[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

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: dinosaur@usc.edu
> 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: tholtz@umd.edu   Phone: 301-405-4084
Office: Centreville 1216                        
Senior Lecturer, Vertebrate Paleontology
Dept. of Geology, University of Maryland
Fax: 301-314-9661               

Faculty Director, Earth, Life & Time Program, College Park Scholars
Fax: 301-405-0796

Mailing Address:        Thomas R. Holtz, Jr.
                        Department of Geology
                        Building 237, Room 1117
                        University of Maryland
                        College Park, MD 20742 USA