How to Build a Dinosaur Read Online Free PDF

history. This is not a depositional environment, for human culture or rock. The badlands erode and the people leave. The past remains. About a million acres of Garfield County are occupied by the Charles M. Russell National Wildlife Refuge. The rest is a mix of public land overseen by the federal Bureau of Land Management and private ranches. All of it is badlands, crisscrossed with a grid of gravel roads that organize what would otherwise feel truly desolate. The landscape can be beautiful when deep shadow and blinding light fragment the geometry of the gullies and bluffs. It is raw and unpolished, by people or nature.
    Leaving Jordan for fossil hunting, you take gravel, or plain dirt roads. You establish a camp, with all the amenities of the modern age that you can muster. Electronics are easier than plumbing. You can set up a satellite dish for broadband computer access. You can even webcast from camp. But outhouses are the rule. When you leave camp for the day to prospect, or dig, you leave the outhouses behind.
    Once you are in the field and you are excavating the thighbone of a tyrannosaur, you have gone millions of years back in time. You stand, with parched throat and sweat-soaked shirt, without shade or water, in the present. But you are really back in the Cretaceous, as the fossils and geology show, in a marshy river delta on the shores of a shallow sea that bisected the North American continent from the Arctic to the Gulf of Mexico.
    And you can see all this in the rocks. This readability of the earth’s past is a wonder many of us take for granted, speaking of the Cretaceous or the Jurassic, offhandedly describing the animals that lived then, the environment, the weather, temperature, and the arrangement of the continents. But our ability to look back at the past, to re-create it with some confidence, at least in broad strokes, is a wonder that far surpasses the tales told by any religion.
    We are now multiplying this wonder, adding the tales told by molecular fossils, and the history of life’s evolution written in the DNA of living animals. What we find gives us new understanding of the past, and new ways to try to reconstruct it. And some of the most astonishing finds, as has been true for at least a century, came from the Hell Creek Formation in Garfield County.

THE DINOSAURS
    To understand the place of the Hell Creek Formation in the history of life on earth it is necessary to step back a bit, perhaps not to the origin of the planet four and a half billion years ago, but at least to the beginning of the dinosaurs’ reign. By the time of the nonavian dinosaurs’ extinction, this extraordinary group of animals had already had quite a successful run.
    All of life’s history is of a piece, so it is awkward to step in at any given point. At the time of the origin of dinosaurs 225 million years ago, during the Triassic period, the big stories in the evolution of life were finished. The first hints of life appeared about 3.8 billion years before the present, and the first, most primitive soft-bodied animals not until about 650 million years ago.
    This was just before an enormous blooming of animal forms in the Cambrian period that filled the seas with wriggling, swimming, voracious life. Vertebrates evolved. And fish. About 360 million years ago animals and insects began to colonize the land. That was when the first tetrapod appeared. Tetrapods, four-limbed vertebrates, are, or should be, near and dear to us, since we ourselves are tetrapods. We are one variation on the tetrapod theme that has been sung by natural selection for several hundred million years. We may not be able to claim the antiquity of jellyfish, the variety of insects, the biomass of bacteria. But still, we have reason to take some satisfaction in how successful this basic body plan has been. Reptiles are one highly successful variation, and among the reptiles the much-beloved dinosaurs are unarguably memorable.
    We cannot point to a