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

[Mickey Mortimer <Mickey_Mortimer111@msn.com>]

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