Pubis evolution

http://pterosaurheresies.files.wordpress.com/2011/09/prepubes588.jpg
Pterosaur pubis (in green) and prepubis (in yellow). The drawing of MPUM 6009 is the most relevant.

The pterosaur pubis (green) is homologous with the basal paraves superior pubic ramus and pubic body.
The pterosaur prepubis (yellow) is homologous with the basal paraves inferior pubic ramus.


http://archosaurmusings.wordpress.com/2009/12/24/back-to-that-pterosaur-sacrum-pelvis/

pterosaurs also have a fourth pelvic bone in the form of the pre-pubis. This pair of bones (one for each side) lie, and no points for guessing this, in front of, and articulate with, the pubes.

http://pterosaurheresies.wordpress.com/tag/pterosaur-evolution/page/6/

The prepubis of pterosaurs is a pelvic bone not found in the vast majority of tetrapods. It is not homologous with the prepubis of monotremes and marsupials. Nor is it homologous with the so-called “prepubic” bones of crocodilians, which are homologous with the pubic bones of other amniotes (Seeley 1901). The prepubis of ornithischian dinosaurs is a process of the pubis and not a separate ossification.

For example:
The pubis/prepubis parts of MPUM 6009 above, correspond to the 3 parts of the paraves pubis, as seen in the oviraptor pubis in drawing "C" below. 

http://qilong.files.wordpress.com/2011/07/caenagnathid-ilia.jpg?w=932&h=549

Feet

Pterosaur feet are like basal paraves feet. Dinosaur feet are not like basal paraves feet.

ivpp.cas.cn/qt/papers/201403/P020140314393548274893.pdf

Distally the [Epidendrosaurus] trochlea of metatarsal I aligns with those of II and III as in advanced perching birds, but not in other known dinosaurs.

The foot of Epidendrosaurus [a Scansoriopterygidae] is unique among nonavian
theropods. Although it does not preserve a reversed
hallux, metatarsal I is articulated with metatarsal II at
such a low position that the trochleae of metatarsals I–IV
are almost on the same level (see Figs. 1, 2d), which
is similar to those of perching birds including the Early
Cretaceous flying birds Sinornis (Sereno 1992) and
Longipteryx (Zhang and Zhou 2001), as well as many arboreal
pterosaurs.

http://en.wikipedia.org/wiki/Scansoriopteryx

It [Scansoriopteryx] also had an unusually large first toe, or hallux, which was low on the foot and may have been reversed, allowing some grasping ability.[1]

The Scansoriopterygidae are among the most basal members of Paraves.


http://www.nature.com/nature/journal.../391886a0.html

Other features of digits I-IV of the D. weintraubi foot indicate a capacity for grasping that is consistent with an ability to climb but is unexpected in an obligate cursor. The claws are moderately curved (nearly as strongly as the claws of the manus); all phalanges except the most proximal have well developed flexor tubercles for the insertion of digital flexors (Fig. 2); and all of the IP joints allow for extensive flexion of the digits (as exhibited by digit IV; Fig. 2). Furthermore, the phalangeal proportions of the digits of Dimorphodon and other basal pterosaurs are similar to those of birds with grasping feet (that is, perching, climbing, and raptorial species) and unlike those of primarily ground-living birds, bipedal dinosaurs and the primitive dinosauromorphs Lagerpeton and Marasuchus.

Notable

http://www.ivpp.ac.cn/qt/papers/201206/P020120604508520389814.pdf

The [Epidendrosaurus] material described in this paper was collected from a new locality, Daohugou, in east Nei Mongol, northeast China, which is west of Liaoning Province. Many salamanders(Wang 2000), plants and insects (Zhang 2002)have recently been discovered from this new locality. It is notable that an anurognathid rhamphorhynchoid pterosaur [Jeholopterus] with beautiful hair [pycnofibers] covering the whole body has also been reported from this locality (Wang et al. 2002). The estimated age of the deposit at this locality is very controversial and ranges from the Middle Jurassic or the Early Cretaceous according to various authors (Wang etal. 2000; Zhang 2002); however, most workers currently regard it as being Late Jurassic.

Epidendrosaurus is a Scansoriopterygidae and one of the most basal members of Paraves.


http://link.springer.com/article/10.1360/02tb9054#page-1

We report a new and nearly completely articulated rhamphorhynchoid pterosaur, Jeholopterus ningchengensis gen. et sp. nov., with excellently preserved fibres in the wing membrane and “hairs” in the neck, body and tail regions.

https://scholar.google.com/scholar_lookup?title=A+nearly+completely+articulated+rhamphorhynchoid+pterosaur+with+exceptionally+well-preserved+wing+membranes+and+%22hairs%22+from+Inner+Mongolia,+northeast+China&author=WANG+X&author=ZHOU+Z&author=ZHANG+F&author=XU+X&publication_year=2002&journal=Chin+Sci+Bull&volume=47&pages=226-230

http://en.wikipedia.org/wiki/Jeholopterus

Jeholopterus was a small anurognathid pterosaur from the Middle to Late Jurassic^[1]Daohugou Beds of the Tiaojishan Formation of Inner Mongolia, China , preserved with hair-like pycnofibres and skin remains.

http://en.wikipedia.org/wiki/Yi_%28dinosaur%29

The only known Yi qi fossil was found in rocks assigned to the Tiaojishan Formation, dating to the Callovian-Oxfordian age of the Middle-Late Jurassic,[1] dated to between 165 and 153 million years ago.[3] This is the same formation (and around the same age) as the other known scansoriopterygids Epidexipteryx and Scansoriopteryx.

Yi qi

Vocabulary

It needs to be kept in mind that the vocabulary that is routinely used in discussing the origin of birds is based on the dino to bird theory. The vocabulary is not neutral. It assumes the dino to bird theory*.
This makes it tricky to even describe the pterosaur to bird theory. You have to use very qualified expressions, which even then, imply a dino to bird theory.
For example, I often use the phrase "basal paraves". This is intended to mean the long-bony-tailed feathered flying and secondarily flightless creatures. For example, Scansoriopterygidae.
But the category "paraves" is defined WITHIN the dino to bird theory. It assumes the dino to bird theory. So I obviously do not mean to include the baggage that the term "paraves" carries within the dino to bird theory.
For example, I do not mean that basal paraves evolved from dinosaurs and I do not mean to exclude oviraptors from the paraves group.


* for example consider this:
http://en.wikipedia.org/wiki/Paraves

Paraves is a branch-based clade defined to include all dinosaurs which are more closely related to birds than to oviraptorosaurs.

Intramandibular joint

PTEROSAURS

http://dml.cmnh.org/2002Sep/msg00187.html

The unusual intra-mandibular joint described above is found only in herrerasaurids and theropods among dinosaurs. Dinosaurian outgroups (pterosaurs, crurotarsal archosaurs) also lack an intra-mandibular joint.

BASAL PARAVES

Page 21:
http://books.google.ca/books?id=kZqJAAAAQBAJ&pg=PA21&lpg=PA21&dq=Archaeopteryx+intramandibular+joint&source=bl&ots=RKECg3KMdM&sig=0b_OE2jWhNOIFTxjXSdvNt4E-dU&hl=en&sa=X&ei=ocV7VKDBBfSZsQSk6YGwCw&ved=0CCYQ6AEwAg#v=onepage&q=Archaeopteryx%20intramandibular%20joint&f=false

[Archaeopteryx] does not appear to have had an intramandibular joint

http://en.wikipedia.org/wiki/Odontognathae

.....intramandibular articulation something that is actually absent in Archaeopteryx, but found in many of its theropod relatives.[2]

DINOSAURS 

http://biology.kenyon.edu/courses/biol241/bird%20flight%202005%20Feduccia_Alan.pdf

It would not tax the imagination to engender a long list of obstacles for the now dominant model of a theropod origin of birds, including....the sliding lower jaw joint [sliding intramandibular joint] of theropods (absent in birds)

http://dml.cmnh.org/2002Sep/msg00187.html

"Kinetic dentary-surangular and splenial-angular articulations are also
present in theropods (e.g., Ceratosaurus, Fig. 10C; Carnotaurus, Bonparte et
al. 1990). In theropods, however, the articular surfaces of the
splenial-angular sliding joint are the reverse of that in Herrerasaurus and
Staurikosaurus; the tongue-shaped process of the splenial has a convex
dorsal articular surface that slides against a concave depression on the
angular. The dentary-splenial joint is also present in theropods, but the
posterodorsal process of the dentary is not elongated as in H.
ischigualastensis. The unusual intra-mandibular joint described above is
found only in herrerasaurids and theropods among dinosaurs. Dinosaurian
outgroups (pterosaurs, crurotarsal archosaurs) also lack an intra-mandibular
joint."

http://www.geol.umd.edu/~tholtz/G104/lectures/104therop.html

The traits uniting Theropoda seem to include:
.........
An intramandibular joint between the dentary and post-dentary bones: this may have served as a shock absorber while feeding on live prey. (Herrerasaurs have a slightly different configuration of the intramandibular joint, and thus may be convergent.)

http://www.bio.fsu.edu/James/Ornithological%20Monographs%202009.pdf

the analysis of Benton (2004) demonstrated that the only unequivocal synapomorphy diagnosing Theropoda is the presence of an intramandibular joint.

http://palaeos.com/vertebrates/coelurosauria/oviraptorosauria.html

Oviraptorosauria:

intramandibular joint absent

https://academic.oup.com/icb/article/55/1/85/617835

Although the majority of teleost fishes possess a fused lower jaw (or mandible), some lineages have acquired a secondary joint in the lower jaw, termed the intramandibular joint (IMJ). The IMJ is a new module that formed within the already exceptionally complex teleost head, and disarticulation of two bony elements of the mandible potentially creates a “double-jointed” jaw. The apparent independent acquisition of this new functional module in divergent lineages raises a suite of questions. 

Although the majority of teleosts possess a fused lower jaw as described above, some species have acquired an additional joint termed the intramandibular (“within the mandible”) joint, or the IMJ. The IMJ facilitates intramandibular bending, or movement that occurs between two individual bony components of the lower jaw; during this movement, the dentary bone rotates about its articulation with the angular-articular. The disarticulation of formerly fused bony elements of the mandible (via unknown developmental mechanisms) creates a “double-jointed” jaw in the species that possess this morphology. Thus, the IMJ is a new module that has formed within the already exceptionally complex teleost head. Remarkably, an intramandibular joint appears to have evolved independently multiple times (Fig. 2)—each time creating a “secondary” jaw joint and disarticulating two formerly fused elements of the lower jaw (Fig. 1).

http://dml.cmnh.org/2002Sep/msg00154.html

Not all carnivores have such a joint. Only neotheropods appear have this, plus *Herrerasaurus* distinctly. Prosauropods and sauropods have flush dentary/postdentary margins or a semi-fixed herrerasaur pattern, and all ornithischians have reduced fenestra in the jaws that correlate with peg-in-notch and scarf joints between the two mandibular halves. The most dynamic predators today, such as falconiforms and cats, have very fixed,immobile jaws. Innovations in the joint were to increase gape and volume of the bite withing increasing skull size.

http://palaeos.com/vertebrates/coelurosauria/tyrannosauroidea.html

One factor which seems to favor bone-crushing as a significant behavior is the design of the tyrannosauroid jaw. Older reconstruction of tyrannosaurs usually incorporated the typical theropod jaw, which includes an intramandibular joint. This joint connects the anterior dentary, splenial and (if present) supradentary with the posterior surangular, angular, coronoid, prearticular and articular. Since this connection is hinged, the lower jaw bends outward in the middle when it is stressed -- as, for example, when the teeth hit something rather hard. Accordingly, most bone would not be crushed. Rather the teeth would slide over it as the jaw deformed, causing the bone to be swallowed whole or rejected.

This arrangement is certainly operative in carnosaurs, and perhaps even basal tyrannosauroids. However, Hurum & Currie (2000) have shown that tyrannosaurinids block the joint. The supradentary overgrows the joint and fuses with the coronoid. This connection is reinforced by a long process of the prearticular which articulates with both the coronoid and the splenial. An anterior process of the angular also bridges the gap ventrally. In addition, the supradentary sends ridges between the teeth, further immobilizing the lower tooth row.

Summary

Here is a comparison of basal pterosaur, basal paraves and coelurosaur dinosaur.
As we can see, basal paraves are like pterosaurs. Basal paraves are not like dinosaurs.
This is a work in progress.
If anyone would like to contribute to this analysis, please feel free.

	Basal Pterosaur: eg. Rhamphorhynchidae Basal Paraves: eg. Scansoriopterygidae Coelurosaur Dinosaur: eg. Compsognathidae

			Basal		Basal		Coelurosaur
			Pterosaur		Paraves		Dinosaur
		CHARACTERS

Back 1 Notarium: absent (0) present (1) 0 0 0 2 Hyposphene-hypantrum: absent (0) present (1) ? 0 1 Breathing 1 Respiratory air sacs: absent (0) present (1) 1 1 x 0 2 Aspiration pump: absent (0) present (1) 1 1 x 0 3 Rib lever processes: absent (0) present (1) 1 1 x 0 Chest 1 Ossified breastbone: absent (0) present (1)  1 1 x 0 2 Symmetric furcula: absent (0) present (1) 1       1  x 0 3 Interclavicle: absent (0) present (1) 1 ? 0 Leg 1 Thigh bone: horizontal (0) not horizontal (1) 0 0 x 1 2 Splayed hindlimbs: absent (0) present (1) 1 1 x 0 3 4th trochanter on femur: present (0) much reduced (1) 1 1 x 0 Foot 1 Hyperextended second toe: absent (0) present (1) 0 0 0 2 Hinge-like ankle joint: absent (0) present (1) 1 1 1 3 Trochleae of metatarsals I–IV: align (0) not align (1) 0 0 x 1 Pelvis 1 Pubic bone: pointing to back (0) to front (1) down (2) 1 1 1 2 Pubic bones: not fused (0) fused (1) 0 ? ? 3 Acetabulum: not perforated (0) partial (1) full (2) 0 x 1 x 2 4 Pelvic bones: not fused (0) fused (1) 1 ? ? 5 Pre-pubic bone: absent (0) present (1) 1 ** ** 6 Supra-acetabular shelf: not present (0) present (1) 0 0 x 1 7 Antitrochanter: absent (0) present (1) 0 0 x 1 8 Sacrum: present (0) not present (1) 0 0 0 9.   Lunate surface: present (0) not present (1) 0 0 x 1 Tail 1 Caudal vertebrae: less than 15 (0) greater than 15 (1) 1 1 1 2 Caudal rods: absent (0) present (1) 1 1 x 0 3 Muscle mass of M. caudofemoralis longus: small (0) large (1) 0 0 x 1 Skull 1 Beak like jaw: absent (0) present (1) 1 1 x 0 2 Teeth: absent (0) present (1) 1 1 1 3 Crest: absent (0) present (1)  1 * 0 4 Neck attaches to skull; from rear (0) from below (1) 0 0 0 5 Serrated teeth: absent (0) present (1) 1 1 1 6 Semicircular canals:  expanded (0) not expanded (1) 0 ? ? 7 Intramandibular joint: absent (0) present (1) 0 * * 8 Mandibular fenestra: absent (0) present (1) * * * 9  Procumbent teeth: absent (0) present (1)                             1        1              ? Shoulder 1 Strap-like scapula: absent (0) present (1) 1 1 ? 2 Scapula oriented to backbone: subparallel  (0) parallel (1) 1 1 x 0 3 Glenoid fossa: elevated (0) not elevated (1) 0 0 x 1 4 Scapula and coracoid: separate (0) fused (1) 1 1 ? Feather 1 Stage 2 feathers: absent (0) present (1) 1 1 x 0 2 Pennaceous feathers: absent (0) present (1) 0 x 1 x 0 Wing 1 Propatagium: absent (0) present (1) 1 1 x 0 2 Patagium: absent (0) present (1)  1 1 x 0 3 Wing membrane: absent (0) present (1) 1 * 0 4 Elongated outer finger: absent (0) present (1) 1 1 x 0 5 Number of fingers: 2 fingers (2) 3 fingers (3) 4  fingers (4) 4 ** 2/3 6 Pteroid/prepollex: absent (0) present (1) 1 1 x 0 7 Capable of flapping flight: absent (0) present (1) 1 1 x 0 8 Long robust arms: absent (0) present (1) 1 1 x 0 9 Deltopectoral crest: less than 30% (0) more than 30% (1) 0 0 x 1 Wrist 1 Semilunate carpal: absent (0) present (1) 0    x 1 x 0 2 Proximal carpals: not fused (0) fused (1) 1 ? ? 3 Distal carpals: not fused (0) fused (1) 1 1  ? 4 Carpometacarpus: absent (0) present(1) 0 0 0 5 Angle of abduction:  < 25% (0) > 25% (1) ? ? 0 Arm             1    Ulna: bowed (0) not bowed (1)                                            *              * * General 1 Warm blooded: absent (0) present (1) 1 1 x 0 2 Neural flight control system: absent (0) present (1) 1 ? 0 3 Pneumatic bones: absent (0) present (1) 1 1 ? * = varies within group ** = see link x = different MORE: Fibula:    Reduced in birds and pterosaurs, not reduced in dinosaurs Toes:      Pterosaurs 5 toes, basal paravians 4 toes, dinosaur 3 toes http://www.itsdinosaurs.com/6-compsognathus.html Compsognathus had two long and thin legs and feet with three toes each. Antorbital fenestra: Pterosaur present, dinosaur present, basal paraves present? Metacarpals? Ascending process (pretibial):  on astragalus (0) on calcaneum (1) Pterosaur (?) Dinosaur: (0) Basal parvian (1) Humerus https://pterosaurnet.blogspot.com/2017/01/humerus.html Femur head: Dinosaur: Cylindrical and at right angles Pterosaur and paraves: Ball shaped and angled

Shoulder Joint

http://earth.geology.yale.edu/~ajs/1993/11.1993.09Jenkins.pdf

Among living tetrapods, birds are unique in having completely separated the locomotor functions of fore and hindlimbs. The propulsive excursions of the forelimbs, which primarily involve elevation and depression in a transverse plane, differ fundamentally from those of most other tetrapods (pterosaurs and bats excepted) in which the forelimbs protract and retract in anteroposterior planes.

Pterosaurs and birds present a number of striking parallelisms in the structure of their flight apparatus and the glenoid is yet another example of their independent derivation of similar features.
In both rhamphorhynchoid and pterodactyloid pterosaurs the glenoid is distinctly saddle shaped with laterally as well as dorsally facing regions of the articular surface.

The origin of the pterosaurian glenoid must have involved the same evolutionary migration of position and orientation that has been outlined here for the avian lineage.

In contrast to the bulbous humeral head of birds, however, the humerus of pterosaurs bears a saddle-shaped facet, thus constraining the wingbeat excursion. This difference is likely a reflection of the relative structural versatility of the two wing types: an outstretched, sail-like membrane supported principally by a single digit versus a flexible airfoil composed of individual feathers, each with its own structural and functional integrity.

http://books.google.ca/books?id=8CKYxcylOycC&pg=PA243&lpg=PA243&dq=glenoid%20fossa&source=bl&ots=SopV9CAGec&sig=-gWOltWiFGplrU9tcXV8X8pBPUI&hl=en&ei=yTjS5aEBoT6lwf_uMC9Ag&sa=X&oi=book_result&ct=result&resnum=6&ved=0CC8Q6AEwBQ#v=onepage&q=glenoid%20fossa&f=false

From the article on page 267 (by Frey et al.):

As in birds, the glenoid fossa in most pterosaurs is elevated by a dorsolaterally directed elongation of the coracoid and lies almost level with the vertebral column

http://onlinelibrary.wiley.com/doi/10.1111/j.1475-4983.2008.00761.x/full

The [pterodactyl pterosaur] coracoid is about 75 per cent of the length of the scapula. It is expanded at its contact with the scapula, but has a more gentle decrease in width over its length. A small, blunt coracoid process is present, but it is not possible to tell if a groove separates it from the glenoid fossa. The sternal articulation is concave, faces posteroventrally, and lacks a posterior expansion. A large glenoid fossa faces anterodorsally with a dorsoventrally concave and anteroposteriorly convex saddle shape.
Wing skeleton. Both [pterodactyl pterosaur] wings are present in NGMC 99-07-1 (Text-figs 2, 4; Table 2). The humeri are complete though the right deltopectoral crest has become detached and rotated from its anatomical position (Text-fig. 2). The humeral head has an anteroposteriorly concave and dorsoventrally convex, saddle-shaped articulation so that it mirrors the shape of the glenoid.

http://en.wikipedia.org/wiki/Microraptor#Wings_and_flight

Whether or not Microraptor could achieve powered flight or only passive gliding has been controversial. While most researchers have agreed that Microraptor had most of the anatomical characteristics expected in a flying animal, some studies have suggested that the shoulder joint was too primitive to have allowed flapping. The ancestral anatomy of theropod dinosaurs has the shoulder socket facing downward and slightly backward, making it impossible for the animals to raise their arms vertically, a prerequisite for the flapping flight stroke in birds. Some studies of maniraptoran anatomy have suggested that the shoulder socket did not shift into the bird-like position of a high, upward orientation close to the vertebral column until relatively advanced avialans like the enantiornithes appeared.[12] However, other scientists have argued that the shoulder girdle in some paravian theropods, including Microraptor, is curved in such a way that the shoulder joint could only have been positioned high on the back, allowing for a nearly vertical upstroke of the wing. This possibly advanced shoulder anatomy, combined with the presence of a propatagium linking the wrist to the shoulder (which fills the space in front of the flexed wing and may support the wing against drag in modern birds) and an alula or "bastard wing" may indicate that Microraptor was capable of true, powered flight.[13] 

It is not an easy task to get all the needed information about the shoulder joint but this is how it appears:
Rhamphoryncidae had a saddle joint. Both the glenoid fossa and the humerus head were saddle-shaped.
Basal paraves - glenoid fossa was still saddle shaped but the humerus head was bulbous.


PTEROSAUR scapula, coracoid and glenoid

http://fossiladay.files.wordpress.com/2012/06/2012-june27-rhamphorhynchus.jpg

Some pterosaur bones are quite unusual. This scapulo-coracoid is photographed from both sides. The glenoid cavity of the shoulder joint can be seen, where the humerus articulates the wing to the body.

http://onlinelibrary.wiley.com/doi/10.1111/j.1475-4983.2008.00761.x/full

 A large [pterodactyl] glenoid fossa faces anterodorsally with a dorsoventrally concave and anteroposteriorly convex saddle shape.

http://saurian.blogspot.ca/2012/04/weird-world-of-theropod-scapulae.html

Scapula orientation in theropod dinosaurs is quite interesting and it is worth looking, to begin with, at what orientation is displayed in primitive reptiles. The scapula is generally held at an angle of 90 degrees to the horizontal line held by the backbone – in other words it was held in a perpendicular fashion. At the other extreme, extant birds rotated the scapula so that it lies parallel to backbone – a position also evolved by the pterosaurs.

Theropods, and non-avian dinosaurs in general (but not bird-like theropods), evolved a condition that can be described as something in between – an intermediate position if you will. The scapula is held in an oblique position laterally to the ribcage but actually determining the exact position is somewhat problematic. There are not that many fully articulated specimens that can be referred to and there is always the spectre of both taxanomic and taphonomic variation to throw yet another spanner into the works.

https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg8Pv7jaAzYwroXKKX3jU0AJ5aoxbFUFhcOIht6IdtYGyWIRQDQ7729gqhgHcBgwLwvRYnqvGnMYKWw6QV6_UlJNNQS5u-79WUdIgO1Ttqj6hqhgHfzz0t5e4wIiFsYyjEFaVK6XHMuGI0C/s400/rex_pex.jpg

https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg9teTjD45MNGJX6Dvw6rpw-uGQaFED7bcUsu0iqsI59uPPYKpqgOwhoNIiGxkDimq_xYKPNDpyjojrzrE2y4S5TjaBN8vIHDgsUBdWPdaZzkbzkFtqPqn-NshI9HPnUNAMo9EC5bIa4ED6/s1600/glenoid+fossa.jpg

Posteriorly facing glenoid fossa

http://books.google.ca/books?id=BZ5EAAAAQBAJ&pg=PA1&lpg=PA1&dq=avian+ancestors&source=bl&ots=pDLpsHYGGU&sig=YBOgsG7ZpQIXDzzSCSiduB4FZ9s&hl=en&sa=X&ei=haVmVI_ROZD5yQTiuYDIBg&ved=0CEwQ6AEwBg#v=onepage&q=avian%20ancestors&f=false

http://www.researchgate.net/publication/259438884_Agnoln_and_Novas._2013._Avian_ancestors

Agnolín and Novas. 2013. Avian ancestors

In this way, the scapulae of unenlagiids lie close to the vertebral column, dorsal to the ribcage, with the flat costal surface of the scapular blade facing ventrally, a condition seen in microraptorans (i.e. Microraptor), basal avialans (e.g. Archaeopteryx, Rahonavis), and ornithothoracine birds (Senter 2006), in which the shoulder socket sits high on the back, and the margins of the glenoid are smooth, thus this surface becomes shalower and consequently more continuous with the rest of the lateral surface of scapula
(Burnham 2008). In sum, the lateral orientation of the scapular glenoid in unenlagiids
(and probably also in other basal averaptorans), together with the absence
of acute ridges delimitating the glenoid cavity, suggest that the humerus in these
taxa was able to be elevated close to the vertical plane, as proposed by Novas and Puerta (1997) (Figs. 5.1, 5.2).

It is important to mention that scansoriopterygids retained a caudoventrally oriented glenoid, a subrectangular coracoid with reduced biceps tubercle, and a distally fan-shaped scapular blade, all representing plesiomorphic character states in respect to paravians.

=======================================================

Here is a good overview of the shoulder girdle of modern birds:
http://www.shearwater.nl/index.php?file=kop140.php

1. Sternum / breastbone 2.Coracoid 3.Clavicles / furcula    4. Scapula 5.Joint with the wing 6.Foramen trioceum

Here is a very interesting video:
https://www.youtube.com/watch?v=toJwBgjCZMI