[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

Re: (extinction) (long)

----- Original Message -----
From: "John Bois" <jbois@umd5.umd.edu>
Sent: Monday, July 08, 2002 5:39 AM

> Way out of depth, here.  But, can you tell me how these character states
> relate to the discussion, if at all.  This site
> details what they are.  Anyway, to me it looks like the zhelestid is
> to Protungulatum than it is to Zalambdalestes
> http://www.nature.com/nature/journal/v414/n6859/extref/414062aa.doc
> Protungulatum spp.    20?12  11110  11010  11120 01323 34000 00010
> Zalambdalestes lechei 31103 10110  20011  1110?  ?1000 00111 12?10
> Zhelestes temirkazyk  00?11  00100  11010  011?2  1?101 34000 00011

"Dentaries and petrosals are identifiable to Dzharakuduk 'Zhelestidae' and
referable to named taxa on the basis of size." Isn't that horrible? That's
what it says in that file.
        I wouldn't trust dental characters so much... we've seen how they've
fooled people into believing that whales are closer to (even within)
mesonychians than to artiodactyls.
        Of course that paper doesn't cite the JVP abstract. The paper's main
conclusion, that zalambdalestids' lower incisors drag them towards Glires,
has been questioned in an Acta Pal. Pol. paper (URL tomorrow); in any case
zalambdalestids and the rest of Asioryctitheria retained epipubes, so a
Zalambdalestidae-Glires relationship would imply that the latter evolved the
placental way of reproduction independently from us! Now let's wait for a
zhelestid pelvis... there isn't any so far, is there one?
        What I consider the biggest flaw of that study is that it includes
only *Mimotona* (sister to Lagomorpha), *Tribosphenomys* (sister to
Rodentia), *Protungulatum* and *Oxyprimus* (er, Procreodi) of all
(crown-group) Placentalia. Assume they had added *Erinaceus*, like the
*Eomaia* paper did. Assume it would have come out as the sister group of
*Protungulatum* + *Oxyprimus*... they'd have to rename their Ungulatomorpha
to Laurasiatheria. They didn't try. They didn't really test the placement of
Zhelestidae. Same for Glires and Zalambdalestidae.
        Their placement of *Cimolestes*, *Batodon* and *Gypsonictops*
doesn't agree with other studies such as the *Eomaia* paper.
        Also have a look at what happened when they ran their analysis
without the Cenozoic species (Fig. 3 a)... better than every textbook
poly(cho?)tomy. Either they used far too few characters (70 -- should be
enough for 25 taxa, no?), or their characters are very uninformative.

> And, have you looked at Fox 1997 [...]


> "reported arctocyonid and possibly periptychid condylarths in
> association  with typical Lancian vertebrate assemblages and Cretaceous
> palynomorphs in...Southern Saskatchewan..."  Protungulatum is found right
> at the boundary of the Ferris formation, but Fox argues that mammalian
> assemblages attained Paleocene-like aspects slightly prior to this in
> Saskatchewan.

I don't know the Ferris Fm. Such an association is _very_ suggestive of
reworking, however.

> So, how do _you_ explain the appearance of Protungulatum?

How old is the base of the Ferris Fm, and how was it dated? I can remember
the times when they used the lowermost coal bed to find it in the Hell Creek
Fm, but it is diachronous.

> Did it ride in on
> the bolide?  Did it fly in from the coast?  It was right there at the very
> earliest Puercan 1...

When? 1 Ma after the K-T? 5 Ma?

> Bois said about pterosaurs:
> >> Here you may be up against absolute limits in structural design.  Come
> >> think of it, good reason to go extinct.
> >
> > Then please suggest some structural constraints.
> Before I wade into this, can I get away with the idea that feathers confer
> serious advantages for the vertebrate flier.  If I'm wrong about this then
> cry "Uncle"!

The other way around, please. Please tell why you think azhdarchids wouldn't
have been able to do anything sufficient against nest predation by
        Okay, er... feathers certainly confer serious advantages in some
situations that occur in flying. But I think it's probable that a closed
patagium also confers advantages in other situations. I'm not anywhere near
knowledgeable enough in aerodynamics to continue. A chapter of DA is a good
little introduction, though. (Says, BTW, that azhdarchids were capable of
really powerful flapping.)