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Evolutionary relationships and temporal occurrences of the major groups of dinosaurs, depicted in a branching diagram (cladogram). The geologic time scale (with numbers depicting millions of years ago, abbreviated as Ma) is shown on the left. The shaded bars represent time intervals for which the various groups are known. The bird-hipped dinosaurs (ornithischians) are grouped on the left, and lizard-hipped dinosaurs (saurischians) appear on the right. Although not dinosaurs themselves,...

Figure

Variation in body size within theropod dinosaurs (from top to bottom) the tyrannosaur Tyrannosaurus the hummingbird Stellula the dromaeosaur Micro-raptor the dromaeosaur Velociraptor the ceratosaur Ceratosaurus the spinosaur Spinosaurus. Human added for scale. theropods), hummingbirds qualify as the smallest members of the group. Given that a hummingbird may weigh about 0.001 kilogram, the Tyrant King was about 5 million times heavier To refer to the biggest theropods as giants doesn't begin to...

Hidden Strands

It's humbling to stand in the belly of an ancient redwood, to be enveloped by one of the largest living things on Earth. The thick trunk surrounding me on this particular day was heavily charred, its base hollowed out by some long-ago fire, leaving behind an expansive interior cavity. Fires don't ravage this forest often, at least not in the human sense. But measured in redwood lifetimes, sometimes well in excess of 1,000 years, fire is as inevitable as death. Fortunately, evolution has endowed...

Of Hornheads And Duckbills

In the summer of 1987, I was a young, eager, and naive graduate student at the University of Toronto trolling for a great research project. I was already well along the path to becoming a paleontologist and had pretty much settled on dinosaurs as my target group. In particular, I liked the idea of working either on theropods or the horned ceratopsids like Triceratops. But I still needed access to some unstudied fossils. While returning east after digging up ichthyosaurs (those dolphin-like,...

Acknowledgments

Despite the fact that dinosaurs figure prominently in popular culture, relatively few people make a career out of studying them. Many readers will be surprised to learn that only about one hundred professional dinosaur paleontologists are currently active worldwide. We are a small community, and most of us know one another. Conferences like the annual meeting of the Society of Vertebrate Paleontology offer valuable opportunities to exchange ideas and hear about the latest research. I graciously...

The River Of Life

As the first orange-yellow hues of daylight illuminated the California coast, a great horned owl flapped hurriedly past the window, presumably headed to daytime sanctuary. Stars were still plentiful. Off in the east, Venus sat perched like a beacon just above the horizon, looking more like an oncoming 747 than a planetary member of our solar system. A short time later, the sun climbed above the Marin headlands, revealing the Pacific surf pounding the rocky coastline. Above this grand...

Chapter Of Hornheads And Duckbills

Several groups of dinosaurs in particular, hadrosaurs, ceratopsids, and sauropods possess greatly enlarged noses, which may have had a thermoregulatory role, keeping the brain cool by shedding heat from warmer blood and returning cooler blood to the brain region. 2. One of the more famous examples is an innovative experiment conducted by biologist Malte Andersson on African widowbirds. Males of this species tend to have elongate tails, long thought to be useful in attracting mates. Andersson...

Chapter Jurassic Park Dreams

As of the writing of this book, the future of the visitor center at Dinosaur National Monument is in question. The building has been deemed unsafe and closed until it can be repaired. It is my sincere hope that the reopening of the building will include a reinvig-oration of the paleontology program at this famous national landmark. 2. Even for ecologists studying living plants and animals, unraveling diet and other aspects of life history is a remarkable challenge, generally resulting in...

Chapter The Way Of All Creatures

Most biologists are confident we are now in the midst of the sixth great extinction, this one precipitated by humans. See the epilogue for more on this topic. 2. I must credit two individuals, Kirk Johnson and David Fastovsky, who helped inspire my conversion to the other side of this debate. 3. Shortly after the melting of Snowball Earth, large multicellular life exploded in diversity, a coincidence that has led some workers to suggest that the two events were causally linked (Hoffman and...

The Goldilocks Hypothesis

Dinosaur physiology is ONE of the great paleontological mysteries. Were dinosaurs warm-blooded, like birds and mammals, or cold-blooded, like lizards, crocodiles and most other animals Among vertebrates, these divergent strategies are often associated with active or sluggish lifestyles, respectively. The recognition of birds as direct descendants of small, carnivorous dinosaurs makes this enigmatic question all the more intriguing. Did the warm-blooded metabolisms of birds arise after the split...

Stardust Saurians

Being both famous and extinct, dinosaurs tend to be portrayed as poster children for failure. Yet they are one of Nature's great success stories, having persisted for about 160 million years. (In contrast, primates have been around about 55 million years, our hominid cousins 7 million years, and humans a mere 200,000 years or so.) During that time, they evolved into a wondrous diversity of forms and occupied every continent, from pole to pole, becoming the dominant large-bodied land animals of...

Chapter Solar Eating

A tiny fraction of life on Earth exists entirely off the solar grid, obtaining energy from deep sea hydrothermal vents, which channel energy from within the planet. 2. Humans have become extremely adept at exploiting the solar energy stored in these fossil fuels. These ancient remains in actuality, the energy of the sun stored in solid form drive our economies and act as another pathway that returns carbon dioxide to the atmosphere. It is often stated incorrectly that fossil fuels are made from...