Troodon Posted October 21, 2016 Share Posted October 21, 2016 I was going through some matrix, from my last dinosaur dig trip, using a microscope to look for anything small. In that process I found something real small a micro. Its slightly larger than 1 mm. One of the smallest fossils I've ever found. Cephalic hook, dermal denticle or something else? Hell Creek Formation, South Dakota Any input would be appreciated. Sorry its the best picture I can take with my digital scope. Two images with a little different contrast. Thank you for looking. Link to comment Share on other sites More sharing options...
Opisthotriton Posted October 21, 2016 Share Posted October 21, 2016 They are "Squatirhina" shark teeth. Surprisingly common in many Late Cretaceous sediments if you're using a fine enough screen. I put "Squatirhina" in quotation marks because the genus has been revised and divided and I'm not sure what the Hell Creek teeth are currently labeled. Google image search shows some other photos, including this one someone posted here on Fossil Forum: Link to comment Share on other sites More sharing options...
jpc Posted October 21, 2016 Share Posted October 21, 2016 troodon- I am pretty sure this is a dermal denticle of a ray. I find them occasionally. they are so small that they generally pass through any screens I use, so, like this one, I find them on a wee bit of matrix. edit: I will go with ophis's opinion. Let's call it a squatirhina. Link to comment Share on other sites More sharing options...
Troodon Posted October 21, 2016 Author Share Posted October 21, 2016 Thank you Squatirhina it is. Match is perfect. http://www.geo.utexas.edu/courses/302d/Aguja/sharks/squat_index.htm Link to comment Share on other sites More sharing options...
jpc Posted October 21, 2016 Share Posted October 21, 2016 now that I think about it, the ray dermal denticles are much more conical... like little recurved triangles on a wide base. Link to comment Share on other sites More sharing options...
Ridgehiker Posted October 21, 2016 Share Posted October 21, 2016 Good spotting! You may or may not be familiar with the GSA 'Special Paper 361' from 2002 on the Biostratigraphy of vertebrate remains in the Hell Creek Formation of the Dakotas. The study is quite broad and likely has a collecting bias but it provides a starting point. I find the study useful in identifying the relative abundance of specimens found in various types of deposits (channel, etc.) This way, if I recognize the visible macro fossils, I have some sense what might be associated with them when looking at associated matrix under the scope. I've found similar specimens and call them 'Squatirhina' but I'm not that knowledgeable of shark teeth. I only have a few specimens so not sure if they are rare or just rarely found. Link to comment Share on other sites More sharing options...
Troodon Posted October 21, 2016 Author Share Posted October 21, 2016 I have that publication just did not look like a dummy and there is a picture of one in there. Like Opisthotriton said very common and because of size rarely found and I can vouch for that. Link to comment Share on other sites More sharing options...
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