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

Re: Feduccia (was: polarity of bipedality in dinosaurs)



In a message dated 96-09-23 15:37:22 EDT, ornstn@inforamp.net (Ronald
Orenstein) writes:

> I have just purchased, and started to read, The Origin and Evolution of
> Birds by Feduccia.  I have not read much of it yet, just skimmed it, so I
> can't really discuss Feduccia's ideas in detail.  However it seems to me
> that he is dismissive, if not scornful, of any view that birds and theropods
> are "intimately related" even if he does look to things like Longisquama and
> Megalancosaurus as "protobirds" of sorts.  Some of his basic arguments
> (looking past the characters themselves, which I am only doing because I
> haven't read enough yet) seem to be that: 
>
> 1. the similarities between birds and maniraptorian theropods are convergent
> 2. animals like Velociraptor are too big, heavy and earthbound to be bird
> prototypes
> 3.  anyway, they lived too late
> 4.  birds evolved from arboreal ancestors, and Velociraptor isn't the least
> bit arboreal. 

What we have here is one of those paradoxes out of the reconciliation of
which springs new theory. Need I mention what new theory this might be? :-)

BADD dinosaurology says this: Birds are descended from dinosaurs because of
the tremendous number of shared derived characters possessed by bird and
dinosaurs, as uncovered in repeated cladistic studies of the two groups. How
flying birds might have evolved from terrestrial, cursorial forms is nearly
impossible to determine, but it must have happened, to account for all those
synapomorphies.

Paleornithology says this: Birds can't possibly be dinosaur descendants
because no known dinosaurs were properly placed in time or had the kinds of
arboreal or acronomic lifestyles that gave rise to birds. Ergo, everything
the BADD cladistic studies have found must be due to convergence, and true
avian ancestors remain unknown.

BCF reconciles these viewpoints: The shared derived characters found by BADD
cladists in birds and dinosaurs are real, not convergent, and result from the
descent of dinosaurs from small, arboreal archosaurs in the process of
evolving into true (avialan) birds, just the way paleornithologists say they
did.