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

RE: CNN report on the feathered dino



 
Jeff Hecht wrote:

>I couldn't work his comments 
>about the curious placement of an anomalously long feather on the leg 
>into my article, but it isn't where you would expect one. 

The presence of long feathers on the leg and pointing backwards may not be
that incongruous if these predators leaped into the air against prey from
elevated sites - a tree for example.  The long, planar feathers on the arms
and legs would add additional drag to a parachuting descent - and offer the
potential for generating an airfoil.  A great deal depends upon how the
hindlimb feathers were oriented relative to the airflow.  I don't know how
the vanes of the hindlimb feathers of BPM 1 3-13 are oriented relative to
the leg - I haven't seen the specimen, and it isn't clear from the figures.

The specimens of _Archaeopteryx_ do not show hindlimb feathers (contra some
early interpretations).  However, nor does _Archaeopteryx_ show contour
feathers on the body or tertials on the humerus, so these feathers may have
detached prior to preservation.

Though useful in parachuting or gliding descents, hindlimb feathers would
undoubtedly be a hindrance in a running take-off from ground level.
Therefore, I suspect that their absence from _Archaeopteryx_ is real.  If
the absence of long hindlimb feathers from _Archaeopteryx_ and other early
birds is indeed real and not an artifact of decomposition, then the presence
of these feathers is therefore either (a) a derived paravian trait evolved
by dromaeosaurids, or (b) a primitive paravian trait lost in birds
(Avialae).  A feathery troodontid would clear up the matter of which is the
more parsimonious explanation.  At the moment, I'd put money on (b).

By the way, why is this feathered dinosaur a "missing link" if it's been
found?  :-)

Also, from the CNN story, "Norell said that some modern birds such as
certain kinds of hawks have big feathers sticking out of the back of their
limbs.."  Does anyone know why?   



Tim

------------------------------------------------------------ 

Timothy J. Williams 

USDA-ARS Researcher 
Agronomy Hall 
Iowa State University 
Ames IA 50014 

Phone: 515 294 9233 
Fax:   515 294 3163