†Ammonitida

22 specimens 3 localities
Geological time
Triassic Jurassic
ammonitida

Ammonitida is an order of extinct ammonoid cephalopods that lived during the Jurassic and Cretaceous. Most had chambered shells coiled into a flat spiral, although some developed hooks, helices or nearly straight shells.

Their sutures, formed where the internal chamber walls met the shell, were often deeply branched. However, this feature was neither unique nor universal, so classification also considers shell form, ornamentation and geological age.

Ammonitida appeared near the beginning of the Jurassic and evolved rapidly, making them valuable for dating marine rocks. They became extinct around 66 million years ago, during the Creatceous-Paleogene extinction.