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Re: [dinosaur] Apatoraptor, new caenagnathid oviraptorosaur from Late Cretaceous of Alberta, Canada

_Apatoraptor_ is another fascinating oviraptorosaur, a member of the
'elmisaur' group of caenagnathids.  In light of their new discovery,
Funston and Currie (2016) raise a few interesting ideas regarding
oviraptorosaur evolution and paleobiology.  One particularly
intriguing hypothesis is that the presence of a pygostyle (fused
distal caudal vertebrae) might be a character that is dependent upon
the age or gender of the individual.  This is because the pygostyle
has such an erratic distribution among oviraptorosaur taxa, and
because this structure is associated with anchoring a "fan" of
feathers for display.  (A similar situation may exist for cranial
crests in oviraptorosaurs, as a putative display structure that also
has a 'spotty' phylogenetic distribution.)

This has ramifications beyond the oviraptorosaurs.  If caudal
morphology is connected with ontogeny and/or sexual maturity, it could
mean that _Epidendrosaurus_ (juvenile, long tail) and _Epidexipteryx_
(adult with much shorter tail, ending as a pygostyle-like structure)
are actually the same animal. (This isn't my idea - it's been mooted
before, that _Epidexipteryx_ is an adult _Epidendrosaurus_.  If so, it
suggests that only young scansoriopterygids had some of sort of aerial
or flight capability - as also suggested for _Deinonychus_ [Parsons &
Parsons, 2015]).

Funston and Currie further suggest that the presence of a well-muscled
pennibrachium in _Apatoraptor_ (as evidenced by the ulnar papillae)
can be explained as a secondary sex characteristic.  It's also
possible that other characters, such as the laterally-facing glenoid
and large deltopectoral crest of _Apatoraptor_, were also associated
with elaborate - and demanding - courtship displays.  More broadly,
the hypothesis that the 'wing' (pennibrachium) of adult non-avialan
theropods served in sexual display is gaining traction.  It accords
with the view that the initial enlargement of the forelimb feathers in
adult non-avialan theropods had nothing to do with aerial behaviors
(such as WAIR or arboreal gliding), but were involved in
non-locomotory behaviors (display, brooding, etc).

One odd feature of the phylogeny is that it recovers
_Protarchaeopteryx_ as an archaeopterygid, rather than an
oviraptorosaur.  This harks back to the original taxonomic assignment
of _Protarchaeropteryx_ by Ji & Ji (1997) as a primitive
'archaeopterygian' (I'm skeptical).  More significant is the recovery
of _Luoyanggia_ and _Ningyuansaurus_ as basal oviraptorosaurs, of the
same evolutionary grade as caudipterygids.

On Wed, Apr 13, 2016 at 2:14 PM, Ben Creisler <bcreisler@gmail.com> wrote:
> Ben Creisler
> bcreisler@gmail.com
> A new paper:
> Gregory F. Funston & Philip J. Currie (2016)
> A new caenagnathid (Dinosauria: Oviraptorosauria) from the Horseshoe Canyon
> Formation of Alberta, Canada, and a reevaluation of the relationships of
> Caenagnathidae.
> Journal of Vertebrate Paleontology (advance online publication)
> DOI:10.1080/02724634.2016.1160910
> http: // www.tandfonline.com/doi/full/10.1080/02724634.2016.1160910
> Our understanding of caenagnathids has benefited from recent discoveries,
> including nearly complete skeletons from the Hell Creek Formation of
> Montana. However, their phylogenetic relationships remain unclear. A new
> specimen from the Horseshoe Canyon Formation of Alberta has implications for
> the phylogeny and paleobiology of these creatures. The partial skeleton is
> articulated and includes a mandible, a full cervical and dorsal series of
> vertebrae, a right pectoral girdle and arm, a sternum, gastralia, a partial
> ilium, and a partial hind limb. The mandible is edentulous and the articular
> ridge is intermediate in form between Caenagnathus collinsi and
> Chirostenotes pergracilis. The neck is long and composed of at least 11
> well-pneumatized cervical vertebrae with fused cervical ribs. The dorsal
> ribs have finger-like uncinate processes dissimilar in shape to those of
> other oviraptorosaurs. The pectoral girdle is large and typically
> maniraptoran, except that the glenoid of the scapulocoracoid faces laterally
> instead of posteroventrally. The arm is well muscled and can be interpreted
> to have been a pennibrachium, as indicated by ulnar papillae on the ulna.
> The manus is characterized by a short first metacarpal but an elongate
> phalanx I-1 and oviraptorid-like phalangeal proportions in the second digit.
> These and other features indicate that the specimen represents a new taxon,
> Apatoraptor pennatus, gen. et sp. nov. Phylogenetic analysis resolves the
> complicated relationships of Caenagnathidae and allows the evolution of
> display features to be traced throughout Oviraptorosauria.
> http: //
> zoobank.org/urn:lsid:zoobank.org:pub:122957D7-F65F-4A2C-86AF-386AE8AAF2C4