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RE: Aw: RE: Arboreal Theropods: The prize at the bottom of the cracker jack box



Don (etc.):

We have dromeosaurids which leave definite trackways showing their claws, and 
many of them are what we would consider cursorial  - i.e. not quite arboreal.  

Yet, I believe they have the ability to successfully grasp branches and hold 
on, and possibly perch and/or roost in trees and bushes if needed.  I can 
imagine a _Deinonychus_ becoming trapped by a flash flood, and climbing 
whatever was nearby - rocks, trees, sauropods.  :) 

It seems likely, that many of the theropods that have been in question in this 
thread possessed the ability to perch, roost, and climb into trees and bushes, 
prior to becoming paravians - prior to actually flying.

Thereby, the need for a reversed hallux was not a requirement for these 
paravians to be able to climb into trees and fly from them.  

Hope this helps clear up my input (if it doesn't make it more confusing!)

Allan Edels



> Date: Tue, 23 Jul 2013 14:23:09 -0700
> From: d_ohmes@yahoo.com
> To: dinosaur@usc.edu
> Subject: RE: Aw: RE: Arboreal Theropods: The prize at the bottom of the 
> cracker jack box
> 
> 
> 
> On Tue, Jul 23, 2013 5:17 PM EDT Allan Edels wrote:
> 
>>Just a quick question inspired by Don's post (esp. "the hallux leaves no 
>>impression when turkeys walk on firm sand")  -  
>>
>>Don't we have some mud/sand footprint impressions of dromeosaurids, which 
>>shows the claws (including the raised one) being pulled out of the mud/wet 
>>sand?
>>
>>Allan Edels
> 
> I don't doubt it -- and turkeys leave definite impressions of the posterior 
> toe when on soft ground -- but am not sure I take your point.
> 
> Could you expand?
> 
>>
>>> Date: Tue, 23 Jul 2013 14:12:55 -0700
>>> From: d_ohmes@yahoo.com
>>> To: dinosaur@usc.edu
>>> Subject: Re: Aw: RE: Arboreal Theropods: The prize at the bottom of the 
>>> cracker jack box
>>> 
>>> 
>>> 
>>> On Tue, Jul 23, 2013 11:23 AM EDT Jason Brougham wrote:
>>> 
>>>Alright. To recap as succinctly as I can.
>>>
>>>There seems to be consensus here that basal paravians could have engaged
>>>in 'occasional' climbing behaviors.
>>>
>>>Bu
>>>
>>>There are living animals that lack climbing adaptations, or that are even
>>>members of clades that show 'trends' away from climbing, for which trees
>>>are still indispensable parts of their biology. These include murrelets
>>>and petrels, which have secondarily lost halluces. They include chicks and
>>>other birds with limited or absent flight ability (Inaccessible Rail,
>>>Kagu, hatchling tinamous, hatchling chukar).
>>> 
>>> And M gallopavo. I note that the hallux leaves no impression when turkeys 
>>> walk on firm sand, and the claw tip does not extend to the rearward edge of 
>>> the weight-bearing pad. Indeed, if memory serves, it has the gestalt of a 
>>> dewclaw...
>>> 
>>> That said, it may indeed have function when hens are crouching on branches 
>>> in brooding position.
>>> 
>>>Basal paravians, living in habitats such as the Tiaojishan Formation which
>>>had diverse gymnosperm trees, arborescent bennettites, and tree ferns,
>>>could have utilized these habitats in some similar manner. Say, scrambling
>>>a meter or two up them to launch on imperfect wings. Or roosting on fallen
>>>tree limbs. Such behaviors do not require specialized adaptations but,
>>>rather, they could be the precursor of those adaptations. Animals that
>>>routinely entered trees without specializations would be ideal candidates
>>>to adapt to those habi
>>>
>>>The reasons we could suspect this in basal paravians, as opposed to other
>>>dinosaurs that show no climbing adaptations (such as, say, hadrosaurs),
>>>are 1) they are small 2) they are comparatively agile, with long, sharply
>>>clawed, hands and feet 3) they actually ARE the direct ancestors of the
>>>animals that specialized toward arboreality: the Avialae.
>>>
>>>For any given taxon the hypothesis can be tested by biomechanical analyses.
>>> 
>>> True. And I add that the iconic perching foot is most excellent gear for 
>>> landing on a 'branch, or even grasping prey in hawk-like fashion, but what 
>>> advantage would it grant to a flightless quadrupedal climber? 
>>> 
>>> Especially one that fo
>>> 
>>> It would follow that the perching foot is a lagging indicator of flight, 
>>> not a precursor. 
>>> 
>>> 
>>> 
>