Ammonites are members of the cephalopods, a group that includes the very similar looking nautilus, as well as squid, octopus, and cuttlefish. Cephalopods may have originated in the early Cambrian Period around 520 million years ago. And 20 million years later, an early cephalopod called Plectronoceras divided its shell into sealed-off chambers by thin walls called septa that were connected by a tube, or siphuncle. Here at PBS Eons, we’ve nicknamed this little cutie 'Squizard', because it looks like a squid wearing a wizards hat. By the early Devonian Period about 410 million years ago, ammonites appear in the fossil record. They would go on to dominate the seas until 66 million years ago during the Cretaceous-Paleogene mass extinction. During this time they diversified into a wide variety of shapes and sizes. There are estimated to be up to 20,000 species of ammonites and some could reach shell diameters of 2 m (6.6 ft)! This magnet was modeled after the ammonite Douvilleiceras that is known from Cretaceous deposits around the world dating to roughly 125 - 90 million years ago. The genus was named by a French geologist in 1893.

Polyresin cast refrigerator magnet cast from 3D Scans of actual Drotops megalomanicus trilobite fossils. Dimensions: 3 inches (7.6cm). Made by Eons and exclusive to the Complexly Store.

Introducing the second poster from PBS Eons! Enjoy this trip through the 1.8 billion-year-long saga of the supercontinents. Get the poster now!

1000 piece puzzle, made in the USA with recycled paper puzzle dimensions: 19.25" x 26.5". Get it in time for the holidays!

Pack of 3 stickers featuring the Imposter Crab, Megalodon and Plectronoceras. Get the pack now!