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Re: "Feathery fossil shows birds aren't dinosaurs"
At 9:12 PM -0700 6/22/00, Phillip Bigelow wrote:
Is this another better preserved specimen of Longisquama that
preserves good morphology, or is this specimen the same old
hash-on-a-slab holotype that will undoubtably evoke comments
like "It has a furcula!" "No it doesn't!" "Yes it does!"
In other words, is this paper in _Science_ an example of
rehashing old hash?
In a word, yes. They're looking at the single specimen of the
Longisquama extended scales with a partial skeleton (head, front legs
and torso, but no tail or rear torso. They also have five separate
fossils of the extended scales or whatever you want to call them.
They did have the advantage of more modern equipment for examination
than the Russians did 30 years ago, but it's still the same specimen
with cracks and a coating of gunk which obscure some details (notably
critical skull details that diagnose whether or not it's an archosaur.
I have an article coming out in next week's New Scientist (Science's
embargo is very inconvenient for a magazine that hits the streets
Thursday morning), which I'm not going to repeat. But for the list
it's worth thinking about a few points.
Feduccia et al are _not_ saying this was an ancestral bird. They're
saying it's one of a number of bird-like thecodonts (the term
Feduccia prefers) that lived at the time, and they're saying that
feathers may have originated long before Archaeopteryx.
I see two messages in the paper which deserve to be treated
separately. One is an attack on the whole cladistic method of
analysis (which has stimulated a counterattack on that attack from
the paleontological establishment). It's based on the notion that
this is an animal with feathers that doesn't fit all the nice
correlations of characters which show birds are dinosaurs. I'm not an
expert, but I don't think it's a tremendously strong case.
The second is likely to get lost in the shouting over the first
message. Longisquama shows scales have considerably more potential
for interesting structure than is generally assumed. Whether or not
those are true "feathers", they clearly evolved from scales. They may
very well have evolved from scales independently of the feathers on
true birds. Maybe we really need to take a closer look at scales to
better understand feathers. --
Jeff Hecht Boston Correspondent New Scientist magazine
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