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[dinosaur] Sylviornis (was Endothermic mosasaurs? (free pdf) + marine Nanzhang-Yuan′an Fauna from Lower Triassic of China + more papers)



> Trevor H. Worthy,  Miyess Mitri,  Warren D. Handley,  Michael S. Y. Lee, 
> Atholl Anderson & Christophe Sand (2016)
>
> Osteology Supports a Stem-Galliform Affinity for the Giant Extinct Flightless 
> Bird Sylviornis neocaledoniae (Sylviornithidae, Galloanseres).
> PLoS ONE 11(3): e0150871.
> doi:10.1371/journal.pone.0150871
> http: //
> journals.plos.org/plosone/article?id=info%3Adoi%2F10.1371%2Fjournal.pone.0150871


_Sylviornis_ was a fascinating bird... one of a number of extinct
galloanserine birds that was very big and very flightless.
Sylviornithids belong to the same branch of the neognath tree that
also includes gastornithids and dromornithids, two other lineages of
mega-flightless birds.

Alas, _Sylviornis_ is no longer with us, having been hunted to
extinction by humans on New Caledonia several hundred years ago.
(Ditto for its close relative _Megavitiornis_ on Fiji.)

Interestingly, based on the material, _Sylviornis_ is inferred to have
an impressive display plumage along the wings.  The wings were
reduced, but still fairly large for a flightless bird.  The ulnae had
papillae (quill knobs), despite the fact that the wings could not be
used for flight.


"Also, on well preserved ulnae papillae remigales are present.
Together these features
suggest that the primary and secondary feathers were large and could
be manipulated for
display. This wing was thus relatively larger than that of the kiwi
_Apteryx_ sp., which
are functionless and buried within the plumage, but not so large as in the large
palaeognaths _Struthio camelus_ and _Dromaius novaehollandiae_, where
the elongate
wing bones allow for holding display feathers far out from the body.
In _S. neocaledoniae_,
the wings may have been like they were in the dodo [6, 78], with small
but distinct
feather tufts able to be protruded from the body plumage. ...
As in the dodo, short tufted wings would have extended from the
plumage, which together
with the knob-like osseous ornament to the bill that likely supported
brightly coloured
skin as in cracids [81], very likely was used in complex sexual displays."


This reminds me of certain non-avialan theropods that sported large
remiges, but which were likely incapable of flight (because the
forelimbs were too short, or too weak - and/or the animal itself was
too large).  In these forms, the forelimb plumage was presumably used
for display.  For _Sylviornis_, secondary flightlessness led to the
forelimbs being utilized for display (this is not unique to
_Sylviornis_, as the article makes clear).  But display might have
been the major (and perhaps even the exclusive) function of forelimbs
in many non-avian theropods, including the immediate ancestors of
birds.  The traditional view is that non-avian theropods used their
hands and arms in predation (seizing and/or holding prey) - something
that modern birds cannot do.  However, as was discussed recently on
the DML, theropod forelimbs might not have been all that useful for
predation anyway - the forelimbs had limited reach (even in the
'long-armed' taxa), and little if any prehensility.  So the situation
in _Sylviornis_ may have been quite similar to many non-avian
theropods that had an extensive plumage attached to the forelimbs.
Did loss of flight in sylviornithids lead to a reversion to the
pre-flight function of theropod wings?

Also, _Sylviornis_ had quite a large hallux (first toe) with a
"relatively elongate" metatarsal I  (see Fig. 11).  This bird was
clearly terrestrial, so the hallux was not used for perching.  I
suspect that a great many non-avian theropods that have been regarded
as "arboreal" because of their longer or more distal metatarsal I, or
their larger hallux, were in fact almost entirely terrestrial.  After
reading Dececchi et al.'s study in PeerJ PrePrints
(https://urldefense.proofpoint.com/v2/url?u=https-3A__doi.org_10.7287_peerj.preprints.1676v1&d=CwIBaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=oEM3rmWcLCDBBX0AiSdpqHSuKqm8rQwe5qObJS5LLEg&s=klmEvy9e8VzMRvQe1nXQkIvktJ_2HCJUYxCpqvMI1VA&e=
 ), I don't think any
non-avian theropod could perch in a tree unless it could fly up there
from the ground.  I know this is heretical, but I favor the evolution
of avian flight being "ground up" (no 'passive' gliding phase).