The story begins with the PreCambrian SuperEon, the first four billion years of Earth's history, when the planet formed in the solar system. This period includes the Hadean Ion, the Archean Eon, and the Proterozoic Eon. There are many interesting facts about this time such as during the Hadean Ion the moon was close to fifteen times closer to Earth, during the Archean Ion the oceans were much saltier than they are today, and during the Proterozoic Eon the first mega continent formed. It was during the Proterozoic that the Great Oxygenation Event occured.
Life before the dinosaurs in the Paleozoic Era began to colonize land. The Paleozoic Era has been divided into six geological periods: Cambrian, Ordovician, Silurian, Devonian, Carboniferous, and Permian. The Cambrian saw many new life forms develop. This has been termed the Cambrian Explosion in which creatures with the first backbone, the first lungs and the first legs appeared. The Ordovician saw a huge increase in biodiversification, now termed the Ordovician Biodiversification Event that saw the development of jawless fishes, tentacled cephalopods and starfishes. The Late Ordovician experienced a mass extinction event, the first of five such events to occur in geological history. The Silurian Period was a relatively quiet time during which fish continued to evolve.
In the Devonian Period much of the Earth's continents covered by warm, shallow seas." It was the age of fishes and coral reefs. A second mass extinction event, the Late Devonian mass extinction occurred but its cause is unknown. The Carboniferous Period saw swamps and rainforests proliferate. The oxygen content of Earth's atmosphere was also very high at this time as carbon was trapped in the plants and trees. The largest terrestrial invertebrate to ever live, Arthropleura millipede which was eight feet long, inhabited the swamps of the Carboniferous Period.
The Permian Period saw the formation of the giant supercontinent Pangea, surrounded by the global ocean called Panthalassa. Reptiles thrived in the arid, warm interior of the continent. The Permian-Triassic mass extinction event closed out this period.
The Mesozoic Era was the age of the dinosaurs. Three periods have been designated in the Mesozoic: the Triassic, Jurassic and Cretaceous. The Mesozoic Era began with the worst mass extinction and would end with the devastation of an asteroid impact. Earth had no polar ice caps as the planet was very warm. A day in the Mesozoic Era was twenty-three hours.
The Triassic Period saw the development of a new branch of reptiles - the archosaurs that included the dinosaurs. They were not the large creatures expected but were small. The Jurassic Period saw Pangea begin to break apart due to tectonic activitiy. During this time, it became two separate continents, Laurasia and Gondwana. Rainforests replaced the arid deserts of Pangea, providing a significant source of food for dinosaurs. The Cretacious Period was the climax of the dinosaur's reign. Tyrannosaurus rex the apex predator on land, azhdarchid pterosaurs in the air and Mosasaurus in the oceans. An asteroid impacting the Yucatan Peninsula of Mexico would end their reign.
The beginning of the Cenozoic era, the three main mammal groups were already established. These were the monotremes (egg-laying mammals), marsupials (mammals that birth live young and carry them with a pouch), and placentals (mammals who give birth to live young from the womb). During the Cenozoic Era, Earth developed large polar ice caps. There were three periods in the Cenozoic Era: the Paleogene Period, Neogene Period and Quaternary Period.
The Paleogene Period saw large fluctuations in climate. This period was one of mountain building with the creation of the Rocky Mountains and the Himilayan Mountains.
During the Neogene Period the abundance of grasslands saw mammals adapt to running from predators. Early hominids began to evolve to walk upright. The Panama Land Bridge connecting North and South America developed during this time. This land bridge allowed animals and plants to inhabit new areas in what has been called the Great American Biotic Interchange. It also separated the Atlantic and Pacific Oceans, changing ocean currents and weather patterns.
The Quaternanry Period was dominated by multiple ice ages. Animals adapted by becoming large and furry and were known as megafauna. They included mammoths, woolly rhinos and saber-tooth tigers. Modern humans evolved during this period and migrated to all areas of the planet. Humans transformed Earth's ecosystems.
Finally, the Holocene Epoch which represents the last eleven thousand years of Earth history, is the time in which humans formed civilizations.
Discussion
Dinosaurs is a colourfully illustrated and engaging large picture book that offers a detailed summary of the evolution of life on Earth. The title is somewhat misleading as the book's focus is more on geological history rather than exclusively on dinosaurs.
After providing some information on important concepts that will be encountered in the book, Ignotofsky launches into descriptions of life during each of the geological eras and their periods. After introducing each period of geologic time life is described in more detail through several features. The Land and Sea provides an overview of each period and there is also a Fun Facts section. For example, in the Devonian Period Fun Facts, the Australian lungfish which has gills and lungs is featured. Each section also has a fascinating "Stories of Discovery" section which highlights various important discoveries relevant to that geologic time period. Some of the features include the Canadian Burgess Shale, and discoveries in the Silurian rocks near the village of Chuanhegai in China, and on Ellesmere island in the high Arctic of Canada. Once the story moves into the Mesozoic Era, life on Earth is divided into two sections, Life on Land, and Air and Sea.
Each geologic period has a Creature Feature which describes some of the life in that period, hopefully based on fossil evidence, although Ignotofsky doesn't specify what is the basis for the descriptions and illustrations. Nevertheless, this makes for a very interesting part of the book.
Overall, Dinosaurs is a very well done, well-written with many interesting facts, colourful illustrations with a well thought-out layout. But there is just so much information, much of it very detailed, that it is questionable as to what age this will appeal to. For younger readers, the visuals will be most appealing, especially the Creature Feature secction, but the large amount of text, most of it in very small font to accomodate the amount of information may feel daunting. Nevertheless, this adult with a background as a geologist found it very appealing!
Book Details:
Dinosaurs by Rachel Ignotofsky
New York: Ten Speed Press 2025
127 pp.
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