Archimedes
Productid
Meanwhile, back on dry land, the surface of the continent was continuing to buckle and twist. As the Appalachians were thrust upwards, land in the center of the craton was forced to rise along with them. A broad plain formed along the edge of the eastern highlands, sloping gently toward the western sea. When the waters receded, this coastal plain extended all the way west to present-day Alberta and Texas. And even when the sea rose up and flowed across the land, the eastern margin of the plain (roughly from present-day Manitoba south to Kansas and Missouri) was now high enough to escape all but the most severe flooding.
A new frontier for life was emerging not only in North America but on the other continents as well. Land plants, which had put in their first appearance some millions of years before, had never made much of a showing. But as stable new habitats became available, the evolutionary tree began to bud and sprout with explosive energy, producing more and larger species of land plants than ever before. In time, the soggy, boggy landscapes left by the retreating oceans were filled with riotous jungles of giant sphenopsids, or scouring rushes, tree-sized ferns, and leafy conifers. These tremendous swamps, which flourished between about 355 million and 300 million years ago, disappeared soon afterward, probably as a result of a cooling and drying trend in the climate. Buried where they fell—in modern-day Iowa, Missouri, and Kansas, among other places—the swamp plants eventually turned into coal, the characteristic rock of the Pennsylvanian, or Upper Carboniferous, Subperiod.
Through much of the next 50 million years (the Permian Period), the land shriveled in the sun. Swamps decayed, seas shrank, and the exposed plains along the west coast blew with sand and salt. But life was not to be stopped. Insects, which had dominated the wetlands of the Carboniferous, now gave rise to new dry-land forms such as beetles and the distant ancestors of crickets and grasshoppers. Amphibians, too, crawled out of the swamps and began to invent the technology they needed for life on the land—notably a soft-shelled, amniotic egg that could develop out of the water. In time, new life-forms developed that could live their whole lives on land, including massive, lizardlike creatures known as stem reptiles. Basking alongside these primitive organisms on the arid coastal plains were their near-relatives, the synapsids—the direct ancestors of modern mammals. At the root of our family tree is Dimetrodon, a burly, fin-backed synapsid with two stabbing canine teeth, which it used to snap up slow and unwary amphibians. We know these creatures once roamed the savannas of the western plains because wonderfully preserved skeletons of Dimetrodon and many of its equally bizarre contemporaries have been dug out of Permian “red bed” deposits in New Mexico, Texas, and Oklahoma.
So it is that we find ourselves near the end of the Permian, watching a lumpish, beaked synapsid called Kannemeyeria breaking off the tough stem of a broad-leafed conifer somewhere along the west coast of Texas. Under our feet lie the accumulated sediments of 3.5 billion years, or more than 90 percent of the geological timeline. Yet except for the wide spread of the horizon, there is little in this scene to put us in mind of the modern prairies. No grass, no gophers, no pronghorns, no playas or sloughs. Something radical will have to happen to create the landscape that we see around us today. Something revolutionary.
> FOSSIL SUNBEAMS
The modern world runs on energy that originally beamed down from the sun millions of years ago. During the eons when tropical seas lapped over the North American plains, the sun provided heat and light to sustain a thick, salty soup of algae, bacteria, and other simple forms of life. Some of these tiny creatures were capable of photosynthesis, using energy from the sun, along with carbon dioxide and hydrogen, to form glucose. When these organisms (and the others that relied on them for food) died, their energy-rich remains filtered down to the ocean floor, sometimes in and around abandoned reefs and shell middens. Here, entombed in layers of clay, they were eaten and partially digested by bacteria. Eventually, time and heat completed the transformation of solar energy into crude oil. As the black muck migrated through porous layers of rocks, it eventually found its way into reservoirs, where it collected. The pump jacks at work on the plains today are sucking up wealth that was created between 450 million and 100 million years ago.
> FOSSIL HOT SPOTS ON (AND NEAR) THE PRAIRIES
> AGATE FOSSIL BEDS NATIONAL MONUMENT, Gering, Nebraska, features fossils of rhinos, bear-dogs, land beavers, and other animals that lived on the savannas about 20 million years ago.
> BADLANDS NATIONAL PARK, Interior, South Dakota, is rich in fossil mammals, including early rhinos, horses, pigs, and camels that date to between 23 million and 37 million years ago. A much older Tyrannosaurus rex skeleton, nicknamed Sue, was found nearby.
> BURGESS SHALE, Yoho National Park, Field, British Columbia, contains a stunning sample of the sea life that would have flourished on the plains (then the continental shelf) just over half a billion years ago.
> DINOSAUR PROVINCIAL PARK WORLD HERITAGE SITE, Patricia, Alberta, provides access to a stretch of the Red Deer Valley from which the skeletons of more than three hundred Cretaceous dinosaurs have been recovered. Many of them are housed in the Royal Tyrrell Museum of Paleontology in Drumheller, Alberta.
> DINOSAUR NATIONAL MONUMENT, near Dinosaur, Colorado, and Jensen, Utah, preserves the remains of Jurassic dinosaurs—the original Jurassic Park.
> GUADALUPE MOUNTAINS NATIONAL PARK, Salt Flat, Texas, features a 250-million-year-old reef that once lay on the bottom of the sea and now towers over the deserts and plains of west Texas.
> HOT SPRINGS MAMMOTH SITE, Hot Springs, South Dakota, contains the fossilized remains of at least fifty-two mammoths and other Ice Age creatures.
> LUBBOCK LAKE LANDMARK, Lubbock, Texas, preserves evidence of human activities (including hunting) over the last 11,500 years.
> PICKETWIRE CANYONLANDS DINOSAUR TRACKSITE, Commanche National Grassland, near La Junta, Colorado, still bears the imprint of dinosaurs that plodded through the mud 150 million years ago.
> T-REX DISCOVERY CENTER, Eastend, Saskatchewan, focuses on one of the most complete Tyrannosaurus fossils ever uncovered.
> WYOMING DINOSAUR CENTER, Thermopolis, Wyoming, is devoted to the study of Jurassic dinosaurs, such as Allosaurus and Diplodocus.
Beaked synapsid
Dimetrodon
Terrible Lizards
The Permian Period ended in a biological catastrophe—the most severe mass extinction in all of geological history. During a period of several million years, over 95 percent of all the species living in the oceans