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Re: Feathers, Longisquama & Archaeopteryx



>I was currently discussing with a friend the evolution of feathers.  I
>seem to recall hearing somewhere that a sort of modified scale that
>could indicate an early development toward feathers was found in fossils
>of Longisquama (the lizard-like critter with what look like upside-down
>hockey sticks along its back).  Does anyone have any info on this?
>Anyone know where Longisquama fits in the grand scheme of things?  Is it
>considered to be an ornithodire (is it even an archosaur)?  Are there
>any other records of such "proto-feathers" in the fossil record?

I can't speak much to the problems of Longisquama.  To my knoweldge, there
hasn't been that much attention paid to it in recent years.  I seem to
remember someone suggesting that the "hockey-sticks" were in a double row,
and were oriented laterally (outward) rather than upwards, forming a
potential gliding structure.  As to it being ornithodiran, or archosaurian,
I don't know.  Maybe someone on the net has seen the specimen, and could
comment on them?

>Also - is there a significant difference between the feathers on
>Archaeopteryx and those on birds today?

In the basic structure, Archaeopteryx feathers are as advanced as those of
modern birds, with several orders of structure superimposed on each other.
In a recent letter to Nature, it was shown that the feathers of
Archaeopteryx, while somewhat assymetrical (that is, there is more
"feather" on one side of the shaft relative to the other), are not as
assymetrical as those of modern flying birds.  Instead, the values for
Archie fall within those of modern flightless birds.

                                
Thomas R. Holtz, Jr.                                   
tholtz@geochange.er.usgs.gov
Vertebrate Paleontologist in Exile                  Phone:      703-648-5280
U.S. Geological Survey                                FAX:      703-648-5420
Branch of Paleontology & Stratigraphy
MS 970 National Center
Reston, VA  22092
U.S.A.