New Members lynnweissenfels Posted October 5, 2015 New Members Share Posted October 5, 2015 This image is from a fossil in limestone from central Montana. It appears as rib like growth rings??, on what is assumed to be a mollusk of some sort. The sample is about 12 inches top to bottom which makes for a fairly large mollusk. The backside is simply sandy mud stone with one or two smaller smooth mollusks embedded about the size of the smooth casting circle on the left. I am totally at a loss for identification of what would leave this pattern of relief on the rock. I would appreciate any input as to what it might be. These are definitely not layers of sediment. I thought vertebrate ribs at first, but lean toward growth rings on some species of mollusk. Link to comment Share on other sites More sharing options...
Trickworm Posted October 5, 2015 Share Posted October 5, 2015 Looks like a cephalopod A day without sunshine is like, you know, night. Link to comment Share on other sites More sharing options...
Ridgehiker Posted October 5, 2015 Share Posted October 5, 2015 I'd guess an Inoceramus. I bit contorted through preservation It is really big! I have seen many in Montana but not one that large. Our Montana/ Wyoming members may have. Link to comment Share on other sites More sharing options...
jpc Posted October 5, 2015 Share Posted October 5, 2015 confusing. Can we get a few more pix from different angles? Thanks. Link to comment Share on other sites More sharing options...
Auspex Posted October 5, 2015 Share Posted October 5, 2015 It does look like an Inoceramus."clam". LINK "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...
jpc Posted October 5, 2015 Share Posted October 5, 2015 I am not seeing Inoceramus. The ridges are not right. Link to comment Share on other sites More sharing options...
Plax Posted October 5, 2015 Share Posted October 5, 2015 some large ribbed pelecypod that oysters liked to attach to. Agree with JPC that it doesn't look like inoceramid Link to comment Share on other sites More sharing options...
Fossildude19 Posted October 5, 2015 Share Posted October 5, 2015 Any more specific info on location found? The geology in central Montana looks to be a bit of everything. It's kinda all over the place. Regards, Tim - VETERAN SHALE SPLITTER VFOTM --- APRIL - 2015 __________________________________________________ "In every walk with nature one receives far more than he seeks." John Muir ~ ~ ~ ~ ><))))( *> About Me Link to comment Share on other sites More sharing options...
FossilDAWG Posted October 5, 2015 Share Posted October 5, 2015 I would also like to see more photos from different angles. I find it a bit perplexing; the size and the "Ostrea" congesta encrustation suggests a large pelecypod such as an inoceramid, but the ribs don't "feel" right. Don Link to comment Share on other sites More sharing options...
abyssunder Posted October 5, 2015 Share Posted October 5, 2015 I don't see why the ridges would not be right. " 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...
Auspex Posted October 5, 2015 Share Posted October 5, 2015 I don't see why the ridges would not be right. Looking again, I see that the wide "troughs" are raised, and the narrow "ridges" are sunken, sort of backwards for inoceramids. This doesn't quite add up neatly... "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...
abyssunder Posted October 5, 2015 Share Posted October 5, 2015 (edited) Good observation! In some of the Inoceramus sp. the ribs are "inverse folded". I think I see correct. Please, take a look: https://www.google.com/search?q=inoceramus&biw=1360&bih=612&source=lnms&tbm=isch&sa=X&sqi=2&ved=0CAYQ_AUoAWoVChMI_rnmvLmsyAIVQYcaCh3YCwve#imgrc=hj9qIOhq-B79aM%3A Edited October 5, 2015 by abyssunder " 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...
New Members lynnweissenfels Posted October 5, 2015 Author New Members Share Posted October 5, 2015 I originally looked at inoceramids but couldn't find enough examples. Thanks for the great responses! File 6014 shows what might be a ventral view of the original shell and waves. File 6015 shows what may be an outer layer that has eroded away and a similar light colored layer for the left smaller fossil. File 6016 shows what I believe to be a smaller mollusk as a cap on top[3} and an especially interesting layer fragment similar to the periostracum of shells at #4. Taken all together the ribs might be a prismatic layer missing the periostracum which would smooth out the appearance considerably. File 6019-[5] shows what I think is the umbo of a smaller shell that caps the larger shell in question. All this is open to better interpretation. Thanks for sharing your experience end expertise. Link to comment Share on other sites More sharing options...
abyssunder Posted October 5, 2015 Share Posted October 5, 2015 The prismatic structure of the "shell", revealed in pic 6014, I think argue the theory of Inoceramus. " 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...
PFOOLEY Posted October 6, 2015 Share Posted October 6, 2015 (edited) May we some more photos of the smaller molluscs? Edited October 6, 2015 by PFOOLEY "I am glad I shall never be young without wild country to be young in. Of what avail are forty freedoms without a blank spot on the map?" ~Aldo Leopold (1887-1948) New Mexico Museum of Natural History Bulletins Link to comment Share on other sites More sharing options...
New Members lynnweissenfels Posted October 6, 2015 Author New Members Share Posted October 6, 2015 Tim, the fossil was found south of the high wood mountains in a small stream. The mixed beds marked KMK were the likely source. The dorsal view of what may be a relatively smooth shelled smaller clam shown in view with a number 5, and it is not impossible for it to be a part of the larger shell, but without some technology or excavation it seems hard to prove either way. There is only this example and the depression below number 2 on file 6015 to represent smaller clams. Link to comment Share on other sites More sharing options...
PFOOLEY Posted October 6, 2015 Share Posted October 6, 2015 I am thinking your specimen is a portion of the Inoceramid, Volviceramus involutus...which can be found in the outcrops of your area. 4 "I am glad I shall never be young without wild country to be young in. Of what avail are forty freedoms without a blank spot on the map?" ~Aldo Leopold (1887-1948) New Mexico Museum of Natural History Bulletins Link to comment Share on other sites More sharing options...
FossilDAWG Posted October 6, 2015 Share Posted October 6, 2015 I think pfooley has got it. Don Link to comment Share on other sites More sharing options...
Auspex Posted October 6, 2015 Share Posted October 6, 2015 Ah, the opercular valve; no wonder it was hard to make sense of! "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...
PFOOLEY Posted October 6, 2015 Share Posted October 6, 2015 "I am glad I shall never be young without wild country to be young in. Of what avail are forty freedoms without a blank spot on the map?" ~Aldo Leopold (1887-1948) New Mexico Museum of Natural History Bulletins Link to comment Share on other sites More sharing options...
abyssunder Posted October 7, 2015 Share Posted October 7, 2015 Well done! Just to complete: Inoceramus (Volviceramus) (aff.?) involutus Sowerby, 1826 -------------------------------------------------------------------------- Inoceramus involutus Wolleman,1902Volviceramus involutus Woods,1912 Die Lowenberger Kreide und ihre Fauna - Hans Scupin,1912-1913 - Pl.12, Fig.3 Molluscan Fossil Record from the Northeastern Part of the Upper Cretaceous Seaway,Western Interior - William A. Cobban, page7 "Volviceramus involutus is a moderate-sized species that is very inequilateral and extremely inequivalve. The left valve is much larger than the right one, very inflated,spirally coiled, and nearly smooth. The right valve has a nearly oval outline and a very low convexity; it is ornamented by conspicuous concentric rugae." Plate 15, figures 13, 14 https://books.google.ro/books?id=CMhUAAAAYAAJ&pg=PA7&lpg=PA7&dq=volviceramus+involutus&source=bl&ots=17DJvWbdje&sig=SpNWKcYn4arfOCCQzrc8Cd2J6nI&hl=en&sa=X&redir_esc=y#v=onepage&q=volviceramus%20involutus&f=false 1 " 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...
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