Ammonitidae
Ammonitidae is a family of extinct marine mollusks that lived during the Mesozoic era, from the Late Triassic to the Late Cretaceous periods. They are characterized by their distinctive coiled shells, which are often found as fossils in marine sedimentary rocks. Ammonites are believed to have been active predators, using their siphuncle, a spiral structure inside the shell, to pump water through the animal's body. The family Ammonitidae includes a wide variety of genera, each with its own unique shell morphology. Some of the most well-known genera include Ammonites, which are characterized by their smooth, rounded shells, and Ceratites, which have more complex, ribbed shells. Ammonites played a significant role in the marine ecosystem of their time, and their fossils provide valuable insights into the evolution of marine life during the Mesozoic era.