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Re: (extinction) (long)



David said:
> Actually, I could almost get proud of how long I managed to keep
Zhelestidae
> out of this discussion. :-) There's a reason for my doing so: the JVP
> abstract quoted in www.cmnh.org/dinoarch/2001May/msg00796.html. Looks like
> they aren't ungulates or crown-group placentals at all, but instead close
to
> zalambdalestids...
> ... in short, zhelestids (paraphyletic as usual) are not stem ungulates,
but
> stem placentals, stem boreoeutheres (confusing name) or stem
laurasiatheres
> according to this analysis. The authors lament that they didn't include
> enough crown-group placentals to resolve placental relationships (the
matrix
> is already big enough, going down all the way to Tritylodontidae).

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 closer
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

And, have you looked at Fox 1997 Late Cretaceous and Paleocene mammals,
Cypress Hills Region, Saskatchewan in L. McKenzie-McAnally (ed.s) Upper
Cretaceous and Tertiary Stratigraphy and Paleontology  of Southern
Saskatchewan. . Canadian Paleontology Conference. Field Trip Guidebook No.
6. Geological Association of Canada (Paleontology Division) St. Johns,
Newfoundland.  It contains the description of, according to Lillgraven and
Eberle: "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.

So, how do _you_ explain the appearance of Protungulatum?  Did it ride in on
the bolide?  Did it fly in from the coast?  It was right there at the very
earliest Puercan 1...and, apparently, earlier in other NA sites!

> The question in this particular case is when exactly "ungulates"
appeared --
> pretty early in the Paleocene, but how early, does someone know more?
> (There's no question AFAIK that the metatherian extinctions happened right
> at the K-T boundary, and that no "ungulates" were in NA before the K-T.)

Unless Fox is found wanting, not true.

Bois said about pterosaurs:
>> Here you may be up against absolute limits in structural design.  Come to
>> 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 I
cry "Uncle"!