Semilunate carpal

Xu et al (2014)
The homology of the ‘semilunate' carpal has been controversial. 

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4131224/
Homologies and homeotic transformation of the theropod ‘semilunate' carpal
Xing Xu, Fenglu Han, and Qi Zhao (2014)

The homology of the ‘semilunate' carpal, an important structure linking non-avian and avian dinosaurs, has been controversial. 

The distribution of the morphological features pertaining to the trochlear facet across theropod phylogeny is consistent with a partial and gradual homeotic transformation of the ‘semilunate' carpal. Although no direct developmental data are available to support the occurrence of a homeotic transformation, this interpretation is suggested by the positional shift of the topologically unique articular surface from the medial side of the wrist to the lateral side (i.e. the trochlear facet shifts from medial carpals to lateral carpals). 

Interestingly, a key event in the carpal lateral shift appears to have been the reappearance of distal carpal 4 to contribute to the ‘semilunate' articular surface in derived maniraptorans.

The theropod wrist evolution is featured by the sequential occurrences of the following major modifications:

enlargement of distal carpal 2 together with reduction of distal carpal 3 and loss of distal carpal 4,

development of a transverse groove on a composite distal carpal composed of large distal carpal 2 and small distal carpal 3,

development of a transverse trochlea on a large distal carpal composed of distal carpal 2 and enlarged distal carpal 3,

development of a prominent transverse trochlea on a large distal carpal composed of distal carpals 2, 3, and the reappeared distal carpal 4,

and development of a prominent transverse trochlea on the proximolateral portion of the metacarpus composed of distal carpals 3 and 4 .

For comparison (from Figure 4):
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4131224/figure/f4/




1. distal carpal 2 with transversely trochlear proximal articular surface;
2. ‘semilunate' carpal with a prominent mediodorsal process;
3. ‘semilunate' carpal covering proximal end of metacarpal III;
4. distal carpal 4 incorporated into ‘semilunate' carpal to form a ventrolateral process;
5. ‘semilunate' carpal with a prominent ventrolateral process and fused to two lateral metacarpals.

Note that the description of node 4 applies to node 3 as well in the cladogram. In other words the significant change takes place at oviraptor/paraves. 

When you look at Table 1 (in Supplementary Information) you see that the distal carpal 4 (character 9) is present beginning at oviraptors and all the following taxa. But NOT present in the preceding coelurosur dinosaurs.

Table 1. Scorings for 18 characters for 31 theropod taxa

           

Character/taxon	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16	17	18
Herrerasaurus	0	0	0	0	0	0	0	0	0	0	?	?	?	?	?	?	?	?
Coelophysis	0	1	?	0	0	0	0	0	0	0	?	?	?	?	?	?	?	?
Dilophosaurus	0	0	0	0	0	0	0	0	0	0	?	?	?	?	?	?	?	?
Xuanhanosaurus	1	?	1	1	0	1	0	0	1	?	0	0	0	0	0	0	0	0
Allosaurus	1	?	1	1	1	1	0	1	1	?	1	0	0	0	0	0	0	0
Guanlong	1	?	1	1	1	1	0	0	1	?	1	0	0	0	0	0	0	0
Tyrannosaurus	1	?	0	1	1	0	0	0	?	?	1	0	0	1	0	0	0	0
Coelurus	1	?	1	1	1	?	?	?	?	?	1	0	1	0	1	0	0	0
Harpymimus	1	?	1	0	0	1	0	0	?	?	?	?	?	?	?	?	?	?
Nqwebasaurus	1	?	0	0	0	0	0	0	?	?	?	?	?	?	?	?	?	?
Falcarius	1	?	0	1	1	0	1	1	1	?	1	0	1	0	1	0	0	0
Alxasaurus	1	?	0	1	1	0	1	0	1	?	1	0	1	0	1	0	0	0
Haplocheirus	1	?	1	1	1	1	0	0	1	?	1	0	1	0	1	0	0	0
Similicaudipteryx	1	?	0	1	1	0	1	2	0	0	2	1	1	1	1	1	0	0
Oviraptor	1	?	0	1	1	0	1	2	?	?	2	1	1	1	1	1	0	0
Microraptor	1	?	0	1	1	0	1	2	0	1	2	1	1	1	1	1	0	1
Linheraptor	1	?	0	1	1	0	1	2	?	?	2	1	1	1	1	1	0	0
Mei	1	?	0	1	1	0	1	2	0	1	2	1	1	1	1	1	?	?
Sinovenator	1	?	0	1	1	0	1	2	0	1	2	1	1	1	1	1	0	1
Archaeopteryx	1	?	0	1	1	0	1	2	0	1	2	1	1	1	1	1	?	1
Anchiornis	1	?	0	1	1	0	1	2	0	1	2	1	1	1	1	1	0	1
Jeholornis	1	?	0	1	1	0	1	2	0	2	2	2	1	2	1	1	0	2
Sapeornis	1	?	0	1	1	0	1	2	0	2	2	2	1	2	1	1	0	2
Confuciusornis	1	?	?	?	?	?	1	2	0	2	2	2	1	2	1	1	0	2
Protopteryx	1	?	?	?	?	?	1	2	0	2	2	2	1	2	0	2	0	2
Yanornis	1	?	?	?	?	?	1	?	?	2	2	2	1	3	0	2	1	2
Struthio	1	?	?	?	?	2	1	?	0	2	2	2	1	3	0	3	1	2
Gallicrex	1	?	?	?	?	2	1	1	0	2	2	2	?	3	0	3	1	2
Sinosauropteryx	1	?	0	0	1	?	?	?	?	?	0	0	0	0	0	0	0	0
Mononykus	1	?	1	1	1	?	?	?	?	?	2	1	1	1	1	1	1	1
Tanycolagreus	1	?	?	0	0	?	0	1	?	?	0	0	1	0	0	0	0	0

The same is true for characteristics 8, 9, 11, 12 and 16. Things are different beginning at Oviraptors. They are different from the coelurosaur dinosaurs.

8.         Distal carpal 3, fusion to distal carpal 2: absent (0) or occurs late in ontogeny (1) or occurs early in ontogeny (2)

9.         Distal carpal 4: present (0) or absent (1)

10.         Distal carpal 4: fusion to medial distal carpals: absent (0) or present, late in ontogeny (1) or early ontogeny (2)

11.         ‘Semilunate’ carpal (distal carpal element with a transversely trochlear proximal articular facet), proximal margin of ventral surface：straight (0) or moderately convex (1) or strongly convex (2).

12.         ‘Semilunate’ carpal, proximal margin of dorsal surface: straight (0) or moderately convex (1) or strongly convex (2).

13.         ‘Semilunate’ carpal, transverse width: significantly narrower than (0) or close in width (1) to proximal end of metacarpus

14.         ‘Semilunate’ carpal, proximodistal depth relative to transverse width: significantly less than half (0) or smaller but more than half (1) or subequal (2) or much greater (3).

15.         ‘Semilunate’ carpal, dorsomedial process: absent or weak (0) or prominent (1)

16.         Articular facet on proximal surface of metacarpus: medial, facet absent on lateral portion of proximal surface of metacarpus (0) or central, facet present across entire proximal surface of metacarpus (1) or lateral, facet absent on medial portion of proximal surface of metacarpus (2) or extremely lateral, facet absent on medial portion of proximal surface of metacarpus and extends onto poximolateral surface of metacarpus (3).  

17.         ‘Semilunate’ carpal, fusion to medialmost metacarpal: absent (0) or present (1)

18.         ‘Semilunate’ carpal, fusion to two lateral metacarpals: absent (0) or occurs late in ontogeny (1) or occurs early in ontogeny (2)

AND

the ‘semilunate' carpal is not formed by the same carpal elements in all theropods possessing this feature

Distal carpal 4 is not even present in earlier tetanurans:

Although our focus is the evolution of the ‘semilunate' carpal of tetanuran theropods, we also refer to Herrerasaurus13 and Coelophysis14, which exemplify the primitive theropod condition.

And

Fusion, expansion, or reduction of basipodial elements is common in vertebrate evolution. However, it is rare for a shift in position and composition of a unique, functionally significant carpal or tarsal structure to occur without greatly disrupting the structure's topology (Fig. 4). 

Figure 1: Diagram showing the position and general morphology of the transversely trochlear proximal articular facet of the carpometacarpus in selected theropod hands with the phalanges omitted (upper: proximal view; lower: dorsal view; medial side of hand to left).

(a) The basal coelurosaurian condition (based on Guanlong). (b) The basal paravian condition (based on Sinovenator). (c) The neornithine condition (based on Crossoptilon). Yellow indicates the ‘semilunate' carpal; grey-yellow indicates the transverse groove; green indicates the metacarpals.

Sullivan et al (2010)

http://rspb.royalsocietypublishing.org/content/early/2010/02/24/rspb.2009.2281.full

http://rspb.royalsocietypublishing.org/content/royprsb/suppl/2010/02/24/rspb.2009.2281.DC1/rspb20092281supp1.pdf  Supplementary information

Radiale angles in various theropods. 

taxon	angle	specimen/source
Allosaurus fragilis	2°	Chure (2001, fig. 2c)
Huaxiagnathus orientalis	18°	Hwang et al. (2004, fig. 8a)
Sinosauropteryx prima	6°	Currie & Chen (2001, fig. 8a)
Guanlong wucaii	8°	IVPP V14531
Alxasaurus elesitaiensis	39°	IVPP RV93001
Falcarius utahensis	26°	Utah Museum of Natural History, Salt Lake City, USA (UMNH) VP 12294
Caudipteryx sp.	76°	IVPP V12430
Haplocheirus	15°	IVPP V15988
Sinovenator changii	35°	IVPP V14009
Deinonychus antirrhopus	31°	YPM 5208
Eoconfuciusornis zhengi	55°	IVPP V11977
Meleagris gallopavo	59°	IVPP 1222

It is possible that the SLC is not homologous throughout Tetanurae, in that different distal carpal elements may contribute to forming the SLC in different taxa or at least contribute to varying degrees (Chure 2001).

the measured value of 76° in Caudipteryx suggests that the oviraptorosaur wrist may have independently evolved an even greater abductor bias than that existing in avialans.

II–IV, metacarpals II–IV (numbering convention follows extant birds); d, distal carpal; i, intermedium; R, radius; r, radiale; s, semilunate carpal; U, ulna; u, ulnare.

In avians, the functional wrist joint is the articulation between the two proximal carpals, the scapholunar and cuneiform, and the trochlea of the carpometacarpus. The scapholunar is a slab-like bone homologous to the radiale plus intermedium of non-avialan tetrapods (Kundrát 2009), but for convenience is referred to as the radiale hereafter. The cuneiform is probably a neomorphic element rather than a homologue of the primitive ulnare (Gishlick 2007; Kundrát 2009).

Turkey:






VARGAS
http://journals.plos.org/plosbiology/article?id=10.1371/journal.pbio.1001957

New Developmental Evidence Clarifies the Evolution of Wrist Bones in the Dinosaur–Bird Transition

• João Francisco Botelho,
• Luis Ossa-Fuentes,
• Sergio Soto-Acuña,
• Daniel Smith-Paredes,
• Daniel Nuñez-León,
• Miguel Salinas-Saavedra,
• Macarena Ruiz-Flores,
• Alexander O. Vargas 

When birds diverged from nonavian dinosaurs, one of the key adaptations for flight involved a remodelling of the bones of the wrist. However, the correspondence between bird and dinosaur wrist bones is controversial.

In view of recent developmental evidence for 1, 2, 3 [12]–[14], we will use 1, 2, 3 to refer to the digits and, especially so, their associated distal carpals (here, dc1, dc2, and dc3). However, it must be kept in mind that most developmental studies traditionally refer to the same distal carpals as dc2, dc3, and dc4 [3],[8],[15].

 http://journals.plos.org/plosbiology/article/figure/image?size=medium&id=info:doi/10.1371/journal.pbio.1001957.g009

http://dujs.dartmouth.edu/2014/12/the-evolution-of-bird-wrists-from-dinosaurs-wrists/#.V7tAj_krKUk

First, the findings confirm work from the 1970s that suggested that two dinosaur bones, known as distal carpal 1 and distal carpal 2, combined, or “ossificatied,” to form the semi-lunate bone in birds. This bone gets its name from its half-moon shape. Additionally, the study found that two dinosaur bones, the radiale and the intermedium, merged to create a single bird bone called the scapholunare. The previous name of this bone, the radiale+intermedium, mistakenly suggests that the bone is formed by a fusion in the embryonic development, rather than by an evolutionary process. For this reason, the authors of the study suggested “scapholunare” as a more accurate name (2).
The third bone in bird wrists is known to embryologists as “element x.” Originally, embryologists thought that it replaced the dinosaur bone known as the ulnare. However, developmental data from the Vargas study found that the ulnare and element x coexist in bird embryos. Further, they found that element x corresponds to the dinosaur bone known as distal carpal 3 (2).
The researchers discovered that the fourth bone in bird wrists, the pisiform, had a rare evolutionary history. They found that it was lost in dinosaurs, but re-evolved in early birds. The purpose of the re-evolution of the pisiform was probably to facilitate flight. The pisiform enables a forceful downbeat of wings, and restricts the flexibility of the wings on the upbeat (2).

PTEROSAURS

http://www.stuartsumida.com/BIOL524/GatesyAndMiddleton2007.pdf

The two proximal carpals fuse in all but the most primitive pterosaurs.

pterosaur wrist originally contained five carpal bones in two rows

http://www.pterosaur.org.uk/PDB2012/I/wings/carpal.htm

The carpal bones form a structure which allows a limited few degrees of movement at the wrist joint.  They are essentially two apposing saddle shaped bones which rock in two planes.  This can be illustrated in the sketch below.

The proximal carpal is seen articulating with the Ulna and Radius.  This carpal in turn articulates with the Distal Carpal in a saddle like gliding joint.

http://www.visualdictionaryonline.com/human-being/anatomy/skeleton/types-synovial-joints_2.php

https://books.google.ca/books?id=pX_l24sDARwC&pg=PA386&lpg=PA386&dq=bird+wrist+sliding+articulation&source=bl&ots=W5w0dynVsi&sig=Fdnf_MOXljBahJaJCDATUHYf6aY&hl=en&sa=X&ved=0ahUKEwi5wOv2rLXNAhUqxoMKHaxaDvwQ6AEIHTAA#v=onepage&q=bird%20wrist%20sliding%20articulation&f=false

The [bird] semilunate carpal forms a grooved trochlea that articulates with a wedge-shaped radiale in the wrist. A sliding articulation between the groove and the radiale allows the carpometacarpus to be folded up close to the ulna. (Naish)

Mark Witton book "Pterosaurs"

https://books.google.ca/books?id=ND_PzHQuuLgC&pg=PA34&lpg=PA34&dq=thus+it+seems+that+considerable+motion+was+available+at+the+pterosaur+wrist&source=bl&ots=aZ0nhC_4u2&sig=GBwnNS0JqPIxWyGfhMG5I7jropg&hl=en&sa=X&ved=0ahUKEwip1bXz1OTOAhUGlR4KHfzLCakQ6AEIGzAA#v=onepage&q=thus%20it%20seems%20that%20considerable%20motion%20was%20available%20at%20the%20pterosaur%20wrist&f=false

Pterosaur carpal bones "bore a sliding joint permitting at least 30 degrees of rotation between them” (page 33) 

http://onlinelibrary.wiley.com/doi/10.1111/j.1096-3642.2008.00409.x/full

Three-dimensional geometry of a pterosaur wing skeleton, and its implications for aerial and terrestrial locomotion

The [pterosaur] intersyncarpal joint is a sliding articulation. The articular surface of the proximal syncarpal bears a prominent ridge that runs anteroventrally, with concave facets to either side, resembling a short section of a left-handed corkscrew in the right-hand limb (Fig. 10A). The corresponding articular surface of the distal syncarpal fits very closely when the radius/ulna and wing metacarpal are in line, indicating that only a thin layer of cartilage was present. The joint axis is tilted back from the vertical by 40°, and the maximum range of angulation is about 25°. Flexion of the joint retracts the wing metacarpal by 20°, and depresses it by 15°, and is accompanied by a slight posteroventral translation of the distal syncarpal with respect to the proximal.

The very tight fit between the proximal and distal syncarpals has led many workers to believe that it was incapable of muscle-controlled movement (Hankin & Watson, 1914; Bramwell & Whitfield, 1974; Padian, 1984). In this case, the joint would have functioned as a shock absorber, reducing the risk of breakage of the wing in turbulent conditions, for example. Opponents of this idea (Unwin, 1988; Bennett, 2001) have argued that the range of permitted movement is too large to be accounted for solely by nonvoluntary movement. The maximum theoretical range of 25° estimated for the intersyncarpal joint here would indeed be large for a passive joint, but it must be remembered that this range may have been restricted in life by the presence of ligaments. The evidence from the bones alone is clearly inconclusive, and until a detailed reconstruction of these soft tissues is carried out, a definitive pronouncement on this matter cannot be made. 

The pterosaur wrist comprises four elements: the proximal syncarpal, formed by the fusion of the two proximal carpals (Bennett, 1993); the distal syncarpal, formed by the fusion of three distal carpals (Bennett, 1993); the block-like medial carpal (Padian, 1984), also termed the distal lateral (Wellnhofer, 1985) and preaxial carpal (Bennett, 2001); and the long, slender pteroid, which in life supported a membranous propatagium (forewing) in front of the arm (Wellnhofer, 1991a).

In the transition from pterosaur to basal paraves, the two proximal carpals continued to be fused. One distal carpal was lost. The other two distal carpals continued to be fused. 
The lateral carpal needs more analysis.

http://pterosaurnet.blogspot.ca/2014/10/wrists.html

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4181960/
Resolving the Flap over Bird Wrists
Robin Meadows 

Somewhere along the way from early dinosaurs to birds, wrists changed so much that we could be excused for thinking birds don't even have them. Wrists went from straight to bent and hyperflexible, allowing birds to fold their wings neatly against their bodies when not flying. Underlying this change is a drop in the number of wrist bones from nine to just four. Paleontology and embryology tell different stories about how this happened, however. Now, in this issue of PLOS Biology, Alexander Vargas and colleagues resolve this flap, drawing on both fields to clarify the identity and evolution of bird wrist bones.

Video of bird wing folding:

https://www.youtube.com/watch?v=GFCgwglikcY

SUMMARY

Material about the claimed evolution of the semilunate carpal from dinosaur to bird is found in a few studies including:

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4131224/
Homologies and homeotic transformation of the theropod ‘semilunate' carpal
Xing Xu,a,1 Fenglu Han,2 and Qi Zhao1

Interestingly, a key event in the carpal lateral shift [homeotic transformation] appears to have been the reappearance of distal carpal 4 to contribute to the ‘semilunate' articular surface in derived maniraptorans.

and

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4181957/
New Developmental Evidence Clarifies the Evolution of Wrist Bones in the Dinosaur–Bird Transition
João Francisco Botelho, Luis Ossa-Fuentes, Sergio Soto-Acuña, Daniel Smith-Paredes, Daniel Nuñez-León, Miguel Salinas-Saavedra, Macarena Ruiz-Flores, and Alexander O. Vargas

We confirm the proximal–posterior bone is a pisiform in terms of embryonic position and its development as a sesamoid associated to a tendon. However, the pisiform is absent in bird-like dinosaurs, which are known from several articulated specimens. The combined data provide compelling evidence of a remarkable evolutionary reversal : A large, ossified pisiform re-evolved in the lineage leading to birds, after a period in which it was either absent, nonossified, or very small, consistently escaping fossil preservation.

Not only does the dinosaur to bird theory require a “homeotic transformation” and “reappearance of distal carpal 4”, but it also requires a “remarkable evolutionary reversal” of a pisiform.