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Thread: Why aren't Crocodillians considered Dinosaurs?

  1. #1 Why aren't Crocodillians considered Dinosaurs? 
    Forum Professor WVBIG's Avatar
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    All documentaries say they've remained unchanged since the time of the Dinosaurs or before & I know some Dinosaurs were supposed to be as small as chickens. So why aren't Crocodillians considered Dinosaurs?


    Steven
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  3. #2  
    Time Lord Paleoichneum's Avatar
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    Age does not equate to similarity, and overall they have changed a fair bit from their Triassic/Jurassic/Cretaceous relatives.

    The reason though, is that they are a different branch of the reptile line from dinosaurs/birds. they are in the Superorder Crocodylomorpha while dinosaurs are in Dinosauromorpha, two different branches of reptiles.


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  4. #3  
    Forum Cosmic Wizard i_feel_tiredsleepy's Avatar
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    Early crocodilians were contemporary to dinosaurs not descended from them.

    Edit: Paleio beat me by a mile though.
    "I almost went to bed
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    the four white violets
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    and how i kissed you then
    and you kissed me
    shy as though I'd
    never been your lover "
    - Leonard Cohen
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  5. #4  
    Universal Mind John Galt's Avatar
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    Look at the frigging hip joints. If you are going to classify them together you might as well call a daffodil a fir tree!
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  6. #5  
    WYSIWYG Moderator marnixR's Avatar
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    not everything that lived at the time of the dinosaurs were necessarily dinosaurs
    it is claimed that coelacanths haven't changed since the day of the dinosaurs - it doesn't make them dinosaurs though
    "Reality is that which, when you stop believing in it, doesn't go away." (Philip K. Dick)
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  7. #6  
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    I never thought crocodiles were dinosaurs but I have often wondered what makes them so different from lizards.
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  8. #7  
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    It is very interesting to learn that some researchers suggest that some distant ancestors of crocodiles were warm blooded terrestrial predators, and became exothermic again when they adapted to the aquatic niches (where a slow metabolism provides a large benefit).
    I don't know that much about crocodiles and their evolutionary history-I'm not even sure if the endothermic history of crocodiles is generally accepted or not (I just read an article some time ago).
    Their four chambered heart and fossil evidence (of many terrestrial forms) was the primary evidence.

    Crocodiles are definitely very different from lizards (more so than they are different form birds/dinosaur).
    The archosaurs include the crurotarsans and the group which includes both dinosaurs and birds.
    While the crurotarsans were similarly (or slightly more) succesful than dinosaurs during the Triassic, having a greater number of different body types, most of them died out at the end of the Triassic. The crocodillians are the only remaining descendants from that group.
    Lizards are more distantly related, not even being among the archosaurs.
    Hopefully this will provide some idea of the basic evolutionary history of these groups.
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  9. #8  
    WYSIWYG Moderator marnixR's Avatar
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    look at the Sphenosuchians, often considered the most primitive of crocodylians : your first impression is "dinosaur-cousin" rather than "lizard"
    "Reality is that which, when you stop believing in it, doesn't go away." (Philip K. Dick)
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