Q. There are many theories about why dinosaurs became extinct. Which one do YOU think is right?

A. I wasn't there, but I guess that the asteroid which crashed into the Gulf of Mexico didn't help, but I think the weather was getting more extreme anyway; perhaps diseases were spreading across newly united continents; perhaps volcanoes were erupting and many other factors we don't even know about might have contributed to the death of dinosaurs.

Q. Is it possible mammals evolved from dinosaurs like birds did?

A. Mammals evolved from reptilian ancestors long before dinosaurs did — mammals were alive all through dinosaur time but never grew bigger than a house cat while dinosaurs were ruling the earth.

Q. How did Dilophosaurus protect its young?

A. We don't know anything about the behavior of Dilophosaurus since we've only found a few single skeletons. Other meat-eaters such as Oviraptor cared for their eggs and have been found on the nest, so perhaps Dilophosaurus did too.

Q. What were the rarest dinosaurs?

A. We don't know which dinosaurs were the rarest in life. The ones we know least of as fossils include MOST dinosaurs — since we know most from only a single tooth or bone. Among the most bizarre mystery dinosaurs is Deinocheirus, known only from two huge arms — the arms are 8 feet long, but we have no idea what this Mongolian meat-eater looked like or how it behaved.

Q. Why were dinosaurs so big?

A. Some dinosaurs were NOT big, and others were huge. The average size of a dinosaur was about the same as a station wagon. Still, that's big compared to most animals. Perhaps the dinosaurs had better weather, air, or food than exists today — or maybe not much competition among giant animals. It's a mystery!

Q. What are the names of all the flying dinosaurs?

A. There are NO flying dinosaurs except for birds, which descended from meat-eating small dinosaurs. But there were many flying reptiles, more than 160 species, while dinosaurs were alive. These pterosaurs included giant animals with wingspans 40 feet wide!

Q. What was the last dinosaur on earth?

A. We don't know which dinosaur was the very last — Triceratops and T. rex were among the last 65 million years ago.

Q. Where did the dinosaurs'skins go when they died?

A. When dinosaurs died they usually turned to dust. Some were preserved as fossils if covered over swiftly. Sometimes, with the right conditions, the animal can be covered over so soon after death that the flesh doesn't rot right away, and the skin impression is pressed into the rock and we see the skin pattern. To date, no one has found actual dinosaur skin.

Q. What was the last year the dinosaurs were alive?

A. We know dinosaurs to have lived about as late as 65,000,000 years ago, from various sites around the world.

Q. Why didn't dinosaurs grow hair?

A. Dinosaurs didn't grow hair because only mammals grow hair (and nurse their young). Dinosaurs were related to reptiles and birds, both of which have scaly skin like dinosaurs. Some dinosaurs had feathers, but not of the same style as birds, and not for flying.

Q. Were dinosaurs endangered?

A. Dinosaurs were not endangered during most of their 163-million-year reign on the earth. Different kinds of dinosaurs came and went and sometimes just before one or another species was about go extinct, it would be endangered — a small population on the verge of disappearing.

Q. When scientists find a bone, how do they know what kind of dinosaur it came from?

A. It's often VERY hard to tell which dinosaur produced a fossil bone if you have only one bone. If the shape of the bone, or tooth, is very unusual, then it's possible to tell even what species of dinosaur — like the giant banana-sized sharp teeth of T. rex. But usually we need several bones, and best of all those from the skull, to make a clear comparison to other known dinosaurs and tell if we've found a whole new kind of animal.

Q. How many years ago did the dinosaurs live?

A. Dinosaurs lived from 228 million years ago to 65 million years ago. That's a long span of time, across three time periods — the Triassic, Jurassic and Cretaceous — of the middle time or Mesozoic Era of life's history.

Q. How big were prehistoric crocodiles?

A. Crocodile relatives grew to huge proportions in the time of dinosaurs — the largest of all was Deinosuchus, perhaps 40 feet long or more! That would make this reptile even longer than a T. rex. Deinosuchus might have eaten small dinosaurs that strayed too near the shoreline.

Q. Have you ever found footprints of a T. rex or any dinosaur?

A. Yes, I've found footprints of many kinds of meat-eaters and plant-eaters in places as far apart as the hills of western Massachusetts to the deserts of Utah and Argentina. There are THOUSANDS of dinosaurs footprints in some places! But it is hard to tell from a footprint just which species of dinosaur made the trackway.

Q. I know some scientists do not agree that it was a meteor strike that killed off the dinosaurs. What are the other theories for why they became extinct?

A. A meteor or asteroid, or more than one, probably did strike the earth at the time the dinosaurs seem to have died out. But dinosaurs seem to have been declining in number and diversity already. So maybe there were other causes, such as slow climate change, disease, or volcanic eruptions which affected weather. We just don't know and may never know!

Q. How many teeth did a T. rex have?

A. T. rex had about 50 teeth, big, thick daggers that could crunch bone and slice meat. And every time one of these teeth broke off, T. rex could grow another!

Q. If I were a dinosaur I think I'd be a pterodactyl so I could fly away from those nasty T. Rexes. What kind of dinosaur would you be?

A. Great choice, but pterodactyls are flying reptiles, not dinosaurs, from the same time period. Good idea to run from a T. rex. I'd be the T. rex and then I wouldn't have to run from anyone. Problem is I don't think I'd like to eat dinosaur meat!

Q. Do you think there could still be a dinosaur out there?

A. There are THOUSANDS of fossil dinosaurs still to be found. But if you mean finding a live dinosaur (other than a bird) I would say the chances are about as good as finding a potato in your ear. Dinosaurs have been extinct for 65 million years. If they were to survive somewhere remote from people, they would need a large enough population to breed all that time — dozens of dinosaurs! If that was so, I think by now we'd have some evidence of one. I'm happy to see them in the movies and go home knowing there are no dinosaurs under my bed!

Q. How many rows of teeth did the T.Rex have?

A. T. rex had just one row of teeth showing, with 50 teeth the size of bananas. But beneath the gum line it had more teeth starting to grow, and ready to fill in whenever it broke off one of its big teeth. It took about 18 months for a T. rex to grow a new tooth and it could do so anytime it needed to. You and I only get two sets of teeth, unless the dentist makes us more!

Q. Was T. rex considered a scavenger or a hunter?

A. T. rex was probably BOTH a scavenger and a hunter. Like lions today, hunting dinosaurs probably missed their prey most of the time. Where there were plenty of plant-eaters around, some dead, others sick or dying, it was easier for T. rex to be a scavenger than try to eat by hunting.

Q. Were any dinosaur bones found in Italy?

A. Yes, dinosaurs have been found in Italy including a small meat-eater called Scipionyx, which was recently found so well preserved that the soft insides of its throat appear to be still preserved. A few bones of a large plant-eater were also reported recently from Italy. But in Italy and most of Europe, good dinosaur skeletons are hard to find — Europe was under water much of dinosaur time.

Q. Did T.rex grow over 14.5m tall?

A. T. rex didn't stand tall like we do. It tilted on its hips, more horizontal than vertical. So it was probably about 13 meters (40 feet) long at the most, but stood about 12 feet tall or less. The only dinosaurs which we know of among meat-eaters that grew to 15 meters long were the giganotosaurs from South America.

Q. About how many dinosaurs were there?

A. Scientists have named about 800 kinds of dinosaurs in the nearly 200 years we have been identifying dinosaurs. We are finding them at a record rate now, almost one new species a month. But most dinosaurs are known from just a single tooth or bone, and many of the dinosaurs named are probably not truly different species. In time we will probably find thousands of kinds of dinosaurs, since they lived all over the world for more than 163 million years.

Q. What's the fattest dinosaur you ever heard of?

A. Dinosaurs probably weren't fat at all — they were muscular. After all they were active and didn't eat junk food, so why would they get fat. The heaviest dinosaur known is Argentinosaurus, a 100-ton plant-eater that lived 100 million years ago. It weighed as much as 20 huge elephants.

Q. What is the largest dinosaur?

A. The longest dinosaur was Seismosaurus, the "earth shaker" that measured more than 120 feet long. The tallest dinosaur was Brachiosaurus, which stood as tall as 50 feet high. The heaviest dinosaur was the 100-ton Argentinosaurus plant-eater from Argentina, of course!

Q. Why do scientists think there was a comet that wiped out the dinosaurs?

A. We don't know for sure what killed off the dinosaurs. We do know that we have no evidence of dinosaurs after 65 million years ago. We do have evidence of a large crater in the Gulf of Mexico from this time formed by an asteroid striking the earth. That asteroid, and perhaps others at that time, might have caused changes in the weather, from fires, dust, cold or hot weather, and volcanic eruptions that might have killed off the dinosaurs. Still, it is just a theory, and there might have been many other reasons, several at the same time, that could have helped wipe out the dinosaurs. But I don't think dinosaurs died from watching too much TV!

Q. How long do you think the longest Seismosaurus could be?

A. We only have one Seismosaurus and we aren't even sure from the parts we have just how big that animal grew. It could have grown, I think, to 150 feet long, much of it a long tail and neck. It certainly could have lived up to its name, "the earth shaker", since it was big enough to make the earth rumble beneath its heavy feet.

Q. How do dinosaurs brush their teeth?

A. Dinosaurs didn’t brush their teeth, and they probably had pretty foul breath. But who wants to get that close?

Q. How can they be people’s friends?

A. Dinosaurs could mow your lawn and bring in our newspapers but problem is they went extinct millions of years before grass and 64 million years before people.

Q. When Mommy lays her eggs where is the Daddy? (He wasn’t with mommy in the book we read.)

A. The Daddy could be with the Mommy or off finding other mates. Among some birds, which are close to dinosaurs, the male sits on the nest.

Q. What did they drink?

A. Dinosaurs drank dino-juice. Actually, they drank water.

Q. What do they do when they get boo-boos?

A. Dinosaurs didn’t have big band aids. They simply lived with their hurts until they healed or else got infected and caused great pain or death to the dinosaurs.

Q. Can genetic tissues be found in dinosaur fossils? If so can’t science use them to recreate dinosaurs (not dangerous ones like T.rex), just like scientists hope to recreate the mammoth?

A. Yes, we have DNA in dinosaur bone. But we have only highly degraded fragments from so long ago. I don’t think we’ll recreate dinosaurs or mammoths, for ethical reasons, the expense, and the complications.

Q. When was the first dinosaur discovered and did the person who discovered it mean to discover it or just started to dig and found it?

A. The first dinosaur discovered as a fossil was an Iguanodon tooth found by stone quarry workers in Tilgate, England, in the 1920’s. They sold it to Dr. Gideon Mantell, a local doctor interested in fossils. He identified and named Iguanodon.

Q. Do you know whether the Loch Ness monster has a relationship between the dinos and mutation or is it just superstition?

A. Loch Ness is either superstition or a mistaken large eel or other strange living creature. For a plesiosaur to survive for 65 million years it would have had to survive in a group of 50 or more hidden for all that time.

Q. Is T.rex the biggest meat eater?

A. Giganotosaurus was 47 feet long, 7 feet longer than the biggest T. rex. It lived 100 million years ago.

Q. Which dinosaur do you think is the best?

A. I don’t know what’s best but I do love Troodon — the smartest dinosaur and no bigger than a kid.

Q. Could dinosaurs come back to life?

A. We can't bring dinosaurs back to life, thank goodness! I'd hate to end up a Happy Meal for T. rex. Life wouldn't be so good for the dinosaurs now either — different weather, different plants, even different air. Jurassic Park brought them back with the idea of DNA trapped in mosquitoes and then cloned with parts of frogs. Frogs aren't closely related to dinosaurs, we don't have enough dinosaur DNA, and besides, whatever a mosquito might have sucked up 65 million years ago could have been something other than the blood of a dinosaur.

Q. How did dinosaurs pick their mates?

A. We don't know how dinosaurs chose their mates. For many animals, the female chooses among the males by the one which is fastest, strongest, most colorful, or fierce — that would be the one which might do the best job of protecting their young.

Q. How big was the first dinosaur bone that was discovered?

A. There have been dinosaur bones discovered for centuries, without knowing they belonged to dinosaurs. The first bone identified as that of a dinosaur was a foot-long chunk of a jawbone of a large Jurassic meat-eater, Megalosaurus, found in southern England in the 1820s, with teeth still in it!

Q. How many spikes did an average Stegosaurus have?

A. Stegosaurus had a dozen or more plates on its back and six long spikes on its tail. We just found out recently, thanks to some newly discovered good skeletons, that the spikes stuck out sideways from the tail of the stegosaur.

Q. What was the smallest dinosaur?

A. There were many tiny dinosaurs, and as an adult the smallest of these was the size of a large chicken. Compsognathus was a small meat-eater, probably as big as a turkey once it grew up (it was originally identified from a youngster that was chicken-sized). Heterodontosaurus, Fabrosaurus, and other plant-eaters were even smaller.

Q. What did plant-eaters like to eat the best?

A. Different plant-eaters ate different foods, which helped them live together without competing for the very same foods. Many dinosaurs ate cycads, ferns and other plants with flowers, since flowers and fruits didn't come along until late in dinosaur time. The taller dinosaurs probably ate branches and cones off of conifer trees and leaves of tall palm-tree like cycads.

Q. I am very interested in becoming a paleontologist. Can you tell me how to get started? Are there any digs that a 12 year old can go on in or near California? What college or university would you recommend for this occupation?

A. I hope you will become a paleontologist; it is a fascinating career. There are many digs run by museums that take youngsters of your age or even younger, sometimes with parents. You might try the California Academy in San Francisco or Lawrence Hall in Berkeley at the University of California or in Los Angeles at the L.A. County Museum of Natural History for programs they offer. Many colleges have excellent graduate programs, such as the universities of Texas, California/Berkeley, and Chicago. But first it's best to learn as much science, from biology to geology, as an undergraduate and to go on digs and always read and ask questions!

Q. How do we really know that the dinosaurs existed if people weren't alive back then?

A. We know about dinosaurs and many things that lived before humans from fossils. We can tell how old the fossils are by ancient magnetic patterns, changes in the seafloor over time, and by chemical testing of the rocks in which dinosaurs and other fossils are found.

Q. What color was a T. rex? Were different dinosaurs different colors?

A. We don't know what color T. rex or any dinosaurs were. Since we do know that dinosaurs were very visual animals, with large nerves and brain centers for vision, they probably responded to color and had lots of colors on them. Perhaps they had camouflage patterns for hiding in the woods if they were prey animals. Maybe they had colorful feathers too — we know some small meat-eaters had feathers. Big animals don't usually have bright colors, just as elephants and rhinos are drab today — they don't need to hide or show off. So maybe small dinosaurs were very colorful like their close relatives today, birds. And big dinosaurs might have been dull in color.

Q. What dinosaur was the meanest?

A. It's hard to so say which animal was the meanest, but I'd vote for Utahraptor. It was the largest of the slashing-clawed raptor dinosaurs, as big as an ice-cream truck. It weighed a ton but could run fast, with sharp foot-long claws, and pointy teeth in strong jaws. I'm getting scared even thinking about it!

About Dinosaur Expert Don Lessem

Born in New York, Don Lessem outgrew his initial interest in dinosaurs at age eight, and went on to become an animal behaviorist and a science journalist for The Boston Globe and many other publications. He grew into dinosaurs again at age 35, while working on journalism at the Massachusetts Institute of Technology. Reporting on dinosaur digs in Montana and Utah, he became fascinated with not only dinosaurs but their world and the scientists who study them. He has traveled to Arctic Alaska, Mongolia, Argentina, Europe and Australia in search of dinosaurs.


Lessem has written 21 books on dinosaurs, including The Dinosaur Society Dinosaur Encyclopedia (with Donald Glut), the NSTA award winning Jack Horner: Living with Dinosaurs, and Digging up Tyrannosaurus Rex (with Dr. Horner). He has also written 18 children's books about dinosaurs, including Dinosaurs to Dodos.

The company Lessem started, Dinosaur Productions, has constructed the world's largest dinosaur exhibit, including both the Giganotosaurus and the largest plant eater, the Argentinosaurus. You can find photos from the making of this exhibit in our online photo story about Argentinosaurus.

People magazine has called Don Lessem, "Mr. Dinosaur." But to many kids who love dinosaurs, he is simply, "Dino" Don.