(541 – 485 million years ago) — Mascot: Anomalocaris — During the Cambrian, animal life diversified rapidly. The oldest ancestors of boney animals appeared. With a name meaning “abnormal shrimp,” the sea creature Anomalocaris most likely captured prey with its long arms and bit them with its ringed mouth, which it could not fully close. Anomalocaris was four feet (1 m) long, and roughly as big as a medium sized dog.

(485 – 444 million years ago) — Mascot: Trilobite — The Ordovician might as well be called, “The Golden Age of Trilobites.” This creature’s name in Greek means “”three lobes,” due to the distinctive three parts of its segmented exoskeleton. Trilobites are one of the most diverse groups in the fossil record, with over 17,000 different species flourishing during the Paleozoic Era. Their heyday was the Ordovician.

(444 – 419 million years ago) — Mascot: Eurypterid — During the Silurian, many groups of boney fishes appeared, swimming alongside some truly fantastical marine life. Eurypterid’s name comes from “eury” or “wide” and “pteron” or “wing,” because of its broad swimming paddles. The biggest species of Eurypterid were over eight feet (1.5 m) long. These “sea scorpions” lived in fresh or saline water, and may have spent some time on land.

(419 – 359 million years ago) — Mascot: Tiktaalik — Life during the Devonian bifurcated into land and ocean. The first vertebrate animals capable of venturing out of the water appear. Tiktaalik is a primitive lobe finned fish named for the Inuit word for a species of modern day cod. But the Devonian is also known as “The Age of Fish,” due to the rapid diversification of boney fish and sharks.

(359 – 299 million years ago) — Mascot: Meganeura — The Carboniferous is also known as “The Coal Age.” Land life proliferates and primitive reptiles appear. Giant scale “trees” dominate the lush landscape, and insect life balloons to truly gigantic proportions. Its name meaning “large-nerved” in Greek, due to the system of veins running throughout its wings, the dragonfly Meganeura ruled the skies and became the first life form to take flight. Its wingspan was around three feet (1 m) wide.

(299 – 252 million years ago) — Mascot: Diplocaulus — The Permian witnessed the fusing together of all the major tectonic plates, forming the Earth’s second supercontinent, Pangea. The interior of Pangea dried out significantly from the Carboniferous. Giant finned reptiles appeared. For obvious reasons, the boomerang-domed Diplocaulus derives its name from the Greek for “double cowl,” or “double helmet.” The biggest species of this amphibian was about a yard long (1 m). They burrowed in the mud to escape drought.

(252 – 201 million years ago) — Mascot: Plateosaurus — While dinosaurs make their debut at the end of the Triassic, this period was mostly dominated by advanced crocodillians. Plateosaurus were some of the first large dinosaurs. They most likely ate plants, although some paleontologists think their sharp teeth indicate they were meat eaters. While frequently depicted as walking on all fours, Plateosaurus was probably bipedal.

(201 – 145 million years ago) — Mascot: Stegosaurus — During the Late Jurassic, dinosaur life grows gigantic, and birds appear. Originally scientists thought that a Stegosaurus’ back plates lay flat along its spine, like shingles on a roof. Thus its name, “roof reptile.” Stegosaurus armatus is the largest known of this genus, and was discovered nearby. Fossil evidence suggests that these dinosaurs started life as small as modern day kittens. An infant Stegosaurus could curl up and sleep in the hind paw track of its mother or father.

(145 – 66 million years ago) — Mascot: Parasaurolophus — Flowering plants evolved, and dinosaurs grew bigger and bigger through the middle of the Cretaceous. The end of this period witnessed the extinction of all dinosaurs except birds. With a name meaning, “near crested lizard,” Parasaurolophus was a social dinosaur using the resonating chamber in its hollow crest to bugle and communicate.

(66 – 23 million years ago) — Mascot: Uintatherium — The Paleogene was hot, wet and swampy. Uintatherium was first discovered in Utah during the 1870s, and this herbivore’s name means “Beast of the Uinta Mountains.” Uintatherium were six horned and sabre toothed, and amongst the first big mammals to appear. They have no living descendants today. Behind the Uintatherium runs a herd of Hyracotherium, early ancestors of the horse.

(23 million years ago — Present Day) — Quaternary Mascot: Mammoth — During the latter half of the Cenozoic Era, life became more familiar to modern eyes. Elephants evolved. Mammoth is the popular name for a family of extinct elephantines known as proboscideans, named for their size. The Quaternary Period saw the first humans appear. Present Day Mascots: Homo sapiens O.C. Marsh & E.D. Cope — No, these are not two hobos fighting by the back door. The Human Era is represented by two squabbling Nineteenth Century paleontologists, who famously launched the Bone Wars with their fierce scientific rivalry. It was agents of Marsh and Cope who dug up the first Jurassic giant dinosaurs in Colorado. They introduced the world to many famous prehistoric creatures, showing people how truly colossal life grew during the Mesozoic. Here Marsh and Cope tussle over an academic paper, each struggling to enter the building first.