Shark tooth identification

[David in Japan]

Hi TFF friends,

 

Last time I went fossil hunting I found this pretty beaten shark tooth on the surface of a rock lying on the beach.

 

Himenoura formation,

Late cretaceous, -85MYA

Kumamoto japan.

 

 

The apex is missing but it is none the less an interesting tooth.

At first I thought it was my first Squalicorax tooth but when I looked under magnification I was not able to see any serrations and noticed a nutrient groove and a small cusplet here on the left side of the root in the photo below.

 

After extracting completely the tooth from the rock at home, I discovered a lot of folds at the base of the crown. 

 

The tooth is 100mm wide for 50mm high.

 

Even though this tooth size is quite bigger than the tooth I found, I am now thinking it could be a Protolamna sp. Posterior tooth. In the past, I found from the same location a Protolamna sp. anterior tooth (30mm wide for 40mm high), and this genus is also mentionned in the literature.

 

What do you think?

 

 

From above with nutrient groove visible

 

What looks like a cusplet

 

[David in Japan]

OK, I will disagree with myself as I realized it can't be a Protolamna tooth because the tooth I found has a nutrient groove on the root.

Well, the mystery grows thicker for me.

 

By the way, I am sorry for the poor quality of the photos, I realized they are all blurry. When I uploaded them with my phone and looked at the post with it, they looked very fine but now that I opened the post with a computer they look odd. I will re-upload them later.

[bthemoose]

I’m not sure what it is, but are your measurements off by a factor of 10 maybe? 

[David in Japan]

3 hours ago, bthemoose said:

I’m not sure what it is, but are your measurements off by a factor of 10 maybe? 

WoW completely!  

 

it's 10mm by 5mm!

 

thank you