Isurus retroflexus posterior tooth?

[bthemoose 195]

After I remarked that the little tooth below (found on Morris Island, South Carolina) looked interesting on his trip report thread, forum member @Family Fun kindly gifted it to me, asking only that I help identify the species and share the result. My assessment is that this is an Isurus retroflexus posterior tooth, but hopefully others here can either confirm or correct that ID. This tooth has a non-serrated crown that is still fairly sharp and to my eyes at least has the raised labial platform indicative of I. retroflexus. There is a single cusplet on one side.

 

Thanks for your help with this one, and thank you @Family Fun for your generosity!

 

(Unfortunately, the tooth split down the middle on its journey to me, which is the crack you can see in the photos, but I was able to glue it back together.)

 

[fifbrindacier 4,739]

I can't help you, but i find the colors of that tooth amazing.

[WhodamanHD 3,070]

I believe this is a thresher extreme posterior, likely giant thresher given the robustness. Unfortunately our reference material for positional variants in Giant threshers is scant and retros are fairly convergent with them so my ID comes with a grain of salt. 

[bthemoose 195]

Thanks, @WhodamanHD! Now that you mention it, I can see that as a strong possibility. I'll send these photos to Dr. Kent at UMD to see if he might weigh in.

[bthemoose 195]

@WhodamanHD, do you think this one might be retroflexus? I found it today at Matoaka.

 

[WhodamanHD 3,070]

3 hours ago, bthemoose said:

 

@WhodamanHD, do you think this one might be retroflexus? I found it today at Matoaka

 

That would be my guess

[siteseer 1,715]

I would expect the crown to be a little flatter but maybe.

[bthemoose 195]

12 hours ago, siteseer said:

I would expect the crown to be a little flatter but maybe.

Thanks for looking! Do you have other thoughts on what it might be?

[siteseer 1,715]

6 minutes ago, bthemoose said:

Thanks for looking! Do you have other thoughts on what it might be?

 

It's more likely an I. oxyrinchus posterior tooth.

 

Jess