exaptations; dinosaur to bird? (Introduction)

by David Turell , Wednesday, April 29, 2015, 18:57 (3645 days ago) @ David Turell

Could the new tiny dinosaur with an extra bone be an exaptation on the way to birds?-http://www.nature.com/news/more-on-unicorns-1.17419?WT.ec_id=NATURE-20150430-"Except that Yi qi is different. Attached to each wrist is a strut, made of bone or calcified cartilage, which cannot simply be homologized with regular wrist or hand bones. The strut seems to be a new structure made from an accessory wrist bone, possibly a sesamoid — the kind of bone usually embedded in a tendon or muscle. The ‘thumb' of the giant panda is made of just such a bone. The sesamoid of Yi qi (if that's what it is) is much larger, however, in relation to the animal as a whole — equal in length to the bones of the forearm. It had to be there for a reason, but what was it?-"It is here that we enter unicorn territory — for no dinosaur, however unusual, has been found with anything like this feature. The authors are appropriately cautious, therefore, in their interpretation. They point to the hint of a suggestion that some soft tissue, preserved alongside these curious elements, represents what might have been a membrane that the sesamoid bone supported. From that, they suggest that Yi qi had membranous wings and might have glided from branch to branch, in much the same way as various tree-living mammals and reptiles do today. But it was probably not capable of powered flight as birds and bats are — and as were, presumably, the extinct pterosaurs, which were (one must stress) only distant relatives of dinosaurs and birds."