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

Re: Tail length & preening



David Marjanovic (david.marjanovic@gmx.at) wrote:

<Almost certainly impossible. Judging from the photos of the tails of *M.
zhaoianus* specimens in the AMNH Novitates paper, the tail was a total
broomstick. A bend of a few degrees was enough to break one of them.>

  I personally doubt for many reasons that the tail was as easily
breakable or completely inflexible caudal to the first few vertebrae
(which lacked the inter-woven caudal rods). I have two reasons:

  1) In *Velociraptor* and *Deinonychus*, or instance, the tail where the
caudal rods persisted are usually found flexed to some degree, either
dorsally or laterally. In one specimen, this curvature exceeds 30 degrees.
In *Bambiraptor*, the tail curves more than 150 degrees around, and
includes both a lateral and a ventral curve. One of the specimens
described by Hwang et al. also describes a shallow, but distinctive curve,
and I see no reason that these caudal rods prevented flexure, as they may
have easily have slid past one another, without bending too much.

  NOTE: No one has done a study to date that shows the relative
flexibility possible in these bones. A study by Ostrom, 1969, showed that
the section of the bones were filled with long hollow chambers, and lots
of them, with a distinctly cancellous nature. This kind of bone, as can be
seen in fibular shafts and other small-diameter bones of the mammalian and
avian skeletons, can and do bend, even during life. In some cases, during
locomotion, they must be able to bend to accomodate torsional forces.

  2) Most animals that groom usually rely on themselves to do the deed,
and it's similarly unlikely that *Microraptor* was unable to clean its
tail.

  Cheers,

=====
Jaime A. Headden

  Little steps are often the hardest to take.  We are too used to making leaps 
in the face of adversity, that a simple skip is so hard to do.  We should all 
learn to walk soft, walk small, see the world around us rather than zoom by it.

"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)

__________________________________________________
Do you Yahoo!?
Yahoo! Mail Plus - Powerful. Affordable. Sign up now.
http://mailplus.yahoo.com