Re: Hone and Benton 2007 (their second paper)

[Tim Williams <twilliams_alpha@hotmail.com>]

Jim Cunningham wrote:

> Comments inserted below.  Caution, my tongue may be in cheek, and that 
> interferes with my >typing (so does most everything else -- typing's not my 
> bag....)

Right back at you Jim.  ;-)  No harm, no foul.  There are a lot of fruit 
bats ("flying foxes") where I'm living, and I've seen the consequences of 
what happens when they do become "whacked" or snagged in a tree (or, more 
often, by power lines)  It's not at all pleasant, and I can see why a 
pterosaur would likewise want to avoid such a fate.

> For a large pterosaur, wouldn't that require a very specialized tree shape, 
> in order to keep tree limbs from whacking the wings or vice versa?  :-)

That may not have been such a problem for most of the Mesozoic, until the 
angiosperm explosion in the Cretaceous.  During the "Mesophytic Era" most of 
the "big" trees came in the form of conifers, cycadophytes, and cycadeoids 
(especially bennettitaleans).  Those last two tend to be unbranched, or 
sparsely branched - so for a pterosaur leaping or diving from atop the 
plant, having the wings being "whacked" on the way down may not have been 
such a problem.  Same for leaping off the trunk, although in this case the 
launch would be accompanied by a 'twist' - I would guess this would be 
similar to the way modern leaping primates when they leap from trunks, but I 
have no idea how pterosaurs coordinated this.

I have no idea how a pterosaur would have clambered to the top of a 
cycad/cycadeoid, but once there it would have been an easy path down.  
However, conifers, like many angiosperms, presented a problem - unless the 
pterosaur was leaping from the lower branches of the crown (although even 
the lowermost branches may be a considerable distance from terra firma).

> At someone's request,  I once calculated that a tree only a few hundred 
> feet tall should adequately suffice for northropi to perform this maneuver 
> without assistance from flapping, with most of  the height consumed in a 
> circular transition from vertical to horizontal flight.

A few hundred feet?  Is that all?  :-)

I was thinking of the smaller and/or more insectivorous pterosaurs, such as 
_Dimorphodon_ and (especially) the anurognathids.

> It would help if the tree had only two limbs, preferably located at the 
> top.  One treelimb would be for supporting the forelimbs, and the other, 
> the hindlimbs.

Cycads/cycadeoids do tend to have the "branches" clustered at the very top.  
However, I'm not certain how ideal the crown was in terms of the 
availability of handholds and footholds.

> Keep in mind also that pterosaur wings don't fold as closely as bird wings, 
> so climbing the tree is clumsier and more difficult for pterosaurs as well.

Is this "difficulty" associated with simply scaling a vertical surface (like 
a tree trunk), or because the pterosaur's wings could get snagged on 
branches on the way up?

> I agree, but suspect that most pterosaurs launched from ground level.

I agree.  But there is morphological evidence that certain pterosaurs could 
climb trees.  I guess I'm curious what these particular pterosaurs did to 
launch themselves into the air.

Thanks for the response.

Cheers

Tim

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