Midlothian Ptychodus

[Dantheman135]

Found this in some midlothian matrix. Is it possible to tell what species of ptychodus this is from these photos? I originally assumed posterior p. whippeli but I am not great at identifying ptychodus teeth. Any help would be much appreciated.
6mm long

[DPS Ammonite]

Do you mean that this is from Midlothian, Texas? Is this from the Atco Formation that is found in at least one cement mine?

[Dantheman135]

9 hours ago, DPS Ammonite said:

Do you mean that this is from Midlothian, Texas? Is this from the Atco Formation that is found in at least one cement mine?

Yes. I didn’t even realized I forgot to mention the formation. This is from the lower Atco Formation of North Texas.

[LSCHNELLE]

I think that this is a very difficult tooth to ID.  Also, posteriors and outer laterals are very difficult to pin down in Ptychodus species. 

 

If it is basal Atco and not older or younger strata, then you pretty much eliminate P. anonymous - to which it has an affinity.  Then, you narrow down to moderate to high crown teeth - because of the small bump.  That means P. latissimus, P. mortoni (radial), and P. martini are out.  Then, you are left with P. whipplei, P. mammillaris, P. atcoensis, and P. rugosus. It has no chevron ridges like P. atcoensis. P. rugosus is not present in the lowermost Atco. It has semi-parallel ridges extending out to near the edge.  I think that those may occur more in posterior teeth than in laterals. So, it most likely P. whipplei or P. mammillaris in my opinion.  But, outer laterals and posteriors in those teeth can look similar. I think that the posteriors from P. whipplei are more prone to your tooth's extreme marginal shape than P. mammillaris. So, you are likely correct!