LK Ammonite Cleoniceras
Cleoniceras besairiei
Lower Cretaceous (Albian)
Mahajanga Basin
Here is an excellent example of C. besairiei that has been cut in cross section to expose the very fine detail of the internal septa. The ammonite is 9 inches across.
These Lower Cretaceous ammonites are quarried commercially in Madagascar. They are found in a hard basal glauconitic sandstone layer known as the Cleoniceras Zone.