Oreodons, sometimes called prehistoric "ruminating hogs," were a family of cud-chewing plant-eater with a short face and tusk-like canine teeth. As their name implies, some of the better known forms were generally hog-like, and the group was once thought to be a member of Suina, the pigs, peccaries and their ancestors, though recent work indicate they were more closely related to camels.[2] The scientific name means Mountain teeth and refer to the appearance of the molars. Most oreodonts were sheep-sized, though some genera grew to the size of cattle. They were heavy bodied, with short four-toed hooves. Unlike any modern ruminant, they had long tails.

Trilobites are a well-known fossil group of extinct marine arthropods that form the class Trilobita. The first appearance of trilobites in the fossil record defines the base of the Atdabanian stage of the Early Cambrian period (526 million years ago), and they flourished throughout the lower Paleozoic era before beginning a drawn-out decline to extinction when, during the Devonian, almost all trilobite orders, with the sole exception of Proetida, died out. Trilobites finally disappeared in the mass extinction at the end of the Permian about 250 million years ago. The trilobites were among the most successful of all early animals, roaming the oceans for over 270 million years.