Re: Hone and Benton 2007 (their second paper)

[Michael Habib <mhabib5@jhmi.edu>]

> This reminds me of another question I had.  (Keep in mind that I'm not 
> very knowledgeable about pterosaur aerodynamics, so bear with me...)  
> Certain pterosaurs (e.g., _Dimorphodon_) appear to have grasping 
> adaptations in the feet, including similar phalangeal proportions to 
> arboreal birds (Clark et al., 1998).  So it's been suggested that 
> these pterosaurs were capable of climbing.  If true, how would a 
> pterosaur launch itself from a tree?  Having both grasping manual and 
> pedal claws would allow the pterosaur to grip the tree with all four 
> limbs, but how would it launch itself into the air?

Being in a tree actually makes launching quite easy, since the animal 
can use a gravity-assisted launch.  Essentially, an arboreal pterosaur 
could simply drop off the tree and then start flapping.  It would hit 
flight speed quite rapidly using gravity-assisted launch, so the animal 
need not fall very far.  Arboreal birds use gravity assisted launches, 
as do cliff-dwellers like tropicbirds.  Arboreal birds do not require 
gravity assistance, while tropicbirds (and frigatebirds) often do.  
However, in both cases, the vertical descent prior to reaching cruising 
speed is quite short.  You can see it if you look for it, however.  
Like arboreal birds, a tree-dwelling pterosaur would not require a 
gravity assisted launch, but it saves energy if you happen to be at a 
high point already.

If a pterosaur were launching from a tree (be it a trunk or a branch), 
it could either use gravity-assistance, or a leaping launch (just as 
from the ground for a branch launch; there would be a twist after the 
initial leap involved for trunk launching).  More than likely, arboreal 
pterosaurs would use a combination of both gravity assistance and 
leaping (which is what arboreal birds tend to do, especially larger 
ones).

I hope that helps; definitely an excellent question.

Cheers,

--Mike H.