Late in the summer of 1993, Robert Hall, Chairman of the Department of Geology, Indiana University-Purdue University at Indianapolis (IUPUI) thought it would be a good idea to invite a couple of dinosaur workers to campus to capitalize on the frenzy of enthusiasm for dinosaurs that the movie, Jurassic Park, had generated. However, what originally was to have been a couple of guest lectures quickly evolved into a three-day affair that was probably the first scientific conference–certainly the first paleontologic conference–for the general public, raising important issues about public involvement in science.

Although they have been extinct for more than 60 million years, dinosaurs are a familiar part of our culture. Featured regularly in entertainment, advertising and the news, they are recognized more readily in today's society than many living animals. Dinosaurs also function as a powerful educational tool, stimulating the interest of children and adults in the natural world. Moreover, they serve as a primary symbol of evolution, extinction and the long history of life on Earth. Yet, few people realize how radically our understanding of dinosaurs has changed since their discovery 170 years ago.

The initial recognition of dinosaurs as a distinct group of extinct animals was one of the major accomplishments of nineteenth century science. When first discovered, dinosaurs were an unexpected and almost alien life form whose interpretation was inhibited by a scarcity of good fossils and absence of close living relatives. For this reason, early nineteenth century dinosaur reconstructions, which were later ridiculed for their inaccuracies, may seem simplistic and conservative. In reality, they were quite innovative. Examination of this early work reveals just how profound these ideas actually were in light of the limited evidence available and demonstrates how interpretations changed as new fossil discoveries were made.

Dinosaurs were enormously successful animals. They inhabited all seven continents, including polar regions during the Mesozoic. Their temporal range, as currently understood, extends from the Carnian stage of the Late Triassic beginning 228 Ma, to the Maastrichtian stage of the Late Cretaceous, ending 65 Ma. With a temporal span of 163 million years, dinosaurs cannot be judged as failures by puny naked bipeds who have been here for two million years or less and who threaten not only their own existence but that of much of the biosphere. The fossil record of dinosaurs is a complex document that cannot merely be read at face value but which must be carefully evaluated with respect to its inherent biases. There is much we wish to ask about dinosaurs that can only be answered with a mature reliable record. The object of this essay is to discuss some of the factors that impact both on dinosaur diversity itself, and on our understanding of that diversity. While fossils have an objective existence in the rocks, our understanding of their record is the result of a very human process of scientific discovery, subject to the contingencies and biases of history (Dodson, and Dawson, 1991).

Everybody knows what dinosaurs are- or were. They were land animals which appeared first in the late Triassic, about 210 million years ago, and became extinct at the end of the Cretaceous, about 65 million years ago. They were extremely successful, being the most conspicuous and diverse terrestrial vertebrates for about 145 million years. The most impressive feature of dinosaurs is their large size, and though much is made of adult dinosaurs no bigger than a chicken, the fact remains that the smallest of these were larger than more than 70% of living mammals (Hotton, 1980).

If one were to ask a group of paleontologists “How do dinosaurs fit into the history of life on Earth?” the answers would all be different. The question is so big that it surpasses the vision of a single person, and the answers would be as diverse as those of the blind men describing an elephant from its parts. The answer which follows is also from someone who cannot see the whole “elephant.” It is so simple that it is surely grossly inadequate, like lamely describing the hypnotically beautiful appearance of the Earth from space as spherical.

In 1915 the Carnegie Museum of Natural History's magnificent skeleton of the sauropod dinosaur Apatosaurus louisae, discovered in 1909 at what is now Dinosaur National Monument in northeastern Utah, took its place alongside the equally impressive skeleton of Diplodocus carnegii in the Hall of Dinosaurs. At that time and for the next 17 years, however, it stood conspicuously headless. It was not until December of 1932 that the skeleton was completed, and then with the wrong head—a Camarasaurus skull. How this came about and how the error was corrected requires the untangling of a long series of events that began with the first discoveries and descriptions of the giant sauropod dinosaurs of North America over a century ago.

“…SPEAK TO THE EARTH, AND LET IT TEACH YOU.” (Job 12:8 NASB)

Ambitious collectors have been gathering fossils for centuries and should be allowed to continue. A glimpse at fossil collecting through history gives us an idea of how paleontology affects people. A Roman ruler, Gauis Caesar, better known as Caligula, did some field work in paleontology. Caligula was most likely mad. One of the common proofs pulled from history affirming his madness is the fact that he made his horse a councilman advisor to the senate. There are so many stories of the perverted life Caligula led, it is likely the term “caliginous,” which describes dark and gloomy aspects, came from his name.

I have always loved dinosaurs, and I feel fortunate to be able to teach teachers and students about dinosaurs as part of my profession; and yes, my name is really Dinah. Every year for the past 10 years, I have worked with thousands of teachers and students across the United States. During this time, I have made a startling discovery not mentioned in any of the classic human growth and development textbooks. I have found that most Americans pass through the following developmental stages, based upon dinosaurs:

We are surrounded by dinosaurs. From toilet paper to teacups, television specials and Hollywood films, and more than 300 current books, dinosaurs are as ubiquitous as Ninja Turtles. But dinosaurs are no fad, as merchandisers have belatedly realized. They are a rite-of-passage for the young, a fascination that grips every generation.

Our love for dinosaurs is beyond reason. We loved dinosaurs when they were presented as elephantine behemoths, as cold-blooded sluggards. And we love them all the more now that explorations indicate some were as smart as ostriches, as swift as foxes (not as swift as cheetahs nor as smart as chimpanzees, except in the imaginations of Messrs. Crichton and Spielberg), as small as turkeys, as maternal as Donna Reed, as hot-blooded as Madonna, and that all endured far longer than we. World-dominant and immensely varied in form, habitat and behavior for 160,000,000 years, dinosaurs were, arguably, the greatest of all evolutionary success stories.

Speculation about the behavior and life activities of any kind of extinct animal seems to be a waste of time. But people are curious, and they do it all the time. Their favorite subjects, of course are dinosaurs. You don't have to be an expert and it doesn't cost any money. Anybody can do it. Did Diplodocus swim? Or just soak in those Mesozoic lakes and streams? Did Tyrannosaurus chase its prey, or did it just scavenge on left-overs? Did Mononykus burrow in the ground to hide its head, or did it just scratch its arm pits? It is obvious that it didn't fly, but it must have run fast. You don't have to be a paleontologist, or an ethologist. In fact, it is probably an advantage not to be a scientist at all. (How come? Then you're free to let your imagination run wild. That sure would help Mononykus.) The only equipment you need is a powerful imagination, some common sense, and a certain amount of evidence. That evidence will be the clues, the tips that stimulate your imagination–in this case, how a long-dead animal that lived many millions of years ago behaved. Let me show you how that works.

The discovery in recent years of several well preserved and partially articulated skeletons of Tyrannosaurus rex has provided the impetus for a study of sexual dimorphism in dinosaurs. The fifteen significant specimens of Tyrannosaurus rex discovered to date may be divided into “robust” and “gracile” morphotypes. Examinations of extant crocodiles and birds show a link between musculature of sexual organs and sexual dimorphism of osteoskeletons. Analogous differences in articulated dinosaur remains point to a method of determining the gender of individual dinosaur skeletons and the presence of an intromittent organ in at least some species. For theropods, and particularly for Tyrannosaurus rex, the larger and more robust individuals are almost certainly female.

I'll begin with the obvious question, how many people saw the movie “Jurassic Park”? How many people believed it? In the movie, “Jurassic Park”, there were basically two stars. Tyrannosaurus rex was one of them and the Velociraptors (or Deinonychus, or whatever they happened to be) were the others. What you might also know is that I was an advisor on the movie. All I was able to do was basically tell them when the dinosaurs were walking right and tell Laura Dern how to pronounce her words.

Any time the dinosaurs were going to do something, any time Steven Spielberg wanted to have the dinosaurs do something in the movie, he would ask me if I thought they could do that. If I said yes or no, he would take that as an answer. But if I said maybe, he would just do whatever he wanted. That's fiction.

Large theropod dinosaurs like tyrannosaurs were the biggest land-living predators in earth history. Because of this, there has been considerable interest in reconstructing the paleobiology of these immense carnivores (Bakker, 1986; Bakker et al., 1988; Paul, 1988; Molnar and Farlow, 1990; Farlow et al., 1991; Abler, 1992; Farlow, 1993, in press; Horner and Lessem, 1993). In the present paper we consider a topic relevant to interpretations of how tyrannosaurs used their teeth during feeding: the incidence of wear surfaces on tyrannosaur teeth.

Among dinosaurs, megadinosaurs (those over one tonne) have been considered among the best candidates for having had low metabolic rates (LoMRs). Spotila et al (1991) argued that big dinosaurs were gigantotherms that shared thermal characteristics with the large leatherback sea turtle, and Dodson (1991) suggested that giant dinosaurs lived in the slow lane compared to giant mammals. Coulson (1979), Bennett (1991) and Ruben (1991) restored big dinosaurs as “good reptiles” powered by bursts of reptilian hyperanaerobiosis rather than the sustained tachyaerobiosis that powers birds and mammals. Farlow (1990) suggested that large dinosaurs were “damned good reptiles” with fluctuating metabolic rates (MRs), and in 1993 he argued that dinosaurs used a combination of rapid reproduction and intermediate metabolic rates (InMRs) to grow bigger than land mammals. All the above workers, and McNab (1983) and Dunham et al. (1989), have modeled big dinosaurs as LoMR or InMR inertial homeotherms that maintained constant body temperatures on a daily basis.

Dinosaur activity has been the object of speculation since the first skeletal reconstructions were completed in the last century. Charles Knight, the famous artist, painted dinosaurs as active agile animals whereas researchers later portrayed them as slow moving and clumsy due to some similarities with modern reptiles. Modern research leans toward an active lifestyle for such enormous animals. This implies that dinosaurs needed a lot of oxygen to supply the necessary energy for these activities, but is it possible to estimate just how much this really was? Modern investigations confirm that the ability to supply oxygen to active tissues such as muscle is the factor most likely to set the limits of performance.

A study of the anatomy and morphology of a fossil skeleton indicates the overall size, posture, and form of the animal. Even various functional aspects of the skeleton such as preferred mode of locomotion and chewing mechanisms can be deduced from such studies. But the desire to understand dinosaurs as dynamic, once-living animals and not merely as taxonomic entities arranged in phylogenetic schemes, goes beyond this. In 1842, Sir Richard Owen not only presented dinosaurs taxonomically but he also initiated the quest to understand the biology of these animals. In recent decades, the study of dinosaur paleobiology has blossomed, and has provided a crucial link between studies of morphology (structures) and that of function and physiology.

The most tangible clues to the existence and lifestyle of extinct vertebrates are the fossilized bones preserved in sedimentary rocks. During the past two hundred years, scientists have excavated, prepared and reassembled the often fragmentary remains of dinosaurs, enabling them to reconstruct the size, proportions and general anatomy of these Mesozoic reptiles. However, the information available from the bones is not restricted to details of the hard tissues themselves. Bone is a living tissue that interacts with the soft tissues of the body and retains evidence of this interaction after death. As a result, paleontologists are able to use preserved bones and other hard tissues to predict traits of physiological processes and of soft tissues. Prime examples of this approach have been the attempts to predict the thermal regime of dinosaurs. Histological structure of bone has been shown to vary with thermal regime in living vertebrates (Ricqles, 1976; Reid, 1987), and the preserved fine-structure of fossilized dinosaur bone has allowed direct comparison with the bone of living vertebrates. Other examples of reconstruction of lifestyle and soft tissues from bony remains include use of the muscle scars on dinosaur bone to predict size and orientation of muscles (Gatesy, 1990), and of dentition and jaw geometry to predict dietary regime (Weishampel and Norman, 1989).

Dinosaurs were an abundant group of reptiles that originated in the mid-Triassic. They rapidly diversified, filling all of the ecological niches for large-bodied terrestrial vertebrates by the Late Triassic and dominated this landscape for 163 m.y. Yet due to the lack of direct evidence little is known about their metabolism. The question as to whether dinosaurs were “warm-blooded” or “cold-blooded” has been debated for over 25 years. Knowledge of dinosaur thermal physiology is critical if we are to understand how they lived and functioned. This knowledge can then be used to help answer questions regarding to their origin, diversification, and their eventual extinction. The question that is being resolved here is, “How do you stick a thermometer into dinosaur bone?”.

Paleontologists study past life through analysis of the fossil record. Vertebrate paleontologists are particularly interested in studying those animals with vertebral columns (backbones). The biology of vertebrates is dictated by the millions of cells that make up these complex animals. Histology is the science concerned with the microscopic anatomy of cells, tissues and organs. All life forms are made of cells (membrane-bound bodies within which the chemical reactions necessary to sustain life occur). In complex animals, such as vertebrates, similar cells work together in associations called tissues. Typically, only the harder tissues of the vertebrate body become preserved as fossils. An example of a hard tissue is bone. Our ability to derive information from a fossil is dependent on how well it is preserved and on the techniques we use to study the specimen. Certain fossilization regimes conserve cellular and sub-cellular structure and microscopic examination of appropriately prepared specimens permits detailed study of fossil bone histology (Barreto and Albrecht 1993). The microscopic structure of bone reflects the activity of the cells that produced it. All organisms on earth, and all the cells that compose them are descended from a common ancestral cell; and we have no reason to believe that cells that produced bone millions of years ago were different from bone cells we can study in living animals today. It is possible to compare the cellular structure of well preserved fossil bone to modern bone. Such research, called “paleohistology,” allows interpretation of the biology of extinct vertebrates (Reid 1984; Ricqles 1976; Ricqles 1980).