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Did feathered dinosaurs exist?

evidence relating to the tridactyl hand, which is composed of digits 1-2-3 in dinosaurs, the most critical characteristic linking birds to derived theropods.

Feduccia, Lingham-Soliar and Hinchliffe found no evidence for the existence of protofeathers on dinosaurs and no evidence in support of the morphogenesis of the feather from putative filamentous protofeathers. They suggest that 'protofeathers' described on fossil findings "are probably the remains of collagenous fiber 'meshworks' that reinforced the dinosaur integument." Based on their examination of fossilized remains of dinosaurs with no relationship to birds, they suggest that decomposition of skin can lead to patterns resembling feathers.

Birds have been thought to be related to theropod dinosaurs because both groups have a hand reduced to three digits. Theropods are known from fossil evidence to exhibit a hand with digits 1-2-3, the thumb and next two digits. However, the researchers found that the vast majority of evidence supports a 2-3-4 digit identity for bird wings. The bird hand "appears different from that in theropod dinosaurs," they say, and casts doubt upon the theropod derivation hypothesis. Finally, they discuss the significance of the Chinese discoveries with respect to bird origin and flight.

The authors emphasize that the totality of evidence from various branches of science must be included if we are ever to solve the mystery of bird origins and the origin of avian flight. From their careful examination of the available evidence they offer an interim attempt to define morphologically the most salient features of Aves: "Birds are mesotarsal bipedal archosaurs with pennaceous feathers, and a tridactyl avian hand composed of digits 2-3-4."

It is too early to abandon debate on the origin of birds, the authors say. However, mounting evidence suggests that "a possible solution to the disparate data is that Aves plus birdlike maniraptoran theropods (e.g., micror
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Source:John Wiley & Sons, Inc.


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