The paleontologist never mentions the ornithologist’s qualifications. Rather, the paleontologist questions whether the ornithologist’s evidence is sufficient, based on the example of a modern bird.

The paleontologist does not deny that curved claws enable birds to perch in trees, nor does he deny that Archeopteryx could perch in trees. He just denies that this proves that Archeopteryx was a tree-dwelling bird.

This accurately describes the palaeontologist's argument. The parallel case the paleontologist uses is the case of chickens, which also have the ability to perch in trees--implying they have curved claws--but are primarily ground-dwelling birds. The palaeontologist uses this example to undermine the ornithologist's claim that Archeopteryx's curved claws show it was a tree-dwelling bird.

The paleontologist does not claim that the ornithologist’s hypothesis contradicts one of the premises offered in support of it. Rather, the paleontologist claims that the ornithologist’s premises are not sufficient to support the hypothesis: the fact that Archeopteryx had curved claws isn't enough to establish that it was tree-dwelling.

The paleontologist does not support the ornithologist’s argument. The paleontologist begins by denying the sufficiency of the ornithologist’s evidence.