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Re: Dietary factors & giant land mammals - birds



John Bois said <<And yet, to see a bird with the mass of a bison or a 
wilderbeest would be impressive enough.  I suppose there are food processing 
limitations on
this.>>
  Speeking of food processing limitations. Maybe the reason birds did not 
become gigantic was simply because they could not get enough food.   
  How easy is it to peck an animal to death.  Without teeth, especially 
replaceable teeth, it would be extremely hard to kill any large animal, or 
catch enough small ones to grow extremely big.  I wouldn't be surprised if the 
lack of replaceable teeth also limits current land mammal predator size. 
 
  For a plant eating bird, the lack of teeth probably prevents chewing hard 
plant tissue, at least enough to build a large body.  While it is possible to 
have evolved a system to use stomach stones to help digestion, was it possible 
to clip enough food with a beak?  The lack of replaceable teeth in mammals may 
also be a reason they did not evolve larger.  Elephants appear to be headed 
towards the dinosaur condition, but not there yet.
  I understand the reason some of us say birds are dinosaurs, meaning Aves 
belongs to the clade dinosauria, but with the loss of teeth, tail, and hand
claws (relying totally on flight at some point) in birds is where, in my mind, 
they quit being (classic) dinosaurs and birds, but just birds.  
  I wish we had a word to seperate the bulk of dinosaurs from the feathered, 
toothless, tailess, handclaw-less dinosaurs, similar to what the
semi-scientific term dinosaur used to mean! Either that or say dinosauria or 
dinosaur clade when we want to include birds and dinosaur when we don't. I do 
not understand why redefining dinosauria means the word dinosaur must also be 
redefined. (My 35 books with the term dinosaur and even this mailing list all 
imply (birds not included).  If man evolved from bacteria, I would not like to 
hear the statement (men are bacteria -or fish for that matter) although a 
similar form (men are scum) is understandable in some cases.  The reason we 
apply scientific names is to seperate and identify items for easy 
understanding.  Changing the meaning of common well known words does not.
  Mammal was origionally defined to include bats.  As bats and flightless 
mammals both exist today, it is a great combination.  The term dinosaur has the 
element of extinction to it, meant to classify an extinct group with a common 
trait.

Mark Shelly