Re: [dinosaur] Why birds are living dinosaurs

I suspect people who say this have no real idea (beyond Jurassic Park and their kidsâ toys) of what dinosaurs are like. In very simple terms, you should say that no one is saying that birds are descendants of âsomething like T. rexâ. Instead we are saying that dinosaurs came in many sizes, and birds are descendants of cousins of T. rex that were already small, already insulated, and probably agile and warm-blooded as well. In fact many of the features we think of as âbird-likeâ had already appeared in their ancestors before âtrueâ birds emerged, and the only reason we think about things like maniraptorians today as dinosaurs instead of as weird early birds is that there is nothing like them running around today, and the popular idea of what a bird is comes from our knowledge of the varieties that are still around.

You might point out that evolution does not always run to bigger and more massive, and that living miniature frogs and lizards in Madagascar (for example) are far smaller than their ancestors or living relatives (I would suspect that the mass difference between the tiniest Malagasy chameleon and a Komodo Dragon might well exceed that between a T. rex and, say, an Ostrich). For that matter, if an elephant and a hyrax can be close relatives, what difference does size actually make?

On Apr 12, 2021, 8:17 AM -0400, Thomas Richard Holtz <tholtz@umd.edu>, wrote:

Because in modern biological classification you don't stop being a member of a group just because you start to be something new as well. In modern classification all groups are clades (monophyletic groups: an ancestor and all of its descendants, no matter how transformed).

Aves didn't stop being part of Dinosauria when they became birds as well. Chiroptera didn't stop being part of Mammalia when they became bats as well. Tetrapoda didn't stop being part of Osteichthyes when they became tetrapods as well.

And people say ignorant things because they are literally ignorant: they don't know that classification has changed, and so operate under an old typological-based thinking rather than genealogical-based thinking.

On Mon, Apr 12, 2021 at 2:44 AM Poekilopleuron <dinosaurtom2015@seznam.cz> wrote:

Good day!

If you were to answer this question, how would you put it? Because birds evolved directly from the dinosaurian ancestors? Because they still carry the dinosaur genetic heritage? Because they are in fact a specialised group of living maniraptoran theropods? I've heard some people say ignorant things like "birds can not be dinosaurs, because they are so different, mostly very small and there is no way that such an agile warmblooded insulated animal could be a descendant of something like T. rex".

Thank you for your thoughts! Tom

--

Thomas R. Holtz, Jr.
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