Bloody feathers & flicky tails (was: Feathers as fossilized behaviour)

["John V Jackson" <jjackson@interalpha.co.uk>]

In response to:  Ronald Orenstein <ornstn@home.com>
Date: Thu, 18 Feb 1999 14:04:50 -0500


Good point about arm feathers getting in the way of anything except flying
(and all right, just possibly brooding!).

Recently I've been pondering the treatment body feathers would get on such
as Deinonychus which attacked larger prey.  Lions do a lot of rolling
around when they're attacking zebra's etc., and both Bakker on p 310 of
"..Heresies" and Knight in his "Laelaps" picture show "Rolling on the back"
behaviour - frozen of course in the fighting pair.  The bigger the
animal, the higher the pressure on any back or side feathers, and I
personally don't see neat structured feathers lasting long on Deinonychus
etc (though birds of prey sometimes roll around on the ground during an
attack).
In fact I also suspect tyrannosaurs originally had feathers, whereas
we know of an example, at least on the base of the tail, where they have
been completely transformed if they ever existed.  What fun if droms turned
out to be simply furry - or better still - scaly!  (Ah but...)


    ---#---


While perusing the fighting pair I noticed that *the stiff bit* of the _V_'s
tail bent through 60 degrees.  In an earlier incarnation I became highly
familiar with flicking bendy sword blades, and found of course that it
worked best when the characteristics of the blade suited the speed at which
you could reverse the direction of the movement, and the strength available.
And conversly, the effect on the wielder of the blade/tail etc during a
flick will depend on the characteristics of both "tail" and ... base of the
tail.  Since slicing through the skin of a Tenontosaurus would require a
powerful thrust - so powerful that the conventional "fast leg design" had to
be seriously compromised to power it - the user of such a sickle claw would
experience a very strong upwards impulse in the process.  Sometimes this
could be opposed by standing on the prey and pulling up with the hands, but
not if effectively clinging on to a near vertical cliff-face.  In this case
the force the claw could apply would be limited, at least in duration, by
the tendency for the leg to straighten and the attacker to shoot up into the
wide blue yonder before it had done much damage.

How useful then, if the momentum generated could be channelled away from the
pelvis and trunk, into some other part - say the tail?  If the tail could be
flicked up rapidly during the claw thrust, the leg could stay more bent and
apply a greater force for longer.  In fact, if the tail had been given a
rapid downward velocity immediately prior to this, the effect could be
further enhanced.

The only bird we know that retained the sickle claw through the Cretaceous
was also the only one to retain the long stiff tail.  Looking at the tails
and sickle claws of Velociraptor, Rahonavis, Archaeopteryx, Troodon, and
non-sickle-clawed types, it appears that the extent of development of the
sickle claw seems to match the extent to which the tail could be used to
deliver/receive a large and sudden lump of vertical momentum.  If the tail
had feathers, it could actually push up against the air as well (and for the
wings to take part too would only require a movement of wings and legs very
similar to that used in take off).  For this to work best, the tail feathers
would angle up, opposite to the angle depicted for
Caudipteryx/Protarchaeopteryx.


JJ