Message 2001-06-0134: Two mammal clade alternatives

Sun, 01 Jul 2001 14:36:22 -0600 (MDT)

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Date: Sun, 01 Jul 2001 14:36:22 -0600 (MDT)
Subject: Two mammal clade alternatives

David et al.,

Alternative No. 1:
    Well, to me there is only one logical place to mark the beginning of
Mammalia  (which I have always done and continue to do, as do most tradit=
mammalogists). It is character-based, but to put it into cladistic node-b=
terminology, it would be:
    The common ancestor of Adelobasileus and therians, and all of their
descendants (you could add a monotreme as a third specifier, but this doe=
seem necessary).

Aternative No. 2:
     Unfortunately, phylocoders will probably give the above taxon the na=
Mammaliformes or whatever, and therefore attach the name Mammalia to some=

less-inclusive and unstable grouping.  I don't like this, but if you are =
to do it, I think the following would be better than a strict crown group=

(although it might end up being one):
     The common ancestor of Triconodon, monotremes, and therians, and all=
their descendants.  If you want to substitute a specific monotreme genus =
and a
specific therian genus, makes no difference to me.    =

     In any case, I will continue to recognize the broader Mammalia
(alternative 1), which is both more stable in content and also matches th=
traditional literature (which is anchored on characters, rather than taxa=
namely the synapomorphic mammal jaw joint and three ear ossicles).
             ---------Ken Kinman
"David Marjanovic" <> wrote:
----- Original Message -----
From: <>
To: <>
Sent: Monday, June 25, 2001 1:32 AM
Subject: My final (stern) warning about Mammalia

> [...]
>      Since I began as a mammalian neontologist (Honacki, Kinman and
> 1982; Mammal Species of the World), you would think I would actually
prefer a
> crown group Mammalia.   But when I realized just how cladistically
> the position of monotremes is, vis-a-vis several major groups of fossil=

> mammals, I clearly saw what a dumb idea a formal crown group of mammals=

> was. [...]
>      Beyond the good chance that triconodonts and multituberculates wou=
> excluded from such a crown group, some cladistic topologies proposed
> years ago would also exclude symmetrodonts and even dryolestids.
>      If you have to anchor Mammalia, for heaven's sake anchor it on a
> triconodont, so it would be both more stable in content and much closer=
> traditional usage.

Even though this has become largely off-topic, and I'm still not sure how=

good ideas crown groups are, I think I should repeat that the position of=

monotremes is no longer as Heisenberg-uncertain as it used to be, due to =
recognition of Australosphenida and of the dual origin of tribosphenic
molars. Means, Mammalia anchored on Monotremata always includes
triconodonts, multituberculates, most of what has remained of the
paraphyletic Symmetrodonta and (quite near to Theria) the dryolestids.

Anchoring it on "a triconodont" (old Triconodonta and apparently even
Eutriconodonta are paraphyletic) probably, but not surely, includes
Multituberculata (they share some brain and foot features with the
eutriconodont *Jeholodens* and may be the sister group of Eutriconodonta =
something similar, according to a recent paper in Paleontology), surely
includes symmetrodonts and dryolestoids, and quite certainly EXCLUDES
Monotremata. That's not what you want, if I have understood you correctly=

If Mammalia is anchored on a monotreme

> [...] the only non-mammalian Mammaliaformes would be
> sinoconodonts, morganucodonts, and docodonts

and the new *Hadrocodium* (shown in natural size on a recent Science cove=

> Anchoring Mammalia on
> fossil-poor monotremes continues to leave[...] in a
> perpetual state of uncertain position (all of them Mammalia; none of th=
> Mammalia; of something in between).

Perpetual? Are you really so pessimistic? ~:-|

What is really a problem, however, is that Monotremata itself seems to be=

poor of synapomorphies. Neontologists used to cite the poison spur of
males -- this is a plesiomorphy, also found in the symmetrodont
*Zhangheotherium* and in *Jeholodens*, if I recall correctly. (It does no=
affect the anchor of crown-group Mammalia, however, because this is
*Ornithorhynchus anatinus* alone.) Tooth characters are totally inapplica=
to echidnas. Is someone onlist who knows better? =


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