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Re: Microraptor hanqingi, new species from China.



On 5/24/2012 9:46 AM, evelyn sobielski wrote:

But altogether, I don't see any reason to presume that in the Cretaceous there 
was a lot of true arboreality. Critters that could make it up a tree safely and 
down adain just as safely, no problem with that. But critters that spend most 
of their lifes in trees? Not many.

Given that cursoriality and incipient arboreality have to coexist for true 
arboreality to evolve in a terrestrial lineage, it may be we are looking for 
the wrong things. Adaptations to climbing are fairly trivial, but they are NOT 
evidence for true arboreality, only for low-level adaptation to a woodland 
habitat.

It has been mentioned onlist many times that the basal theropod body-plan was not well-suited to active foraging in trees or exploitation of the terminal branch environment, even with modification of distal limb elements.

Once minimal powered flight was achieved, however, modification of the foot to facilitate flap-flying ('or flap-jumping') from branch-to-branch seems straight-forward, from the selective perspective.

In other words -- assuming minimal vertical climbing ability, modification of the pes away from the cursorial condition ("loss of cursorial adaptations") might have occurred _after_ powered flight was achieved, not _as_ it was achieved -- and logically a fully arboreal theropod life-style awaited the development of powered flight, even if flight evolved in the strict tree's-down mode.

I grant it seems a little messy, but even if it can be shown that the perching foot evolved well after powered flight was achieved, the strict 'tree-down' flight-evolution scenario is not excluded -- sleeping in a tree after a day (or night, in the nocturnal case) of ground-foraging is an entirely reasonable life-style, and lots of critters do it...