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RE: weird jurassic dinobird with very weird feathers



After entering it in my modified version of Senter's matrix, Epidexipteryx does 
indeed fall out as a scansoriopterygid.  The topology is basically the same as 
the authors', except Archaeopterygidae is paraphyletic, Protopteryx is sister 
to Pygostylia (probably due to insufficient included avialan characters), 
alvarezsaurids are further from birds than therizinosaurs, and Ornitholestes is 
outside Maniraptoriformes.

Scansoriopterygid synapomorphies include-
- Wide distal expansion of scapula (>1.9 times minimum shaft width) present.
- Humerus longer than femur.
- Length of radius between 2/3 and 1× femoral length.
- Preacetabular portion of ilium markedly longer (>120%) than postacetabular 
part.
- Distal pubis with reduced anteroposterior projections.
- Ischium more than 70% of pubic length.
- Obturator process of ischium absent.

Avialan characters of scansoriopterygids include-
- Hyposphene -hypantrum articulations in trunk vertebrae absent (according to 
Senter).
- Transition point in caudal series begins proximal to 10th caudal vertebra.
- Anteriormost haemal arches  I should have noted, however, that what I saw as 
a furcula, in the line drawing, corresponds to a rib. Oops. No such element is 
preserved. Contrary to paravians, the coracoid of the near preserved is 
preserved inline with the scapula. Mickey has argued previously that the 
coracoid shoudl articulate, as birds do, into a tight angle, and likens the 
element to *Bambiraptor* in hsi last post. This element appears to be preserved 
such that the articular glenoid is oriented ventrally, rather than posteriorly 
or laterally. The same element of the other side is disarticulated from the 
scapula. This seems at odds with previous arguments that the shoulder is 
"incipiently" avian.

The lower (right?) coracoid doesn't seem to be articulated with the scapula 
either, with its narrow proximal neck lower than and partially overlapping the 
base of the scapula.  I would argue the coracoid would be bent so that the neck 
is in a different plane from the oval distal end, and this makes the C-shape we 
see in the Epidendrosaurus and Scansoriopteryx holotypes.  The glenoid may be 
oriented ventrally or laterally- I cannot discern it.

> The jugal has a strongly posteriorly ascending process, and may very well 
> have lacked a contact with the postorbital, which is otherwise poorly 
> preserved on both slabs. However, what may be the ascending process of the 
> jugal appears to be expanded distally. This suggests a closed postorbital bar.

The postorbital process I see is a very narrow splint-like process curving 
posteriorly, right above the posterior edge of the external mandibular 
fenestra.  I cannot distinguish any part of the postorbital, which was 
therefore probably highly reduced.  Since the posterior orbital margin seems to 
curve down far in front of the jugal's postorbital process, I doubt there was a 
connection between any postorbital and the latter.

> The posterior process of the jugal, the quadratojugal ramus, appears to be 
> forked, and may preserve portions of an element of the quadratjugal itself.

Maybe so.  The quadratojugal would then lack a dorsal process, as in Shuvuuia 
and ornithurines (sensu Chiappe).

> The quadrate (~12.4mm) is about as high as the orbit is tall (~14mm), which 
> is far from the derived condition in paravians in which the vertical height 
> of the quadrate is reduced relative to the orbital height or overall cranial 
> height.

I agree, but Sapeornis and Archaeopteryx both have fairly tall quadrates (~87% 
and 84% of orbit+jugal height respectively), though not as tall as in 
Epidexipteryx.

> The mandible in aspect is as similar to *Confuciusornis* as said avian is to 
> an egret. The mandible is strongly downcurved, with prodigious dental roots 
> (at least 60%+ of the teeth as preserved are above the root/crown margin and 
> the mandibular edge); there is no invasive process of the surangular into the 
> external mandibular fenestra, and the fenestra is roughly evenly ovate rather 
> than oblate (expanded more to one said than the other, as an egg) in shape; 
> there does not appear to be a large surangular foramen, and there does appear 
> to be a long, but not deep and short retroarticular process, although the 
> elements appear broken.

I said the posterior mandible was similar.  The anterior dentary is indeed 
quite different.  I was thinking particularily of Confuciusornis dui, which 
doesn't have the invasive surangular process of C. sanctus or seemingly the 
large surangular fenestra.  The retroarticular process of Epidexipteryx is 
indeed longer than in Confuciusornis.

> There is a large lachrymal foramen.

Maybe.  The left slab might have two small foramina, and the right slab may 
have a slit (like Incisivosaurus), but they could all be damage too.

> There are no pennate feathers. At least even basal dromaeosaurs, 
> oviraptorosaurs, and probably troodontids had true feathers. This places the 
> taxon at least in either 1) a degenerate state, in which case it should lack 
> features associated with a flight apparatus a la therizinosauroids, or 2) it 
> is not as close to birds as the authors of the paper positioned it. The 
> matrix would be better suited to looking at their codings.

Well, the retrices have vanes, similar to confuciusornithids and 
enantiornithines, though we don't know if the vanes were distally barbed as in 
those taxa.  The lack of remiges is interesting, but we've had similar 
situations in Jinfengopteryx and NGMC 91.  Unpreserved?  Secondarily reduced?  
Ontogenetic?  Who knows.

> The distal ends of the scapula are expanded. This was proposed for 
> *Scansoriopteryx*, as it was argued the element found on the slab was the 
> distal end, but others have argued it as the proximal element. A broad distal 
> expansion is also not in keeping with this taxon's placement closer to birds 
> than to deinonychosaurians, which produced reduced distal expansions to none 
> at all, as in Avialae.

Archaeopteryx and Confuciusornis have fairly large scapular expansions (~1.45 
times the minimum blade width) and Jinfengopteryx (placed as a basal avialan in 
my modified Senter matrix) has an even larger one (~2.3 times), which is 
similar to Scansoriopteryx's holotype (~2.5 times).

> I am not sure why an animal that is so closely aligned in morphology to other 
> "scansoriopterygids" would have a reduce tail, as if the extreme modification 
> would be coincident with pelvic modifications due to anteriorized center of 
> gravity; such do not appear to occur, and the dorsal column reminds me of 
> compsognathids in being long and low, much longer at least than the tibia by 
> about 20%. Comparatively, *Confuciusornis* dorsal/tibial lengths are close to 
> equal, *Gallimimus* is roughly 10% longer in the dorsum, and *Velociraptor* 
> appears to be about 15% or so. (I'm guestimating from images of Scott 
> Hartman's and Greg Paul's skeletals here.) The body adaptations do not agree 
> with a short tail, and given the intactness of the distal segment and the 
> disarticulated aspect of the proximal, I would strongly urge a disconnect, 
> and therefore lack of confidence as to the tail's length overall.

You may be right, but basal avialans did seem to reduce their tail length with 
age.  For instance, juvenile enantiornithines have tails 1.59 (Dalingheornis) 
or 1.36 (Liaoxiornis) times their femoral length, while the ratio is lower for 
older individuals- .88 in Iberomesornis or .90 in Sinornis.  Eoconfuciusornis 
is a juvenile with a ratio of 1.24, while adult Confuciusornis has a ratio of 
.98.  If Zhongornis is a juvenile confuciusornithid, it would fit the trend 
with a ratio of 1.54.
Furthermore, the distal tail base looks like it was proximal in nature- having 
short centra with transverse processes.  The sudden elongation of centra isn't 
seen in the last seven caudals of any theropod I know of, whereas it is seen in 
the tail base of paravians.

Mickey Mortimer
The Theropod Database- http://home.comcast.net/~eoraptor/Home.html