[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

Re: Deinonychus claw, er, no, still Catch-22, really...



On 12/15/2011 11:01 PM, Tim Williams wrote:

Mostly.  I tend to think that roosting requires arboreal
adaptations, because it requires remaining still (or fairly still) in
a tree for a prolonged period of time.

Comfort is not a component of selection.

What I was talking about was hypothesis testing.  If you were to say
"Hey theropods didn't need arboreal adaptations in order to get up
trees, and stay there - they could simply use the abilities they
already have", it becomes very difficult to test this scientifically.

I disagree. Even in the absence of a robotic model, a human could wear a clawed "theropod suit" which constrains motion and posture to that inferred for the relevant theropods to test *ability*.

And even juvenile
hoatzins have excellent branch-grasping feet.

Personally I doubt the implication that juv Hoatzins need the hallux to vertical-climb is correct -- this at least could be tested in vivo.

But if we going to put non-avian theropods in
trees (such as to sleep, seek refuge, or perch-hunt), I want to see
*positive evidence* for an ability to climb or roost in trees.  The
evidence should drive our assumptions, not the other way round.

The evidence that small theropods (like Archie) could climb at least some trees (like cycads) is clear.

Given that evolution is now the null -- large time-spans, diverse environments/lifestyles and many unknown taxa representing the ancestors and descendants of known taxa are core assumptions, and the presence of physical competence in multiple taxa has general implications in re behaviors/lifestyles -- not that they accrue to specific fossils.

The active and blanket claim that pre-birds were not in trees is what needs support.

I should not reply in haste, but I am out of time in more ways than one.

Too bad I never got past the pre-amble on this one, as the remainder was much more interesting and involved actual data, but the endless circling about is time-consuming, is it not? I assume it is entertaining...

"Nice idea, great paper, seems quite strong" to Fowler -- I only see one unaddressed issue (not stroke amplitude). I hope to get a chance to comment later, assuming it still seems a valid point.

C ya...