Dinos as you have never known them

kw: book reviews, nonfiction, science, paleontology, palaeontology, dinosaurs, mesozoic era

For at least a little while my hunger to know "everything" about dinosaurs has been satisfied! I just read The Rise and Fall of the Dinosaurs: A New History of a Lost World by Steve Brusatte. What an amazing book, and it is not enormous as you might expect: a mere 404 pages, index included.

I used to think of the earliest dinosaurs as Dimetrodons or something similar, but they were not ancestral to dinosaurs. Note the splayed legs, like a lizard or crocodile. Dinosaurs had legs under the body like a mammal or bird. These were Synapsids, and one small branch of that order that survived the great Permian extinction went on to give rise to mammals, while a different order altogether became the proto-dinosaurs.

The drawing of a Coelophysis (pronounced "seal-off-a-sis") shown here, from the opening of Chapter 2 of Rise and Fall, represents an early dinosaur, but not the earliest. These critters lived somewhat late in the Triassic, and gave rise to birds, which are the survivors of dinosaurs. That robin, cardinal or jay out in the yard? Just your everyday dinosaur!

Note how the hind legs of Coelophysis are attached to the body similarly to the legs of a chicken. Of course, the forelegs do not have the range of motion of the wings that came along much later.

A note on geologic time. Three big Eras divide up the last 541 million years:

1. Paleozoic (Old Life) Era, from 541-252 million years ago
2. Mesozoic (Middle Life) Era, from 252-66 million years ago
3. Phanerozoic (Recent Life) Era, since 66 million years ago

Each era has a few Periods. The last period of the Paleozoic Era is called the Permian, and ended with a terrible ecological catastrophe, probably caused by enormous and long-lasting eruptions of lava in the middle of Asia. More than 90% of all species went extinct, and more than 99% of all living things died. Among those that survived were some synapsids (the mammal ancestors) and a few groups of "saurians" (lizardlike animals) two groups of which became the dinosaurs about 10 million years after the end-Permian extinction event.

The three periods after the Permian, that make up the Mesozoic Era, are the Triassic, the Jurassic, and the Cretaceous. Dinosaurs were present from early in the Triassic until another disaster caused by the crash of a mountain-size asteroid killed off at least 70% of all species (on land at least) and more than 90% of all land-based living things. Certain smaller dinosaurs, the birds, survived into the Phanerozoic and from them all the 10,000 or more species of bird we see around us today have evolved.

That isn't really a summary of the book, just an introduction to its landscape in time. I have read portions of the book over the past few years because they were published in briefer form as articles in Scientific American, to which I subscribe. Dr. Brusatte is one of the talented young scientists of a generation about half my age, that are discovering new dinosaurs at the rate of about one per week, describing not only the animals but the environments they lived in, and in books such as this, presenting them to the public.

As the author describes, he has been present to witness or participate in some of the scientific revolutions that produced this comprehensive view of the true "Age of Dinosaurs", which is still going on! The first ones evolved about 243 million years ago, and though they did not become dominant until the latest Triassic or very early Jurassic period, they then remained dominant until the asteroid came along to level the playing field.

So, although today we speak of the "Age of Mammals", and the largest creatures now living are indeed mammals, there are about 5,400 species of mammals now in existence, and slightly more than 10,000 species of birds. We cannot count our modern dinosaurs out; they outnumber mammals two-to-one. And, if you ever tangle with an Emu or Cassowary, you'll get a taste of what life was like for mammals when dinosaurs ruled the land. Though our son was nearly four when he met an Emu willing to be hand fed, I suspect he hasn't forgotten this "dinosaur encounter"!

The author devotes two chapters to the development and life of tyrannosaurs. They are the iconic theropods, and theropods are ancestral to birds. The ultra-famous Tyrannosaurus rex probably had feathers, although it may have had just a smattering of them, the way an elephant or rhino has a few tufts of hair. A large animal doesn't need much insulation from the cold. Interestingly, dynamic analysis of specimens of Tyrannosaurus that were of different ages shows that the younger ones were better runners, while their huge elders were not as fast, and operated more by stealth and ambush. It makes me wonder, though, how well stealth works when you're roughly twice the size of an elephant.

I cannot close without mentioning the many micro-biographies of the people—dinosaur hunters, paleo-ecologists, and others—that have over the past centuries pieced together the evidence for the amazing lives and living of the dinosaurs. The book has a larger "cast" than most novels, and introduces them to us in all their variety (and scientists come in all varieties!).

If you read only one book about dinosaurs this year, read this one.