T. rex was a huge meat-eating dinosaur that lived during the late Cretaceous period, about 85 million to 65 million years ago. T. rex lived in a humid, semi-tropical environment, in open forests with nearby rivers and in coastal forested swamps. The seasons were mild. Until recently, Tyrannosaurus rex was the biggest known carnivorous dinosaur; Giganotosaurus and Carcharodontosaurus are slightly bigger. Tyrannosaurus rex was a fierce predator that walked on two powerful legs. This meat-eater had a huge head with large, pointed, replaceable teeth and well-developed jaw muscles. It had tiny arms, each with two fingers. Each bird-like foot had three large toes, all equipped with claws (plus a little dewclaw on a tiny, vestigial fourth toe). T. rex had a slim, stiff, pointed tail that provided balance and allowed quick turns while running. T. rex's neck was short and muscular. Its body was solidly built but its bones were hollow.Tyrannosaurus rex was up to 40 feet (12.4 m) long, about 15 to 20 feet (4.6 to 6 m) tall. The arms were only about 3 feet (1 m) long. Tyrannosaurus rex was roughly 5 to 7 tons in weight. The enormous skull was about 5 feet (1.5 m) long. The eye sockets in the skull are 4 inches (10.2 cm) across; the eyeballs would have been about 3 inches (7.6 cm) in diameter. T. rex left footprints 1.55 feet (46 cm) long (although its feet were much longer, about 3.3 feet (1 m) long; T. rex, like other dinosaurs, walked on its toes). It had a stride length of up to 12 to 15 feet (3.7-4.6 m). T. rex may have run at up to 15 mph (24 kph).
The most bird-like dinosaur ever discovered is the 90-million-year-old Unenlagia comahuensis, a flightless, 4-foot tall, 7.5-foot-long carnivore. It is the size of an ostrich, but shaped like Velociraptor. Unenlagia had flexible arm movement (up and down movements were possible, like that which a bird uses in flying) - it could also grasp with its clawed, short, wing-like forearms. This new fossil helps show how dinosaur forearms evolved into the wings of modern-day birds.Unenlagia had a shoulder structure that allowed its short arms to move forwards, backwards, inwards (for grasping prey), and up and down (for a flapping motion). This flapping motion was not used for flying, because its wing-like arms were too short to support the heavy dinosaur. Perhaps these proto-wings were used for balancing, turning, and a bit of lift during high-speed running. Although there is no fossil evidence of feathers from Unenlagia, it may well have had them, further adding lift to each upstroke of the proto-wings.
Utahraptor was a large, terrifying mid-Cretaceous predator with 9-15 inch long middle-toe claws. It was a lightly built, fast-moving, agile, bipedal (walked on two legs), bird-like dinosaur. It had a curved, flexible neck and a big head. Sharp, serrated teeth were set into very powerful jaws. Each of its three fingers on each arm had large, sharp, curved claw. It had four-toed feet; the second toe had a 9-15 inch (23-38 cm) sickle-like claw and the other toes had smaller claws. Its long tail had bony rods running along the spine giving it rigidity; the tail was used for balance and fast turning ability. It had a relatively large brain and large, keen, eyes. Utahraptor was 16-23 feet (5-7 m) long and may have weighed about 1 ton.
Utahraptor lived in the early Cretaceous period, about 125 million years
ago.Utahraptor, like other dromaeosaurids, may have hunted in packs, attacking
even very large animals, perhaps even large sauropods and ankylosaurids.
Utahraptor was a carnivore, a meat eater. It probably ate just about anything it could slash and tear apart. When hunting in packs, Utahraptor could probably kill any prey it desired.
Yangchuanosaurus was a large, powerful meat-eater. It walked on two large, muscular legs, had short arms, a strong, short neck, a big head with powerful jaws, and large, serrated teeth. It had a long, massive tail that was about half of its length. Its feet had three toes, each with a large claw. Its arms were short, and it had three clawed fingers on each hand.Yangchuanosaurus was up to 33 feet long (10 m). It weighed roughly 5200 pounds (2350 kg). It had a large skull up to 3.5 feet (1.1 m) long with ridges and a bony knob on its snout. It was slightly smaller but very similar to its close relative Allosaurus.Yangchuanosaurus lived during the late Jurassic period to the early Cretaceous period, about 163-145 million years ago. Yangchuanosaurus was a hunter that may have stalked its prey in packs.
Velociraptor was a fast-running, two-legged (bipedal) dinosaur. This meat-eater had about 80 very sharp, curved teeth in a long, flat snout; some of the teeth were over an inch (2.5 cm) long. This predator had an s-shaped neck, arms with three-fingered clawed hands, long thin legs, and four-toed clawed feet. Velociraptor's head was about 7 inches (18 cm) long. Velociraptor may have been able to run up to roughly 40 mph (60 km/hr) for short bursts.Velociraptor was about 5 to 6 feet long (1.5-2 m), and 3 feet tall (1 m). It may have weighed about 15 to 33 pounds (7 to 15 kg). It had a stiff tail that worked as a counterbalance and let it make very quick turns. Velociraptor's brain was relatively large in comparison to its body size (this is true for all the Dromaeosaurid dinosaurs, who were the most intelligent dinosaurs).Velociraptor lived during the late Cretaceous period, about 85 - 80 million years ago. Among the contemporaries of Velociraptor were Protoceratops, Gallimimus, Oviraptor, Edmontosaurus, Maiasaura, and Saurolophus. Velociraptor lived in a hot, dry environment - a desert-like environment that had some streams.Velociraptor was a carnivore, a meat eater. It probably ate just about anything it could slash and tear apart. It may have hunted in packs. It ate Protoceratops (one was found fossilized with Velociraptor in a battle to the death) and probably ate many other plant-eaters, like hadrosaurs (duck-billed dinosaurs).
Zigongosaurus was a huge, long-necked, long-tailed, plant-eating dinosaur that lived roughly 150 million years ago.Zigongosaurus was a large quadrupedal (walked on four legs) herbivore. It was a about 35 feet (10.7 m) long and may have weighed about 20 tons. It had a long neck, a long tail, a small head with spoon-shaped teeth, and thick, elephant-like legs.Zigongosaurus lived during the late Jurassic period. Zigongosaurus was an herbivore, a plant eater. It stripped foliage with spoon-shaped teeth. Zigongosaurus may have traveled in herds and migrated when they depleted their local food supply. Zigongosaurus 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. Sauropods life spans may have been in the order of 100 years.Zigongosaurus 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 track ways.
Iguanodon was a plant-eating dinosaur that had a conical spike on each
thumb. This 30-foot-long dinosaur lived during the early Cretaceous period,
about 135 to 125 million years ago.Iguanodon was a dinosaur that had a
horny, toothless beak and tightly-packed cheek teeth. On each hand, Iguanodon
had four fingers plus a conical thumb spike on each hand (that was perpendicular
to the other fingers). The thumb spikes may have been used for defense
or in obtaining food; it ranged from 2 to 6 inches long. Iguanodon had
a flat, stiff tail and three-toed hind feet with hoof-like claws. Its
legs were much larger than its arms.Iguanodon averaged about 30 feet long
(9.3 m), 16 feet tall (5 m), 9 ft (2.7 m) tall at the hips, and may have
weighed 4 to 5 tons. Iguanodon lived in the early Cretaceous period, about
135-125 million years ago, toward the end of the Mesozoic. The super continent
Pangaea was breaking up at this time, but Iguanodon managed to spread
to all the continents except Antarctica. Among the contemporaries of Iguanodon
were Baryonyx, Brachiosaurus, and Hypsilophodon.Iguanodon was probably
a herding animal, as evidenced by bonebed discoveries in Belgium. In these
bone beds, dozens of Iguanodon fossils were found together, suggesting
that they congregated during their lives.