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Portals to the Past

By Shelly Fischman

Posterback

Dinosaurs: Facts and Fiction

Activity

Reptiles Rule! Masters of Their Mesozoic Universe
T he"Portals to the Past" poster simultaneously portrays scenes from the late Cenozoic, Mesozoic, and Paleozoic eras along with various types of fossilization, fossil-bearing stratigraphy, and a few paleontologists. A talus slope at the base of a low cliff sets the scene. Three of the rocks in the talus provide portals to the past. Other rocks in the talus display different types of fossilization of creatures that are generally reflective of those seen in the portals.

The late Cenozoic portal is a scene with a ground sloth, zebra-type horses, mastodonts (ancient elephants), and extinct peccaries (Platygonis pearcei). A beaver is also featured staring down one of the peccaries.

A Tyrannosaurus and a Styracosaurus are prominent in the Mesozoic portal. Oblivious to the impending confrontation, a cockroach crawls along on a fern.

The Paleozoic era is represented by a Silurian sea. In the foreground of this portal, a cephalopod makes a meal of a trilobite. The background features other (straight-shelled) cephalopods and a eurypterid looking for food. Other denizens of this community include corals (both solitary and colonial), brachiopods (the Lingula still exists today!), and crinoids. 

The talus slope is a paleontologist's dream; fossils are everywhere. In the rock below the Cenozoic portal are casts and molds of Paleozoic brachiopods, gastropods, and cephalopods. The remains of Menoceras (a Miocene rhinoceros) appear just above the Mesozoic portal. Some Dimetrodon tracks are present in a rock just to their right. The mineral replacement of crinoids can be observed below the Paleozoic portal and immediately to their right, fossilized eurypterids. Moving farther to the right, in some unconsolidated gravels, are eroded and redeposited dinosaur remains: a skull, teeth, and a claw.

The cliff in the background shows the host strata of the talus: blue-gray Paleozoic limestones; multicolored rocks of the Mesozoic (with a dinosaur skeleton); and buff-colored sands, gravels, and silts of the Cenozoic. Paleontologists, hot and dust-covered, eagerly descend on the scene.

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Last updated: 11-13-2009