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Re: New PaleoBios paper & Daanosaurus revisited

On 10/3/05, Tim Williams <twilliams_alpha@hotmail.com> wrote:
> One way around this is to define Mamenchisauridae to be (_Mamenchisaurus_ +
> _Omeisaurus_, but not _Diplodocus_ or _Saltasaurus_), such that the
> definition includes an internal caveat.

This is actually a bit ambiguous, because it could mean:

a) The last common ancestor of _Mamenchisaurus_ and _Omeisaurus_, plus
all descendants thereof, provided that that ancestor is not ancestral
to _Diplodocus_ or _Saltasaurus_. (node-based with qualifying clause)

b) The first ancestor of _Mamenchisaurus_ and _Omeisaurus_ which is
not ancestral to _Diplodocus_ or _Saltasaurus_, plus all descendants
thereof. (stem-based, with multiple internal specifiers)

It would be perfectly possible for some organisms (e.g.,
_Bellusaurus_?) to be part of (b) but not part of (a) (assuming they
are not both null clades).

Mike Keesey
The Dinosauricon: http://dino.lm.com
Parry & Carney: http://parryandcarney.com