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Re: OCCAM'S RAZOR & THERIZINOSAURS



Dinogeorge@aol.com wrote:

> Actually, secondary flightlessness is the simplest and most parsimonous way to
> describe the relationship between birds and theropod dinosaurs. In BCF, the
> wing does not go through a state in which it is a short forelimb before it
> once again becomes a long forelimb (as in primitive archosaurs); it starts out
> as a long, grasping forelimb in quadrupedal tree-climbing archosaurs and it
> remains a long forelimb in dino-birds and birds. The short forelimbs of
> theropods are >derived< proto-wings, just as the short forelimbs of extant
> flightless birds are derived neo-wings.

So, which theropods are secondarily flightless "birds?"  All of them?

> In BCF, birds do not go through a
> state in which they become large, heavy, ground-dwelling cursorial bipeds
> before once more becoming small; they start out as small, lightweight,
> arboreal forms (probably as far back as the Permian) and remain so. The large,
> unflightworthy size and bipedal cursorial lifestyle of theropods are derived
> relative to the common ancestor of birds and theropods.

The _Permian_??  I just checked a couple of my references, and they say
_archosaurs_ weren't even around for most of the Permian.  The earliest known
archosaur is either _Protorosaurus_ or _Archosaurus_, but both are from the Late
Permian.  Something doesn't make any sense here.  If birds are descended from 
any
kind of archosaurs, then how can they pre-date archosaurs?

I might also point out that I don't know of anyone who would argue that all
theropods were large, heavy bipeds.  Bipedal they all were, but undoubtedly 
there
were many small ones as well as large ones.

-- Jon W.