kerouac22 Posted December 31, 2015 Share Posted December 31, 2015 Hi esteemed forum members, I have several finds I need help identifying, but I'm going to do them in separate posts/threads/topics/whatever. I found this one in some Burlington Limestone in central Missouri. It's super brittle. You can see areas where pieces have just flaked off. The lines you see going across the front of it are raised. The leading theory on this so far is that it's a Rhodocrinites calyx that flattened during diagenesis. I've also attached an image of the small matrix it came off of (I found the calyx, if that's what it is, in situ unattached, just laying there on top of the matrix). Let me know. And stay tuned for other, and probably less exciting, ID requests. Thanks! Link to comment Share on other sites More sharing options...
Auspex Posted December 31, 2015 Share Posted December 31, 2015 My first impression is crinoid holdfast, from the bottom. "There has been an alarming increase in the number of things I know nothing about." - Ashleigh Ellwood Brilliant “Try to learn something about everything and everything about something.” - Thomas Henry Huxley >Paleontology is an evolving science. >May your wonders never cease! Link to comment Share on other sites More sharing options...
FossilDAWG Posted December 31, 2015 Share Posted December 31, 2015 I agree with the holdfast suggestion. The arrangement of plates is irregular, typical of root/holdfast structures, the number of "arms" is not a multiple of 5 (no pentameral symmetry), and the pattern of division of the "arms" is completely irregular. Even if this were a flattened calyx the basic arrangement of calyx plates (infrabasals, basals, radials, interradials) should be apparent, and it is decidedly not. There should be 5 arms, or some multiple of 5 as the arms bifurcate. Close to the calyx, at least, the arms should divide at regular intervals so the pattern of division will look symmetrical, and this is not the case. Don Link to comment Share on other sites More sharing options...
kerouac22 Posted December 31, 2015 Author Share Posted December 31, 2015 I agree with the holdfast suggestion. The arrangement of plates is irregular, typical of root/holdfast structures, the number of "arms" is not a multiple of 5 (no pentameral symmetry), and the pattern of division of the "arms" is completely irregular. Even if this were a flattened calyx the basic arrangement of calyx plates (infrabasals, basals, radials, interradials) should be apparent, and it is decidedly not. There should be 5 arms, or some multiple of 5 as the arms bifurcate. Close to the calyx, at least, the arms should divide at regular intervals so the pattern of division will look symmetrical, and this is not the case. Don Thanks guys. Interesting. So I'm assuming there's not a great way to ID a crinoid by a holdfast? Link to comment Share on other sites More sharing options...
ZiggieCie Posted December 31, 2015 Share Posted December 31, 2015 I would love to see some larger photos of it to see the detail. Something up near the 2 meg limit. It is very interesting. Link to comment Share on other sites More sharing options...
erose Posted December 31, 2015 Share Posted December 31, 2015 I would love to see some larger photos of it to see the detail. Something up near the 2 meg limit. It is very interesting. Agreed. VERY interesting specimen. I've never seen a holdfast with that much of a spread and that many individual plates. I'm not familiar with the Burlington but it would be a great specimen in any collection, with an ID or not. Link to comment Share on other sites More sharing options...
kerouac22 Posted December 31, 2015 Author Share Posted December 31, 2015 I would love to see some larger photos of it to see the detail. Something up near the 2 meg limit. It is very interesting. Agreed. VERY interesting specimen. I've never seen a holdfast with that much of a spread and that many individual plates. I'm not familiar with the Burlington but it would be a great specimen in any collection, with an ID or not. Thanks! Here's a 1.82 MB image. Link to comment Share on other sites More sharing options...
ZiggieCie Posted December 31, 2015 Share Posted December 31, 2015 Great photo THX. Link to comment Share on other sites More sharing options...
Al Dente Posted January 1, 2016 Share Posted January 1, 2016 It is odd looking. I'm thinking it is a steinkern of a crinoid crown, maybe Physetocrinus. Link to comment Share on other sites More sharing options...
kerouac22 Posted January 1, 2016 Author Share Posted January 1, 2016 It is odd looking. I'm thinking it is a steinkern of a crinoid crown, maybe Physetocrinus. Oh, good guess. I've found plenty of Physetocrinus stuff at that site. Link to comment Share on other sites More sharing options...
abyssunder Posted January 2, 2016 Share Posted January 2, 2016 I'm in the camp of crinoid crown. The holdfasts are more irregular in crinoids, almost in every species. In the picture above I recognise the pattern of five-fold (pentaradial) symmetry of the echinoderms, in this case the bifurcated five arms and so on, wich I propose to compare with the schematic morphology of the crinoid crown shown here: " We are not separate and independent entities, but like links in a chain, and we could not by any means be what we are without those who went before us and showed us the way. " Thomas Mann My Library Link to comment Share on other sites More sharing options...
TqB Posted January 2, 2016 Share Posted January 2, 2016 I agree with crinoid crown, beautiful specimen. Tarquin Link to comment Share on other sites More sharing options...
Xiphactinus Posted January 2, 2016 Share Posted January 2, 2016 It is odd looking. I'm thinking it is a steinkern of a crinoid crown, maybe Physetocrinus. Bingo! Correct on both the general ID and on the genus. Link to comment Share on other sites More sharing options...
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