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

Re: Crop for seed-eating found in Hongshanornis and Sapeornis

I wrote:

> Further, _Sapeornis_ and _Hongshanornis_ are not as phylogenetically
> remote from each other as the paper states.  _Sapeornis_ is a
> non-ornithuromorph ornithuran (either a basal pygostylian, or the
> sister taxon to Pygostylia),

Sorry, I meant to write "_Sapeornis_ is a non-ornithuromorph
*avialan*.  However, it could also be a non-ornithuromorph ornithuran,
given the competing definitions of Ornithurae in the literature...
which would not be at all helpful, because it would be odd to have
Ornithurae as more inclusive than Ornithuromorpha!

Ornithuromorpha was defined as a node-based clade that includes
_Patagopteryx_ and Ornithurae (Chiappe, 2002) .  However, Ornithurae
has received all sorts of definitions.  When he erected
Ornithuromorpha, Chiappe was using an Ornithurae that he himself
defined as the least inclusive clade including Hesperornithiformes and
Neornithes (Chiappe, 1995).  This was essentially followed by Padian
et al. (1999), and Chiappe (2007), among others.  This definition of
Ornithurae contradicts other definitions that are more inclusive, such
as that of Gauthier (1986): Aves plus all extinct maniraptorans that
are closer to Aves than is _Archaeopteryx_ (Aves being the crown
clade).  This was followed by Sereno (1999) and Senter et al. (2004).

To make things even more confusing, Gauthier and de Queiroz (2001)
proposed an apomorphy-based definition of Ornithurae that captured the
spirit of Haeckel's original (1866) reasoning for erecting Ornithurae.
 However, the apomorphy-based definition would be very tricky to
implement in practice - in light of the stepwise and possibly quite
convoluted construction of the modern "bird tail", specifically the
truncated tail (shorter than the femur) with a "pygostyle of avian

Anyway, the point of this post is to highlight that if the "older",
more inclusive definition of Ornithurae is used - with _Archaeopteryx_
used as the negative specifier - then under the phylogeny recovered in
the _Xiaotingia_ paper, Ornithurae has the same content as Avialae.
Ornithurae would therefore include plesiomorphically "long-tailed"
taxa that lacked a pygostyle, such as _Jeholornis_ and
_Epidendrosaurus_.  Ornithurae would also be more inclusive than
Ornithuromorpha, which is not a good thing.  For these reasons, it's
probably best to limit Ornithurae to a less inclusive clade
(_Hesperornis_ + crown clade), and define both Ornithurae and
Ornithuromorpha such that the former is guaranteed to be a subclade of
the latter.