Cretodus cf. semiplicatus?

[readinghiker]

This is a well worn tooth from the Cabezon fauna.  With the lingual and labial plications, I am assuming this is

a Cretodus.  The narrow cusp leads me towards C. semiplicatus.  However, the accessory cusp is not as triangular as

I would expect to see from this species.  Am I right in my assumption concerning the species, or am I off base?

Thanks!

 

 

 

 

 

 

 

 

[ThePhysicist]

The strong striations and longer, narrow cusplets appear to be consistent with C. semiplicatus. 

[readinghiker]

Thanks!  This is what I had assumed, but I wanted to get opinions from others.  There weren't too many cretodus from this site, and they were all worn with no roots, so the possibility of seeing or not seeing a nutritive groove is non-existent.  The vast majority of the thousands of teeth were scapanorhynchus, cretolamna, and squalicorax.

[bthemoose]

3 hours ago, ThePhysicist said:

The strong striations and longer, narrow cusplets appear to be consistent with C. semiplicatus. 

May I ask what feature(s) signal Cretodus rather than Protolamna on this one?

[ThePhysicist]

4 minutes ago, bthemoose said:

May I ask what feature(s) signal Cretodus rather than Protolamna on this one?

Haha, I was just second-guessing myself after looking at your Protolamna.

 

It's a tough call. It's a small, incomplete tooth. I think its small size favors Protolamna sp. 

[readinghiker]

Thanks to both of you!  I am still tending towards C. semiplicatus because of the irregular plications and crown shape.  As to the size,  I am wondering if I have wandered into a pupping area.  This was a barrier island deposit, so there could have been a bay wherein pupping may have occurred.  The vast majority of teeth are very small.  I have found scapanorhynchus in another site that measured over 9cm, but the biggest from this fauna is only around 2cm.  The same is true for the cretolamnas.  Given,  all of these teeth were transported by ants, so that there is some size bias, but there have only been a few adult teeth found, whether in situ in surrounding matrix or loose.  I have literally thousands of teeth that are very small.  Here is another example of what I think is C. semiplicatus.  It would be great if you could convince me otherwise, as I am working on a bulletin dealing with this fauna for the New Mexico Museum of Natural History, and want to get it as accurate as possible before it is sent out for peer review!  Thanks again!