The Dinosaur Book

Henry Fairfield Osborn named Tyrannosaurus rex in 1905. Rex is the Latin word for king. It lived at the very end of the age of dinosaurs. It was one of the last of them.

Its jaws were made for crushing. Its bite was among the strongest of any land animal we know about. The teeth were thick, more like bananas than steak knives. A bite like that could go through bone.

A skeleton named Sue was found in South Dakota in 1990. About nine of every ten bones were there. Sue lives at the Field Museum in Chicago. Her bones show injuries that healed. She had a hard life and she lived through it. Scientists can count growth rings inside a bone, just like rings in a tree. The oldest Tyrannosaurus rex they have found lived to about 28.

Othniel C. Marsh named Allosaurus in 1877. The first bones were a few pieces found in Colorado. Marsh saw that the backbones were light and strange. So he called the animal different lizard. Better skeletons came later from the Morrison Formation, a band of rock across the western United States.

A famous skeleton nicknamed Big Al was found in Wyoming in 1991. About 95 percent of its bones were there. It was a young adult about 26 feet long. Its bones show 19 injuries or sicknesses. These include a broken finger and an infected foot. Scientists think it lived a hard life.

A Stegosaurus neck plate has a U-shaped hole that fits an Allosaurus snout. An Allosaurus tail bone has a healed puncture that fits a Stegosaurus spike. Scientists think Allosaurus hunted big plant eaters. It may also have eaten animals that were already dead. Skin prints show scales. Whether it had any fuzz is unknown.

Rubén Carolini found a leg bone in 1993 near Villa El Chocón in Argentina. He was an amateur fossil hunter driving a dune buggy. Rodolfo Coria and Leonardo Salgado described the animal in 1995. They named it Giganotosaurus carolinii to honor the finder. About 70 percent of the skeleton was found.

Scientists disagree about its size. Length guesses run from about 40 to 43 feet. Weight guesses range widely, from about 4 tons to nearly 14 tons. Some researchers think the biggest numbers are too high. Whether it grew longer than Tyrannosaurus rex is still debated. The skull was probably about 5 to 6 feet long.

The fossils lie in the Candeleros Formation, sandstone laid down by rivers and wind. Sources disagree on its age, from about 112 to 98 million years ago. Scientists think its bite was quick and slicing, and weaker than the bite of a T. rex. A relative named Mapusaurus was found in a bonebed. That may hint at group hunting, but scientists are unsure.

A team led by José Bonaparte dug up the skeleton in 1984 in Chubut Province, Argentina. He named Carnotaurus sastrei in 1985. The second name honors Angel Sastre, the rancher whose land held the fossil. The skeleton included a skull and much of the body. That is rare for a big meat eater.

The rock around the skeleton kept prints of the skin. They show small round scales with larger bumps along the sides. No feathers have been found. Two thick, cone-shaped horns rose above the eyes. Scientists debate how they were used. They may have been for fights with rivals, or for show.

Carnotaurus lived near coasts with river mouths and tidal flats. Its arms were tiny and its fingers were joined. Big muscles at the base of the tail suggest it ran fast. Scientists disagree about its bite. Some think it took quick bites of small prey. Others think it could bring down large animals.

Ernst Stromer named Spinosaurus in 1915. The bones came from Egypt and were found in 1912. They were kept in a museum in Munich. In 1944 a bombing destroyed them. For many years only drawings and notes were left.

In 2020 scientists reported a new tail. It was shaped like a big paddle. A tail like that would push water well. Some scientists think Spinosaurus spent a lot of time in the water. Others disagree. The argument is still going.

Long spines held up the sail on its back. Some were more than five feet tall. Scientists do not agree on what the sail did. It may have been for show. Its nostrils sat far back on its skull. That is a good place for a fish eater to breathe while its snout is in the water.

In January 1983 William Walker found a huge claw at the Smokejack Clay Pit near Ockley in Surrey, England. He was an amateur fossil collector. Experts dug up the skeleton in May and June of that year. Alan Charig and Angela Milner named Baryonyx walkeri in 1986. The second name honors Walker.

In the belly area of the skeleton were fish scales and teeth from a fish called Scheenstia. It was the first sign that a meat-eating dinosaur ate fish. Bones from a young iguanodont, a plant eater, lay there too. So scientists think Baryonyx also hunted or scavenged on land.

The long, low snout looked like a gharial's snout and had a spoon-shaped tip. The thumb claw was about 12 inches long along its curve. Size guesses run from about 25 to 33 feet. The skeleton may not have been fully grown. Scientists think it hunted near rivers and lagoons. How well it swam is debated.

In about 1940 a Navajo man named Jesse Williams found fossil bones near Tuba City, Arizona. A University of California team collected three skeletons in 1942. Samuel Welles first named the best one as a species of Megalosaurus in 1954. A bigger skeleton turned up in 1964. Welles then saw the crests and named Dilophosaurus in 1970.

Dilophosaurus lived in the Kayenta Formation, a dry land cut by rivers and lined with conifers. Small dinosaurs such as Scutellosaurus and Sarahsaurus lived there too. In 2020 Adam Marsh and Timothy Rowe studied all the known skeletons. They found one species. They also found that the skull and jaws were stronger than earlier studies said.

The crests were thin, so scientists think they were for show. Air spaces inside the skull ran into them. Scientists think the animal may have puffed them up. The movie Jurassic Park gave it a frill and venom. No fossil shows either one. One researcher thinks a resting mark in Massachusetts shows feathers from a similar animal. Others say it is just mud.

Edward Drinker Cope described the first Coelophysis bones in 1887. He named the genus in 1889. The name means hollow form, for its hollow limb bones. The first fossils came from New Mexico. Coelophysis was a small, quick hunter with a long neck and tail. Many early dinosaurs were small like this one.

In 1947 a fossil crew worked at Ghost Ranch in New Mexico. George Whitaker found fragments in June, including a claw. Edwin Colbert led the dig and knew it was Coelophysis. The crew uncovered a huge bone bed, now called Whitaker Quarry. Skeletons lay piled together. Scientists have found hundreds, and perhaps more. Only some are fully cleaned, because the work is slow.

Scientists once thought some Coelophysis ate their own young. They saw small bones inside one adult. Later studies said those bones came from other reptiles. The idea is still debated. In 2009 a team reported small Coelophysis bones in a mass the animal may have coughed up. A Coelophysis skull also flew on Space Shuttle Endeavour in 1998.

The first bones were noticed by Victorino Herrera in the late 1950s. He lived in the Andes of Argentina. Sources give 1958 or 1959 for the find. A scientist named Osvaldo Reig named the animal in 1963 and honored Herrera in the name.

In 1988 a team led by Paul Sereno found a skeleton with a skull in Ischigualasto. Before that, scientists knew mostly leg bones. The new find let them build the first good picture of the whole animal. Some skulls also show bite marks. Scientists think a few came from fights between two Herrerasaurus.

Scientists still argue about where Herrerasaurus fits on the dinosaur family tree. Some say it was an early meat eater of the theropod group. Others say it sits near the base of the lizard hipped dinosaurs. It is still not settled. Scientists also do not know if it had feathers. Sources also disagree on its size. Smaller animals were about 10 to 15 feet long and large ones may have reached 20 feet.

A scientist named Ricardo Martinez found Eoraptor in 1991 in the Ischigualasto badlands of Argentina. Paul Sereno was part of the team. In 1993 Sereno and three other scientists gave it a name. The name came from words meaning dawn and plunderer.

The best fossil is an almost complete skeleton. Because it is so complete, scientists can study its whole body. It was only about the size of a fox, and it weighed about 22 pounds or less. Its jaws held two kinds of teeth. The upper ones were sharp and curved. The lower ones were shaped like leaves.

Scientists do not agree on what kind of dinosaur Eoraptor was. In 1993 it was called a meat eater of the theropod group. Many studies since 2012 say it was an early cousin of the long necked giants like Plateosaurus. Its mixed teeth make some scientists think it ate both plants and animals. Others still call it a meat eater. Nobody knows if it had feathers.

A doctor named Johann Friedrich Engelhardt found the first bones in 1834 near Nuremberg in Germany. They were back bones and leg bones. A scientist named Hermann von Meyer gave the animal its name in 1837.

The biggest finds came later. Between 1911 and 1932, diggers at Trossingen in Germany found 35 complete or partial skeletons. Pieces of about 70 more were found there too. Another big site is Frick in Switzerland. Bones from well over 100 animals are known, so scientists can compare many individuals.

Here is a surprise. Plateosaurus adults were not all the same size. Some grew to about 16 feet and some to 33 feet. Scientists think food may have changed how big each one grew. Scientists also used to argue about how it walked. Today most think it stood on two legs, because its arms could not turn the palms down to the ground. One scientist has even suggested it may have eaten small animals now and then. That idea is not settled.

Elmer Riggs named Brachiosaurus altithorax in 1903. The name means arm lizard. The second name means deep chest. His crew from the Field Columbian Museum found the first bones in 1900 near Fruita, Colorado. Harold Menke spotted a huge arm bone that July. The bones now belong to the Field Museum in Chicago.

Only a few Brachiosaurus fossils are known, and the neck was not found with the first skeleton. Many pictures use a close relative named Giraffatitan, found in Tanzania. Brachiosaurus itself lived only in North America. Its fossils come from the Morrison Formation in Colorado, Utah and Wyoming. Scientists estimate it at 59 to 72 feet long. They think the first skeleton was not yet fully grown.

Scientists still argue about how it held its neck. Some think it pointed up, and others think it stayed closer to level. Most think it browsed high in the trees. The nostril position is debated too. Some scientists place the nostrils on top of the head, and others place them at the front. Brachiosaurus appeared in the 1993 film Jurassic Park.

Othniel Charles Marsh named Diplodocus in 1878. The name means double beam, for the two-pronged bones under the tail. The first fossils were collected in 1877 at Garden Park near Canon City, Colorado. That first skeleton was very broken. Marsh described it anyway. It gave scientists a first look at a long-necked giant.

John Bell Hatcher named Diplodocus carnegii in 1901, after Andrew Carnegie. Its main skeleton was found in 1899 at Sheep Creek, Wyoming. It is about 80 to 85 feet long. Carnegie paid for plaster casts that went to museums around the world. One reached London in 1905. People called it Dippy. King Edward VII had asked for a copy.

Scientists still debate how Diplodocus held its neck. Some think it stayed near level, and others think the head rose higher. Skin impressions show pointed spines up to 7 inches long, mostly on the tail. Another species, Diplodocus hallorum, may have reached 95 feet or more. It was longer than the famous skeleton, though sizes for it are still debated.

Argentine scientists Jose Bonaparte and Rodolfo Coria named Argentinosaurus in 1993. A farmer named Guillermo Heredia found the first bone in 1987. It lay on his land near Plaza Huincul in Neuquen Province. He thought it was petrified wood. A dig in 1989 found more bones. The name means Argentina lizard.

Only some bones have been found. They include back vertebrae, part of the hips, a rib and a leg bone. Scientists compare them with better known relatives to guess the rest. Estimates run from about 98 to 115 feet long. Weight guesses run from about 65 to 80 tons. Some studies give higher numbers, and those have large error ranges.

Argentinosaurus is one of the largest land animals known. Scientists do not agree on whether it was the very largest. Patagotitan and other giants may have been about the same size. Some other sauropods, such as Diplodocus, may have been longer but much lighter. A 2013 study modeled a top speed of about 5 miles per hour.

Othniel Marsh named Stegosaurus in 1877. He thought the plates lay flat across the back like roof tiles. That is where roofed lizard comes from. Later finds showed the plates stood up on edge.

Stegosaurus lived about 150 million years ago. Tyrannosaurus rex did not show up until more than 80 million years after that. Tyrannosaurus rex lived closer in time to you than to Stegosaurus. Think about that for a minute.

Its back legs were longer than its front legs. Its head hung low to the ground. It ate ferns and other low plants. Scientists still argue about the plates. Some think they were for show. Some think they helped the body warm up and cool down. One Allosaurus bone has a hole that seems to fit a Stegosaurus tail spike.

Triceratops lived about 67 million years ago. It was one of the last dinosaurs of all. Its skull could grow six to eight feet long. That is one of the biggest skulls of any land animal.

The brow horns could be about three feet long. The frill was solid bone. Some scientists think it was for show. Some think it helped the animals know their own kind. A few skulls carry healed marks that look like horn wounds.

The mouth ended in a hard beak. Behind the beak sat rows of teeth stacked in columns. Hundreds of teeth worked together like scissors on tough plants. When one wore down, another rose up behind it.

Lawrence Lambe named Styracosaurus in 1913. The name means spiked lizard. The first skull came from Alberta, Canada, in what is now Dinosaur Provincial Park. A skeleton found in 1935 was matched with that skull in 1955. Together they became the main specimen for the species. Later finds in Alberta added more skulls and skeletons.

Styracosaurus grew about 17 to 18 feet long. It stood about 6 feet tall and weighed roughly 2 to 3 tons, scientists think. Its cheek teeth formed rows that sliced plants. It likely ate low plants, though it may have knocked down taller ones. A smaller horn stuck out from each cheek.

Bonebeds in the Dinosaur Park rocks hold many Styracosaurus. Scientists think some died near a waterhole during a drought. The big frill had a job. Many scientists now think it was for display, maybe to attract mates or show who belonged to which kind. Others suggest defense or cooling. Nobody knows for sure.

Barnum Brown found the first Ankylosaurus in Montana in 1906. He named it in 1908. It lived about 67 million years ago. It was one of the last armored dinosaurs.

Bone grew right inside its skin. Those bones are called osteoderms. They covered its back, its neck and its head. Some of its close relatives even had bony eyelids. It was wide and low and it weighed several tons.

The club on its tail was made of bone knobs joined into one piece. The bones near the end of the tail were stiff, so the tail worked like a handle. Scientists have tested what a swing like that could do. They think it could break the leg bone of an attacker.

Barnum Brown and Erich Schlaikjer named Pachycephalosaurus in 1943. Charles Gilmore had described an earlier partial skull from Wyoming in 1931 under a different name. Another key fossil was a nearly whole skull from near Ekalaka, Montana. Most finds are skull parts, and few full skeletons are known. The thick dome bone makes the skulls the best known part of this animal.

Adults reached about 15 feet long, scientists think. They weighed roughly 820 to 990 pounds. The dome was about 9 to 10 inches thick. Some scientists think males rammed heads like bighorn sheep. Others think they bumped sides or used the dome to show off. Damage on some domes hints at fights. Nobody knows for sure.

In 2024 a team found a Pachycephalosaurus skull in the Hell Creek rocks of South Dakota. It is headed for the Smithsonian. Scientists think the animal was still growing. Some scientists also debate whether spiky relatives, such as Stygimoloch, were young Pachycephalosaurus. Others say they were a separate kind. The question is still open.

Jack Horner and Bob Makela named Maiasaura in 1979. It is the state fossil of Montana. It was a duck-billed dinosaur. Its wide, flat beak was good for clipping plants.

Scientists found nests, eggs and baby bones together in Montana. The nests were bowl-shaped holes about the size of a small room. They sat close together. A group of nests like that is called a colony.

The baby bones told a story. The babies in the nest had worn teeth. That means they had been chewing. Yet their leg bones were not ready for walking. Scientists think the parents brought them food. That is where the name good mother lizard comes from.

William Parks named Parasaurolophus in 1922. A University of Toronto crew had found the first skeleton in 1920 along the Red Deer River in Alberta. It was named for Byron Edmund Walker, the head of the Royal Ontario Museum board. The name means near the crested lizard, since it looked like Saurolophus.

The crest holds air tubes. Each tube runs from a nostril up the crest, turns, and comes back down to the throat. Scientists think it helped make sounds. In the 1990s Sandia National Laboratories scanned a skull from New Mexico and ran a computer model. It suggested low, rumbling calls. Others think the crest also helped animals recognize each other.

Fossils come from Alberta, New Mexico and Utah. Scientists know of three species. A baby nicknamed Joe was about one year old and had only a small, low crest. The crest grew larger as animals grew up. Scientists think it walked on four legs while feeding and ran on two. Some skin impressions show small bumpy scales.

Lawrence Lambe named Edmontosaurus in 1917. The name means Edmonton lizard. His first bones came from Alberta, Canada. Othniel Charles Marsh had named another species in 1892 under a different name. Today scientists accept two species. One lived about 73 million years ago. The other lived about 66 million years ago, just before the great extinction.

Edmontosaurus was big. Adults were about 36 to 39 feet long, scientists think. They weighed roughly 4 to 6 tons. A few huge bones hint at rare giants near 49 feet. The front of the beak had no teeth. Hundreds of small teeth sat behind it in packed rows. Worn teeth fell out and new ones pushed up. That helped it chew tough plants.

Some Edmontosaurus fossils are called mummies. They kept prints of skin before the rock hardened. One, nicknamed Dakota, was found in North Dakota in 1999 and announced in 2007. One tail fossil has tooth marks. Some scientists think a T. rex bit it and the animal healed. Other scientists disagree. The question is still open.

The first Iguanodon teeth were found around 1822 near a road in Sussex, England. The Natural History Museum says Mary Ann Mantell spotted them. Her husband Gideon Mantell studied them. The French expert Georges Cuvier first guessed they came from a fish. Gideon named Iguanodon in 1825. The teeth looked like an iguana's, only much bigger.

Early drawings put the spike on the nose. Later bones showed it was a thumb spike. In 1878 miners in Bernissart, Belgium, dug into clay about 1,050 feet underground. They found bones coated in fool's gold. Over three years workers dug up dozens of Iguanodon skeletons. It was the first look at nearly whole dinosaur skeletons.

Early scientists pictured Iguanodon standing upright with its tail dragging. Now they think the tail was stiff and held out behind. The body stayed level. It could walk on two legs or on four. Adults reached about 30 to 36 feet long and up to about 4.5 tons. Its beak snipped twigs and shoots. Its cheek teeth ground them up.

Velociraptor lived about 75 million years ago in what is now Mongolia. That land was dry, with sand dunes and seasonal rivers. Scientists first found its bones there in 1923.

One fossil is called the fighting dinosaurs. It was found in 1971. A Velociraptor and a Protoceratops are locked together in the sand. Sand seems to have buried them in the middle of the fight. They have been that way for about 75 million years.

Each foot had one big curved claw. The Velociraptor held it up off the ground while it walked. The claw was about two and a half inches long. Small bumps on a forearm bone show where long feathers once attached. Birds are living dinosaurs, and Velociraptor was one of their cousins.

John Ostrom named Deinonychus in 1969. He led a Yale team near Bridger, Montana, in 1964 and found the first of its bones. Over later summers the team dug out more than 1,000 bones from at least three animals. Earlier, in 1931, Barnum Brown had found some bones nearby, but he had not named them.

Ostrom studied the light, fast build and the big toe claw. He argued that dinosaurs were active animals, not slow lizards. His work helped start what is called the dinosaur renaissance. Deinonychus grew about 11 feet long and weighed maybe 130 to 220 pounds, though estimates vary.

Many Deinonychus teeth have been found near a plant eater called Tenontosaurus. Scientists disagree on whether Deinonychus hunted in packs. Ostrom thought the claw slashed prey. Later tests suggest it may have pinned prey down while the animal bit. No feathers have been found with it, but scientists think it had them.

Xu Xing named Microraptor in 2000. The first fossil was sold as part of a fake, and it was only later that Xu found the matching pieces. Since then about 300 specimens have been dug up in Liaoning, China. That is more than any other cousin of Velociraptor. The rocks are called the Jiufotang Formation.

In 2003 Xu and his team described the long leg feathers and called it a four-winged dinosaur. Scientists still argue about how it flew. Some think it glided from branch to branch. Newer studies suggest it could flap and fly, though not as well as a modern bird.

Fossil stomachs hold clues. One held fish scales. Others held a lizard, a bird and a mammal foot. So scientists think Microraptor ate many kinds of food. In 2012 scientists looked at tiny color-making parts in its feathers. They think the feathers were glossy black with a rainbow shine.

In 1861 a single feather was found in Germany, and Hermann von Meyer named it Archaeopteryx. That same year workers found a skeleton with feather prints near Langenaltheim. The Natural History Museum in London bought it in 1862. It appeared just two years after Charles Darwin published his big book on evolution.

The Berlin specimen turned up around 1874 near Eichstatt. It is one of the best, with clear wings, teeth and a long tail. The fossils come from the Solnhofen limestone of Bavaria. Back then the area was a warm lagoon dotted with small islands. Archaeopteryx grew up to about 20 inches long.

Scientists still argue about how well it flew. Its feathers had uneven sides, which helps with flight. Some studies say it flapped and flew. Others say it glided and flapped only a little. In 2011 scientists studied the first feather and said it was probably black. Many scientists now call it a dinosaur.

Johann Wagner named Compsognathus longipes in 1859. The first skeleton came from fine limestone in Bavaria, Germany. A doctor named Joseph Oberndorfer owned it. Nobody knows exactly when or where it was dug up. Scientists think it was found in the 1850s. The collection moved to a Munich museum in 1866. Its French cousin was found around 1971.

That German skeleton is about 2 to 3 feet long. Scientists think it was a young animal. Small lizard bones lay in its belly area. A second skeleton, found in France around 1971, is bigger at about 4 feet. Its belly also held bones of small lizard-like animals. So scientists think Compsognathus hunted small, quick prey.

The scientist Thomas Huxley compared Compsognathus with Archaeopteryx. He called it a bird-like reptile. That helped make it famous. No feather prints have been found with it. Some relatives in China had fuzz. Some scientists think Compsognathus had scaly skin. Artists have to guess. Its true look is still open.

Gallimimus was named in 1972 by Halszka Osmolska, Ewa Roniewicz and Rinchen Barsbold. The first skeleton turned up in 1964 in the Gobi Desert of Mongolia. A Polish and Mongolian team found it. It lay on its back with the skull tucked under the hips. The rocks are called the Nemegt Formation.

An adult grew about 20 feet long and weighed roughly 900 to 1,100 pounds. Scientists also found young ones. One youngster was only about 7 feet long. Several skeletons were found close together. Some scientists think Gallimimus may have lived in groups, though that idea is still being tested.

What did it eat? Scientists disagree. Some think it snapped up small animals. Others think it browsed on leaves and tough plants. A 2019 study suggested it ate more plants than its cousins did. Its name says chicken mimic, yet it was no close relative of chickens or ostriches. It only looked a bit like an ostrich.

The first bones were found in 1948 by a Soviet and Mongolian team in the Gobi Desert. Evgeny Maleev named Therizinosaurus in 1954. He only had three giant claws. He guessed they belonged to a huge turtle-like sea animal that raked up seaweed. Later finds of arms and legs showed it was a dinosaur.

Scientists still know it from only a few pieces, mostly claws, arms, legs and some other bones. So any full picture is partly a good guess. Estimates say it grew about 30 to 33 feet long and stood maybe 13 to 16 feet tall. Weight guesses run from a few tons to around 6 tons.

Close cousins such as Beipiaosaurus from China had feathers, so scientists think Therizinosaurus had some too. No feather has been found with it yet. Scientists think the claws were better for hooking plants than for fighting. They may also have been used to show off or look scary.

Pteranodon lived about 85 million years ago over a sea that covered the middle of North America. Its fossils turn up in Kansas. The sea is gone now. The chalk it left behind is still there.

Its wings spread up to about 20 feet. Its bones were hollow with very thin walls. That kept it light. A long crest stood out from the back of its head. Some scientists think the crest was for showing off.

Pterosaurs were the first animals with a backbone to fly under their own power. Birds came later. Bats came later still. Pterosaurs were not the ancestors of birds. Birds came from a different branch of the family tree. Birds are living dinosaurs. Pteranodon was not a dinosaur at all.

A doctor found the first Elasmosaurus bones in Kansas in 1867. Edward Drinker Cope named it in 1868. Then he made a mistake. He put the head on the end of the tail. Another scientist saw it right away. The mistake became one of the most famous in science.

Its neck was about half the length of its body. It had four flippers like big paddles. It swam with them the way a sea turtle does. It ate fish and other small sea animals. Some of its close relatives were found with stones in their stomachs.

Elasmosaurus was a plesiosaur. It was not a dinosaur. It lived in the same sea that Pteranodon had flown over, a little earlier. That sea once covered Kansas. Today farms and wheat fields lie where it was.

In 1764 workers in a chalk mine near Maastricht, in the Netherlands, found a huge skull. People argued about what it was. French soldiers carried it to Paris about 1795. A scientist named Georges Cuvier studied it. In 1808 he said it was a giant lizard of the sea. That idea was new then.

William Conybeare gave it the name Mosasaurus in 1822. It had flippers. Its tail ended in a big fin. It breathed air. It had a second row of small teeth on the roof of its mouth. That helped it hold slippery prey.

Mosasaurs were close cousins of snakes and monitor lizards. They were not dinosaurs. They died out about 66 million years ago, in the same disaster that ended the dinosaurs.