Gordywahl Posted August 9, 2014 Share Posted August 9, 2014 Hi, I took my two sons (9 and 7) on a fossil hunt this week in Montana. We really have no idea yet what we are doing, but found a book "Roadside Geology of Montana". We found this in the Sun River Canyon near Gibson Dam. I believe the rock may be cretaceous limestone, and I thought it might be an ammonite but this is smooth and looks like none of the pictures I've seen posted. Any help? Thanks, Gordy Link to comment Share on other sites More sharing options...
tmaier Posted August 9, 2014 Share Posted August 9, 2014 (edited) Wow! Great catch for a rookie! Fossil on right is nautiloid? Fossil on left needs to be exposed more, but maybe the same thing. Edit: Doh! that IS the same fossil in all three photos. The nautiloid has popped out. Edited August 9, 2014 by tmaier Link to comment Share on other sites More sharing options...
Mattalic Posted August 9, 2014 Share Posted August 9, 2014 Great find! Link to comment Share on other sites More sharing options...
Pumpkinhead Posted August 9, 2014 Share Posted August 9, 2014 (edited) The fossil on the right does look like some sort of a cephalopod. If the rock there is Cretaceous then it is an ammonite. Some different angles in the other fossil would be helpful for identification. Nice finds Doh. What the guy above me said. It's getting late here and I'm confused- I'll see if those all look like the same fossil again tomorrow... Edited August 9, 2014 by Pumpkinhead Link to comment Share on other sites More sharing options...
fossilized6s Posted August 9, 2014 Share Posted August 9, 2014 Cool! Im not the best at IDing inverts, but it does look like a coiled Cephalopod. Congrats! ~Charlie~ "There are those that look at things the way they are, and ask why.....i dream of things that never were, and ask why not?" ~RFK ->Get your Mosasaur print ->How to spot a fake Trilobite ->How to identify a CONCRETION from a DINOSAUR EGG Link to comment Share on other sites More sharing options...
Ludwigia Posted August 9, 2014 Share Posted August 9, 2014 It's an ammonite. You can see the rest of the living chamber still in the matrix in the picture on the right. Greetings from the Lake of Constance. Roger http://www.steinkern.de/ Link to comment Share on other sites More sharing options...
FossilDAWG Posted August 9, 2014 Share Posted August 9, 2014 Correct me if I'm wrong, but I think all 3 photos are the same specimen, with the 3rd photo showing the fossil cracked out of the rock. I am a bit mystified why everybody seems to feel this fossil is a cephalopod. I don't see any sign of suture lines or camerae (chambers). Also, the shell seems to be relatively thick and calcitic, not like any ammonite shell I'm familiar with. I think the specimen is a large planispirally coiled snail, either Straparollus something close to that. These snails are common in certain Pennsylvanian and Permian limestones. Don 1 Link to comment Share on other sites More sharing options...
Auspex Posted August 9, 2014 Share Posted August 9, 2014 ...I think the specimen is a large planispirally coiled snail... This idea better fits the available evidence, IMHO. "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...
RyanNREMTP Posted August 9, 2014 Share Posted August 9, 2014 Either way it's a great first find. Link to comment Share on other sites More sharing options...
TqB Posted August 9, 2014 Share Posted August 9, 2014 Correct me if I'm wrong, but I think all 3 photos are the same specimen, with the 3rd photo showing the fossil cracked out of the rock. I am a bit mystified why everybody seems to feel this fossil is a cephalopod. I don't see any sign of suture lines or camerae (chambers). Also, the shell seems to be relatively thick and calcitic, not like any ammonite shell I'm familiar with. I think the specimen is a large planispirally coiled snail, either Straparollus something close to that. These snails are common in certain Pennsylvanian and Permian limestones. Don My thoughts too - are erratics of that age possible there? Tarquin Link to comment Share on other sites More sharing options...
howard_l Posted August 9, 2014 Share Posted August 9, 2014 Not a Gastropod, looks a lot like a Carboniferous Nautiloid but could be a Cretaceous Ammonite. The only way to tell is by examining the suture pattern and the placement of the siphuncle. A photo of the broken ends might give enough detail to see. Also the inner wholes might show some detail. Also look at the rock itself and see if there are any other fossils in the Limestone a clam or brachiopod or other fossil could give a clue to the age. Howard_L http://triloman.wix.com/kentucky-fossils Link to comment Share on other sites More sharing options...
piranha Posted August 9, 2014 Share Posted August 9, 2014 I also agree with Don's ID of gastropod. Besides Cretaceous, Sun River Canyon also has Paleozoic possibilities listed in this report: Mudge, M.R. (1972). Structural geology of the Sun River Canyon and adjacent areas, northwestern Montana USGS Survey Professional Paper, 663B:1-52 LINK Link to comment Share on other sites More sharing options...
howard_l Posted August 9, 2014 Share Posted August 9, 2014 That report listed a great deal of Mississippian age units, the majority was lower Mississippian. Here is Vestinautilus from the Lower Mississippian of Kentucky and are common in other lower Mississippian units around the County. With out examining the sutures (or lack of them) I can not be sure but it has the same general shape. Howard_L http://triloman.wix.com/kentucky-fossils Link to comment Share on other sites More sharing options...
piranha Posted August 9, 2014 Share Posted August 9, 2014 Just as Don predicted, one of the formations from the USGS report has Straparollus sp. in the Mississippian. Here's the record from Paleobiology Database: Link to comment Share on other sites More sharing options...
howard_l Posted August 9, 2014 Share Posted August 9, 2014 Here is a photo of Straparollus sp. Which also resembles the fossil in general shape. Now we just need to know if there is any evidence of sutures/siphuncle or as I said lack of them to be sure. Howard_L http://triloman.wix.com/kentucky-fossils Link to comment Share on other sites More sharing options...
FossilDAWG Posted August 10, 2014 Share Posted August 10, 2014 Gordywahl, a clear close up photo of the specimen showing the whorls would help settle the question. Unfortunately the whorls are in shadow in photo 3, which makes details a bit hard to see. From what I can see from photo 3, the shell remained attached to the matrix and the free specimen shows an internal cast of the inner whorls. I see no sign of sutures, which should be quite evident on an internal cast. However a clear photo in good light would make the issue unambiguous. Don Link to comment Share on other sites More sharing options...
Auspex Posted August 10, 2014 Share Posted August 10, 2014 Enhanced: (click to enlarge) "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...
Ludwigia Posted August 10, 2014 Share Posted August 10, 2014 I stand corrected. Now that I'm looking closer I don't see any sutures or other indications that it's an ammonite. I was just assuming cretaceous....I agree now with the gastropod diagnosis. Greetings from the Lake of Constance. Roger http://www.steinkern.de/ Link to comment Share on other sites More sharing options...
Gordywahl Posted August 11, 2014 Author Share Posted August 11, 2014 (edited) Wow you guys, thanks so much. Yes, all three photos are the same specimen, the one on the right is the fossil removed from the matrix. When I first found it we thought ammonite too, but no suture lines at all. And yes this rock had other small shell like bits, also found other similar rocks nearby that were clearly clamshells. Any idea of the age of this? Edited August 11, 2014 by Gordywahl Link to comment Share on other sites More sharing options...
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