Kohler Palaeontology Posted September 8 Share Posted September 8 (edited) Hello, I was looking at one of my troodontid teeth (Albertavenator curriei) and noticed some very interesting wear facets. I decided to look at some of my favorite teeth and/or the ones with the strangest wear facet and check out all their wear facets. I wanted to share them with the community. You can clearly see scratches of where the tooth entered the flesh, especially on the first one. Here's the first tooth, it looks blacker in person, the photo makes it look brown. Here's another troodontid tooth, there are marks on the wear facet, it is just harder to make out and this tooth was a challenge to photograph. I made this diagram years ago, all the others I made today. There are at least 2 prominent scratches. This diagram shows the puncture and pull method of most theropod dinosaurs. Puncture-and-Pull Biomechanics in the Teeth of Predatory Coelurosaurian Dinosaurs. Hope you all enjoyed, I will not be able to reply for next 4-5 days, as I am going south to Victoria to see the world's most complete Triceratops and Victoria the Tyrannosaurus on display at a museum, I will probably make a post about that when I can. Kind Regards, Kohler Palaeontology Edited September 8 by Kohler Palaeontology 4 Link to comment Share on other sites More sharing options...
Kohler Palaeontology Posted September 8 Author Share Posted September 8 (edited) The image of the rex tooth at the end, don't know why it's there, I tried to edit it out, but it won't delete, oh well... it doesn't matter, I don't think. Edited September 8 by Kohler Palaeontology Link to comment Share on other sites More sharing options...
Kohler Palaeontology Posted September 8 Author Share Posted September 8 (edited) I'm sure someone will correct me if I'm wrong, but... I was wondering if I could use the scratches on the wear facet to determine whether you have a dentary or maxillary tooth, pre-max teeth are usually pretty self-explanatory. I made this diagram using a picture from the paper I described earlier. Atop of each picture are lines showing the orientation of those scratches on the wear facet according to the orientation I present the tooth. If this can be applied, this would show that I have a dentary tooth, correct? I am using my Albertavenator tooth as it has the best, most prominent scratches. Maybe the scratches form from rubbing against another tooth. I don't think you would be able to tell whether it is an upper or lower jaw tooth if that's the case, maybe. Although it is food for thought. I am not 100% if this truly does work, however, any opinions would be appreciated. I have never heard of using scratches on wear facets like this before, so I don't know if others have done it before me. --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- "Nature can do whatever it desires" - me About me: Kohler Palaeontology - The Fossil Forum Edited September 8 by Kohler Palaeontology Link to comment Share on other sites More sharing options...
rocket Posted September 8 Share Posted September 8 interesting. I did some research on this (not published) because we have had several teeth with "similar marks". I show two, one from a rex, the other one is a Nano (about the Nano I am a little bit unsure if it was an old wear facet or not. Rims are not sharp, I think it is an original one 1 2 Link to comment Share on other sites More sharing options...
ThePhysicist Posted September 8 Share Posted September 8 First, very nice imagery and specimens! I've always found feeding traces and tooth wear features very interesting. I would however like to clarify on some of the features you're observing. There are two broad forms of tooth wear that are the result of different causes: wear facets and spalled surfaces. - Wear facets: these are elliptical, uniformly flat surfaces whose long axis usually closely aligns with the long axis of the tooth, and are usually only on the lingual or labial face. They often have parallel grooves within them. They are caused by repeated tooth-tooth contact, and suggest some dinosaurs had tight shearing occlusion. The parallel grooves within the facets are caused by fine grit caught between the teeth, gouging at the softer dentine during feeding - they have no relation to tooth-prey contact or to the extent to which the tooth pierced flesh as you suggested. The grooves' orientation does reflect the relative tooth motion, but since at least in tyrannosaurs the orientation seems to be uniform across tooth positions, they likely can't be used to distinguish upper/lower. Your troodontid teeth are good examples of this wear feature, I don't see wear facets in your other teeth. Shubert & Ungar 2005 - spalled surfaces: these are mostly short, squat irregular features, typically are near the apex, have conchoidal fracturing, and whose edges are often smoothed-over from continued use. They are caused by tooth-prey contact breaking/flaking off parts of the tooth. If you've ever flint knapped these should look like pressure flaking scars. This is more common say in tyrannosaurs which consumed bone and often broke their teeth despite their robustness. Your Megalania tooth is an example of tooth spalling. Shubert & Ungar 2005 I refer you to the paper below for further reading. There are many other papers out there on tooth wear features, but this is a start. For example is microwear, which the paper you referenced (Torices et al. 2018) uses to infer puncture-pull feeding behavior, but those features aren't related to the parallel striations within wear facets. Schubert, B.W. and Ungar, P.S. 2005. Wear facets and enamel spalling in tyrannosaurid dinosaurs. Acta Palaeontologica Polonica 50 (1): 93–99. Torices A, Wilkinson R, Arbour VM, Ruiz-Omeñaca JI, Currie PJ. Puncture-and-Pull Biomechanics in the Teeth of Predatory Coelurosaurian Dinosaurs. Curr Biol. 2018 May 7;28(9):1467-1474.e2. doi: 10.1016/j.cub.2018.03.042. Epub 2018 Apr 26. PMID: 29706515. 2 1 1 1 Forever a student of Nature Link to comment Share on other sites More sharing options...
rocket Posted September 8 Share Posted September 8 @ThePhysicist: I completely agree that the literature cited is the best to understand the facets. I add the paper as pdf, might be it is interesting for others Wear_facets_and_enamel_spalling_in_tyrannosaurid_d.pdf 1 Link to comment Share on other sites More sharing options...
Kohler Palaeontology Posted September 9 Author Share Posted September 9 (edited) Thanks everyone for your replies, they were very interesting. I said I wouldn't be able to reply, but I realised I have a phone of which I never use, so I am still able to reply. I will be sure to check out that paper. I did forget to clarify, the daspletosaur? tooth is from the Judith River Formation, you probably knew by the county it was found and the species, but just wanted to clear that up. Edited September 9 by Kohler Palaeontology 1 Link to comment Share on other sites More sharing options...
Kohler Palaeontology Posted September 9 Author Share Posted September 9 And those teeth you have are very nice, rocket. Did you discover them yourself? Link to comment Share on other sites More sharing options...
Kohler Palaeontology Posted September 9 Author Share Posted September 9 (edited) The facet or spalled surface on the char tooth is on the front. So you can't really see it in the photos. If you would like, i'd be happy to show a photo and f the front (mesial) Edited September 9 by Kohler Palaeontology Link to comment Share on other sites More sharing options...
rocket Posted September 9 Share Posted September 9 4 hours ago, Kohler Palaeontology said: And those teeth you have are very nice, rocket. Did you discover them yourself? No, I would be delighted if that were the case. But we have bought both . I have never been in the US to dig Dinosaur-fossils, hope to do it one day. I found some in Europe (remains, not complete...) and Africa, but never in US. Link to comment Share on other sites More sharing options...
Kohler Palaeontology Posted September 9 Author Share Posted September 9 Oh it would be my dream to hunt in the US too. It's just so expensive! Link to comment Share on other sites More sharing options...
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