A hundred million years ago, dinosaurs inhabited a wide range of geographical areas, ranging from dense forests to dusty plains to dry deserts. Here's a list of the 10 most important dinosaur habitats of the Mesozoic Era.
The vast, windswept plains of the Cretaceous period were very similar to those of today, with one major exception: 100 million years ago, grass had yet to evolve, so these ecosystems were covered with ferns and other prehistoric plants. As you might expect, these plains were populated by herds of herbivorous dinosaurs (including ceratopsians, hadrosaurs and ornithopods), interspersed with a healthy assortment of the large, hungry theropods that preyed on them.
Wetlands are soggy, low-lying plains that have been flooded with sediments from nearby hills and mountains. Paleontologically speaking, the most famous wetlands were the ones that covered much of modern Europe during the early Cretaceous period, yielding numerous specimens of Iguanodon, Polacanthus and the tiny Hypsilophodon. These herbivorous dinosaurs fed not on grass (which had yet to evolve) but more primitive plants known as horesetails.
3. Riparian Forests
A riparian forest consists of lush trees and vegetation growing alongside a river or marsh; this type of habitat provides ample food for its denizens, but is also prone to periodic flooding. The most famous riparian forest of the Mesozoic Era was located in late Jurassic North America, and is known today as the Morrison Formation--a rich fossil source that has provided numerous specimens of sauropods, ornithopods and theropods, including the giant Diplodocus and the fierce Allosaurus.
4. Swamp Forests
Swamp forests are very similar to riparian forests (above), with one important exception: the swamp forests of the late Cretaceous period were matted with flowers and other late-evolving plants, providing an important source of nutrition to huge herds of duck-billed dinosaurs. In turn, these "cows of the Cretaceous" were preyed on by smarter, more agile theropods, ranging from Troodon to Tyrannosaurus Rex.
Deserts present a harsh ecological challenge to all forms of life, and dinosaurs were no exception. The most famous desert of the Mesozoic Era, the Gobi of central Asia, was prowled by three very familiar dinosaurs--Protoceratops, Oviraptor and Velociraptor. In fact, the fossil of a Protoceratops locked in combat with a Velociraptor was preserved by a sudden, violent sandstorm one unlucky day during the late Cretaceous period!
Lagoons--large bodies of calm, tepid water trapped behind reefs--weren't necessarily more common in the Mesozoic Era than they are today, but they're overrepresented in the fossil record (because dead organisms that sink to the bottom of lagoons often become preserved in silt). The most famous prehistoric lagoons can be found in Europe; for example, Solnhofen in Germany has yielded numerous specimens of Archaeopteryx, Compsognathus and assorted pterosaurs.
7. Polar Regions
During the Mesozoic Era, the North and South Poles weren't nearly as cold as they are today--but they were still plunged in darkness for a significant portion of the year. That explains the existence of Australian dinosaurs like the tiny, big-eyed Leaellynasaura, as well as the unusually small-brained Minmi, a presumably cold-blooded ankylosaur that couldn't fuel its metabolism with the same amount of sunlight as its relatives up north.
8. Rivers and Lakes
Although dinosaurs didn't actually live in rivers and lakes--that was the prerogative of their marine reptile cousins--they did prowl around the edges of these bodies of water, sometimes with startling results, evolution-wise. For example, some of the biggest theropod dinosaurs of South America and Eurasia--including Baryonyx, Spinosaurus and Suchomimus--fed primarily on fish, to judge by these carnivores' long, crocodile-like snouts.
The world's continents were arranged very differently 100 million years ago than they are today, but their lakes and shorelines were still studded with tiny islands. The most famous example is Hatzeg Island in present-day Romania, which has yielded the remains of the "dwarf" titanosaur Magyarosaurus and the unusually "basal" ornithopod Telmatosaurus. Clearly, millions of years of confinement on island habitats had a pronounced effect on dinosaur body plans!
Like modern humans, dinosaurs enjoyed spending time by the shore--but the shorelines of the Mesozoic Era were located in some very odd places. For example, preserved footprints hint at the existence of a vast, north-south dinosaur migration route along the western edge of the Western Interior Sea, which ran through Colorado and New Mexico. Carnivores and herbivores alike traversed this well-worn path, probably in pursuit of more ample food.