Rhizoprionodon tooth?

[Kolya]

Hello!

Help please with identification. Is it Rhizoprionodon?
Length - 4 mm.
Age - Eocene.
Location - Western Ukraine.
Thanks in advance!

[siteseer]

It's impossible to be sure when a tooth is that worn.  Is it early Eocene?  The epoch is so long that it would help the ID possibilities to know that.  Shark faunas of the early Eocene are different from late Eocene ones and middle Eocene faunas can contain elements of both.  With that said, it could be a Physogaleus tooth or perhaps an early Sphyrna tooth.  Rhizoprionodon generally has a narrower cusp but it's hard to say.  

[abyssunder]

1 hour ago, siteseer said:

It's impossible to be sure when a tooth is that worn.  Is it early Eocene?  The epoch is so long that it would help the ID possibilities to know that.  Shark faunas of the early Eocene are different from late Eocene ones and middle Eocene faunas can contain elements of both.  With that said, it could be a Physogaleus tooth or perhaps an early Sphyrna tooth.  Rhizoprionodon generally has a narrower cusp but it's hard to say.  

I agree!

[PermianOkie]

First I'll start by saying I'm far from an expert, but have been obsessively researching Russian sharks teeth over the last two weeks. 

Is there any chance that this tooth may have come from a formation dating back to the Cretaceous? If so I would say it's a Palaeoanacorax sp. As it shows a lot of similarities to examples I have been seeing on a russian fossil forum. The enamel portion of the tooth does appear to all be there except for a little wear, the root of the tooth is damaged but I feel it isn't impossible to identify this specimen.

I'd post some example pictures, but I'm not sure if that would be allowed since their not my pictures and are from a different website. I'm still needing to add a Palaeoanacorax to my personal collection, or I would share an example that way.