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RE: What exactly IS a dinosaur?
> From: owner-DINOSAUR@usc.edu [mailto:owner-DINOSAUR@usc.edu]
> On Behalf Of Brandon Pilcher
> Sent: Sunday, April 13, 2008 10:18 PM
> To: firstname.lastname@example.org
> Subject: What exactly IS a dinosaur?
> Hello all,
> I am currently working on a Powerpoint for a high school
> project due around the beginning of June. The subject of my
> presentation will be dinosaurs; it will be a general FAQ on
> dinosaurs and various debates about them (for example,
> warm-bloodedness, theropod foraging behavior, relationship to
> birds, etc.). The first question that I will answer in my
> presentation will be, "What is a dinosaur?" The problem is,
> I'm not 100% sure how to answer that question. What
> distinguishes dinosaurs from, say, pterosaurs, plesiosaurs,
> or saber-toothed cats? What are some characteristics shared
> universally among dinosaurs that other animals do not have?
> P.S. Since my presentation in its entirety (which will be
> between 30 mins and 1 hour, I'm guessing) will have a mostly
> adolescent audience, I would also appreciate knowing how to
> communicate this technical sort of information in an
> easily-grasped manner.
A dinosaur is the most recent common ancestor of Iguanodon and Megalosaurus
or any of its descendants. If an animal is a descendant of that ancestor, it
is a dinosaur; if it isn't, it is not.
Dinosaurs are distinguished from most of the closest relatives by:
* Hindlimbs that were directly underneath the body and feet standing "on
their toes", allowing for a striding gait
* An "open" hip socket (one where the inside was lined only with cartilage,
not with bone)
* More than 2 hip vertebrae
* A grasping hand with a semiopposable thumb and shortened ring and pinky
Note that some of these traits were modified in later evolution in each of
the major dinosaur groups.
Thomas R. Holtz, Jr.
Email: email@example.com Phone: 301-405-4084
Office: Centreville 1216
Senior Lecturer, Vertebrate Paleontology
Dept. of Geology, University of Maryland
Faculty Director, Earth, Life & Time Program, College Park Scholars
Mailing Address: Thomas R. Holtz, Jr.
Department of Geology
Building 237, Room 1117
University of Maryland
College Park, MD 20742 USA