Lower Jurassic Ammonites From Charmouth / Uk

[araucaria1959]

Hello,

I got a small collection of ammonites from the lower jurassic (upper sinemurium) from Charmouth, Jurassic Coast, UK.

There are typical ammonites like Crucilobiceras densinodulum, C. ornatilobatum, Echioceras raricostatum, Oxynoticeras lymense, Eoderoceras obesum, E. bispinigerium, Promicroceras sp., Polymorphites sp., Tragophylloceras sp., Xipheroceras sp., Microderoceras sp., Acanthopleuroceras sp.,

but among them there are a few ones, mostly comparatively small, where I'm not sure about their ID.

Perhaps someone knows?

There are 5 specimens; for specimen 4, I show two pics. The second specimen is quite small (diameter of the ammonite about 5 mm)

(1 = Echioceras ?; 5 = Crucilobiceras densinodulum?).

Thanks!

araucaria1959

[Ammojoe]

Interesting specimens; thanks for sharing. We're in need of a major revision for some of the ammonites from Charmouth - personally I feel there are more Promicroceras and Crucilobiceras species than so far reported - but it could just be sexual dimorphism or individual differences within a species...

1 - I think it's a Crucilobiceras densinodulum.

2 - It's a Cymbites - cannot remember the name of the species (will let you know very soon).

3 - That's a very interesting specimen - the closest thing, off the top of my head, would be a Riparioceras although I haven't heard of any from Charmouth - please could you take some more photos.

4 - I am not sure off the top of my head - not a Polymorphites?

5 - I'd leave it as Promicroceras sp.

I'll have a research around and let you know if I can come up with anything else.

Kind regards,

Joe

[araucaria1959]

Thank you very much.

Here are some more pictures from the third specimen under different conditions of lighting. Perhaps Cymbites too? It is quite small (largest diameter about 12 mm).

araucaria1959

[Ammojoe]

Your Cymbites is very difficult to tell which species it is (laevigatus and neglectus) are found there - I'd leave it as Cymbites sp. Thanks for the additional photos of the other specimen; I do not think it is a Cymbites - I'm not really sure what it is, but perhaps it is a gastropod such as Coelodiscus - could you post some photos from the side of the specimen?

Kind regards,

Joe

Edited March 30, 2013 by Ammojoe

[araucaria1959]

Thanks,

the specimen is not with me (my collection is at a different place), so I can only post pics I already took sometime before. I have some other pics of the specimen, but they yield no additional informations, and there are no pics of the back.The third picture shows the other side of the specimen.

But the back of the specimen shows no special features, it is smooth, the cross-section is about circular, so the specimen is rather thick for its size.

Since there are sutures, I can exclude the possibility that it can be a gastropod.

araucaria1959

[Ammojoe]

OK; thanks for the additional information. Well, that's me stumped - I don't know what it is! Perhaps Roger or Steve may be able to shed some light on it?

Kind regards,

Joe

[JackSnakes]

Hi guys. I realise this is an old thread, but I found this the other day at Charmouth and the one above looked familiar..

[Ammojoe]

Thanks for sharing that with us, Jack. That's a very impressive unusual find. AndyS (over on the UK site) is the man to ask regarding this. I believe he's spot on, he's provided a reference which clarifies that Riparioceras is no longer a valid genus (fairly sure that's right), and therefore what was known as Riparioceras is now regarded as a juvenile Gleviceras. Gleviceras have of course been found at Charmouth.

RE: The original 'Riparioceras' in question; I think it's fair to say that's another juvenile Gleviceras.

Another mystery solved!

[Ludwigia]

Sorry I didn't tune in here back then, Joe, but you were doing much better than I could ever have done.

[Herb]

Nice ammos!