Comment on xkcd #3204: Dinosaurs And Non-Dinosaurs

AmidFuror@fedia.io ⁨2⁩ ⁨weeks⁩ ago

• leftzero@lemmy.dbzer0.com ⁨2⁩ ⁨weeks⁩ ago

  The name (dimetrodon ≈ two teeth sizes) is also a clue, as teeth specialization is very much a synapsid (i.e., mammal and proto-mammal) thing.

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  • Cocodapuf@lemmy.world ⁨2⁩ ⁨weeks⁩ ago

    That’s pretty awesome! I may have gotten old, but I never got tired of learning stuff about dinosaurs prehistoric beasts.

    So what’s the deal with the pterosaurs, what makes them “not dinosaurs”? I believe the really weird looking silhouette is a Quetzalcoatlus, that’s just fun to say.

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    • leftzero@lemmy.dbzer0.com ⁨2⁩ ⁨weeks⁩ ago

      That one I’m not entirely sure about, but it seems that, in the same way being a mammal (from a bone perspective) is all about the teeth and inner ear, being a dinosaur is all about the hips (dinosaurs have an upright stance, with the legs under their bodies; even with the quadruped ones you can see how they’re really something evolved to walk on its hind legs walking on its hands and feet), and pterosaurs and their non-dinosaur ancestors just don’t have the right kind of hip.

      It’s a bit muddy, though. Once you get into archosaurs and before you get into more specialised things like crocodiles, dinosaurs, or pterosaurs it’s mostly “this thing seems to be more closely related to this group than to this other group, so we’ll throw it in with them even if it doesn’t really look anything like them”.

      There’s a small bipedal reptile, for instance, scleromuchlus, that’s been bundled up with pterosaurs because it apparently seems more related to them, even though if you look at an artist’s representation you’d assume it must be a dinosaur, but might in fact not fit in either group and be instead just a basal avemetatarsalian (or maybe even lower in the tree) with no other identified close relatives.

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  • lemming@sh.itjust.works ⁨2⁩ ⁨weeks⁩ ago

    How about snakes?

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    • leftzero@lemmy.dbzer0.com ⁨2⁩ ⁨weeks⁩ ago

      True, (some) snakes have also evolved specialized fangs.

      Several times independently with significantly different designs, it seems.

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      • lemming@sh.itjust.works ⁨2⁩ ⁨weeks⁩ ago

        I’m a little disappointed, I was hoping for some very specific explanation why it’s technically different :-) It’s cool that they are independent, thanks!

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• lugal@lemmy.dbzer0.com ⁨2⁩ ⁨weeks⁩ ago

  They are actually closer related to mammals than to any modern reptile

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• ccunix@lemmy.world ⁨2⁩ ⁨weeks⁩ ago

  What is funny is that you probably struggled to say words like “shoulder”, but “dimetrodon” posed no problem to you.

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