Re: Mesozoic mammals

["David Marjanovic" <david.marjanovic@gmx.at>]

I just wrote...

> >      `--+--Adelobasileus
> >         `--Mammalia
>
> Aw... not another definition for Mammalia. :.-(

Indeed. "We recognize Mammalia (Mammaliaformes in the usage of Rowe 1988;
McKenna and Bell 1997) as a monophyletic group, defined as including the
[last!] common ancestor of *Sinoconodon*, living monotremes, and living
therians, plus all its descendants (Crompton and Sun 1985; Crompton and Luo
1993). This stem-group definition is stable because the taxonomic content or
membership of this clade has been very stable." While the last sentence is
true, this adds a new definition to the existing ones:

- pre-cladistic: when the dentary-squamosal jaw joint appears. Should
include Tritheledontidae, but hardly anybody ever did that. The widespread
occurrence of double jaw joints was also unknown in those days.
- sensu Benton, Kinman (who suggested onlist to make a node-based definition
of this) and many others: some braincase feature. Includes *Adelobasileus*
(only known from a braincase and undescribed teeth) and Mammalia as defined
above. Traditionally most widespread.
- crown-group. Inside Holotheria, excludes even *Hadrocodium*.

<sigh> One more reason for PhyloCode.

Mammaliaformes, BTW, is node-based on *Morganucodon*. It excludes
*Sinoconodon* in all phylogenies where the two aren't in a polytomy.

Sorry for calling *Tinodon* a tooth taxon -- "Data are limited to partial
dentition and mandible". But enough of that now, or I'll run out of my 7
e-mails...