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Re: Arboreal Dinosaurs
BHR (probably someone connected to Gary Riegler) wrote:
> ...I've seen numerous restorations of
>small theropods and ornithopods in trees(ornitholestes &
>hypsilophodon,etc...). I don't know if this has already been discussed
>or is a settled issue...
Oh, it's been discussed alright. Which theropods climbed trees is far from
settled. The extreme cases would be Tyrannosaurus (climbing practically
impossible) and Archaeopteryx (climbing very likely). The chances of any
particular dinosaur climbing depend on its weight and the length and strength
of its forelimbs. Claws are also useful, but I can't think of any theropod
deficient on that score. IMO, the small long-armed theropods such as
Velociraptor and Ornitholestes are plausible climbers.
The leading theory on the origin of bird flight is that an arboreal ancestor
began by jumping between branches, then developed a lifting surface to glide
(like certain squirrels, frogs, snakes, lizards and marsupials). The final
step was evolving a way to flap this wing. And of course the leading theory on
the origin of birds themselves is that they are theropods.
As for Hypsilophodon, this was originally reconstructed/restored with one toe
pointing backwards, as in perching birds. This led to the suggestion that it
climbed trees. That anatomical idea is now considered incorrect, and
Hypsilophodon is not likely to be a climber (mainly because it's too big).
All the best,