2005-01-07 / Columnists

Drawing On Science

by Stephen Yaeger

I am asked many questions about dinosaurs, most from my granddaughter, Brianna and my nephew, Nicholas. I suspect that both or one of them is going to be a paleontologist, a fossil hunter. A number of other kids, as well as adults, have also asked about dinosaurs. So, I thought, “Why not try to answer some of their questions before I am asked.”

During what is known as the Mesozoic (meh-so-ZOH-ik =“middle animal”) Era, dinosaurs ruled the earth. The Mesozoic Era is divided into three geologic periods. The first dinosaurs appeared during the first of these periods called the Triassic Period. The Triassic began 230 million years ago. From that time dinosaurs ruled the earth for 165 million years through the Jurassic and Cretaceous Periods. During each of these geologic periods different types of dinosaurs lived. When you see a science fiction movie about dinosaurs you may see Stegosaurus fighting with Tyrannosaurus. This would not have been possible because Stegy was long dead when Mr. T appeared on earth.

Dinosaurs are divided into two groups. Without getting too scientific let’s just say that one group had hipbones, which were typically reptile-like. The other group of dinosaurs had hipbones very much bird-like. The guys that had reptile type hips included the large plant eaters like Triceratops (try-CEH-rah-tops) and the ferocious two-legged meat eaters like Tyrannosaurus Rex (TIE-ran-oh-SAW-rus recks =“king of the tyrant lizards”). The bird-hip guys included only plant eaters like Camptosaurus (CAMP-toe-SAW-rus =“bent lizard”), and Stegosaurus (STEG-oh-SAW-rus =“roof lizard”).

Dinosaurs came in all sizes. Based on a complete skeleton, the largest dinosaur was Brachiosaurus (BRACK-ee-oh-SAW-rus =“arm lizard”), which reached a length of 90 feet and a height of 40 feet (about as high as a four story building). Some pieces of bones have been found belonging to dinosaurs that may have been two times larger than Brachiosaurus! The smallest dinosaurs were not much larger than chickens. Compsognathus (COMP-sog-NAY-thus =“pretty jaw”) was about 3 feet long and weighed about 6 pounds. The longest dinosaur was Seismosaurus (SIZE-mo-SAW-rus =“earthquake lizard”). This guy was some 170 feet long! The Velociraptors of the movie “Jurassic Park” were shown larger in size than they really were. Real Velociraptors were a bit larger than chickens.

Some scientists believe that the dinosaurs were warm-blooded like humans and birds. The very large dinosaurs may well have been warm- blooded. Large body size would support this belief. The largest animals today are all warm-blooded. Think of elephants and whales. Other scientists say that they were cold-blooded like fish, amphibians, and reptiles. But without real dinosaur muscles and organs, it is hard to tell.

Scientists can determine how fast a dinosaur ran. They do this by comparing footprints of modern animals with fossil prints of dinosaurs. Based on these comparisons it might have been possible for a human to outrun some dinosaurs. Again, if you saw the Jurassic Park movie you might recall the part where T-Rex was chasing the jeep. It is possible that T-Rex may not have been a very fast runner and the characters did not need the jeep to outrun the guy. But then, who knows?

The size of a dinosaur’s heart would have depended on the size of the animal. A large dinosaur would need a large heart, because the blood would have to be pumped harder (and higher in the case of the long-necks) to reach all parts of its body. Maybe dinos such as Brachiosaurus had special pumps in their necks to help raise the blood to the head. Because only fossil bones survive, the color of dinosaur skin cannot be determined. But we can look at the color of present day animal skins to guess what a dinosaur’s skin color may have been. Many animals today camouflage themselves. They blend in with their environment. There’s no reason, then, to believe that dinosaurs did not have the same adaptation. Some dinosaurs may very well have been camouflaged for protection. Their skin color may have ranged from green, to red, to pale blue or some combination of colors. Armored guys like Euoplocephalus (YOU-plo-SEF-al-us) did not need camouflage. It had horn-like bones sticking out of its head, back, and sides. It also had a tail with a humongous club at the end. Imagine getting hit with that thing!

The longest named dinosaur is Micropachycephalosaurus (MY-cro-PACK-ee-SEF-ah-lo-SAW-rus =“little thick-headed lizard”). The shortest named dinosaur is Minmi (MIN-mee). By the way dinosaur means “terrible lizard.” The Greek word saurus is translated as lizard, but reptile is a more accepted description today. Wherever I’ve used “lizard” you should read “reptile.”

So, why did dinosaurs disappear? There are a number of theories trying to explain the extinction, but one theory is highly accepted today. This is known as the K-T Extinction (K=kreide German word for chalk and T for Tertiary Period). In 1980 two scientists said that an asteroid collided with earth. The asteroid crashed into what is known as the Yucatan Peninsula in the Gulf of Mexico. This impact was so huge that it sent clouds of black dust and debris high into the atmosphere blocking out the sun. The impact caused tsunamis, earthquakes, severe storms, very high winds, chemical changes including acids in the atmosphere, and wiped out many plants and animals. Earth’s temperatures dropped many degrees making it too cold for the warmth-loving dinos. Even volcanic eruptions might have occurred. Without enough plants the surviving plant-eating dinosaurs died out followed by the meat eaters. Only a few small plants, small mammal-like animals, and reptiles such as crocodiles survived. This end of the dinosaur age brought on the Age of Mammals. That’s why we’re here now and don’t have to worry about those big guys. After all would you walk down the street if a T-Rex were looking at you—kind of hungry-like?

Some scientists feel that the dinosaurs did not really die out. They believe that your friendly neighborhood birds are living representatives of dinosaurs. Now, if birds are dinosaurs here are three questions to think about:

1) Why would some scientists think that birds are dinosaurs?

2) What would be the largest dinosaur living today?

3) What would be the smallest dinosaur living today?

If you would like to know the answers, or you think you have the answers e-mail me at the address below. I’ll let you know either way. Questions/comments? E-mail Steve: Drawingonscience@aol.com

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