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Re: *Fruitafossor*



----- Original Message -----
From: "Jaime A. Headden" <qilongia@yahoo.com>
Sent: Wednesday, April 06, 2005 6:57 AM

David Marjanovic (david.marjanovic@gmx.at) wrote:

<IMHO the absence of the epipubes is very important. Epipubes are absent only
in placentals (and apparently in cimolestans, which are either placentals or
their sistergroup), but in all of those. Epipubes make it impossible for the
abdomen to expand much. Thus they make a placental pregnancy impossible. The
loss of the epipubes seems to correspond to a dramatic shift in the mode of
reproduction -- something which doesn't happen often, I think. Indeed, recent
unweighted cladograms put both Zalambdalestidae and Zhelestidae out of
Placentalia.>


I cannot respond on the topic of the biomechanical effect epipubes have on
abdominal expansion, since tests of musculature are lacking in the effect of
their precence in true placentals.

Musculature? Isn't the position of the epipubes with respect to the pelvis and the skin fixed, which means the skin can't bulge out because the epipubic bones hold it in place?


<So you've merely coined a synonym of "basal", which after all means "far away
from the clade I am at this very moment interested in". -- The opposite of
"derived", though, isn't "basal". It's "plesiomorphic".>


No, I am coining a tree-specific set of terms for use of phylogenetics.

That works for "rootward", but not for "crownward", because where is the crown.


<phylon = stem
phyllon = leaf
...therefore phylogram.>

 Or I can use phyllogram, and demonstrate the OTU's not as stems (acts of
divergence or the lineage stemming [ha! see?!] from such an event) but at
terminal events in a lineage known, thus leaves.

In that case you would have invented a wholly new term.

The two words in Greek are virtually uselessly separated,
and most sources I've seen list them as synonyms of *phylon*.

Really? That's hard to imagine.

<Isn't it textbook wisdom that amniotes plesiomorphically have a pro- and a
metacoracoid, and that sauropsids have lost the metacoracoid? -- As for where
our coracoids have ended up, that's from the description of *Zhangheotherium*.>


In the authors' opinions.

Well, they back it up with embryology and monotreme anatomy and more. I haven't seen a better explanation, or in fact any alternative one.


 On this same note, reading the description of
*Pehuenchesuchus,* the new sebecosuchid from the new _JVP_

It's found as the basalmost sebecosuchian; Sebecosuchidae is not found at all in that analysis.


<Actually not. It's related to the rostral and middle parts of Meckel's
cartilage, not to the caudal part that ossifies as the articular.>

I was wondering if anyone would catch it, but when I wrote "basal part" I was
not using a morphological sense but a phylogenetic one.

"Basal part of Meckel's cartilage"???

<*Fruitafossor* sprawled like a monitor lizard or triconodont or
multituberculate.>

Because of the reconstruction? The humerus is at odds with a primary
weight-bearing bone for walking around on. Oh, not saying it didn't walk around
on it, but that the orientation is in keeping with other such humeri you see in
platypi and moles and chrysochlorids: not sprawled, but spread out limbs. The
forearms are oddly inconsistent with this, implying possible transistory
behavior OR I'm getting it all wrong ... or they are.

Doesn't the elbow articulate in the reconstructed position? And of course what about the pelvis and hindlimbs?


<Then why does it mimic the plesiomorphy present in all manner of terrestrial
mammali...morphs?>


Restricted hindlimb behavior can be plesiomorphic as well as functional, and
thus retained in a fossorial lifestyle or developed because of it.

Then why doesn't any other fossorial mammal make those reversals?

<Basal palaeanodonts, like *Arcticanodon*, retain 6 cheek teeth as well -- 3
premolars and 3 molars as interpreted in *Fruitafossor*. The difference is that
in *F.* all teeth are single-rooted, while in *A.* the last premolar and the
molars are double-rooted.>


Very odd that. And this relates to *Articanodon* being a palaeanodont how?

*Arcticanodon* is no less a palaeanodont than the others with 6 cheek teeth, of which some are double-rooted. Perhaps these plesiomorphies mean that I should have written "no more" instead of "no less" -- but the burden of evidence for that is on you. :-)


Because I did bring up a lack of strong corroboration to palaeanodont
affinities based on superficial similarities and the issue of multirooted,
numerous teeth without _TEETH_ to show for the allusion. Superficiality has
been the cause of vague referals in the history of paleontology from
"kink-snout" spinosaurs as coelophysoids or *Elaphrosaurus'* body proportions
as one.... It's not that I disagree with the authors on these matters, but that
I think their details are lacking to support the conclusion they favor. Maybe
it's sexier for their hypothesis without all the trappings of details that some
learned fellow is going to crack like a walnut, or in the case of mammal
relationships, find one thing wrong and suddenly "everything is out the
window." Hence mammalian "Orders" and their lovely names. I think I'd rather
rename everything from the get-go and abandon the last two decades of
gene-based names. Bye bye baggage-ridden Euarchonta (it's carrying Archonta's
baggage, a far superior name, and it's nothing of a "true Archonta" since it
REJECTS Archonta), we'll call it "Monkeybats." Afrotheria is
"Elephanthyraxshrewmanateeaardvarkia," and be done with it.

The confusing thing about this paragraph is that you change the topic at least 3 times in it -- reminds me of my brother when he's angry, and makes it rather difficult to understand...
BTW, while Archonta included bats, Euarchonta doesn't.
Supraprimates: mice and men, Afrotheria: elephants and elephant shrews... :o)


<No wonder, because that is also the multituberculate jaw structure...>

Big wonder, if it looks nothing so much as an odd, if therian-like monotreme.

Which fits the position it has in the cladogram in the paper.

<While I am at it... all characters are unordered! That's not a good idea.>

Are we to make _a priori_ assumptions about order of character state changes
and how reversals are to be treated by the machine and thus influence
bootstraps and tree numbers? Perhaps.

I was not talking about reversals. I meant that multistate characters that form clear morphological series _must_ be ordered unless there's clear evidence that suggests otherwise.