Devonian Goniatite Ammonoid in Matrix

Description:The ammonites shown here are known as having the Goniatite septal pattern. Ammonites developed septa (separations between individual chambers) with intricate folds termed lobes and saddles. There are three basic patterns:

• Goniatiitc: Irregular zigzag
• Ceratitic: Regular wavy
• Ammonitic: Intricate, fernlike

These patterns are evidenced on the exterior of the shell as sutures. The Ammonidea have a rich evolutionary history which began in the Upper Silurian/Lower Devonian. The order began an extensive radiation in the Triassic and Jurassic, and became most diverse during the Cretaceous, only to become extinct during the late Cretaceous extinction event which also saw the demise of the non-avian dinosaurs. The Goniatite forms became extinct during the Permian. This one come from the same location as trilobite Akantharges mbareki (see my other offerings), and self-displays on its matrix block.