[Taxacom] Insects are crustacean descendants vs. "insects ARE crustaceans"

[John Grehan]

This seems to be mixing up naming with systematic relationships.
Cladistics, as far as my admittedly limited understand goes, is that for
any three taxa where A and B are more closely related to each other than
either is to C then one may make a monophyletic A+B, a monophyletic A+b+C
and a monophyletic C, but not a monophyletic B+C or A+C. Whatever one wants
to call these entities is a separate matter. If I have a misunderstanding
about this will some cladist please correct me (I always overlook the
obvious and would trip over my own feet if they did not keep out of the
way).

John Grehan

On Fri, Feb 9, 2018 at 10:10 PM, Kenneth Kinman <kinman at hotmail.com> wrote:

> Hi all,
>        The present discussion about paraphyly reminds me of strict
> cladists insisting that "birds ARE dinosaurs", rather than "birds are
> dinosaur descendants".  I suppose they might think that they are preparing
> the next generation of young dinosaur lovers to support strict cladists and
> perhaps even become future strict cladists.
>
>       But not all dinosaur researchers think that this is a good idea.  In
> his paper Origin of Birds: The Final Solution? (American Zoologist: Vol.
> 40, No. 4, pp. 504-512), Peter Dodson says: "For example, the word dinosaur
> was not previously problematic - it was universally understood. Within
> cladistics it has now been redefined to include birds ... and then a new
> and cumbersome phrase, non-avian dinosaur, has been substituted. This is
> not progress; this is semantic obfuscation not enlightened communication."
>
>        I agree that it is semantic obfuscation.  Saying "Birds are
> dinosaurs" (instead of birds are dinosaur descendants) is  like saying
> "Tetrapods are sarcopterygian fish" (instead of Tetrapods are descendants
> of sarcopterygian fish).  Or how about "Insects are crustaceans", rather
> than "Insects are crustacean descendants."
>
>        In all these cases, you would be trying to force a well-known
> exgroup taxon back into its mother taxon.  In other words, it is a war
> against paraphyletic taxa which would become glaringly absurd if applied
> across the board.  How about "Vertebrates are invertebrates" instead of
> "Vertebrates are invertebrate descendants"?
>                   -----------------Ken Kinman
>
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