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Re: Hanson 2006, Mortimer, Baeker response

Mike Taylor wrote:

But I don't _care_ what such a person would say.  I thought I'd made
that clear.  I love a good, solid clade as much as the next man --
just as I love a good real ale as much as the next man.  But just as
I'd not want to have to commit to never drinnking anything else except
beer, so neither do I want to sign the no-non-monophyletic-taxa
pledge.

Firstly, I had Nick's question in mind - about how some people prefer relative ranks to be encoded in clade names.

Secondly, should you wish to publish anything in a scientific journal, your reviewers (presumably sober) may insist on a 'no-non-monophyletic-taxa pledge'.

Thirdly, stop making me thirsty. It's not yet noon and I have a craving for a stout...

Yes.  Although _Tendaguria_ and _Agustinia_ are (to my eyes at least)
a LOT more way out and freaky than something as relatively pedestrian
as _Jobaria_, which seems to be merely a late-surviving but otherwise
well-behaved "cetiosaurid".  (Ha!  Paraphylylicious! :-)

I would say that morphological distinctiveness, like beauty, often lies in the eye of the beholder. I think this is the problem of monotypic families created to emphasize the perceived distinctiveness of a 'weird' taxon. Say for example we find a new sauropod that appears closely related to _Tendaguria_, but is more basal and shows only one of the 'weird' features seen in _Tendaguria_. Say this new sauropod has the stumpy neural spine, but not the ginormous transverse processes of _Tendaguria_. Is it a "tendaguriid" or not? This is the kind of discussions that phylogenetic taxonomy avoids, by defining clades based on common ancestry, not "morphological distinctiveness". (Unless you want to go for apomorphy-based clades, but that's a whole other can of worms.)

It's stronger than that, of course: it's _impossible_ to define a
node-based taxon based on a single member.

Yes, but even these clades may end up containing only a single member, if the constituent genera used as specifiers are shown to be synonymous.

There's that claim again. Where is this "rule" stated?

Nowhere, AFAIK. But it is firmly ingrained in tradition that families should not include other families. There is a logic behind this: If you are using familes, then you are implicitly accepting ranks, and if you accept ranks, then it is incongruous to have one family contained inside another.

And it that doesn't work, fifteen rounds in a boxing ring should do it
:-)


Or a KO.  Whichever comes first.  :-)

I flatly contradict this assertion.  Given phylogenetic definitions of
Titanosauridae as (_Saltasaurus_ not _Andesaurus_) and Tendaguriidae
as (_Tendaguria_ not _Opisthocoelicaudia_), if we recovered the
phylogeny:

\  _Andesaurus_
 \/
  \      _Tendaguria_
   \    /
    \  /\_Opisthocoelicaudia_
     \/
      \
       _Saltasaurus_

then those two "families" would remain, one inside the other, their
names unmodified, according to every set of phylogenetic nomenclatural
principles I've ever seen.

A careful taxonomist would probably try and prevent this situation from happening in the first place. As Senter puts it, this family-inside-a-family thing is confusing. Besides, I think cladistic-based taxonomy has enough problems being accepted in some quarters; having "families" inside other "families", and "subfamilies" above "families" would be the last straw for some folks.

Cheers

Tim