Page 182 - The Origin of Birds and Flight

180 The Origin of Birds and Flight

onic process is completely different in birds and theropod dinosaurs.
Theropod dinosaurs’ “hands” develop from the first, second and
third finger bones, and the wings of birds from the second, third and
fourth finger bones. This is an important distinction between dinosaurs
and birds, as was noted in a 1997 article in Science magazine:
In reality, there is no easy solution to this question of bird origins. . . .
The problem for this view is the long evolutionary gap, with no convin-
cing intermediates. What we need is a proto-Archaeopteryx find to
complement the numerous post-Archaeopteryx finds that are now being
made. But for the time being this important developmental evidence
that birds have a II-III-IV digital formula, unlike the dinosaurs’ I-II-III,
is the most important barrier to belief in the dinosaur-origin orthodoxy.
137
J. Richard Hinchliffe, of the University of Wales Institute of
Biological Sciences, reached this conclusion by using the modern isotop-
ic technique on embryos. While birds’ wings develop from the second,
third and fourth fingers, those of theropod dinosaurs developed from the
first, second and third. This is a major problem for those who maintain
the relationship between Archaeopteryx and dinosaurs. 138
Hinchliffe’s research and observations were reported in the same
Science article:

Doubts about homology between theropod and bird digits remind us
of some of the other problems in the “dinosaur-origin” hypothesis.
These include the following:

- The much smaller theropod forelimb (relative to body size) in
comparison with the Archaeopteryx wing. Such small limbs are not
convincing as proto-wings for a ground-up origin of flight in the rela-
tively heavy dinosaurs.

- The rarity in theropods of the semilunate wrist bone, known in only
four species (including Deinonychus). Most theropods have relatively
large numbers of wrist elements, difficult to homologize with those of
Archaeopteryx. 139