Inspired by the kiwi weirdness looked at here recently, I thought I'd focus on some other ratite skeletal stuff. But the idea here isn't to identify the animal. This is obviously the skeleton of an ostrich Struthio camelus. The question for you is a simple one: what's going on with the pectoral girdle? What makes it weird? Hmm, I wonder...
Lack of Furcula?
More aptly said, the claviculae (the massive things fused to the coracoids) are not fused to one another, so they're not a real furcula.
Seems that the clavicles are not fused into a furcula, and, instead, each clavicle is fused to the correponding coracoid...
The fused on clavicles make the cracoid look broad, rectangular and fenestrated - pretty much a dead spit for the coracoids of Sinornithosaurus.
Possibly the centrally located foramen of the coracoid?
Are those separate clavicles (strangely plate-shaped ones), or rather huge, huge, huge acromion processes that reach -- on the left side, that is -- all the way to the sternum?
The shape of the coracoid itself is rather unspectacular.
So...is this like some sort of unofficial ratite series, or what? Anyway, I would also say lack of a furcula (as far as I can tell), but it may just be missing on this specimen. Other than that I would say the pectoral weirdness results from the very reason why ratites are ratites; the large, flat breastbone that has no keel on its sternum.
Lack of a keeled sternum? But that's probably too obvious to even mention.
It looks to me as though the clavicles have been fused to the corresponding scapulas, which in turn have rotated closer to the underside of the torso.
I'm also going to go with the clavicles being fused to the coracoids. And of course the lack of a keel on the sternum.
Yeah, what those folks in the other time-zones said: clavicles separate, fused to scapulocoracoids.
In Dromaius (Emu) the clavicles are also separate but much more slender and articulated, not fused to the acromion process of the coracoid.
In Dromornithids, on the other hand, the scapulocoracoids are more widely separated on the sternum (which has a quite massively thickened anterior margin) and nobody has yet found a clavicle. No clavicular facets have been seen on either the sternum or coracoid (I have most of a cf. Bullockornis sternum here with the anterior edge intact; also near-complete scapulocoracoids of this and Barawertornis, but unfortunately their acromion procs are damaged so absence of facets is based on Murray & Vickers-Rich 2004).
If you want unusual Darren try the extinct New Zealand Adzebill, apparently due to the unusual mechanism of the bill they are still trying to figure out what this unusual bird ate.
New Zealand Cryptozoologist