21 Share Posted January 21 (edited) Does anyone recognise this tiny silicified shell? It's about 2mm long. I haven't seen one like it before from the Carboniferous. From the Great Limestone (upper Mississippian, Pendleian Stage) from Weardale, Co. Durham, England. From a piece I've been dissolving in acid, containing silicified brachiopods, gastropods etc. It starts off with an open helical spiral (3rd photo) and then straightens out. It also has clear annular ribs. Although the preservation is imperfect and sugary, I'm sure it's shell replacement rather than internal mould, judging from other fossils in the pece. The various serpulid-like gastropods and microconchids I've come across elsewhere don't have the regular ribbing. Edited January 21 by TqB 7 Tarquin Link to comment Share on other sites More sharing options...
TqB Posted January 21 Author Share Posted January 21 I'm thinking that microconchid looks promising... 1 Tarquin Link to comment Share on other sites More sharing options...
Ludwigia Posted January 21 Share Posted January 21 Yes, I was thinking along those lines when I saw this, although I'm not at all familiar with Carboniferous fauna. It does however look familiar in form to some Serpula tubes I'm used to seeing in Mesozoic sediments. 2 1 Greetings from the Lake of Constance. Roger http://www.steinkern.de/ Link to comment Share on other sites More sharing options...
TqB Posted January 22 Author Share Posted January 22 9 hours ago, Ludwigia said: Yes, I was thinking along those lines when I saw this, although I'm not at all familiar with Carboniferous fauna. It does however look familiar in form to some Serpula tubes I'm used to seeing in Mesozoic sediments. Little tubes are a minefield! Serpulids themselves only go back (just) to the upper Permian. I'll keep looking at microconchids though those regular ribs don't match anything I've seen yet. From this paper: https://www.researchgate.net/publication/269704428_Written_in_stone_History_of_serpulid_polychaetes_through_time 2 Tarquin Link to comment Share on other sites More sharing options...
TqB Posted January 23 Author Share Posted January 23 (edited) Another silicified specimen has appeared after more acid treatment of the block. The diameter and ornament is the same and it tapers somewhat. It doesn't have the sharply tapering, helical twist of the other one so it may well represent an extension of that. I'm looking at things like Helicoconchus (Permian) for comparison but it would need internal detail (partitions) and probably ultrastructure to confirm it as a microconchid. The annular ribs are still unusual but have precedent in Annuliconchus (Ordovician) for example. About 6mm long. (I like the pareidolic resemblance to a snake with jaw and eye! ) Edited May 2 by TqB 5 Tarquin Link to comment Share on other sites More sharing options...
TqB Posted May 2 Author Share Posted May 2 (edited) I'm no further with this one though I still think microconchid looks good. I've just found two more specimens which confirm the morphology of the first, an initial spiral (all three I've found go the same way) followed by a sinuous tube at right angles to it. First one. Second one; the annular ribs aren't showing well but it's otherwise the same. Blurry mm scale at the edge. Edited May 2 by TqB wrong photos 3 Tarquin Link to comment Share on other sites More sharing options...
TqB Posted May 26 Author Share Posted May 26 These keep turning up every few acid extractions and I've become a bit obsessed by them. I spent 15 minutes arranging them for a photo in their padded case. All the same morphology as mentioned in the last post, dextral spiral followed by sinuous extension more or less perpendicular to the original plane. (The one in matrix on the left is upside down.) Each tube is under 1mm in diameter. 5 Tarquin Link to comment Share on other sites More sharing options...
westcoast Posted May 26 Share Posted May 26 Microconchid is the only option for these I think. Good luck with any further classification. 1 1 Link to comment Share on other sites More sharing options...
TqB Posted May 27 Author Share Posted May 27 11 hours ago, westcoast said: Microconchid is the only option for these I think. Good luck with any further classification. Thank you! After reading a few more papers, I agree. I can't find an exact match but this slightly larger Triassic one is strikingly similar. From: https://www.researchgate.net/publication/222089788_Shell_structure_of_helically_coiled_microconchids_from_the_Middle_Triassic_Anisian_of_Germany 6 Tarquin Link to comment Share on other sites More sharing options...
TqB Posted August 1 Author Share Posted August 1 Collection so far, including what seems to be a different species with much wider spacing between the annular ribs - second along at the top. Scale in mm. 1 2 Tarquin Link to comment Share on other sites More sharing options...
marguy Posted August 2 Share Posted August 2 On 1/21/2024 at 8:58 PM, TqB said: The various serpulid-like gastropods and microconchids I've come across elsewhere don't have the regular ribbing. here is a Microconchid that I found , in compression, with ribs, in a lacustrine limestone of the Lower Permian, Brive basin, France (scale in mm; I have no species identification) 1 Link to comment Share on other sites More sharing options...
TqB Posted August 2 Author Share Posted August 2 46 minutes ago, marguy said: here is a Microconchid that I found , in compression, with ribs, in a lacustrine limestone of the Lower Permian, Brive basin, France (scale in mm; I have no species identification) Thanks, that's useful. Neat specimen! 1 Tarquin Link to comment Share on other sites More sharing options...
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