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RE: Chaoyangia redescribed with new phylogeny of Mesozoic birds



Well, hesperornithines do preserve some forelimb elements (humeri in 
Hesperornis and Parahesperornis; humerus, radius and ulna in Baptornis; 
humerus, radius, ulna and carpometacarpus in Pasquiaornis; humeri in 
Enaliornis).  O'Connor et al. find Limenavis to be hesperornithine based on-

Distal end of the humerus very compressed craniocaudally: present (1). (also in 
Apsaravis)
Humerus, m. humerotricipitalis groove: absent (0). (also in Jianchangornis, 
Longicrusavis, Patagopteryx and Yixianornis)

So pretty weak evidence.  I think it's more likely to be a lithornithid- 
http://home.comcast.net/~eoraptor/Aves.htm#Limenavispatagonica

Mickey Mortimer

----------------------------------------
> Date: Thu, 21 Jun 2012 12:36:51 +1000
> From: tijawi@gmail.com
> To: dinosaur@usc.edu
> Subject: Re: Chaoyangia redescribed with new phylogeny of Mesozoic birds
>
> This new phylogeny recovers a clade comprising _Limenavis_ and
> hesperornithiforms. I find this quite curious, because _Limenavis_ is
> known only from the wing skeleton of a volant bird, and the wings of
> hesperornithiforms were vestigial. What characters could possibly
> unite a _Limenavis_ + Hesperornithiformes clade?
>
>
>
>
> On Thu, Jun 21, 2012 at 1:38 AM, Ben Creisler <bcreisler@gmail.com> wrote:
> > From: Ben Creisler
> > bcreisler@gmail.com
> >
> > A new online paper:
> >
> > Jingmai K. O’Connor & Zhonghe Zhou (2012)
> > A redescription of Chaoyangia beishanensis (Aves) and a comprehensive
> > phylogeny of Mesozoic birds.
> > Journal of Systematic Palaeontology (advance online publication)
> > DOI:10.1080/14772019.2012.690455
> > http://www.tandfonline.com/doi/abs/10.1080/14772019.2012.690455
> >
> >
> >
> > We review the enigmatic Chaoyangia beishanensis, one of the earliest
> > birds described from the Jiufotang Formation, north-eastern China, and
> > the first to be identified as an ornithurine (Aves: Ornithothoraces)
> > and thus a member of the clade that includes living birds. A complete
> > discussion of the validity of this taxon, which once included the
> > holotype of Songlingornis, is provided, along with a revised
> > diagnosis. The morphology of Chaoyangia is described, including
> > extensive comparison with better known, recently discovered
> > ornithurines as well as several other groups of Mesozoic birds
> > (Confuciusornithiformes, Sapeornithiformes, Enantiornithes). Although
> > preserved information is limited, the large number of fused sacral
> > vertebrae and presence of a distal dorsal process on the ischium are
> > among the features supporting early hypotheses that the only known
> > specimen of Chaoyangia represents an ornithurine. Unique among
> > ornithurines, Chaoyangia possesses two dorsal processes on the
> > ischium, and thus remains a valid taxon. We include this taxon in a
> > cladistic analysis to test morphological hypotheses regarding its
> > systematic position. Although the results of the analysis are highly
> > resolved and support the referral of Chaoyangia and Zhongjianornis to
> > Ornithurae, support for the tree overall is very low. Recently
> > discovered taxa have blurred the once clear morphological gap
> > separating the two ornithothoracine clades (Ornithurae and
> > Enantiornithes), and thus the increase in taxonomic diversity has
> > caused a decrease in the stability of hypothetical relationships.