Some theropod species may have been predominantly arboreal, and under pressures to further enhance their leaping abilities. (Realistic dinosaur costume)While working on bird origins, Robert Bakker and I concluded that Archoeopterry was just such a climber. This is a key issue, for to understand the beginnings of bird flight we must understand what the protobirds were up to. Archaeoptersnr’s inner toe, the hallux, is not as well-developed as those of modern perching birds, but we should not expect it to already be at the songbird level. What is more telling is that the halhx was a larger, more backward-pointing, and better grasping toe than in any other theropod. In 1984, Derik Yalden showed that ArchaeopterSa’s sharp-tipped claws, the hand claws especially, are most like those of modern climbing animals. (walking dinosaur costume)The strength of the forelimbs is also vital because they are longer and more powerful than the hind limbs. Such extreme forelimb dominance cannot be explained as display organs or insect traps, but only if they had become the protobird’s main locomotory organs. The long, slender fingers are useless for walking. Hence climbing, flytng, and swimming are the potential locomotory uses. At the same time, ArchoeopterSm is really not as well built for running as is often thought, since the hips and knee crest are smaller than in any other theropod. (Animatronic dinosaur costume)But the short iliac blade behind the hip socket and the small knee crest, and the slender leg muscles they supported, are rather like those of leaping tree frogs and monkeys.
The leaping and climbing abilities of Archceopteryx cannot be used as absolute proof of arboreality in and Jurassic proto birds, because Archaeopteryx could be an exception that evolved from running protobirds.