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

Re: Origin of Birds




> >> (Feduccia and Martin have both published on the fact that they
> "know"
> >> cladistic analytical methodology MUST be wrong, because it keeps on
> putting
> >> birds within the coelurosaur dinosaurs, even when different peoples
>
> >> different data sets are used...)
> >
> >Did I read that right?  Feduccia and Martin dismiss cladistic
> analysis
> >out-of-hand, simply because it conflicts with their assumptions about
>
> >bird origins?
>
> >   If memory serves, Feduccia says this outright in the _Audubon_
> article
> >about _Sinosauropteryx_.

In the Audubon article Feduccia does not claim that the cladistic
methodology MUST be wrong. Neither does he claim that in  The Origin and
Evolution of Birds. In the Audubon article Feduccia briefly recaps the
argument of the book:

 Theropods were not adapted for climbing trees. Flight began in the
trees. Convergence is not rare and is the limiting factor of the
cladistic methodology. Birds likely originated in the Triassic from a
thecodonts such as Megalancosaurs.

I do not claim to agree with Feduccia, though I feel the need to defend
him.  I question how both parities in the argument can be so confident
given the relatively scant evidence.  Archaeopteryx displays
considerable evolutionary history as a bird. If Protoavis is valid, then
Arachaeopteryx is a relic of an early Triassic lineage. Two species, at
most, representing 50 million years does not seem to be a very
representative sample. Variability is not unlimited, but constrained,
similarity often represents adaptation under constraint rather than
common ancestry. Feduccia gives the example of ostriches and emus.

I am an amateur naturalist with a particular interest in birds and
brachiopods. Brachiopod evolution is a tale of repeated convergence's.
Cladistic analysis is extremely difficult. Molecular and character based
phylogenetic results frequently differ.

If Feduccia?s most recent paper is correct that bird and theropod digits
are not homologous, the current cladistic analysis is incorrect, a
victim of bad data. Likewise if a feathered theropod is found today,
Feduccia?s hunch is wrong, birds are dinosaurs. I admit Feduccia?s tone
is arrogant, but the Dinosaur people have been rather in your face with
?Birds are dinosaurs.?.  I think it is most appropriate to say birds are
probably dinosaurs.

I am reading Chatterjee?s book The Rise of Birds. Chatterjee suggests an
arboreal theropod ancestry for birds and feels Archaeopteryx was a
living fossil in its time. Protoavis was the descendent of a primitive
Archaeopteryx-like Triassic bird. He does not abandon the standard
cladistic phylogeny despite the odd temporal sequence of the known
fossils. This must be a disappointment to Martin and Feduccia.

 Chatterjee?s seemed the most objective in tone of the three bird
evolution books to come out during the past year. (The Origin and
Evolution of Birds, The Mistaken Extinction, The Rise of Birds).

Bruce Moore

>
>
>