Jump to content

FossilDAWG

Recommended Posts

The other day I bought a set of ammonites from a dealer who was selling off specimens from an old collection.  Two of the ammonites were labeled, probably correctly, as the Triassic species Ceratites nodosus and Acanthoceratites spinosus.  A third specimen was also labeled as a ceratitid, but it is clearly different.  For example the suture line is not at all ceratites-like, and is definitely an ammonite.  To my eye several features suggest Placenticeras, a late Cretaceous genus.  These include a flat venter with alternating clavi (elongated nodes), nodes at about mid flank, possible faint umbilical nodes, and a very complex suture line.  If it is a Placenticeras it doesn't exactly match the species I am familiar with, and the preservation is also unfamilar.  Note that there is a lot I don't know about the genus.  However it occurs to me that various species of Placenticeras are found in Europe.  Of course, it also could be something else entirely.  I am asking the community, and especially my fellow ammonite aficionados ( @rocket @Ludwigia @PFOOLEY et al) if they recognize the species and/or the mode of preservation.  

 

General aspect:

 

20221211_175327.jpg

 

Flank with nodes:

 

20221212_095656.jpg

 

20221212_095516.jpg

 

Venter showing flat edge with clavi (elongated nodes) on either side:

 

20221211_175512.jpg

 

Suture line:

 

20221212_095533.jpg

 

I forgot to get a photo of the profile with the aperture, I will add that this evening when I get home.

 

Don

 

 

 

20221212_095516.jpg

20221212_095533.jpg

20221211_175512.jpg

20221211_175327.jpg

  • I found this Informative 1
Link to post
Share on other sites

@Heteromorph

 

In the meantime, compare to Placenticeras syrtale as a possibility.

  • I found this Informative 1
Link to post
Share on other sites

I'm afraid that I can't be of much help here since I'm not really up on my cretaceous ammonites, although I can at least definitely confirm that this is not a ceratite.

Link to post
Share on other sites

great pics, let me take some time in the evening to compare

Do not know for 100% now but think I can identify next day :eyeroll:

Definitely cretaceous, was wrong with my first idea that it´s a jurassic one

Link to post
Share on other sites

I would agree to Placenticeras cf. intercalare

I am not absolutely sure, but do not know, why. It´s the "nose" we say in Germany. You feel something but cannot justify. Very cool preservation, never seen one in this condition before, and I love cretaceous fossils since decades...

  • I found this Informative 1
Link to post
Share on other sites

Thanks all for the suggestions.  John, I agree that Placenticeras syrtale is very close.  This specimen is a bit more involute than my P. syrtale specimens from Alabama, but they are a little flattened which might distort the umbilicus a bit.  Placenticeras intercalare is also close.  The illustrations I have found show specimens with the shell, and mine is a steinkern, which complicates comparison.  Placenticeras intercalare has more prominent umbilical nodes and stronger ribbing, but that could easily be due to the shell vs internal mould issue.  I'll post again when/if I get it figured out.

 

Don

  • I found this Informative 1
  • Enjoyed 2
Link to post
Share on other sites
  • 1 month later...

What a great specimen of Placenticeras, Don...excellent acquisition! 

 

Due to the nodes, P. interclare and P. syrtale are good starting points but my S.W.A.G. would be Placenticeras costatum...they too carry similar ornament, but it is not as pronounced. 

 

@Foshunter has some great P. syrtale from the Blossom Sand to use as a reference.

  • I found this Informative 4
Link to post
Share on other sites

Thanks Mike.  That is quite useful.  One potential complication is that the specimen came without provenance (actually, with the wrong label) from an old collection that contained both European and North American fossils.  There are some European Placenticeras that are very similar to some North American species such as Placenticeras syrtale, so I have to run down literature on those too.  Unfortunately there was a very nice web site on French ammonites that was shut down recently in protest against new French restrictions on collecting.  That could have been useful.

 

Don

Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
  • Recently Browsing   0 members

    No registered users viewing this page.

×
×
  • Create New...