Scientists still uncovering the mysteries of the dinosaurs

Katherine Crawford's fifth-graders at West Oak Middle School in Mundelein asked, “What kind of habitats did dinosaurs live in?”

The world was a very different place when supersized reptiles called dinosaurs dominated the earth more than 200 million years ago.

When they initially emerged, the earth consisted of one giant land mass called Pangaea, and dinosaurs weren't the predatory menaces we think of when we learn about Tyrannosaurus Rex and Triceratops.

Scientists are still uncovering the mysteries of the dinosaurs. Earliest evidence is now believed to have come from Argentina dating to 230 million years ago. A pint-size dinosaur named Eodromaeus, or “dawn runner,” recently was discovered. It was the size of a very small dog.

“The temperature was hotter, the oceans were all warm from pole to pole, there were no glaciers covering the north or south poles,” said Dennis Kinzig, a docent at the Field Museum of Natural History in Chicago. “The atmosphere had more carbon dioxide and oxygen in it than today.”

Fossils are the best tools experts use to piece together the puzzle of what the world was like in the Mesozoic era — the 165 million-year time span when dinosaurs lived.

The “Evolving Planet” exhibit at Chicago's Field Museum shows some 2,000 fossil examples of plants and animals from our distant past.

“The plants, animals, and most environments were very different back then and each specific location changed considerably over the 165 million years,” Kinzig said. “We do know there were some kinds of deserts and various kinds of forests and swamps, but not exactly like ours today. The environments all over the earth varied from warm and humid to dry, forested, swampy, and cool. They lived along rivers lakes, oceans, and swamps, mixed forests, mountains and desert plains.”

During the Mesozoic era, Pangaea split apart into separate continents.

Dinosaurs became extinct when a giant meteorite smashed into the Yucatán Peninsula in eastern Mexico shutting off sunlight and causing mass destruction of plant and animal life. Sea levels, which had been 100 feet higher than today's levels, dropped as mountains began to lift up, reducing the habitat for sea-dwellers.

One dinosaur that survived the mass extinction and has continued to adapt over the millions of years since is the bird, which likely is a distant ancestor of a small meat-eating dinosaur.