Saturday, July 12, 2014

Douvilleiceras mammilatum ammonite from Madagascar

Most of the ammonites that one sees for sale from Madagascar are Cleoniceras but sometimes you will see specimens of Douvilleiceras mammilatum for sale. They are nicknamed "Tractor Tires" due to their shape. They come from Albian stage (Cretaceous) aged rocks on the northwest coast of Madagascar in a region called Mahajanga.

Specimen #1

Specimen #2 - This specimen is a little beat up but you get to see some interesting features as a result.

A broken section of shell shows off some of the internal sutures in cross section
While on the outside the more elaborate surture pattern is revealed when the shell coating it is removed.

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