Re: [dinosaur] Paravian Phylogeny and the Dinosaur-Bird Transition (free pdf)

[Tim Williams <tijawi@gmail.com>]

I found this statement from Agnolin et al. to be a bit surprising:

"Accordingly, their forelimb movements [from anterodorsal to
posteroventral] differed from those of flying neognathans, and basal
avialans including _Archaeopteryx_ were very probably not capable of
powered flight. This is in agreement with other lines of evidence,
including feather morphology and bone geometry (Feo et al., 2015;
Voeten et al., 2018), that suggest flight capability was low or absent
in basal avialans."

This is not correct.  I'd say that Agnolin et al.'s citation of both
references (Feo et al., 2015; Voeten et al., 2018) is inapt.  Feo et
al. were somewhat neutral on the question of whether _Archaeopteryx_
was capable of powered flight or not; _Archaeopteryx_ shared the same
feather morphology (e.g., barb geometry) as _Microraptor_,
_Confuciusornis_ and _Sapeornis_.  So, following Agnolin et al.'s
logic, based on feather morphology, if _Archaeopteryx_ was not capable
of powered flight, nor was _Confuciusornis_ or _Sapeornis_.  This
doesn't sound plausible (e.g. the highly specialized soaring flight
proposed for _Sapeornis_, Serrano & Chiappe, 2017).

As for wing bone geometry, Voeten et al.were unequivocal in their view
that _Archaeopteryx_ was capable of powered flight.  Their study was
actually entitled "Wing bone geometry reveals active flight in
_Archaeopteryx_".  As Voten et al. phrase it: "We therefore interpret
that _Archaeopteryx_ actively employed wing flapping to take to the
air through a more anterodorsally posteroventrally oriented flight
stroke than used by modern birds."  This directly contradicts Agnolin
et al. w.r.t. the inferred flight abilities of _Archaeopteryx_, so
it's perplexing that they chose to cite Voeten et al. here.

Both studies (Feo et al., 2015; Voeten et al., 2018) hypothesize that
_Archaeopteryx_ had a different style of flight (including wing
stroke) to modern birds.  But they did not rule out powered flight.
Voeten et al. proposed that _Archaeopteryx_ could fly, using an
anterodorsally-posteroventrally oriented flight stroke cycle with
minimal excursion above the dorsum, that was closer to the grasping
motion of non-avialan maniraptorans.


On Wed, Feb 13, 2019 at 6:20 AM Ben Creisler <bcreisler@gmail.com> wrote:
>
>
>
> Ben Creisler
> bcreisler@gmail.com
>
>
> Now out in full form (posted earlier as an abstract only):
>
> Free pdf:
>
> Federico L. Agnolin, Matias J. Motta, Federico BrissÃn Egli, GastÃn Lo Coco 
> and Fernando E. Novas (2019)
> Paravian Phylogeny and the Dinosaur-Bird Transition: An Overview.
> Frontiers in Earth Science 6:252
> doi:  
> https://urldefense.proofpoint.com/v2/url?u=https-3A__doi.org_10.3389_feart.2018.00252&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=ITz_VFvURMxW0178lWlv43h0Oag8X8KdcfMeoAXvxNw&s=4-Dek5WK0avqyqKB_wAaBB6SHtcxGyymMiaGTii35Gk&e=
> https://urldefense.proofpoint.com/v2/url?u=https-3A__www.frontiersin.org_articles_10.3389_feart.2018.00252_full&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=ITz_VFvURMxW0178lWlv43h0Oag8X8KdcfMeoAXvxNw&s=DB9TxpvmuEHWxkSlqHFo0RKp1pOlEFrDuN_BgP2nTd0&e=
>
>
> Recent years witnessed the discovery of a great diversity of early birds as 
> well as closely related non-avian theropods, which modified previous 
> conceptions about the origin of birds and their flight. We here present a 
> review of the taxonomic composition and main anatomical characteristics of 
> those theropod families closely related with early birds, with the aim of 
> analyzing and discussing the main competing hypotheses pertaining to avian 
> origins. We reject the postulated troodontid affinities of anchiornithines, 
> and the dromaeosaurid affinities of microraptorians and unenlagiids, and 
> instead place these groups as successive sister taxa to Avialae. Aiming to 
> evaluate previous phylogenetic analyses, we recoded unenlagiids in the 
> traditional TWiG data matrix, which resulted in a large polytomy at the base 
> of Pennaraptora. This indicates that the TWiG phylogenetic scheme needs a 
> deep revision. Regarding character evolution, we found that: (1) the presence 
> of an ossified sternum goes hand in hand with that of ossified uncinate 
> processes; (2) the presence of foldable forelimbs in basal archosaurs 
> indicates widespread distribution of this trait among reptiles, contradicting 
> previous proposals that forelimb folding driven by propatagial and associated 
> tendons was exclusive to the avian lineage; (3) in basal paravians and 
> avialans (e.g., Archaeopteryx, Anchiornis) the wings are relatively large and 
> wide, with relatively short rectricial feathers, a rounded alar contour, and 
> a convex leading margin. These taxa exhibit restricted forelimb folding 
> capability with respect to more derived birds, their hands being preserved at 
> angles of flexion (with respect to the radius/ulna) of no less than 90Â. In 
> more derived birds, however, the rectrices are notably elongate and the angle 
> between the hand and forearm is much less than 90Â, indicating not only 
> increased forelimb folding capability but also an increased variety of 
> wingbeat movements during flight. Because of the strong similarities in 
> pectoral girdle configuration between ratites and basal avialans and 
> paravians, it is possible to infer that the main forelimb movements were 
> similar in all these taxa, lacking the complex dorsoventral wing excursion 
> characteristic of living neognathans.
>
>
> Virus-free. www.avg.com