The great majority of paleontologists study fossil invertebrates (“shellfish” in the broad sense). Others specialties include paleobotany (study of fossil plants), micropaleontology (study of microscopic fossils), and…

• Most vertebrate paleontologists do not study dinosaurs. Other groups include mammals, pterosaurs (flying reptiles), marine and other non-dinosaurian reptiles, amphibians, and the many groups of fish.
• Until recently, there were many more specialists in fossil mammals than in fossil dinosaurs: however, in recent years the number of active dinosaur specialists has caught up with the number of paleomammalogists.
• Even so, there are still only a few dozens of dinosaur specialists in the world: the textbook's 47 authors include about one half to one third the number of professional dinosaur researchers (professors and graduate students, museum curators, etc.) in the world today.

Some vertebrates that are NOT dinosaurs:

• Living mammals (humans, cats, dogs, whales, horses, kangaroos, platypi, etc.)
• Extinct mammals (sabretoothed cats, mammoths, giant ground sloths, etc.)
• The finbacked creatures of the Paleozoic, such as Dimetrodon (not a dinosaur, not even a reptile, but actually closer to mammals than to dinosaurs, lizards, turtles, and other true reptiles)
• The marine reptiles of the Mesozoic (ichthyosaurs, plesiosaurs, mosasaurs, and the like)
• Pterosaurs (flying reptiles such as the pterodactyls and their ancestors) (however, these are the closest major group to the dinosaurs)

Dinosaurs started as relatively small (1 m long) bipedal animals with upright hindlimbs around 235 million years ago. During the following millions of years they evolved into many diverse forms:

• Armored dinosaurs
• Horned headed and dome headed dinosaurs
• Beaked herbivores of many kinds, including the duckbills
• Long necked herbivores, including the largest animals ever to live on land
• And many kinds of bipedal carnivorous dinosaurs.

Dinosaur fossils have been found in Mesozoic Era rocks from every continent, including Antarctica.

Types of fossils:

• Isolated bones and teeth
• Skeletons, in varying degrees of completeness
• Footprints and trackways
• Skin impressions
• Feathers
• Mineralized soft tissue (muscles, intestines, possible heart)
• Eggs (some with embryos) and nests
• Coprolites (fossilized feces)

Dinosaur fossils have been weathering out of the rock since long before humans were around. For many millennia they have been explained in a variety of ways. In the early 1800s various British fossils were recognized as coming from giant land-dwelling reptiles with certain shared features (extra hip vertebrae, upright hindlimbs, etc.). In 1842 Sir Richard Owen coined the name Dinosauria for this group:

• Greek deinos “fearfully great” (i.e., not just big, but SCARY BIG!), and sauros “lizard”
• Note: hundreds of books to the contrary, Owen did not say Dinosauria meant “terrible lizard”

Science:

• Is NOT simply a body of knowledge
• Is a way of understanding the physical universe
• Uses the method of testing hypotheses
  • Observations of natural phenomena lead to possible explanations (hypotheses)
  • These hypotheses must be falsifiable (i.e., there must be some test, experiment, or observation which can demonstrate that the hypothesis is untrue)
  • Until the hypothesis is tested, it is only considered a speculation
  • If the hypothesis survives a test (or tests) of falsification, it is tentatively (or provisionally) accepted (keeping in mind that additional tests might potentially overturn the hypothesis)
• Proceeds by publication of ideas
  • Allows others to check the original scientist's observations
  • Allows others (including later generations) to independently test the hypotheses
  • Allows ideas to be widely transmitted

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