Paraceltites Permian Ammonite from China

Description: The ammonites shown here are known as having the Ceratitiic 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. These ammonites have been polished to show the sutures in all their glory. 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 Ceratite forms arose during the Permian, and became extinct at the end of the Triassic.