Lappets

[POD-L]

Yes Kevin
Unfortunately my macro doesn't show this feature due to preservation but I was glad the micro was so complete.
I don't know of to many late Cretaceous ammonites which show this.
Rick

 

[PaleoProgrammer]

Russian perisphinctid microconchs

Here's two Russian Jurassic perisphinctid ammonites (Indosphinctes sp.), 49 and 53 mm, with lappets. There are microconchs, from the Lower Callovian beds in Ryazan region.

 

[PaleoProgrammer]

macroconch Indosphinctes sp.

And a Russian Jurassic macroconch ammonite Indosphinctes sp. from the Lower Callovian beds in Ryazan region.

 

[Architeuthoceras]

Some very nice specimens, and a nice comparison of Macroconchs and microconchs, thanks for posting them.

and to TONMO

 

[POD-L]

Very cool Jurassic examples thanks for showing them!!

 

[Terri]

PaleoProgrammer! Beautiful specimens!

 

[PaleoProgrammer]

Thank you very much!
Here's another one Russian Jurassic ammonite - Pavlovia raricostata, 45 mm, from Late Jurassic (Tithonian). These ammonites, both microconchs and macroconhs have simple apertures without lappets.

 

[Architeuthoceras]

There does seem to be a slight lengthening (or bulge) of the ventral shell at the aperture, a rostrum? And maybe some small mature modifications on the dorsal part of the aperture? Again, thanks for the great pictures.

 

[PaleoProgrammer]

Thank you very much! Yes, there is a very small lengthening on the ventral side at the aperture, like a small wide rostrum. I think, it may be microconch. Macroconchs Pavlovia have more smooth edges of the aperture.

 

[Hajar]

Rescuing old books being discarded from a library this lunchtime I came across this 1895 image of Hoplites hyatti (type specimen) in an article on "Cretaceous Paleontology of the Pacific Coast" by Timothy Stanton.

 

[Terri]

Nice image Hajar!I would say that's a lunchtime well spent, great to know there are those of us still around that value the worth of books, old or not!

 

[Hajar]

This is pretty. Kosmoceras compressum from the Jurassic Oxford Clay of Sleaford, Lincolnshire, UK.

 

[DWhatley]

Amazing how intricate some of the patterns are. This one would have surely been something exceptional to see. I wonder if the animal was more complex or visually ornate in the more complex shells.

 

[Hajar]

Yes, like this?

 

[DWhatley]

It is not hard to imagine they looked more like that than how we normally picture the animal part. I wonder if color was always a part of life rather than something that evolved. If you think about it minerals were likely more exposed and plentiful so you might expect animals to take on the colors through eating.