Mexican Fossil ammonite ID pachydiscus

[Jaime]

Hi guys,

 

I bought this ammonite at antique store, It measures 25 CM. Could anyone help me ID the fossil? Baja California, México.

 

It could be pachydiscus?

 

Thank you!

 

Best regards!

[Tidgy's Dad]

Nice specimen! 

I think these suture lines look ceratitic, Pachydiscus has much more complicated ammonitic sutures. 

 

Edit: Hmm looking again it does look like ammonitic sutures are visible on the bottom of the first photo? 

Edited April 19, 2022 by Tidgy's Dad

[FossilDAWG]

The specimen has been worn down, by natural weathering or by "polishing", or a combination of the two.  Either way, the sutures do not reflect the natural condition of the intact surface.  No matter how complex the suture line might be on the surface, it becomes simpler and more "ceratitic" as more and more of the surface is removed.  Note how the septa of ammonites become simple curves when the ammonite is sectioned right through the middle.

 

Don

[Jaime]

Thanks!

[Jaime]

3 hours ago, Tidgy's Dad said:

Nice specimen! 

I think these suture lines look ceratitic, Pachydiscus has much more complicated ammonitic sutures. 

 

Edit: Hmm looking again it does look like ammonitic sutures are visible on the bottom of the first photo? 

Thanks, i Will upload a closed up photo tonight.

[Tidgy's Dad]

59 minutes ago, Jaime said:

Thanks, i Will upload a closed up photo tonight.

Yes, as Don said, I was originally fooled by the septa, though these look a bit more wavy than usual. 

A detailed look at the septa will help decide if this is a Pachydiscus. 

The suture pattern should look rather like diagram h) shown below.

 

This is of P. neubergicus, so other species might be a bit different, but fairly close to this. 

From :

Maastrichtian_shallow-water ammonites of Northeastern Mexico by Christina Ifrin et al. 

Edited April 20, 2022 by Tidgy's Dad

[Jaime]

Thanks a lot, i Will Chek It out! This is new to me.  Tomorrow with daylight Will be the Best.

 

Best regards!