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Re: flapping from gliding



At 12:44 27/09/96 -0500, NIck Longrich wrote:

>Arboreal gliding faunas:
>
>       Flying squirrels
>               (two distinct radiations)

I presume you mean sciurids and anomalures?

>       Flying frogs
>               ( I only know of one- more a parachuter, really)

In addition to the Rhacophorid flying frogs of Asia, some new world hylids
(eg Phyllomedusa) can also parachute using the webbing of the toes - though
not as well.

>       That thing with the big scales on it's back George talks about a
>lot and I can't remember the name of. (extinct)

Longisquama

>       Arboreal gliders: ~15 , insectivorous leapers/aerobatic
>runners/leapers: ZERO. 
>
>       Gliding is a VERY common adaptation. Most branches of the
>amniotes except turtles (for obvious reasons) fill it:

Gamera?

>       The point:
>The arboreal hypothesis has two main strengths. a) the leap between
>gliding flight->powered flight seems to me to be, both conceptually and
>evolutionarily, an easier one, than the one between a running or leaping
>predator and powered flight.

EXCEPT - if gliding has evolved so frequently and reached such extreme
degrees in some forms (eg Dermapterans) why did powered flight evolve only
three times in tetrapods?  If this were indeed the pathway I would have
expected a lot more flyers.  The fact that flight has evolved so rarely
suggests to me that it developed by an infrequently, not a frequently,
"chosen" pathway.

>We don't know of ANY predators that spend much of their time
>pursuing the prey in other ways hypothesized.

Actually there are a number of birds that regularly pursue ground prey by
sitting on a perch and pouncing downwards.  These include some kingfishers
(eg the kookaburra), puffbirds and a number of other so-called
"sit-and-wait" predators.

My suggestion, though, was different - instead of pouncing downwards I
postulated flight as an aid to an arboreal creature leaping upwards to get
prey items on leaves, the tips of thin branches etc (something a great many
living birds do, using their wings of course!).
--
Ronald I. Orenstein                           Phone: (905) 820-7886 (home)
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