Thresher tooth?

[Fin Lover]

Found this tooth in the Summerville area yesterday in a creek that has both Oligocene and Miocene fossils (Miocene comes from a Pleistocene lag deposit).  My guess is a thresher of some sort, as I found 3 other threshers there yesterday, but this one looks different than the others (and the 4 or 5 other ones I've found in the last year).  I just don't know what else it could be, if not thresher.

 

The root here made me think Paratodus, but it otherwise doesn't look like a benedini:

 

Two more typical threshers found in same creek yesterday (ones I find usually have little cusps also):

 

New tooth on right, tooth previously IDed on forum as thresher on the left:

 

14 mm slant height.  Root is 4 mm thick at thickest part, while the blade is only 1-3 mm.

 

Thanks for any input!

[Shellseeker]

Nice finds...  I think your new one might be a Mako...

[debivort]

I think I'm 60/40 oxyrhinchus-desori / hastalis.

[Meganeura]

I was initially thinking Isurus of some kind, but the blade doesn't seem to fit. Seems like the root comes down onto the crown a little, which doesn't happen with Isurus (to my knowledge, anyway). 

[debivort]

I think I see what you mean, but does the root come down onto the crown of a hastalis?

 

Here's an anterior oxyrhinchus that has a similar side profile to @Fin Lover's tooth.

[Meganeura]

Just now, debivort said:

I think I see what you mean, but does the root come down onto the crown of a hastalis?

 

Here's an anterior oxyrhinchus that has a similar side profile to @Fin Lover's tooth.

The root doesn’t come down onto Hastalis crowns. Also I’ve never seen a lower Hastalis remotely similar to this tooth.

[Fin Lover]

I just came across a picture that looks very similar to my tooth in question, when trying to ID something else.  This is listed as being Alopias cf. A. vulpinus.

 

 

Compared to mine:

 

Of course, it's difficult to tell from one small picture, but what do you all think?

 

Screen shot is from Geology and Paleontology of the Lee Creek Mine, North Carolina, III, which I will attach for anyone interested, as it has a ton of information (it's a large file).

SCtP-0090-Lo_res.pdf

 

 

 

[ThePhysicist]

I'm in the anterior thresher camp. The crown is erect / symmetric, suggestive of an anterior position. The crown height / root height ratio is much closer to thresher than to a Lamnid. Note also the long and splayed root lobes, and the small size.

 

Modern A. vulpinus:

^ http://naka.na.coocan.jp/JAWAlopiidae.html

 

Compare to the modern white shark (essentially the same as C. hastalis, just with serrations):

^ http://naka.na.coocan.jp/JAWLamnida.html

 

... and a modern mako, I. paucus:

^ http://naka.na.coocan.jp/JAWLamnida.html

It is superficially similar to lower Carcharhinus, but there is of course no obvious nutrient groove, so that possibility is unlikely.