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Re: the start




On Mon, 6 Jun 1994, Gary Vatnsdal wrote:

> There has been so much talk on this list lately of how the dinosaurs came
> to their sorry end I was wondering if anyone would take a minute to
> explain to me where it all began for dinosaurs. Was there a bunch of
> little lizards of various types that just got so competitive that only the
> bigger and bigger and bigger survived? Were these little lizards (if there
> were any) some kind of fish turned land animal? Or did the dinosaurs
> develop first in the water and arrive on land big already? I guess my real
> question is what came before the dinosaurs? Thanks for anyones help.
> 
> Gary
> 
> ***********************************************************************
> Gary Vatnsdal                        Red River Community College
> (204) 632-2332                       2055 Notre Dame Avenue
> RRLGARY@CC.UMANITOBA.CA             Winnipeg, Manitoba
> FAX (204) 697-4791                   Canada  R3H 0J9
> ***********************************************************************
> 
> 
> 
Gary, dinosaurs belong to a group of reptiles called Archosaurs which evolved
from reptiles called thecodonts during the middle/late Triassic.
Archosaurs include all Dinosaurs, pterosaurs (winged reptiles), birds, and
Crocodilians.  Thecondonts evolved from early Diapsid reptiles.  Reptiles
evolved from Amphibians. Amphibians evolved from early lung fish or
coelcanths. 
How the early Dinosaurs took over was a combination of good luck and
improvements in the hips (erect stance).  The good luck came in the form
of ...yes... here we go again ... an impact during the Triassic/Jurassic.
During that impact the world was devastated and the dinosaurs and many
other archosaurians, although greatly reduced in number, were able to
quickly seize most of the land niches. Early Mammals also survived but
could not compete with the dinosaurs and remained small throughout the
Mesozoic until the Cretaceous/Teritary disaster.
--
John Schneiderman
dino@cwis.unomaha.edu