kate_rose Posted May 25, 2019 Share Posted May 25, 2019 (edited) Hello, I am new here and new to fossil identification. These are shark teeth from the Aquia formation on the Maryland side of the Potomac. They come from Charles County. I have shark teeth of the world and so my IDs are based on that and the internet. I think all of these are Stratiolamia striata based on the grooves. Ruler is in mm and squares are 1/4" on each side. The last picture with only 2 teeth nearly touching seem different to me in that the striations don't extend very far up onto the teeth (unlike the others where they cover much of the crown. I am not sure if S. macrota also occurs at this site?? They are supposed to have striation only near the root. I have more from this trip but limited time so it will have to dribble out. Thanks for your time, Kate Edited May 25, 2019 by kate_rose Link to comment Share on other sites More sharing options...
hemipristis Posted May 25, 2019 Share Posted May 25, 2019 I'd say that you're spot on! (though I offer some thoughts about this tooth style in your other post). It would seem that you have quite the mix: uppers, lowers, anteriors and laterals. 'Those who cannot remember the past are condemned to repeat it.' George Santayana Link to comment Share on other sites More sharing options...
Gizmo Posted May 25, 2019 Share Posted May 25, 2019 https://www.fossilguy.com/sites/potomac/liv_col.htm Link to comment Share on other sites More sharing options...
hemipristis Posted May 25, 2019 Share Posted May 25, 2019 Late Palaeocene Sharks & Rays of the Chesapeake Bay Region http://www.elasmo.com 'Those who cannot remember the past are condemned to repeat it.' George Santayana Link to comment Share on other sites More sharing options...
kate_rose Posted May 25, 2019 Author Share Posted May 25, 2019 Hemipristis, Is it bad to have a mix of teeth from different positions in the mouth? Should I only show the anteriors or something?? By offer thoughts did you mean explaining the nomenclature and morphology confusion with this group? Also thanks for the extra reference. I am off to read some more Maybe that will help quell all the questions. Kate Link to comment Share on other sites More sharing options...
hemipristis Posted May 25, 2019 Share Posted May 25, 2019 4 hours ago, kate_rose said: Hemipristis, Is it bad to have a mix of teeth from different positions in the mouth? Should I only show the anteriors or something?? By offer thoughts did you mean explaining the nomenclature and morphology confusion with this group? Also thanks for the extra reference. I am off to read some more Maybe that will help quell all the questions. Kate Kate, there is nothing wrong with displaying teeth from different positions within the mouth. I was just complimenting you on the variety of finds! :). I also meant to point out (but forgot) to note that the Scapanorhynchus/Striatolamia/Carcharias dentition contains quite a variety of tooth shapes for one mouth (a heterodont dentition), unlike Tiger Sharks (for instance), where their teeth don't change all that much from top jaw to bottom jaw, front to back (called an isodont dentition). You are correct regarding my thoughts/mini-ramble on these type of teeth. There are still some questions about them, as you can see, so I figured I'd let you in on the fun, LOL. The four species' teeth are very close morphologically, and its often hard to ID what species it is unless you know the formation that it came from, which some of us believe problematic. The question I (and others) pose is if you can't really tell the difference, or the differences are very subtle, why use 4 species when one might suffice? 'Those who cannot remember the past are condemned to repeat it.' George Santayana Link to comment Share on other sites More sharing options...
Randyw Posted May 26, 2019 Share Posted May 26, 2019 5 hours ago, kate_rose said: Hemipristis, Is it bad to have a mix of teeth from different positions in the mouth? Should I only show the anteriors or something?? Kate Nothing wrong with showing a mix of positions at all! Looks like a great collection to me. If it was me I’d arrange by placement in mouth and show them all together! Link to comment Share on other sites More sharing options...
kate_rose Posted May 26, 2019 Author Share Posted May 26, 2019 Randy, Ordering by position in the mouth sounds challenging. I can tell anteriors from laterals and posteriors but I would think I would need a reference collection to really get them in order. Hemi, OK I can see why one "species" might suffice if the 4 are really that mixed up but as a biologist I would guess that by just looking at the teeth we are probably missing some "cryptic species" anyway that have similar enough dentition that we can't really tell the difference. So maybe we can't tell the 4 apart reliably but by definition species can look the same as long as they don't interbreed with each other either because they don't overlap geographically or don't have a mating dance the other recognizes. Temporal isolation or not being able to interbreed because they didn't exist at the same time is in my book the same as geographical isolation so in my mind strata/location/age info should never be separated from the specimen. It should be inherent to the specimen. IF the 4 are lumped it should be one species but a "morphological grouping" or something since they aren't even all the same species so "species group" wouldn't work. I haven't read responses on the other post so hopefully I am not missing anything. Link to comment Share on other sites More sharing options...
Randyw Posted May 26, 2019 Share Posted May 26, 2019 58 minutes ago, kate_rose said: Randy, Ordering by position in the mouth sounds challenging. I can tell anteriors from laterals and posteriors but I would think I would need a reference collection to really get them in order. Anterior lateral and posterior would be good enough to satisfy me in my collection Link to comment Share on other sites More sharing options...
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