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

Re: Just this n that



At 06:12 PM 3/18/97 -0800, Betty Cunningham wrote:
>> << Birds seem to be unique among
>>  vertebrate flyers and gliders in that there is no evidence of a typical
>>  flat-bodied gliding stage in their evolution. >>
>> 
>> The retroverted pubis of dromaeosaurids can be considered evidence of such a
>> stage.
>
>I don't think dromosaurids are as flat-bodied as what Tom is referring
>to.  
>I think he's thinking of animals that are more parallel to the ground
>(and thus having a body in a plane to glide in naturally) than any
>bipedal dinosaur OR bird has been.

Bingo!

Exactly.  To put it another way, it is difficult if not impossible to splay
out the hindlimbs of extinct and extant birds (and other theropods): compare
the death positions of the Archaeopteryx specimens (or Compsognathus, or
what have you) to the death position in pterosaurs, bats, etc.  In the
theropod examples, both legs are generally preserved on the same side of the
body; in the other forms, the legs are preserved spread out.  (Okay, there
are exceptions to this: I've seen a Confuciusornis with the legs spread out,
for example).

Thomas R. Holtz, Jr.
Vertebrate Paleontologist     Webpage: http://www.geol.umd.edu
Dept. of Geology              Email:th81@umail.umd.edu
University of Maryland        Phone:301-405-4084
College Park, MD  20742       Fax:  301-314-9661