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Re: Hone and Benton 2007 (their second paper)



Comments inserted below.
Jim

----- Original Message ----- From: "Tim Williams" <twilliams_alpha@hotmail.com>
To: <dinosaur@usc.edu>
Sent: Monday, May 28, 2007 7:03 PM
Subject: Re: Hone and Benton 2007 (their second paper)



Jim Cunningham wrote:

- 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.

Assuming they could get up the trunk in the first place, I would expect them to be oriented 'heads up', with one possibility being to push off hard with the arms while releasing with the feet, thereby going inverted and head down, followed by a partial extension of one wing to half roll upright in a steep dive, followed by extension of both wings, and a pullout into level flight. I do not have an opinion on how they might have grasped the tree to initiate the process and doubt that many, if any, did it. Note though, that I do believe arboreal pterosaurs are possible. If arboreal goats are possible (and they are), then anything is possible........

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

The presumption was no flapping. A second presumption was that the wings should not be structurally overloaded during the pullout to level flight. I didn't put a lot of effort into the process, and don't consider it to be an accurate or dependable estimate. Suffice it to say that it would take a big-a** tree (northropi and Hatz would measure very roughly about 21 to maybe 23 feet from tail to snout).

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

I know you were. My sense of humor wouldn't let me miss the chance to take it to the extreme.


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 was thinking in terms of snagging, but have some unsubstantiated doubts about the ability to climb a vertical surface. I don't actually doubt that some pterosaurs may have had the ability to climb and launch from trees. I just doubt that many did.


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.

Were it me, I'd jump, dive, and then flap to beat sixty for about 30 seconds. If the surface were solid, I'd just jump and flap.