Vegetarian dinosaurs couldn't eat the good stuff most modern vegetarians eat,
grass, because grass had not evolved yet, their main diet was something
similar to pine needles, and you need to eat about twice as much to get equal
food value. That's not the only problem, pine needles take far longer to
digest than grass. Also, the teeth of these dinosaurs were simple pegs, they
didn't have anything like molar teeth that modern animals use to grind up
there vegetable food before swallowing, they had to swallow their pine
needles whole. All this means that if you want to make a living in this way
you're going to need a very large stomach and gut, the rest of the body will
be scaled up proportionally. You end with something like a huge fermentation
tank with legs.
Another reason we don't see land animals as big as the largest dinosaurs is
simply chance, nearly all the species of animals that have ever existed are
extinct, there is no reason to expect we'd be lucky enough to be around at the
same time the very largest ones were. We were extraordinary lucky as far as
sea animals are concerned, no beast has ever been as large as the Blue Whale.
John K Clark johnkc@well.com
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