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Tyrannosaurus rex was
a meat-eater about 40 feet long, about 15-20 feet tall, and about 5-7 tons in weight. T.
rex probably had about 200 bones, roughly the same as us (no one knows exactly how many it had, since no complete T. rex skeletons have been found). About a dozen T. rex skeletons have been found. |
SKULL AND JAWS
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T. rex's jaws were up to 4 feet long and had 50 to 60 thick, conical,bone-crunching teeth that were up to 9 inches long. |
T. rex dung has been found
containing crushed bone - its teeth were capable of inflicting an enormous amount of
damage on other creatures. This ability to crush bones and obtain the nutrition contained
within (the marrow) would have allowed T. rex to be an efficient scavenger, perhaps in
addition to actively hunting.
T. rex, like the other dinosaurs, was a diapsid (as are all reptiles except turtles).
Diapsids are animals that have two extra holes in the sides of their skulls.
Legs
Like all other
dinosaurs, T. rex walked on its toes; the scientific term for this is digitigrade. Other
animals that are digitigrade include dogs, cat, and chickens. There is a pad of tissue on
the back of the feet on these animals that acts like a shock absorber. People, bears, and
crocodiles walk differently; they are plantigrade (flat-footed).
T. rex had three clawed toes on each foot (pes) and one dew claw (or hallux, a very small,
virtually useless toe). Its legs were very strong and powerful.
SHOULDERS AND ARMS
T. rex had tiny arms in comparison with the rest of its body. The upper part of the arm
was imbedded in its body, rendering the arms almost useless and with a very limited range
of motion. T rex's arms couldn't even reach its mouth!
T. rex had two clawed fingers on each hand (manus).
Pelvis
T. rex was a saurischian dinosaur,
a "lizard-hipped dinosaur. This type of dinosaur
had a hip structure in which the pubis bone pointed forwards and downwards (unlike
the ornithischian dinosaurs in which the pubis pointed backwards and downwards).
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Brachiosaurus was one
of the tallest and largest dinosaurs yet found. It had a long neck, small head, and
relatively short, thick tail. Brachiosaurus walked on four legs and, like the other Brachiosaurids and unlike most dinosaurs, its front legs were longer than its hind legs. |
These unusual front legs together with its very long neck gave Brachiosaurus a giraffe-like stance and great height, up to 40-50 feet tall.
Brachiosaurus was about 85 feet
long , and weighed about 50-80 tons. It had a claw on the first toe of each front foot and
claws on the first three toes
of each rear foot (each foot had five toes with fleshy pads).
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Like other
Brachiosaurids, it had chisel-like teeth, its nostrils were on the top of its head, and it
had large nasal openings indicating that it may have had a good sense of smell. Brachiosaurus had 26 teeth on its top jaw and 26 on the bottom for a total of 52 teeth towards the front of the mouth. |
DIET
Brachiosaurus was an herbivore, a plant eater. It probably ate the tops of tall trees with
its large spatulate (chisel-shaped) teeth. It swallowed its food whole, without chewing
it, digesting the plant material in its gut.
WHEN BRACHIOSAURUS LIVED
Brachiosaurus lived in the middle to late Jurassic period, about 156-145 million years
ago, near the middle of the Mesozoic Era, the Age of Reptiles. Some dating estimates
have Brachiosaurus surviving until 140 million years ago, during the dawn of the
Cretaceous period.
Among the contemporaries of
Brachiosaurus were other giant Sauropods including Camarasaurus, Supersaurus, Ultrasauros,
and Haplocanthosaurus.
HABITAT
Brachiosaurus was a terrestrial animal. It was assumed for many years that giant sauropods
spent most of their time in water, letting the water support their weighty bodies while
breathing through their lofty nostrils. Now it is believed that they were fully
terrestrial, just as Elmer S. Riggs, who first described Brachiosaurus, argued in a 1904
article. He believed, as most modern scientists do, that Brachiosaurus' feet and limbs
were not broad enough to support the heavy animal in mud, that its back was flexible
enough to support it on land, and that its chest was narrow and deep, which is
insufficient for breathing underwater, and inconsistent with modern-day water-dwelling
large animals (like hippos).
POSSIBLE PREDATORS
A healthy, adult Brachiosaurus probably had no predators. The largest-known meat-eaters
from that time (the late Jurassic period) and place (North America and Africa) were
Allosaurus, Ceratosaurus, and Torvosaurus. These theropods were less than half the size of
Brachiosaurus, and probably had much easier prey to hunt (like smaller sauropods and
ornithischians like stegosaurs).
BLOOD PRESSURE PROBLEMS
Brachiosaurus and some of the other large sauropods (the huge long-necked plant-eaters)
needed to have large, powerful hearts and very high blood pressure in order to pump blood
up the long neck to the head and brain. The heads (and brains) of Brachiosaurus was held
high (many meters) above its heart. This presents a problem in blood-flow engineering. In
order to pump enough oxygenated blood to the head to operate Brachiosaurus' brain (even
its tiny sauropod brain) would require a large,
powerful heart, tremendously high blood pressure, and wide, muscular blood vessels with
many valves (to prevent the back-flow of blood). Brachiosaurus' blood pressure was
probably over 400 mm Mercury, three or four times as high as ours.
BEHAVIOR
Herds: Brachiosaurus probably travelled in herds
and may have migrated when they depleted their local food supply.
Eggs: Brachiosaurus may have hatched from eggs,
like other sauropods. Sauropod eggs have been found in a linear pattern and not in nests;
presumably the eggs were laid as the animal was walking. It is thought that sauropods did
not take care of their eggs.
Life Span: Sauropod life spans may have been in the
order of 100 years.
Defense: Brachiosaurus' best defense was size. In
addition, its long tail could whip away most attackers. Also, they had leathery skin,
although this wasn't much of a defense against long, sharp theropod teeth. They also had
clawed feet that were more pronounced in the young.
INTELLIGENCE
It used to be thought that the sauropods (like Brachiosaurus and Apatosaurus) and
Stegosaurus had a second brain. Paleontologists now realize that what they thought was a
second brain was an enlargement in the spinal cord in the hip area containing fatty tissue
and nerves. This area was larger than the animal's tiny brain and may have controlled the
animal's hind legs and tail.
Brachiosaurus was a sauropod, whose intelligence (as measured by its relative brain to
body weight, or EQ) was the among the lowest of the dinosaurs.
LOCOMOTION
Brachiosaurus was quadrupedal, walking on four legs. Unlike most other dinosaurs, the
front legs were longer than the hind legs.
DISCOVERY OF FOSSILS
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Brachiosaurus was first found in the Grand River Valley, in western Colorado, USA, in 1900. This incomplete skeleton was described by paleontologist Elmer S. Riggs, who named Brachiosaurus in 1903. In 1909, Werner Janensch found manyBrachiosaurus fossils in Tanzania, |
Africa. Many Brachiosaurus fossils have been found, mostly in North America, and Africa.
QUETZALCOATLUS
Named after the Aztec feathered god Quetzalcoatl
ANATOMY
Quetzalcoatlus was a flying reptile whose wing-span was over 40 feet wide. It was the
largest flying animal ever found. It had hollow bones, was lightly built, and had a small
body. Even though it was very big, it probably weighed only about 110 pounds. It had a
long, thin beak, toothless jaws, a small head, and a long neck.
They had large brains and good eyesight. Fur covered their bodies, and a light-weight,
bony crests on the head may have acted as a rudder for flying. The crest may also have
been a sexual characteristic.
| Quetzalcoatlus wings
were covered by a leathery membrane. This thin but tough membrane stretched between its
body, the top of its legs and its elongated fourth fingers, forming the structure of the
wing. |
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Claws protruded from the other
fingers. Quetzalcoatlus probably relied on updrafts (rising warm air) and breezes to help
it in flying.
WHEN
QUETZALCOATLUS LIVED
Quetzalcoatlus lived during the late Cretaceous period and died out about 65 million years
ago, during the K-T mass extinction.
DIET
Quetzalcoatlus was a carnivore and probably also a scavenger. It lived inland from the
sea, near fresh-water ponds (so its diet was not primarily sea fishes and marine mollusks
like other pterosaurs). It probably ate arthropods (like early crayfish) and also
available carcasses and dying animals. It probably hunted its prey by gliding toward the
ground and swooping up its meals (in a manner similar to modern-day vultures). It filtered
its food through its long, pointed, toothless jaws. Quetzalcoatlus must have had good
eyesight in order to spot meals from the air.
LOCOMOTION
Quetzalcoatlus flew long distances using large, light-weight wings.
DISCOVERY OF
FOSSILS
| The first Quetzalcoatlus fossil was found in Big Bend National Park, Texas, USA, by Douglas A. Lawson (who was then a geology graduate student at the University of Texas, Austin) in 1971. Lawson named Quetzalcoatlus 1975. Other smaller specimens have been found. |  . |
CLASSIFICATION
Quetzalcoatlus was a Pterosaur. Pterosaurs were reptiles, but not dinosaurs. By
definition, all dinosaurs were diapsid reptiles with an upright stance. Pterosaurs
probably had a semi-upright stance. There is a small minority of paleontologists who think
that the pterosaurs' stance could have been upright and that pterosaurs should therefore
be included in the clade of dinosaurs (being derived theropods). Either way,
dinosaurs and pterosaurs are certainly closely related.
Pterosaurs are:
vertebrates
tetrapods
Diapsids - these include all the reptiles (except turtles) and birds. They are
distinguished by having two holes in the rear upper part of their skulls and two holes
behind the eyes.
Archosaurs - this group includes dinosaurs, crocodilians, pterosaurs, birds, etc.
Pterosauria - flying reptiles. There are two type of pterosaurs:
Rhamphorhynchoids ("prow beaks") - early pterosaurs that appeared during the
Triassic period and went extinct at the end of the Jurassic, that had long tails, short
necks, and long, narrow wings. These were the first flying vertebrates. Examples include
Dimorphodon, Rhamphorhynchus, and Sordes. Pterodactyloids ("wing finger") -
their descendants that appeared late in the Jurassic and died in the K-T extinction, 65
million years ago, that had shorter tails. Examples include Dsungaripterus, Pterodactylus,
Pteranodon, and Quetzalcoatlus.
RIOJASAURUS
"Lizard from Rioja (a province in Argentina) "
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ANATOMY Riojasaurus was a massive quadrupedal (walked on four legs) herbivore. It was a about 30-36 feet long and was heavily built. It had a long neck, a long tail, a small |
head, a long, bulky body, and
thick, elephant-like legs with claws. The back legs were only slightly larger than the
front legs. Its limb bones were solid and thick, but its backbone was hollow. It had
spoon-shaped, serrated teeth.
WHEN RIOJASAURUS LIVED
Riojasaurus lived during the late Triassic and early Jurassic periods, about 225-219
million years ago.
DIET
Riojasaurus was an herbivore, a plant eater. Given its leg and ankle structure, it
probably couldn't rear up on its back legs to graze or run.
INTELLIGENCE
Riojasaurus was a sauropodomorpha, whose intelligence (as measured by its relative brain
to body weight, or EQ) was the lowest among the dinosaurs.
LOCOMOTION
Riojasaurus walked on four massive, elephant-like legs and was relatively slow. Dinosaur
speeds are estimated using their morphology (characteristics like leg length and estimated
body mass) and fossilized trackways.
DISCOVERY OF
FOSSILS
An almost complete Riojasaurus skeleton was found in northwest Argentina, in La Rioja
Province. It was named by the Argentinian paleontologist Jos� F. Bonaparte in 1969.
CLASSIFICATION
Riojasaurus was a Saurischian dinosaur, the order of lizard-hipped dinosaurs. It was a
sauropodomorpha (quadrupedal herbivores) and a melanorosauridae (the
largest prosauropods; quadrupedal, thick-limbed herbivores).
Triceratops horridus
"Horrible Three-horned Face"
ANATOMY
Triceratops was a rhinoceros-like dinosaur. It walked on four sturdy legs and had
three horns on its face along with a large bony plate projecting from the back of its
skull (a frill). One short horn above its parrot-like beak and two longer horns (over 3
feet or 1 m long) above its eyes probably provided protection from predators. The
horns were possibly used in mating rivalry and rituals. It had a large skull, up to 10
feet (3 m) long, one of the largest skulls of any land animal ever discovered. Its head
was nearly one-third as long as its body. Triceratops hatched from eggs.
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Triceratops was about
30 feet long, 10 feet tall, and weighed up to 6-12 tons. It had a short, pointed tail, a
bulky body, column-like legs with hoof-like claws, and a bony neck frill rimmed with bony
bumps. It had a parrot-like beak, many cheek teeth, and powerful jaws. |
WHEN TRICERATOPS LIVED
Triceratops lived in the late Cretaceous period, about 72 to 65 million years ago, toward
the end of the Mesozoic, the Age of Reptiles. It was among the last of the dinosaur
species to evolve before the Cretaceous-Tertiary extinction 65 million years ago. Among
the contemporaries of Triceratops were Tyrannosaurus rex (which probably preyed upon
Triceratops), Ankylosaurus (an armored herbivore), Corythosaurus (a crested dinosaur), and
Dryptosaurus (a meat-eating dinosaur).
BEHAVIOR
Triceratops was probably a herding animal, like the other Ceratopsians. This hypothesis is
supported by the finding of bone beds, large deposits of bones of the same species in an
area. Triceratops hatched from eggs, which may have been cared for by adults.
When threatened by predators, Triceratops probably charged into its enemy like the
modern-day rhinoceros does. This was probably a very effective defense.
INTELLIGENCE
Triceratops was a ceratopsian, whose intelligence (as measured by its relative brain to
body weight, or EQ) was intermediate among the dinosaurs.
DIET, TEETH, AND TRICERATOPS POSITION IN THE FOOD CHAIN
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Triceratops was an herbivore, a plant eater (a primary consumer). It probably ate cycads, palms, and other low-lying plants with its tough beak. Triceratops could chew well with its cheek teeth (like other Ceratopsians, but unlike most other dinosaurs). |
LOCOMOTION
Triceratops walked on four short legs; it was a relatively slow dinosaur. Dinosaur
speeds are estimated using their morphology (characteristics like leg length and estimated
body mass) and fossilized trackways.
LOCATIONS AND DISCOVERY OF FOSSILS
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Many Triceratops fossils have been found, mostly in western Canada and the western United States. Paleontologist Othniel Marsh named Triceratops from a fossil found near Denver, Colorado, USA, in 1889. At first this fossil was mistakenly identified as an extinct species of buffalo. |
The first Triceratops skull was found in 1888 by John Bell Hatcher. About about 50 Triceratops skulls and some partial skeletons have been found.
CLASSIFICATION
Triceratops was a late Ornithischian dinosaur, the order of bird-hipped, herbivorous
dinosaurs. It was a member of the suborder Marginocephalia, and the family of large,
horned, herding herbivores, the Ceratopsians. The ceratopsians were one of the last major
group of dinosaurs to evolve, and include Psittacosaurus, Leptoceratops, Pachyrhinosaurus,
Montanoceratops, Chasmosaurus, Centrosaurus, Triceratops, Styracosaurus, Protoceratops,
and others. There is some disagreement about how many species of Triceratops have been
found. Some paleontologists (notably Ostrom and Welnhoffer, 1990) believe there is one
species, Triceratops horridus. Others believe that there are two (C. Forster, 1996) or
more species, including: Triceratops horridus, Triceratops prorsus, Triceratops
albertensis, Triceratops ingens, Triceratops alticornis, and perhaps others.
MEGALOSAURUS
"Great Lizard"
ANATOMY
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Megalosaurus walked on two powerful legs, had a strong, short neck, and a large head with sharp, serrated teeth. It had a massive tail, a bulky body, toes also had sharp claws, and heavy bones. Its arms were short and had three-fingered hands with sharp claws. Megalosaurus was up to 30 feet long, 10 feet tall, and weighed about 1 ton. |
WHEN MEGALOSAURUS LIVED
Megalosaurus lived in the early Jurassic period to the early Cretaceous period, about
175-155 million years ago.
DIET
Megalosaurus was a carnivore, a meat eater. It was a large, fierce predator that could
kill even large sauropods. Megalosaurus may also have been a scavenger.
INTELLIGENCE
Megalosaurus was a carnosaur, whose intelligence (as measured by its relative brain to
body weight, or EQ) was high among the dinosaurs.
LOCOMOTION
Megalosaurus walked on two muscular legs and was a relatively fast runner. Dinosaur speeds
are estimated using their morphology (characteristics like leg length and estimated body
mass) and fossilized trackways.
DISCOVERY OF FOSSILS
Megalosaurus was the first dinosaur fossil discovered (in England in 1676). It was also
the first dinosaur given a scientific name - by William Buckland in 1824. Megalosaurus
trackways have been found in limestone in southern England.
CLASSIFICATION
Megalosaurus was a Saurischian ("lizard-hipped") dinosaur. It was a theropod, a
carnosaur, and a megalosaurid (the earliest carnosaurs; they included Torvosaurus,
Poikilopleuron, and others).
