Re: Feduccia's delusion

["T. Mike Keesey" <tmk@dinosauricon.com>]

On Sat, 1 Dec 2001 Dinogeorge@aol.com wrote:

> In a message dated 12/1/01 0:40:27 AM EST, tmk@dinosauricon.com writes:
>
> << Problem here is that the node of the node-stem triplet *is* a crown group.
>  (And would we really want "Archosaurolepidosauria" anyway?) >>
>
> Wait a minute--how can a node all by itself be a crown group?

A crown clade is a type of node-based clade in which all the specifiers
are extant. The specifiers for this clade are _Crocodylia_, _Neornithes_
(=_Aves sensu stricto_), and _Lepidosauria sensu stricto_, all of which
are extant. Hence it is a crown clade.

> My understanding of a node-stem triplet is that it is a clade
> comprising a node and its two descendant stem groups.

I thought it was a set of three clades (a node-based and two internal
stem-based ones).

> Also, isn't a crown group bounded by extant taxa (so that, for
> example, Archaeopteryx would not be included in the crown group Aves)?

Yep. But Archie would be included in the crown clade _Archosauria_, and
the crown clade _Sauria_.

> I wouldn't use a combo name if there were a better, long-standing name
> already available, of course. The combo name here would be
> Archolepidosauria--no need to multiply the saurias.

Indeed, you can abbreviate it to just _Sauria_.

> Would be nice to use Diapsida, but there are other diapsids besides
> archosaurs and lepidosaurs.

Does anyone know what the phylogenetic definition of _Diapsida_ is?

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