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Re: [dinosaur] Anchiornis muscles and soft tissues revealed with lasers (free pdf)



This is brilliant work. In light of phylogenetic bracketing, the
presence of a propatagium in _Anchiornis_ (a basal paravian) should
not come as a huge surprise - though it is wonderful to be able to
visualize it.  _Caudipteryx_ (a basal oviraptorosaur) is reported to
have a propatagium, and a propatagium is found in crown birds, so the
feature is likely primitive for the Pennaraptora (oviraptorosaurs +
paravians).

Unfortunately, I fear the BANDits will misrepresent some of the
findings to support the misguided idea that _Anchiornis_ is a bird,
not a dinosaur.  Previously, the presence of a propatagium in
_Scansoriopteryx_ and _Caudipteryx_ were cited as 'proof' that these
critters were birds (Czerkas & Feduccia, 2014 DOI
10.1007/s10336-014-1098-9; Feduccia & Czerkas, 2015 DOI
10.1007/s10336-015-1190-9); in the case of _Caudipteryx_, it was
regarded as a secondarily flightless bird.  The flawed 'logic' they
will follow is (1) the propatagium is a flight-related character; (2)
birds can fly, dinosaurs could not; therefore (3) _Anchiornis_is a
bird.

The propatagium is certainly an important component of the avian
flight apparatus.  However, like so many avian flight characters, it
may not have started out that way.   Wang &c seem to take this line,
when they say "Propatagia also have a deep non-flight-related
non-avian theropod origin for example, those in _Caudipteryx_".  There
is a temptation to regard _Anchiornis_ as being volant (glider or
powered flier) on account of its fairly large wings composed of long
pennaceous feathers.  But, like the wings, it cannot be assumed that
_Anchiornis_' propatagium was used either for gliding or flying.  The
propatagium certainly contributed toward the size and shape of the
wing surface.  We can't be certain what _Anchiornis_ actually used its
wings for, so the precise function of its propatagium is likewise
unsettled.  The same is true of _Caudipteryx_, which was certainly
incapable of flight, or even gliding. One could argue that volancy is
primitive for pennaraptorans, and secondarily lost in _Caudipteryx_
(and _Anchiornis_?).  But, at this stage, the evidence does not
support this 'neoflightless' hypothesis for non-volant pennaraptorans
outside the bird clade (Avialae).

The second and third fingers of _Anchiornis_ were bound together,
which means they were syndactylous, and the hand was functionally
didactyl. This would presumably compromise the grasping ability of the
hands, especially for climbing.  So the hands of _Anchiornis_ would be
poorly adapted for grasping branches, which severely undermines the
restoration of _Anchiornis_ as an arboreal climber or glider.
(Arboreal marsupials belonging to the Diprotodontia have syndactylous
pedal digits; but the articulation surface of these digits are closely
aligned along their lengths, with the paired claws positioned side by
side.)

In the tenth specimen of _Archaeopteryx_ the "second and third fingers
are tightly joined" (Mayr et al., 2007 Zool J Linn Soc 149: 97-116).
_Caudipteryx_ had a functionally didactyl manus, due to the highly
reduced third digit.  Syndactylous digits (II and III) were mentioned
as a possibility for the hand of _Chirostenotes_, based on the extreme
slenderness of the third finger (Currie & Russell, 1988 Can J Earth
Sci 25: 972-986); but the authors decided against this interpretation,
based on the inferred range of motion of the third finger independent
of the second.  The idea of a syndactylous _Chirostenotes_ might need
revisiting.  In fact, maybe having a functionally didactyl manus
(including having the second and third fingers being bound together by
skin) is primitive for Pennaraptora?



On Thu, Mar 2, 2017 at 4:10 AM, Ben Creisler <bcreisler@gmail.com> wrote:
>
> The paper is now out in open access:
>
>
> Hartman & Xing Xu (2017)
> Basal paravian functional anatomy illuminated by high-detail body outline.
> Nature Communications 8, Article number: 14576 (2017)
> doi:10.1038/ncomms14576
> https://urldefense.proofpoint.com/v2/url?u=http-3A__www.nature.com_articles_ncomms14576&d=DwIBaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=GjrFtjBuKDGR9SYaZGjMdH76teTUKNQYA2D7gAHTMd4&s=3y676QyC6WoiUGJZaaz4eQjl--V-73CHzEfV9AZBQzQ&e=
>  
>
> Body shape is a fundamental expression of organismal biology, but its
> quantitative reconstruction in fossil vertebrates is rare. Due to the
> absence of fossilized soft tissue evidence, the functional consequences of
> basal paravian body shape and its implications for the origins of avians and
> flight are not yet fully understood. Here we reconstruct the quantitative
> body outline of a fossil paravian Anchiornis based on high-definition images
> of soft tissues revealed by laser-stimulated fluorescence. This body outline
> confirms patagia-bearing arms, drumstick-shaped legs and a slender tail,
> features that were probably widespread among paravians. Finely preserved
> details also reveal similarities in propatagial and footpad form between
> basal paravians and modern birds, extending their record to the Late
> Jurassic. The body outline and soft tissue details suggest significant
> functional decoupling between the legs and tail in at least some basal
> paravians. The number of seemingly modern propatagial traits hint that
> feathering was a significant factor in how basal paravians utilized arm, leg
> and tail function for aerodynamic benefit.
>
>
>
> ---------- Forwarded message ----------
> From: Ben Creisler <bcreisler@gmail.com>
> Date: Tue, Feb 28, 2017 at 10:30 AM
> Subject: Anchiornis muscles revealed with lasers
> To: dinosaur-l@usc.edu
>
>
>
>
> Ben Creisler
> bcreisler@gmail.com
>
>
> The actual paper has not been posted online  yet, but here are some news
> items on a new study of Anchiornis soft tissue using lasers:
>
>
> https://urldefense.proofpoint.com/v2/url?u=https-3A__phys.org_news_2017-2D02-2Dlasers-2Dflesh-2Ddino-2Dbird-2Dprofile.html&d=DwIBaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=GjrFtjBuKDGR9SYaZGjMdH76teTUKNQYA2D7gAHTMd4&s=lR8BOizPhYdsA8GBQhQMF-WqVo-27VmIAisuETeTWRE&e=
>  
>
> https://urldefense.proofpoint.com/v2/url?u=http-3A__www.scmp.com_news_china_policies-2Dpolitics_article_2074841_new-2Dlook-2Dfossils-2Dnorthern-2Dchina-2Dmay-2Dshow-2Devolution&d=DwIBaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=GjrFtjBuKDGR9SYaZGjMdH76teTUKNQYA2D7gAHTMd4&s=aefiUqToipC-z7kwNiRdqvtsGwGX13TnRQnzc4TjwRA&e=
>  
>
> https://urldefense.proofpoint.com/v2/url?u=http-3A__news.nationalgeographic.com_2017_02_anchiornis-2Dbird-2Dlike-2Ddinosaur-2Dfeathers-2Dlasers-2Dsoft-2Dtissue-2Dscience_&d=DwIBaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=GjrFtjBuKDGR9SYaZGjMdH76teTUKNQYA2D7gAHTMd4&s=NQ9xJ2qdV3hzY51Vrv3_OsuOaHpZllZ-xnNZjClzWzU&e=
>  
>
> https://urldefense.proofpoint.com/v2/url?u=http-3A__gizmodo.com_this-2Dlaser-2Dreconstruction-2Dof-2Da-2Dfour-2Dwinged-2Ddinosaur-2Dis-2D1792800473&d=DwIBaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=GjrFtjBuKDGR9SYaZGjMdH76teTUKNQYA2D7gAHTMd4&s=G5HJ1C_LDVgiQvjzTGkEpzw2_oP04aHoxSSj7QJOINc&e=
>  
>
>
> Video
>
> HKU Earth Scientist Reconstructs Feathered Dinosaurs in the Flesh with High
> Power Lasers
>
> https://urldefense.proofpoint.com/v2/url?u=https-3A__www.youtube.com_watch-3Fv-3D4IfoZ9yw6EE&d=DwIBaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=GjrFtjBuKDGR9SYaZGjMdH76teTUKNQYA2D7gAHTMd4&s=-XCL3cRJV3ZxhWYyxHGWOYN1M24DjVRfH5PpD41gLuc&e=
>  
>
>
>
>