[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

RE: flight stroke (pretty short)

Waylon Rowley wrote:

> The problem I see is that when an animal uses an organ
> for a new purpose, it usually uses it for a purpose
> similar to whatever came before. Legs came from fins,
> and wings came from arms....they all revolve around
> the need for locomotion. 

Ah, you've hit upon an important point here.  Theropods did not use their
forelimbs for locomotion (unless you include the suggestion that they
climbed trees in quadrupedal fashion, like baby hoatzins).  Theropod
forelimbs were designed for catching prey - and maniraptoran forelimbs were
specialized for this (hence 'Maniraptora').

> Wouldn't incipient flappers be quickly out-competed by more derived 
> flappers? 

_Rahonavis_ (probably a weak flier) lived near the end of the Cretaceous.
More flapping requires more energy; and besides, _Rahonavis_ may have
deliberately kept a conservative anatomy (and physiology) because it suited
its lifestyle.  

>I like the idea of vertical running, [snip] Wouldn't  branches stop the 
> progression up the tree before it reached the top, too?

The 'pro-avian' might then use its forelimbs to grab the branches and climb
up the tree.  Certain of these hypothetical models (Dial's 'vertical
running' included) are mutually compatible.

David Marjanovic wrote:

> There are still 2 genera or so of long-tailed bats 

I'll have to check on this, but I'm not sure that any long-tailed bats
actually use their tails in aerial locomotion (e.g. 'free-tailed' molossids
in which the tail extends far behind the uropatagium - the tail is used as a
sort of 'feeler' when the bat is on the ground)