Re: "Dinosaurs Died Within Hours After Asteroid Hit Earth..."

[Dora Smith <villandra@austin.rr.com>]

The way I understand it, although many scientists think that archaeopterix
is ancestral to birds, others think that they were an evolutionary dead end
and not necessarily more closely related to birds than caudipteryx.

I know that all other theropods including caudipteryx and the two other
bird-like ones differed more from modern birds than archeopterix did, but
not by much; what is more, they and several other therapod dinosaurs were
undergoing structural changes like those that modern birds have; in bone
structure, foot structure, arm and wing structure, tail structure, and
feathers.

I notice that, for instance, there is uncertainty that Confuciornis is a
bird and not a non-avian therapod.    In addition to uncertainty that
caudipteryx and several others were not birds.   Partly because their
feathers and other features might make them necessarily descended from
whoever the nearest common ancestor whose existence defines class Aves was.

Yours,
Dora Smith
Austin, Texas
villandra@austin.rr.com
----- Original Message -----
From: "Mickey Mortimer" <Mickey_Mortimer111@msn.com>
To: <dinosaur@usc.edu>
Sent: Saturday, May 29, 2004 2:00 PM
Subject: Re: "Dinosaurs Died Within Hours After Asteroid Hit Earth..."


> Dora Smith wrote-
>
>
> > "> By definition yes, the most recent common ancestor of modern birds
was
> a
> > > member of Aves, following any reasonable phylogeny.  This holds for
> > Gauthier
> > > and de Queiroz's definition (Struthio maximus + Tinamus major + Vultur
> > > gryphus) or Chiappe's (Archaeopteryx lithographica + Vultur gryphus).
> > > "Bird" can be defined basically any way you want.  I equate it with
> Aves,
> > > but Microraptor's about as birdy as Archaeopteryx, so including all
> > > eumaniraptorans doesn't seem too odd."
> >
> > By what definition of Aves?   If Bird can be defined any way one wants
and
> > Microraptor, which was a member of another line of dinosaurs, qualifies
as
> > much as a bird as archaeopteryx does, then is "Aves" anything with
> feathers?
> > If so, then any coelorusaurian dinosaur would qualify as a member of
Aves.
>
> I equate "bird" with Chiappe's definition of Aves (basically, the common
> ancestor of Archaeopteryx and living birds, and all its descendents),
which
> is the one I use.  I figure Archaeopteryx has been the most primitive
known
> bird for so long, we might as well keep it that way.  But colloquial terms
> like "bird" that don't have a taxonomic counterpart aren't assigned exact
> definitions by any group.  So people are free to use whatever definition
> they want.
> Aves is a taxonomic term, so is assigned an exact definition.
> Unfortunately, the definitions of some bird groups are controversial (e.g.
> Aves, Avialae, Ornithurae, Carinatae), primarily due to Gauthier and de
> Queiroz's (2001) attempts to make them apomorphy-based.  Most phylogenetic
> taxonomists dislike apomorphy-based definitions, including me.  But Clarke
> is following them, though Chiappe continues to use the more popular node-
> and stem-based definitions.  1-1-200n can't come soon enough.
>
> Avialae Gauthier, 1986
> (Vultur gryphus <- Deinonychus antirrhopus) (Gauthier, 1986)
> (Archaeopteryx lithographica + Vultur gryphus) (Gauthier and Wagner, 2001)
> (feathered wings homologous with Vultur gryphus and used for powered
flight)
> (Gauthier and de Queiroz, 2001)
>
> Aves Linnaeus, 1758
> (Struthio camelus + Tinamus major + Vultur gryphus) (Gauthier, 1986)
> (Archaeopteryx lithographica + Vultur gryphus) (Chiappe, 1992)
>
> Avebrevicauda Paul, 2002
> (ten or fewer free caudals homologous with Vultur gryphus) (Paul, 2002)
>
> Pygostylia Chatterjee, 1997
> (Confuciusornis sanctus + Vultur gryphus) (Chiappe, 2001)
> (fused distal caudal vertebrae homologous with Vultur gryphus) (Gauthier
and
> de Queiroz, 2001)
>
> Euornithes Sanz and Buscalioni, 1992
> (Iberomesornis romerali + Vultur gryphus) (Sanz and Buscalioni, 1992)
> (Vultur gryphus <- Sinornis santensis) (Sereno, 1998)
>
> Ornithopectae Chiappe, 1991
> (Iberomesornis romerali + Vultur gryphus) (Chiappe, 1991)
>
> Ornithothoraces Chiappe and Calvo, 1995
> (Iberomesornis romerali + Vultur gryphus) (Chiappe, 1995)
>
> Ornithuromorpha Chiappe, 2001
> (Vorona berivotrensis + Patagopteryx deferrariisi + Vultur gryphus)
> (Chiappe, 2001)
>
> Ornithurae Haeckel, 1866
> (Vultur gryphus <- Archaeopteryx lithographica) (Gauthier, 1986)
> (Hesperornis regalis + Vultur gryphus) (Chiappe, 1991)
> (tail shorter than the femur and with an upturned and ploughshare-shaped
> compressed pygostyle in the adult, composed of less than six segments, and
> shorter than the less than eight free caudals homologous with Vultur
> gryphus) (Gauthier and de Queiroz, 2001)
>
> Carinatae Merrem, 1813
> (Vultur gryphus <- Hesperornis regalis) (Cracraft, 1986)
> (Ichthyornis dispar + Vultur gryphus) (Chiappe, 1995)
> (keeled sternum homologous with Vultur gryphus) (Gauthier and de Queiroz,
> 2001)
>
> Neornithes Gadow 1892
> I think this is defined in Chiappe 1995 as the most recent common ancestor
> of living birds and all their descendents, but cannot check.  Anyone have
a
> copy?  (it's the Nature paper "The first 85 million years of avian
> evolution", 378: 349-355)
>
> > What I am wondering is if birds really did come from just one narrow
line
> of
> > coelorusaurs.
>
> Nobody has presented a viable alternative yet.  The only recent attempt
was
> Zweers and Vanden Burge (1998), who have the following topology-
> |--+--Dromaeosauridae
> |  `--+--Archaeopteryx
> |     |--Alvarezsauridae
> |     `--Enantiornithes
> |--+--Ornithomimosauria
> |  |--Hesperornithes
> |  |--Ichthyornis
> |  `--+--Palaeognathae
> |     |--Gruidae
> |     `--Opisthocomidae
> `--+--Troodontidae
>    `--+--Confuciusornithidae
>       `--Neognathae
> No one else has really questioned the monophyly of recent birds.  You get
> people putting various traditionally non-bird dinosaurs (ornithomimosaurs,
> alvarezsaurids, segnosaurs, oviraptorosaurs, deinonychosaurs) as closer to
> birds than Archaeopteryx (Thulborn 1984, Paul 1988, 2002, Chiappe et al.
> 1993, Elzanowski 1999, Maryanska et al. 2002, Lu et al., 2002).  And you
> have those who support pygostylous birds evolving twice (Martin, Feduccia,
> Hou, Zhou, etc.), with known long-tailed birds related to
confuciusornithids
> and enantiornithines.  But none of these hypotheses are generally
accepted.
>
> Mickey Mortimer