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Re: Avian Ancestors, new book on theropods
Thomas R. Holtz, Jr. <email@example.com> wrote:
>> I'm not sure the new name Averaptora is essential. Zhang et al.
>> (2008) previously defined Avialae as the most inclusive clade
>> including crown birds but not dromaeosaurids (specified by
>> _Deinonychus_). So their Avialae is equivalent in content to Agnolin
>> and Novas' new clade Averaptora.
> Ummm... GAUTHIER (1986, p. 36) defined it in this manner (Aves and all
> taxa closer to Aves than to Deinonychosauria).
My reading of Gauthier (1986, p.36) is a bit less clear-cut than that.
In fact, I would say that his original Avialae was a bit of a mess.
According to Gauthier “the name Avialae is applied to Ornithurae plus
all extinct maniraptorans that are closer to Ornithurae than they are
to Deinonychosauria” - clearly a stem-based definition. However,
Gauthier intended the new clade Avialae to be a replacement for the
traditional Aves, which included _Archaeopteryx_. So although
Gauthier didn't use _Archaeopteryx_ as an internal specifier as part
of a node-based definition, the implication is that he intended his
Avialae to include _Archaeopteryx_. At least, that's my take on it.
Thus, subsequent studies have disagreed over whether Avialae is
stem-based (including crown birds, excluding dromaeosaurids) or
node-based (including _Archaeopteryx_ + crown birds).
Either way, Agnolin and Novas seem to have used Avialae for the
_Archaeopteryx_ + crown bird clade. This is against the explicit
stem-based definition of Gauthier for Avialae, but agrees with
Gauthier in the inclusion of _Archaeopteryx_ - but nothing more basal
than _Archaeopteryx_. So if Agnolin and Novas had applied Gauthier's
1986 definition of Avialae, it would make their Averaptora redundant.
P.S. I only mentioned the definition of Avialae given by Zhang et al.
(2008) because their stem-based definition has species-level
specifiers, in accordance with PhyloCode: the most inclusive clade
including _Vultur gryphus_ but not_Deinonychus antirrhopus_. Although
I could equally have used Maryanska (2000): _Passer domesticus_ but
not _Dromaeosaurus albertensis_ or _Troodon formosus_.