Questions relating to Cretalamna Appendiculata.

[David in Japan]

Hi,

just a recap of my situation:

I live in south of Japan in a city called Kumamoto and I prospect mainly for fossil shell the Himenoura formation which is an upper cretaceous (santonian) marine deposit formation.

Even if I know that a lot of shark teeth were found at my usual spot, I never looked for it until my Super Secret Santa send me some superb cosmopolitodus Hastalli tooth and I caught shark tooth virus.

Since then, I looked more carefully to this little beauty and found some.

As my knowledge in shark tooth is still pretty limited, I ask to a japanese friend of mine who's more into teeth and who told me that the tooth I found was lamna's one.

here is the picture of my the one I found.

however I have some question about these tooth. As I was looking for information concerning cretalamna in order to determine the place of the tooth I noticed that all cretalamna tooth had cusp.

Like this picture from an old post:

http://www.thefossilforum.com/uploads/monthly_07_2015/post-3940-0-35234500-1436898635.jpg

Did I misidentified the tooth or is there some cretalamna sub species which would have tooth without cusps ?

Thank you very much for your help and I hope taht this post will help for futur lamna's teeth identification.

David

[Troodon]

Very nice finds from an uncommon location. All cretalamna have cusps. Before you start looking at other possibilities let's first please examine your teeth closely. It's possible that the cusps are broken off. The two teeth on the left are anterior teeth and have smaller cusps than the laterals. A closeup picture of the other side of those two would be helpful.

[David in Japan]

here are the picture in the same order than the picture in my previous post.

Ok, so if there is no trace of cusps (broken one), it is a misidentification.

[Troodon]

David your photos are not as sharp as I would like down by where the cusps are on the root. I think I see possibilities that they existed but cannot be sure.