Tyrannosaurus Rex

Species: Tyrannosaurus Rex
Habitat: North American Forests
Status: Extinct
DAK Locale: Dinoland USA

The T-Rex was a large predatory dinosaur from the late Cretaceous period. In fact, it had a strong population throughout the North American continent as late as 65 million years ago. It was common at the time of the Cretaceous-Tertiary mass extinction.

It was one of the largest meat eaters that ever lived. Its thick four foot long jaw was perfect for tearing into the large herbivore dinosaurs that roamed the forests at that time. It was also prefect for crushing bone. In fact, bones have been found in its fossilized feces. It also had serrated teeth that likely allowed it to grip and tear off flesh in large chunks.

At its maximum, it was about forty feet long and perhaps as tall as 20 feet. It was likely quite fast thanks to its powerful thighs. The short arms probably allowed to hold prey but did not allow it to reach its mouth. Its huge head required a large heavy tail to keep its balance.

Scientists continue to debate the role the animal played in the ecosystem. Some believe the T Rex was a powerful predator. Others believe it was likely a scavenger as its teeth allowed it to break and chew bones. Plus, it seems to have had a strong sense of smell, a common feature in carrion feeders. But that is not the only debate amongst scientists. Some believe that infants may have been covered in feathers like some other closely related dinosaurs at the time. Others also believe that it may have even had a warm blooded metabolism.

In 1990, a paleontologist found a nearly complete (85%) fossil of the dinosaur. That fossil now appears at the Field Museum in Chicago. However, parts of it were worked on and restored at Disney's Animal Kingdom. A replica of the complete fossil is on display near the entrance to the Dinosaur attraction.

Iguanodon

Species: Iguanodon
Habitat: Europe
Status: Extinct
DAK Locale: Dinoland

The Iguanodon in the early Cretaceous Period, which was approximately 125 millions years ago. It was first discovered in England in 1822 by Gideon Mantell. It was the second dinosaur to receive a formal name by scientists. The first being the Megalasauros. Since then, numerous fossils have been uncovered with related species being found in North America and China, as well. As such, it is one of the best understood and studied dinosaurs. Even its footprints have been found repeatedly in Europe.

One excavation uncovered thirty fossils in Belgium. At first, it was felt this meant that the Iguanodon was a herding animal. However, it appears that this find did not represent one catastrophe. In any event, most do believe that they at least lived in small groups if not large herds.

The animal was a herbivore, or plant eater, and a big one. One fossil found was that of a animal over 30 feet tall. It likely weighed as much a three and a half tons. The dinosaur had a beak not unlike that of a turtle which allowed it to break off vegetation. It had a hinged upper jaw that allowed it to grind the upper jaw with the lower jaw. Hence, it was one of the first dinosaurs that could chew. Other dinosaurs and all reptiles cannot chew.

The most distinctive feature of the animal was the thumb, which stood straight out like a spike. It is not exactly known why the animal had an inflexible spike for a thumb. Most believe it was a defensive mechanism. Basically, the Iguanodon had a built in knife to fend off predators. Others believe it was also used to break into seeds and nuts. The rest of the hand was also unusual in that the middle three fingers were bound together with skin. The little finger was flexible allowing it to grasp food. It could rear up on two legs (perhaps to ward off predators or reach food) but likely most often walked on all fours.