types of dinosaurs

Allosaurus: World's No. 1 Predatory DinosaurBy Jennifer Viegas

During the Late Jurassic, Allosaurus was the world's No. 1 predatory dinosaur. There is little argument to the contrary, given extraordinary evidence such as a discovery made at a Utah quarry. Paleontologists at the site uncovered more than 10,000 dinosaur bones. Most belonged to large, plant-eating sauropods, like Camarasaurus and Apatosaurus, which appear to have been victims of Allosaurus. The ratio of predator to prey bones suggests just a few Allosaurus were responsible for the prehistoric dinosaur carnage.

Skull and Head

It's hard to imagine how any creature could have survived an Allosaurus bite. This theropod's teeth were razor sharp, serrated and curved toward the inside of its mouth on the upper jaw. On the lower jaw, the teeth had a more upright position. This allowed the hunter to hack, axe-like, into flesh with its upper teeth, while its lower teeth could then rip flesh from bone before the dinosaur immediately gulped it down. All of this action took place in a huge head that was surprisingly lightweight, due to its bone consistency and large spaces holding the eyes and nose.

Puzzling Head Crests

A ridge of bone formed a crest in front of each eye and extended toward the nasal tip. This gave the dinosaur a sort of double Mohawk look. Paleontologists aren't certain how the crest functioned. It may have protected the eyes during fights with other animals. It also could have housed special, as-of-yet unidentified, glands for the eyes. Alternatively, it might have been an identifying feature, distinguishing males from females.

Built to Kill

Allosaurus was a lean, mean, killing machine. Muscles in its S-shaped neck allowed the dinosaur to grasp and shake large prey, such as multi-ton sauropods. Sturdy clawed limbs supported its 3.6-ton body, with the thick, strong tail adding extra support. It's likely that lone individuals stalked prey before attacking victims with long, sharp claws. The carnivore might have also hunted in packs, being careful not to run too fast. Tripping would have been a concern, since its very short forelimbs could have thrown the fleet-footed beast head over heels if Allosaurus made a wrong move, which probably didn't happen often.

Dinosaur Name: Allosaurus

Order, Suborder, Family: Saurischia, Theropoda, Allosauridae

Name Means: "different lizard," since it possessed unusually lightweight spinal bones

Time Period: Late Jurassic, 156-144 million years ago

Location: Western United States, Portugal, Australia, Tanzania

Length: up to 45 feet

Iguanodon: Dinosaurs of Questionable ClassBy Tracy V. Wilson, HowStuffWorks

Iguanodon isn't a single dinosaur — it's a dinosaur genus that contains multiple species, all of which had four legs and ate plants. Most grew to be about 30 feet long. Today, there's some controversy about Iguanodon. Some paleontologists argue that many of the dinosaurs known as Iguanodon are classified incorrectly, leaving only one or two true Iguanodon species.

First Finds

Mary Ann Mantell discovered the first Iguanodon fossil — a tooth — in Sussex, England, in 1820, before the word "dinosaur" even existed. She decided that the tooth looked like a larger version of an iguana tooth, so she named the specimen Iguanodon. It wasn't until later that paleontologists discovered a more complete skeleton, allowing Mantell to learn what kind of animal her tooth belonged to. The tooth now resides in at Te Papa Museum in New Zealand.

All Thumbs

One of the most distinctive traits of dinosaurs in the Iguanodon genus is a large, spiky thumb. This thumb looked so much like a horn that the first representations of the dinosaur placed it on the nose, not on the hand. The thumb wasn't particularly flexible or mobile, meaning it probably didn't do much to help the creature collect its leafy food. Instead, Iguanodon may have used its spike to defend itself against predators.

Hooves for Hands

Since its discovery in 1820, scientists' portrayal of these dinosaurs has changed significantly. Many early representations showed Iguanodon as a biped, walking only on its back legs. But further study of Iguanodon fossils has revealed that they probably had the ability to stand on two legs but also spent a lot of time on all fours. The biggest piece of evidence is the three middle fingers, each of which resembles a hoof.

Herbivores in Herds

Dinosaurs in the Iguanodon genus didn't have front teeth. Instead, they gathered foliage with their beak-like mouths and used their back teeth to chew. In 1878, fossils of 31 adult Iguanodon were found in a coal mine in Belgium. Most likely, these animals were either traveling or living together, which suggests that Iguanodon lived in herds.

Dinosaur Name: iguana tooth," because its teeth resembled those of an iguana

Order, Suborder, Family: Ornithischia, Cerapoda, Iguanodontidae

Name Means: "iguana tooth," because its teeth resembled those of an iguana

Time: Late Jurassic to Late Cretaceous, 155-99 million years ago

Location: Romania, France, Spain, Austria, United States

Ankylosaurus:Armor-Plated and on the DefenseBy Tracy V. Wilson, HowStuffWorks

Ankylosaurus was a short, squat, heavily armored dinosaur that was a member of the Ankylosauridae family. It was a little like a prehistoric porcupine — it had armor plates called osteoderms covering its back and sides, leaving its belly unprotected. Some of these plates had a ridge called a keel, although scientists aren't sure exactly where on the body these scales appeared. Ankylosaurus also had short, dense legs to hold up its heavy body; it was 25 to 35 feet long and weighed three to four tons.

Ankylosaurus at Bat

Armor wasn't Ankylosaurus' only defense. It also had a club at the end of its tail. This club was formed by a set of tightly packed vertebrae covered in armor and could have been a powerful weapon. Ankylosaurus' tail wasn't particularly flexible, though, so maneuvering it to strike a predator might have been difficult.

Beaks and Horns

Behind each of its eyes, Ankylosaurus had a pair of horns. These may have provided another line of defense against predators like Tyrannosaurus, or they may have been used for display or for fighting against rivals. Its mouth probably didn't pose much of a threat, though. It was beaklike and had small teeth that were good for grabbing and chewing plants.

Not Enough Time

Compared to the other members of the Ankylosauridae family, Ankylosaurus was relatively short-lived. It walked the earth for about 5 million years, while the family as a whole existed for close to 80 million years, throughout the entire Cretaceous period. Paleontologists have also found more fossils belonging to other Ankylosaurs than to Ankylosaurus. In fact, Ankylosaurus fossils are rare — researchers have only found two skulls and fewer than five incomplete skeletons. This means that much of what we know about Ankylosaurus comes from the study of its relatives.

Head to the Ground

Ankylosaurus' front legs were a little shorter than its back legs, and the shape of its vertebrae probably kept it from being able to lift its head. It probably ate low-lying vegetation, like grasses and shrubs.

Dinosaur Name: Ankylosaurus

Order, Suborder, Family: Ornithischia, Thyreophora, Ankylosauridae

Name Means "fused lizard," since the armored plates on its back were connected together

Time: Late Cretaceous, 60-75 million years ago

Location: Northern North America

Maiasaura Peeblesorum: The First Dinosaur in SpaceBy Kiersten Aschauer, HowStuffWorks

Space-travelling dinosaurs may seem like science fiction, but one dinosaur actually made it into space in 1985. Astronaut Loren Acton packed bone fragments from a historic Montana dig before boarding Spacelab 2, making Maiasaura the first dinosaur to orbit the earth.

That might have given some paleontologists reason to grin, but what probably excites them more is taking a look back 65-80 million years before the Maiasaura's trip to the stars, when this duckbilled plant eater lived among the likes of Tyrannosaurs and Velociraptors.

Cheeky Dinos

The duck-billed Maisaura were big dinosaurs and big eaters. These herbivores had fiber-rich diets that consisted of berries, seeds and up to 20 pounds of leaves a day. However, oddly enough, its sharp, enameled teeth lined its cheeks rather than its beak.

Weighing in at about 8,000 pounds, the Maisaura were part of the Hadrosauridae family, growing to be about 30 feet long and 8 feet tall. It could navigate on either two or four legs, but perhaps had a bit of an uneven stance, as it had stubby arms with four-fingered hands and hooved back legs that were much stronger than its front. Its strong tail was presumed to be used as a balancing device. The small crest between its eyes smoothed backward to reveal a flat skull.

Movers, Shakers, Herders and Travelers

The Maisaura specimens found to date have all come from the Late Cretaceous period’s Two Medicine Formation in western Montana. Maisaura's closest relative may have been Brachylophosaurus from southern Alberta and Montana. Because fossils have been discovered in groups totaling up to 10,000, Maisaura are alleged to be herders who needed to travel seasonally in search of food, and then returned annually to breed in their home colonies.

Model Moms

There is a reason the Maisaura have been nicknamed the "good mother lizard." Scientists repeatedly found fossils alongside nests that contained up to 25 grapefruit-sized eggs. It is believed that the Maisaura moms nurtured the hatchlings until they at least doubled in size — longer than many other dinosaurs stayed with their young.

Dinosaur Name: Maiasaura peeblesorum

Order, Suborder, Family: Ornithischia, Ornithopoda, Hadrosauridae

Name Means: "good mother lizard," because it nurtured its young longer than most dinosaurs


Location: Montana

Apatosaurus: The Dinosaur Formerly Known as BrontosaurusBy Jennifer Viegas

When music star Prince changed his name to an unpronounceable glyph, everyone still called him "Prince." Similar confusion surrounds the dinosaur Apatosaurus, which many still refer to as "Brontosaurus." The mix-up goes back to 1879, when paleontologist Othniel Marsh mistakenly stuck a Camarasaurus head on an Apatosaurus and called it a Brontosaurus. When the mistake was discovered years later, scientists erased Brontosaurus from their books, but the incorrect name still lingered in people’s minds.

Anatomy

To add to the confusion, Apatosaurus resembled its close relative, Diplodocus. Both were gigantic plant eaters, but Apatosaurus had a much sturdier build. Its body looked like an amalgamation of other animal parts brought together in a bizarre combination. Apatosaurus possessed elephant-like "toes" at the bottom of hefty, thick, pillar-shaped limbs. A long, whipping tail held together with 82 bones extended from the dinosaur’s 24.6-ton body. At the front was a long, muscular neck capped off by a tiny head, not unlike that of a modern horse, but full of pegged teeth.

Big Body, Big Diet

The small jaws and head of Apatosaurus have puzzled scientists for decades, since it would seem biologically impossible for a dinosaur of such immense size and weight to feed itself properly through such a small orifice. Paleontologists suspect the dinosaur must have eaten all day. After hours of feasting on tree leaves, ferns, shrubs, cycads, conifers, ginkgos and other plants that were prevalent during the Late Jurassic, Apatosaurus probably waded in water to cool off and to kill parasites before taking brief, standing naps. The eating phase then likely started all over again.

A Formidable Opponent

For a large carnivorous dinosaur like Allosaurus or Tyrannosaurus, one Apatosaurus must have made quite a beast feast. Apatosaurus, with its massive body, couldn’t have run fast, so it likely stayed with others to form a protective herd. The huge herbivore was also not entirely defenseless. It could crack

its long tail like a whip, causing serious damage to would-be attackers, perhaps sending them airborne. Apatosaurus also possessed claws on each of its "thumb" digits. It’s possible that this enormous dinosaur reared up on its back legs and then crashed down on its enemies, jabbing claws into them upon impact.

Dinosaur Name: Apatosaurus

Order, Suborder, Family: Saurischia, Sauropodomorpha, Diplodocidae

Name Means: "deceptive Lizard," because its bones were confused with those of other dinosaurs

me Period: Late Jurassic, 156-144 million years ago

Location: Western United States, Northwestern Mexico


Oviraptor philoceratops: Egg Thief or Egg Protector?By Kiersten Aschauer, HowStuffWorks

Early fossil hunters were probably quite curious to know exactly what they found when they stumbled upon a crushed skull and a few bones that would later become known as the Oviraptor philoceratops. This 1932 discovery by scientists from Mongolia and the American Museum of Natural History and other finds by paleontologists during the 50 years that followed allowed for a more complete picture of this small, birdlike creature first dubbed "the egg thief."

Thief or Protector?

As it turns out, the Oviraptor's nickname may be inaccurate. The prehistoric beast may not have stolen unhatched eggs from other nests, as has been suggested. In fact, the opposite may be true: In 1995, the American Museum of Natural History announced the discovery of a fossil of an ostrich-sized Oviraptor covering its own nest of unhatched eggs in a seemingly protective stance.

Cock-a-Doodle Dino

Oviraptors did not look like your typical coloring book dinosaur — more like a strange science experiment where a bird and dinosaur enter the chamber from the movie The Fly. Its most distinctive feature was the rooster-like crest that attached to nostril passages on its beak. Its skull was small with large eye sockets, and its deep jaws were toothless. An adult Oviraptor may have measured about 3 feet tall and around 6 feet long.

If You Can't Join 'Em, Race 'Em

So, how did small the Oviraptor survive in the Mongolian desert with predators like the mighty Carcharodontosaurus lumbering around the neighborhood — especially with a powerful, but small, beak that served as more of a nutcracker than a predatory asset? This has been a topic of debate in the paleontological community. Some scientists say the Oviraptor was a carnivore scavenger that mostly dined on scraps from others’ kills. Others say it was an omnivorous animal that feasted on eggs, fruit, insects and hunted shellfish. Most seem to agree that the animal was an agile runner. We also know

this: The two, bony spikes on the roof of its mouth leads us to believe the Oviraptor crushed its food to make it digestible.

Dinosaur name: Oviraptor philoceratops

Order, Suborder, Family: Saurischia, Theropoda, Oviraptoridae

Name Means: "egg thief," because it may have dined on stolen eggs


Location: Southern Mongolia

Brachiosaurus: One of the Largest DinosaursBy Jennifer Viegas

One of the largest dinosaurs of all time, Brachiosaurus could have towered over most four-story modern office buildings today. At first scientists thought the dinosaur weighed 80 tons, but now they’ve lowered the estimate to around 50 tons, which is equivalent to six or so elephants jammed together on a scale. Brachiosaurus remains one of the biggest, tallest, heaviest and longest known sauropods, although its tail was relatively short when compared with others in this group of diverse plant eaters.

Long Neck

The neck of Brachiosaurus could stretch to around 30 feet in length. Twelve individual vertebrae supported its giraffe-like neck, with each vertebral bone measuring 28 inches or more. Paleontologists are stumped as to how a creature with such a gigantic neck could have supplied an even flow of blood to its brain. Without special adaptations, the dinosaur would have fainted all the time or, even worse, experienced burst blood vessels in the brain when it bent over after raising its tiny head. Scientists theorize that either its heart was extremely powerful, pumping blood at constant high pressure, or the dinosaur kept its head in a position more parallel to the ground, perhaps sweeping it from side to side in search of food.

Feeding and Digestion

Due to its weight, Brachiosaurus would have required approximately 440 pounds of food each day, according to scientific estimates. Since this dinosaur only ate plant materials, it must have spent the majority of its day chewing foliage with its sharp, inwardly curved teeth, gulping the food down its long neck. Gastroliths, otherwise known as "gizzard stones," rested in its gut and helped to further grind down the plant mash.

Long Arms

To support all of the eating action and neck swaying, Brachiosaurus possessed two long "arms." It was the only known dinosaur to have front limbs longer than its hind limbs. Giraffes embody a similar design today, but the front to back difference isn’t as pronounced. The long Brachiosaurus forelimbs allowed the sauropod to raise its chest and shoulder region about 8 feet above ground level. Although

this dinosaur likely was not a fast runner, the limbs could have stepped over obstacles with ease and allowed for better access to leaves on tall trees.

Rivals and Defense

Voracious meat eaters like Allosaurus probably preyed upon young or sick Brachiosaurus individuals, but carnivores might have steered clear of adults, due to their intimidating size. Brachiosaurus also possessed sharp claws on its feet that could have gored intruders with one swift kick. Additionally, this dinosaur probably traveled in small herds, gaining protection in numbers.

Dinosaur Name: Brachiosaurus

Order, Suborder, Family: Saurischia, Sauropodomorpha, Brachiosauridae

Name Means "arm Lizard," since its forelegs were so much longer than its hind legs


Location: Western United States, Southern Europe, Northern Africa


Protoceratops Andrewsi: Horned, Frilled Dinosaur AncestorBy Tracy V. Wilson, HowStuffWorks

Protoceratops andrewsi was a four-legged, herbivorous dinosaur with a bony frill around the back of its neck. This made it look like a miniature version of Triceratops, only without the distinctive three-horned profile. It also looked a lot like a smaller version of its relative Protoceratops hellenikorhinus. P. andrewsi had a beaklike mouth, which it used to eat foliage.

Precursor to Horns

Protoceratops had a bump on its nose in the place where many later ceratopsians had horns. It also had thickened areas of bone above its eye sockets — another spot for horns in dinosaurs like Triceratops. For this reason, some researchers believe Protoceratops was an ancestor of many other horned, frilled dinosaurs.

A Case of Mistaken Identity

One of the first dinosaur eggs ever matched up with its species was, scientists believed, from a Protoceratops. The eggs had been found beneath a skeleton dubbed Oviraptor philoceratops or "egg stealer that likes ceratops." Researchers believed the dinosaur had been stealing the eggs when it died. In 1995, another team called this identification into question. It turns out that Oviraptor was probably guarding its own eggs rather than stealing the eggs of a Protoceratops.

Protoceratops vs. Velociraptor

Another major discovery occurred in 1971, when paleontologists found a unique Protoceratops fossil in the Gobi Desert. This specimen died while fighting a Velociraptor. The bones of the two dinosaurs show the Velociraptor attacking the Protoceratops' neck with its clawed toe. But Protoceratops wasn't going down without a fight — it bit and possibly broke Velociraptor's arm before both dinosaurs were buried in sediment that preserved their bodies mid-fight.

My Pet Protoceratops

If dinosaurs were alive today, Protoceratops might be one people would keep as pets or livestock. These dinosaurs didn't eat meat, so they wouldn't be a big threat to pets or children. They were also about the size of a sheep. However, being nuzzled by a Protoceratops might not be a pleasant experience — it could weigh at least two to four times as much as an adult sheep.

Dinosaur Name: Protoceratops andrewsi

Order, Suborder, Family: Ornithischia, Cerapoda, Protoceratopsidae

Name Means: "first horned face," because it's believed to be the first of the ceratopsians

Time: Late Cretaceous, 85 to 80 million years ago

Location: Inner Mongolia; Mongolia

Brachylophosaurus: The Elvis of DinosaursBy Jennifer Viegas

Brachylophosaurus may be its official name, but many affectionately know this relatively "new" dinosaur as "Elvis," due to its unusual head crest that resembles the famous rock 'n roll singer’s hair. Fossil collector and paleontologist Charles Sternberg first the dinosaur described it in 1953. No other specimens existed until noted dinosaur expert Jack Horner identified another Brachylophosaurus skeleton from Montana’s Judith River Formation during the 1980s.

Head Crest

The solid boned head crest extended from the snout, laid over the top of the dinosaur’s flat head and then finished with a stylish spike at the back. Aside from the Elvis hair comparison, it also looked a bit like a modern bike racing helmet, and perhaps served a similar head-protecting function. It’s possible that Brachylophosaurus engaged in head to head pushing contests, similar to how male animals with antlers or horns today will often fight for leadership status or choice females during the mating season.

Teeth and Diet

Brachylophosaurus was a duck-billed dinosaur, but its upper beak was larger and broader than that of most hadrosaurs. Both its upper and lower beaks encased jaws set with hundreds of teeth. Their position and the jaw structure suggest Brachylophosaurus chewed plant material from side to side, as cows and horses do today. Analysis of the preserved stomach contents of one individual reveal it ate ferns, conifers, magnolias and the pollen of more than 40 different plants.

Cancer

Paleontologists in 2003 were surprised to discover the dinosaur suffered from cancer. They found at least four forms of the deadly disease in numerous Brachylophosaurus skeletons. Cancer appears to have been rare in other dinosaurs, or perhaps even limited to this species. Experts aren’t sure why, but they suspect genetic or environmental factors were to blame.

Guinness World Record Holder

Since its discovery in the early 1950s, a number of extremely well preserved Brachylophosaurus remains have been excavated. In 2003, a specimen, named Leonardo, was honored by the Guinness Book of Records as being "the best preserved dinosaur remains in the world." The certificate went on to say, "around 90 percent of the body is covered with fossilized soft tissue." Paleontologists value such dinosaur "mummies," since they provide rare tissue samples in addition to bone.

Dinosaur Name: Brachylophosaurus

Order, Suborder, Family: Ornithischia, Ornithopoda, Hadrosauridae

Name Means: "Short-Crested Lizard", because of its small crest

Time Period: Late Cretaceous, 75-65 million years ago

Location: Western United States, Canada


Spinosaurus: World's Largest Carnivorous DinosaurBy Jennifer Viegas

A recent movie battle pitted a Spinosaurus against Tyrannosaurus rex, with the former portrayed as a victor after it snapped its rival’s neck. While Spinosaurus and T. rex never fought in real life, since they lived millions of miles and thousands of years apart, Spinosaurus holds the world record for being the largest known carnivorous dinosaur, given its impressive length and 9.9-ton build.

Sail

The imposing dinosaur’s most unusual feature was its large sail. Whenever Spinosaurus would arch its back, the sail, made of lengthy spines covered with skin, would rise into the air. The sail alone was the height of a human basketball star. Paleontologists continue to debate its function, but most suspect the sail helped to regulate body temperature and was used to woo the opposite sex or to scare off competing males.

Teeth and Diet

It’s no wonder Spinosaurus often makes film appearances, since this dinosaur flashed a million-dollar "smile." While most carnivorous dinos had curved teeth, the teeth of Spinosaurus were straight and probably functioned like knives, skewering often-slippery prey. Like modern grizzly bears, Spinosaurus probably spent a lot of time grabbing fish in, or near, water. A dinosaur of such girth, however, likely did not subsist on an all seafood diet. It probably killed and consumed smaller dinosaurs too, along with scavenging flesh from corpses.

Big Head

Such feasting would not have posed a challenge, since Spinosaurus possessed what was arguably the longest head of any known carnivorous dinosaur. Measuring close to 6 feet in length, the head featured a narrow snout — all the better for showcasing its straight teeth — with tiny ears on either side. Scaly skin covered its neck.

Rivals

Few enemies probably dared to challenge Spinosaurus, considering that its large body could look even twice as big once its sail was instantaneously raised, scaring most would-be attackers. Humans turned out to be a significant threat, to its fossils at least, since a World War II bomb raid destroyed the first known Spinosaurus remains, which were collected by German paleontologist Ernst Stromer. Luckily, Stromer documented his find or else no one would ever have known about the distinctive dinosaur.

Dinosaur Name: Spinosaurus

Order, Suborder, Family: Saurischia, Theropoda, Spinosauridae

Name Means: "spine lizard," due to its flat, large back spines

Time Period: Middle Cretaceous, 100-93 million years ago

Location: Egypt, Morocco, Republic of Niger


Carcharodontosaurus: The Shark LizardBy Kiersten Aschauer, HowStuffWorks

The dinosaur known by the common name "shark-toothed lizard" is obviously not a shark, nor a lizard. In fact, if the Carcharodontosaurus were to have a closest living relative it would be a member of the order Crocodylia. The inside of its skull and inner ear, as well as its brain size, are similar to some modern reptiles.

Early Finds

Though Charles Depéret and J. Savornin were the first to unearth some of the first Carcharodontosaurus fossils during a North African dig in 1927, it was a discovery in the 1990s that gave a clearer picture of this creature. A 1996 expedition to Morocco led by paleontologist Paul C. Sereno revealed a huge skull and partial skeleton of a Carcharodontosaurus saharicus. It appeared to be larger than North America’s Tyrannosaurus rex and a close relative to South America’s Giganotosaurus. The skull alone measured 5 feet 4 inches long.

Just a year after celebrating that find, Sereno and paleontologist Stephen Brusatte found a second species: Carcharodontosaurus Iiguidensis. Also a member of the Carcharodontosauridae family, C. liguidensis had many similar characteristics to the C. saharicus, but Brusatte found apparent differences in the bones in the nose and around the brain.

A Born Hunter

One thing was for sure: This "shark-toothed lizard" was a hunter. Its short arms sprouted sharp, three-fingered claws and it had serrated, 8-inch-long teeth made for eating meat. Along with its sharp claws and impressive teeth, the bipedal Carcharodontosaurus was speedy and sported a wide body, weighing around 16,000 pounds. It grew up to 45 feet in length and stood 17 feet high, making it one of the largest carnivores on the planet, according to scientists.

Hunters Get Hunted Too

With such an intimidating physical structure, you might think the Carcharodontosaurus would be free of rivals. Not the case. Though it is suspected they could take on some of the largest dinosaurs alive,

including the sauropods, their biggest rival was the Spinosaurus, also known as the "spine lizard," which grew up to 60 feet in length.

An Expedited Extinction?

Dr. Angela Milner, deputy keeper of paleontology at London’s Natural History Museum, has speculated that the Carcharodontosaurus might have been a victim of "allopatric speciation." This is when "biological populations are physically isolated by a barrier, in this case a seaway, and evolve in reproductive isolation," she said in a NHM London press release. "If the barrier breaks down later, individuals of the populations can no longer interbreed."

Dinosaur Name: Carcharodontosaurus

Order, Suborder, Family: Sauropsida, Theropoda, Carcharodontosauridae

Name Means: "shark-toothed lizard," because it's named after the great white shark

Time: Cretaceous, 110-90 million years ago

Location: Egypt, Morocco, Tunisia, Algeria, Libya, Niger

Stegosaurus: The Solar Paneled DinosaurBy Jennifer Viegas

Stegosaurus is the most well-known member of the Stegosauria dinosaur group, which consisted of "bird-hipped" plant eaters. All species within the Stegosauria group during the Late Jurassic possessed two other hard-to-miss defining characteristics: leaf-shaped plates that jutted out of their backs and pointy spines for defense. Meat eaters would not have had trouble spotting the lumbering veggie-loving "fashion plates," but two-ton Stegosaurus could have put up a good fight.

Stegosaurus Plates

The Stegosaurus plate display consisted of 17 thin, leaflike, bony protrusions running from the back of the dinosaur’s head to the middle of its tail. Some measured up to 3 feet in height. Since the plates were rather fragile, these structures likely didn’t help with defense. Instead, they served as the Jurassic version of solar heating and cooling. Blood vessels within the plates could either absorb or release heat, depending on weather conditions and the direction in which Stegosaurus moved. On a hot day, for example, the dinosaur could let a breeze hit the plates, as for a sail, allowing blood vessels to release heat and provide a cooling sensation that would have soothed the beast’s entire body.

Beak, Teeth and Diet

We humans can release a lot of heat from our heads, but the Stegosaurus head was very small when compared to the size of the rest of its body. The dinosaur’s narrow snout featured a tiny beak that enclosed teeth full of multiple ridges that resembled notches on a blunt, triangular, serrated knife. These permitted it to chew plant materials, which it also might have fermented in its gut to release extra nutrients.

Rivals and Defense

The stocky Stegosaurus must have been like a hamburger on legs for carnivorous predators, such as Allosaurus and Ceratosaurus, which coexisted in North America with the flashy herbivore. Stegosaurus had a good chance of surviving attacks, however, due to its protective, disc-shaped plates that safeguarded its hips, along with bony studs that lined its otherwise vulnerable throat. If those defensive measures didn’t work, it could then swipe at rivals with four sharp spikes that stuck out of its

tail. These caudal spikes might have also inflicted serious injuries if the Stegosaurus, either intentionally or not, backed up into another individual.

Dinosaur Name: Stegosaurus

Order, Suborder, Family: Ornithischia, Thyreophora, Stegosauridae

Name Means: "roofed lizard," because of its bony back plates


Location: Western United States, Southern India, China, Southern Africa


Deinonychus: One of the Deadliest DinosaursBy Jennifer Viegas

Although Deinonychus was only about as big as a two-passenger compact car, every inch of this dinosaur contributed to its reputation as being one of the world’s deadliest dinosaurs. When its powerful jaws opened, over 60 daggerlike teeth flashed, ready to dig into much larger dinosaurs such as Sauropelta and Tenontosaurus. Claws on its grasping hands could inflict severe damage that would have been compounded if Deinonychus decided to karate-kick unfortunate victims with one, or both, of its toe claws.

Terrible Claws

When a more complete fossil of Deinonychus was unearthed in the 1960s, paleontologists for the first time discovered that this dinosaur wielded sickle-shaped claws on the second toe of each "foot." It could retract these like a switchblade but, to preserve the sharpness of its valuable weapons, Deinonychus held the claws upright and instead walked on its third and fourth toes. Thus, the "terrible claws" didn’t drag on the ground, where they could catch or become blunt. A thick, horny sheath, similar to what covers bird and cat claws today, surrounded both its hand and foot claws.

Deinonychus Gangs

While an individual Deinonychus would have made a formidable opponent, this species probably gathered in gangs to fell especially large, meaty dinosaurs. One intriguing piece of evidence for this is a fossil site containing the remains of a brutalized Tenontosaurus surrounded by the bones of four Deinonychus dinosaurs. One interpretation is that Tenontosaurus, which could grow up to 27 feet in length, put up a good fight, but was killed and consumed by other members of the Deinonychus gang. The winners perhaps then disappeared, leaving behind their less fortunate cohorts.

Attack Techniques

Despite possible heavy Deinonychus losses during battles, this carnivore could attack in multiple ways. Since its tail was strong, it might have balanced itself on one foot while it gored and disemboweled victims with a toe claw. Given its muscular legs, it could have also jumped directly on prey, digging its claws into the victim as it landed. If multiple Deinonychus performed such moves simultaneously, it’s no wonder the 165-pound predator probably feasted on multiton beasts.

Built Like a Fierce Bird

Featherlike structures linked to close relatives of Deinonychus suggest feathers covered the dinosaur’s muscular, yet lightweight, body. The dino also shared certain anatomical features with today’s birds, such as the shape and structure of its pelvic bones. It additionally could move like a flightless bird, swerving, running and balancing itself with relative ease.

Dinosaur Name: Deinonychus

Order, Suborder, Family: Saurischia, Theropoda, Dromaeosauridae

Name Means: "terrible claw," because of the large, sickle-like

Time Period: Early Cretaceous, 121-98 million years ago

Location: Western United States


Triceratops: Largest, Heaviest and Most Common Horned DinosaurBy Jennifer Viegas

When an odd pair of horns was excavated at the high plains east of the Rocky Mountains in the 1880s, paleontologists thought they had found the remains of a prehistoric bison. What they really discovered were two of the three horns of Triceratops, a dinosaur that holds three records among all horned dinosaurs. It was the largest, heaviest and, in its time, most common ceratopsid. These were four-legged, plant-eating dinosaurs characterized by broad, bony frills and well-developed brow horns.

Large Skull, Small Brain

Massive Triceratops could weigh up to six tons and, unlike some dinosaurs whose heads were much smaller than their bodies, this dinosaur’s head was mighty big. The head alone was as long as an adult human. While brain tissue does not exist for any dino, researchers can use existing skulls to estimate brain size and shape. Based on such studies, the Triceratops brain was about the same size as a human fist, suggesting the dinosaur did not have very acute senses and wasn’t the brightest of beasts. Nevertheless, it was adept at fending for itself, using its scissorlike teeth to slice through vegetation.

Frill

The bony neck frill on Triceratops could extend to over 6.5 feet in width. Several theories have been proposed for its function. Some scientists think the frill protected the dinosaur’s vulnerable neck area against predators. Tyrannosaurus bite marks observed within frill remains, however, suggest it wasn’t always successful in deterring attackers. Other researchers suspect it helped to regulate body temperature, while still other paleontologists theorize it was used in mating displays and in helping the dinosaur to identify members of its species.

Horns

Triceratops horn fossils look impressive enough. In real life, though, its horns were much sturdier weapons. Antler-like material would have covered the existing cores, making them much longer and sharper. The dinosaur could gore or impale carnivore rivals with its short nose horn or its two long

brow horns, which jutted out over each eye. If that didn’t scare away the threat, Triceratops might have pecked at the assailant with its toothless, yet pointy, beak.

Rhino and Elephant Comparisons

Triceratops somewhat resembled today’s elephants and rhinoceroses. Its girth was comparable to that of an elephant and it too possessed heavy legs. Like a rhino, it had short, broad feet with padded toes to help cushion the weight as it pounded the dirt. It’s possible Triceratops lived the rhino lifestyle as well, by munching on plants most of the time and then putting its horns into action whenever predators approached.

Dinosaur Name: Triceratops

Order, Suborder, Family: Ornithischia, Marginocephalia, Ceratopsidae

Name Means: "three-horned face," due to its nose horn and two long brow horns


Location: Western United States, Southwest Canada


Diplodocus: One of the Longest Animals to Walk the EarthBy Tracy V. Wilson, HowStuffWorks

Diplodocus was a genus of several four-legged, plant-eating dinosaurs with very long necks, whiplike tails and a specialized claw on one toe of each foot. Its tail and claw may have been defensive weapons, but paleontologists haven't confirmed this theory. These dinosaurs were among the longest land animals ever to walk the Earth. But while they were very long, they weren't bulky. Diplodocus weighed less than half as much as similarly shaped dinosaurs like Apatosaurus.

Keep Your Head Down

Old Diplodocus illustrations often show it using its long neck to reach food in the tops of trees. Newer research suggests that the dinosaur wasn't built to move this way -- it probably couldn't lift its head far above its shoulders. It could, however, move its head in great arcs from side to side. Instead of grazing from the tops of trees, it probably stripped vegetation from a wide swath of plants.

These Teeth Were Made for Nipping

As it grazed, Diplodocus didn't do a lot of chomping. All of Diplodocus' teeth were in the front of its mouth, so it couldn't chew its food. Instead, it nipped at vegetation and swallowed it whole. These large chunks of vegetation would have been hard to digest, so Diplodocus got some help from rocks. It swallowed stones, known as gastroliths, which helped grind the leaves inside the dinosaur's digestive system.

The Nose Knows

Many depictions of Diplodocus show its nostrils on top of its head, near its eyes. In 2001, researcher Lawrence Witmer published a paper in the journal Science that refuted this idea. Witmer claims that the dinosaur's nostrils didn't line up with the nasal cavity in its skull. Instead, the nostrils were much closer to the mouth, allowing the nasal passageway to act as a heat exchanger and move excess heat away from the dinosaur's brain.

(Not) Bringing Up Baby

There's evidence to suggest that some dinosaurs warmed their nests with their bodies and cared for their young. Diplodocus wasn't one of them. Paleontologists have found lines of fossilized Diplodocus eggs, suggesting that these animals lay eggs while on the move and left them behind.

Dinosaur Name: Diplodocus

Order, Suborder, Family: Saurischia, Sauropodomorpha, Diplodocidae

Name Means: "double-beamed lizard," because the vertebral projections of the midsection of its tail formed an inverted "T" or double beam

Time: Late Jurassic, 161-146 million years ago

Location: Western North America

Troodon formosus: One of the World's Smartest DinosaursBy Tracy V. Wilson, HowStuffWorks

The diminutive dinosaur Troodon formosus was about 6 feet tall and weighed about 110 pounds. It was a predator with sharp, serrated teeth, but it was only big enough to eat small creatures, like lizards and early mammals. Like Velociraptor, Troodon moved around on its hind legs only, using its forelegs to hold prey.

Magnificent Brains

Troodon was about the size of a man. Like a man, the size of its brain was fairly big when compared to the size of the rest of its body. This means Troodon may have been one of the most intelligent dinosaurs to have lived.

Seeing in the Dark

According to fossils of its skull, Troodon probably had good eyesight, which may have allowed it to hunt at night. Its eyes were also close enough together on the front of its head to allow it to have binocular vision, which would have given it the depth perception needed to be a more efficient hunter.

Thumbs and Claws

Both of Troodon's three-toed back feet sported a large claw that it held off the ground as it ran. This claw, combined with Troodon's agility, was probably a formidable weapon. This dinosaur's hands gave it an advantage, too. Its thumbs were partly opposable, giving it the ability to grasp objects.

For the Birds

Some fossils show Troodon adults sitting on or near clutches of eggs, suggesting that they brooded their eggs the way today's birds do. According to the fossil evidence, these dinosaurs probably lay and incubated eggs one or two at a time, also similar to today's birds. Another similarity is that Troodon was descended from feathered dinosaurs, although there's not a lot of conclusive evidence to prove whether it possessed them as well. Finally, Troodon could fold its arms the way birds fold their wings.

Because of all these similarities, some paleontologists see Troodon as an evolutionary link between theropods and modern birds.

Dinosaur Name: Troodon formosus

Order, Suborder, Family: Saurischia, Therapoda, Troodontidae

Name Means: "wounding tooth," because of its curved, sharp, serrated teeth


Location: Mexico, Canada, Montana, Wyoming

Dromaeosaur albertensis: Feathered, Clawed and JawedBy Kiersten Aschauer, HowStuffWorks

Call the Dromaeosaur albertensis an "odd bird" and you’d be right in more ways than one. While this Late Cretaceous specimen is reported to have had feathers, it also had the luck of sharing the same "secret weapon" as similar theropods. At the end of its slender but powerful legs were two curved toes and a strange-looking" sickle claw" jutting out from the top of the foot. Though smaller than some other Dromaesaurs, it’s believed that this carnivore used the claw to clamp down on prey and kill it.

Piecing Together the Dromaeosaurus Puzzle

While the Dromaeosaur is a well-known prehistoric character in many books and movies, there is still much to be learned about the species. Paleontologists have pieced together what this member of the Saurischia order may have looked like, but a full skeleton hasn’t been discovered yet. Paleontologist Barnum Brown discovered the earliest remains during a 1914 American Museum of Natural History expedition, collecting a partial skull and some bone fragments and starting the hunt for more clues to the life of this creature.

Evolution

Dromaeosaur may have evolved between 76 and 74 million years ago on the watery islands of Europe, hunting in packs to survive. The group probably became extinct at the end of the Cretaceous period.

Scary Claws, Long Jaws

Dromaeosaurs grew to be approximately 6 feet in length and weighed about 33 pounds. It was probably the size of a large dog. It even had a flexible tail that was, at times, flipped upright. Keen eyesight and hearing may have contributed to this creature’s hunting skills, along with its trademark sickle claw. But its long jaws with rows of sharp teeth probably came in quite handy at dinnertime as well.

Relatively Speaking

Some paleontologists suspect that Dromaeosaurs could be the closest known relatives to birds (as has been thought about many dinosaurs of this era).

Dinosaur Name: Dromaeosaur albertensis

Order, Suborder, Family: Saurischia, Theropoda, Dromaeosauridae

Name Means: "swift-running lizard," because the bipedal dino was able to run after their prey


Location: Europe

Tyrannosaurus: One of the Biggest Flesh-Eating Predators of All TimeBy Jennifer Viegas

Paleontologists were shocked when they unearthed a near-complete skeleton of Tyrannosaurus in 1902. By its bones alone, the scientists knew they had found one of the biggest flesh-eating predators of all time. Its head was the size of an adult person. The Tyrannosaurus body could extend the entire width of a tennis court. Up to seven tons of muscle and other tissues filled out the rest of its sturdy frame. This was a monster carnivore that must have terrified all other dinosaurs during the Late Cretaceous.

Bone-Crushing Teeth

Evidence supports Tyrannosaurus’ killer reputation. A Triceratops hipbone, for example, was found covered in Tyrannosaur bite marks, including a large chunk of missing bone. This suggests the predator could bite through every part of its victims with its 8-inch-long, cone-shaped, razor-sharp teeth. A fossilized lump of Tyrannosaurus dung, when analyzed, was found to contain multiple Edmontosaurus bones, further proving the claims. Recent studies also suggest that today’s lions — formidable predators in their own right — only have one-third the biting force of the Late Cretaceous predator.

The Tyrannosaurus Walk

The Tyrannosaurus strutted its stuff back in the day. Research indicates the dinosaur kept its back level, held its tail still and then moved forward with a purposeful march. At least 11 different muscle groups in its legs allowed this natural athlete to haul its heavy body with a proud, erect forward motion.

Leggy Runner With Tiny Arms

At times Tyrannosaurus likely sprinted over short distances at speeds of up to 20 miles per hour, which is very close to speeds run by human Olympians. Each pillar-shaped hind limb ended with a four-toed foot that had heavy claws for grasping prey and for traction. Its extremely short forelimbs looked

weak, but Tyrannosaurus could have bench-pressed two adult humans at once with just a single arm. Its hands also featured two fingers capped off by two ultra-sharp claws.

Hunting Tactics

It's theorized that Tyrannosaurus patiently waited for unsuspecting victims before charging at them with toothy jaws agape. A "puncture and pull" technique then felled the target. The dinosaur’s other feeding method would have involved scavenging meat from corpses. Most scavengers subsist on rotting, unappetizing meat, but imposing Tyrannosaurus likely scared away other carnivorous dinosaurs and stole their kills, thus earning its "tyrant" name.

Dinosaur Name: Tyrannosaurus

Order, Suborder, Family: Saurischia, Theropoda, Tyrannosauridae

Name Means: "tyrant lizard," due to its imposing head and teeth


Location: Western United States, Southwest Canada, Asia


Velociraptor mongoliensis: The Dinosaur of "Jurassic Park" FameBy Kiersten Aschauer, HowStuffWorks

Most people think they know the Velociraptor from its portrayal in the popular Jurassic Park movies and books. But Hollywood took many liberties with its interpretation of this dinosaur, heavily leveraging the dinosaur’s Latin name velox (swift) and raptor (predator, plunderer) on-screen. The reality is that the history of how we’ve come to know the raptor is a story all its own.

The talebegins with a 1922 expedition to the Gobi Desert in Mongolia, when a group of scientists from the American Museum of Natural History discovered a complete Velociraptor skull and a claw. The story continues 50 years later with another telling discovery.

A Battle Preserved in Time

In Mongolia in 1971, a Mongolian-Polish team unearthed a well-preserved fossil of a Velociraptor battling another dinosaur. The specimen showed the raptor’s claws embedded in the head and stomach of a Protoceratops. Aside from being the first significant findings of these species, it was also a breakthrough for scientists’ understanding of how dinosaurs lived, offering a clue to how (and if) certain dinosaurs coexisted during the Late Cretaceous period.

If a Basketball Player Had Claws …

Despite its larger-than-life persona in the movies, an upright-standing Velociraptor was actually about the height of a modern-day basketball player — approximately 6 feet. But what it lacked in size, it made up for in other areas. Most importantly, Velociraptors were intelligent compared to many of their peers. They also had a heightened sense of smell and binocular vision.

This quick, two-legged predator had a few secret weapons, too. The first was a 3.5-inch retractable claw that could quickly wound an enemy with a 3-foot gash. The second was a mouthful of 80 spiky teeth, some up to an inch in length. Their sleek bodies and ability to run at speeds of 24 miles per hour also helped them survive in a world of much larger predators. Scientists have discovered quill knobs on the Velociraptor. These quill knobs may not have implied that they could fly, but provide clues that

feathers could have been used for other reasons, such as to help regulate body temperature, protect eggs in the nest or as a mating display.

Pack-Hunting Carnivores

The Velociraptor was a tiny meat-eating machine that likely ate whatever it could. Because Velociraptor fossils are often found in close vicinity to each other, it is thought that they likely hunted in packs. This hunting tactic could lead a small group of raptors to prey on one larger predator with speed and ferocity.

Dinosaur Name: Velociraptor mongoliensis

Order, Suborder, Family: Sauropsida, Dinosauria, Dromaeosauridae

Name Means: "swift predator," which refers to its ability to run after prey

Time Period: ate Cretaceous, 84-80 million years ago

Location: China, Mongolia, former Soviet Union


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