North Sulphur River Teeth identification

[James Puls]

Hey all!

 

I need some help confirming the identity of some teeth I've collected in north Texas over the years. I've been fossil hunting the North Sulphur River since I was a kid, and I've found some odd fossils over the years down there. Since I moved to Savannah, I am going back through the boxes of fossils I packed away and doing a better job at photographing and cataloging the various fossils I have in my collection. It has been good for me to go back through my collection because I am learning now that some things I had labeled as one species are really another species entirely. I am going to be doing these in batches like this, so I don't confuse anyone by having a billion pictures in one post. As for this post, I need some help confirming the identity of various teeth I found in the North Sulphur River (NSR) in Northern Texas. These fossils all date to the Cretaceous Period from what was then a part of the Western Interior Seaway for those that are unfamiliar with the area. In the past I have used "A fossil hunters guide to the North Sulphur River" and various online identification sites to identify most of my collection. 

 

The first two pictures (NSR_Croc_1 and 2) show three teeth. The tooth on the far right is a standard mosasaur tooth I have from the NSR for comparison. The two teeth on the left are the only two I have ever found like this. They are completely different than any of the regular teeth like mosasaur or Enchodus teeth I tend to find in the area. The larger of the two seems to have been shed. My best guess is crocodile but because they are so small I am unsure what they could be. Any suggestions or second opinions on this would be appreciated. 

 

The next three photos (Named NSR_1, 2, 3, and 4 respectively) show two teeth I don't have any idea of what they could be. Again, I have the same mosasaur tooth on the far right for comparison. The two teeth on the left are not serrated, are conical in shape, and are curved backwards which rules out crocodile. I believe these are a species of fish, but they are too thick and curved for Xiphactinus and they also don't seem to be Enchodus since those tend to not be as stubby as the far-left tooth. These teeth also both appear to be shed rather than broken. I don't know if the middle tooth that is split in half is the same species as the far-left. Any confirmation or ideas on what these teeth could be would again be much appreciated. Thanks!

 

 

[ThePhysicist]

Your first two teeth could be fish, like Pachyrhizodus which are small, conical, carinated, and have smooth enamel (though I'm more confident saying that for the more complete one). For the second pair, I believe the leftmost could indeed be a juvenile mosasaur (tylosaurine? @pachy-pleuro-whatnot-odon

@Praefectus) with the enamel texture, faceting, basal striations, etc. - very cool; don't think I can say much more that "it's a tooth" for the other fragment.

[pachy-pleuro-whatnot-odon]

11 hours ago, ThePhysicist said:

Your first two teeth could be fish, like Pachyrhizodus which are small, conical, carinated, and have smooth enamel (though I'm more confident saying that for the more complete one). For the second pair, I believe the leftmost could indeed be a juvenile mosasaur (tylosaurine? @pachy-pleuro-whatnot-odon

@Praefectus) with the enamel texture, faceting, basal striations, etc. - very cool; don't think I can say much more that "it's a tooth" for the other fragment.

 

I agree. There not a lot to go on when it comes to the first two teeth, though the somewhat angular/squared off side of the basal cross-section of the larger of the two teeth does suggest this is Pachyrhizodus sp.. Likely the second one is as well, if you've grouped them together. In any case, I don't see any features that'd make them crocodilian in my mind...

 

The second batch appears to comprise mosasaur teeth, with the second, broken, segment being hard to identify due to its fragmentary nature. However, seeing as how tall and conical it is, I suspect it would've been a plioplatecarpine tooth.

 

The first tooth is the more interesting, but also hard to identify based on the currently available information. I'd need additional photographs to be able to make out the three-dimensional shape of the tooth, especially since something strange seems to be going on with the basal cross-section. It's therefore unclear to me, at present, whether the tooth is generally ovoid in shape, or had more of a D-shaped cross-section as would species of the genus Mosasaurus. If the cross-section were ovoid, then the question becomes whether the tooth has one - and only a posterior - carina, or has two of them. If only the posterior carina is present, that could mean this is a palatal tooth, which is also suggested from the high degree of distal curvature and the tooth's diminutive size. Otherwise it could, indeed, be tylosaurine. Though with the curvature it has, halisaurine would then probably be my preferred candidate (although, those, again, have more circular cross-sections).

[James Puls]

Here are some more images of the tooth @pachy-pleuro-whatnot-odon, Hopefully these can help give you a better picture of the 3D shape of the tooth. I was doing some more digging and found a paper published in March 2024 that had similar looing teeth from tylosaurine. Granted, these fossils came from Russia so the fauna at this site was not identical to that found in modern day Texas. But I think the overall shape of the teeth in the paper might be pointing in the right direction. Ill share the link to the paper below if you are curious. I also agree with you and @ThePhysicist on the first set of teeth. I was looking at other papers which covered fossils found in Kansas and Texas and I think the best guess to the first two teeth are Pachyrhizodus. Let me know what you think. 

 

Also, if you have any reading material suggestions about the fauna found in the Western Interior Seaway, please share. I am always trying to read and learn more about these fossils and their environment. 

 

, James 

[James Puls]

I forgot to drop the link to the paper I found. Here it is if you are curious. 

 

Fossil marine vertebrates (Chondrichthyes, Actinopterygii, Reptilia) from the Upper Cretaceous of Akkermanovka (Orenburg Oblast, Southern Urals, Russia) - ScienceDirect

[pachy-pleuro-whatnot-odon]

3 hours ago, James Puls said:

I forgot to drop the link to the paper I found. Here it is if you are curious. 

 

Fossil marine vertebrates (Chondrichthyes, Actinopterygii, Reptilia) from the Upper Cretaceous of Akkermanovka (Orenburg Oblast, Southern Urals, Russia) - ScienceDirect

 

Yeah, I'm familiar with that paper.

 

Problem with your tooth, though, is that it has much more medial curvature than one would expect for tylosaurine. So I'd say it's also plioplatecarpine... As I'm not too familiar with US-species, hopefully @Praefectus will be able to stop by to share his thoughts. But, for me, I'd say this is Platecarpus coryphaeus.