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TARSITANO AND _MEGALANCOSAURUS_
> I just got my JVP and SVP abstracts the other day. I noticed that
>John Ruben is apparently now advocating Fedduccia's baby
>Megalanica[big sic] as an alternative to theropods in bird origens.
I did not get my SVP abstracts yet so I haven't read his reasoning. I
did read a bit in _Bioscience_ on Ruben's views on bird origins. Ruben
apparently thinks that _Megalancosaurus_ is a definitive proavis, even
with a patagium. Apparently, ANY small avian-like archosaur with
arboreal features is an avian ancestor.
And also, to be fair to Sam Tarsitano, the whole _Megalancosaurus_/ bird
connection is pretty much his doing (and Rupert Wild). In 1985
(Archaeo. Conference Book), Tarsitano gave a progression as to how
"thecodonts" can evolve into birds and _Megalancosaurus_ was hinted to
be the first in such a series. In _Origins of the Higher Groups of
Tetrapods_ (1991), Tarsitano expanded the view more and said that most
of the features that unite birds and theropods are found in
_Megalancosaurus_, even a semi-lunate carpal.
Basically, Tarsitano (1991) says that birds are some of the most basal
members in the "Thecodontia" as evidenced by the plesiomorphic lack of a
verticalized basioccipital (detailed in Tarsitano, 1985b), something
that birds lack and all other archosaurs have except for
_Megalancosaurus_. He also discounts coelurosaurs from the ancestry of
birds because they lack a siphonium (quadrate-articular pneumaticity;
according to him is present in tyrannosaurs, which are coelurosaurs),
"are too large to evolve flight", lack a fenestra "rotunda" (most
authors contradict him and use fenestra pseudorotunda), and various
other things.
Matt Troutman
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