Teacher's Guide T. REX banner

Background

How Science Works
Scientists explore, make discoveries, hypothesize (propose an explanation), test, evaluate, and form conclusions about their hypothesis. This exhibition hypothesizes that T. rex, a carnivorous dinosaur, was a scavenger feeding on dead animals rather than a predator hunting and killing its food. Fossils and exhibit text are used to explain the characteristics associated with predators and scavengers. Viewers are asked to examine the evidence presented and to decide whether T. rex was a predator, scavenger, or something in between.

Fossils
Giganotosaurus skull photo by Tim Murray
Giganotosaurus skull
Paleontologists are scientists who study fossils. Fossils are indicators of past life. There are many types of fossils, such as bones, feces, plant material that has become mineralized, footprints or impressions of skin that have been preserved in stone, or simply something that indicates a certain lifestyle such as gastroliths--stones swallowed to aid digestion.

Paleontologists use a variety of methods to learn about ancient life. These include reconstructing fossils, comparing unidentified specimens with known specimens, looking for repeating patterns (nests that are all the same distance apart), building models, and comparing fossils with living plants and animals. Some paleontologists study dinosaurs--a type of land-dwelling reptile that lived during the Mesozoic Era about 250 to 65 million years ago.

Dinosaur Classification
Dinosaurs are generally divided into two major groups according to their hip structure--the lizard-hipped and the bird-hipped. The lizard-hipped (Saurischia) are also divided into subgroups--sauropods (large plant-eaters like Apatosaurus) and theropods (carnivores such as Tyrannosaurus rex). The plant-eating, bird-hipped (Ornithischia) dinosaurs are subdivided into groups such as the stegosaurs, ceratopsia, ankylosaurs, and ornithopods.

A simple diagram of dinosaur classification:

Saurischia
("lizard-hipped")
a. Ilium
b. Pubis
c. Ischium
Sketch of Saurischia hip bone      Ornithischia
   ("bird-hipped")
   a. Ilium
   b. Pubis
   c. Ischium
Sketch of Ornithischia  hip bone  
Theropoda
Small silhouette of  Carnosauria
Carnosauria carnivore    Small silhouette of Stegosauria     Stegosauria herbivore
Small silhouette of Coelurosauria Coelurosauria carnivore      Small silhouette of Ankylosauria Ankylosauria herbivore
Sauropodomorpha        Small silhouette of Ornithopoda Ornithopoda herbivore
Small silhouette of Prosauropoda Prosauropoda herbivore        Small silhouette of Ceratopsia Ceratopsia herbivore
Small silhouette of Sauropoda Sauropoda herbivore  


Theropods
Theropods are the primary focus of this exhibition. These dinosaurs lived throughout the Mesozoic Era from the Triassic Period through the Jurassic and Cretaceous Periods. Megalosaurus, the first theropod fossil to be discovered, was found in England by William Buckland in 1819. Since then, theropod discoveries have been made in many areas of the world. While some T. rex bones were found in Wyoming in 1900, the type specimen was discovered in Montana in 1902. In 1988 a nearly complete skeleton of T. rex was found in Montana by Kathy Wankel, and an even larger and more complete skeleton, "Sue," was found in South Dakota by Sue Henderson in 1990. Even bigger than Tyrannosaurus rex are the recent discoveries of theropods such as Carcharodontosaurus, Giganotosaurus, and Acrocanthosaurus.

Some theropods such as Compsognathus, were small (2 feet); while others such as Carcharodontosaurus were quite large (52 feet). Theropods walked on two feet, had three or fewer toes on each foot, and had hollow bones. Most of them moved fast, had sharp teeth and claws, and were not cold-blooded. All theropods were carnivores; that is, they ate other animals.

Carnivore--Scavenger versus Predator
Carnivores acquire food by killing another animal or by eating one that is already dead. Predators--carnivores that chase and kill their prey--are usually fast and agile. They have adaptations for rapid movement and often have good eyesight. Scavengers--carnivores that feed on dead animals--often have a good sense of smell that is useful for finding dead animals. Scavengers do not need to run as fast as predators. It is probable that some theropods were predators, some were scavengers, and others may have been both predator and scavenger. T. rex is possibly the most famous of all the carnivorous dinosaurs. Was Tyrannosaurus a predator, a scavenger or something in between? This question forms the basis for the exhibition T. REX ON TRIAL.

Giganotosaurus skull photo by Tim Murray
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Evidence

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