Scipionyx & Rahona lacked pulmonary liver pistons

[GSP1954 <GSP1954@aol.com>]

The recent claim that Sinosauropteryx has a well preserved liver of any kind -
much less the type associated with a crocodilian-like liver pump that
ventilates the lungs - is entirely unfounded. There DOES appear to be a liver
preserved along with some other internal organs in the extraordinary Scipionyx
(which is very well illustrated in the March 26 Nature paper). So what does
this tell us? 

The Scipionyx liver is small, much less deep than the pubes are long, and is
placed antero-ventrally. This is similar to the condition seen in birds, and
is compatible with the presence of 

small, dorsally sited preavian lungs (the shortness of the chest ribs are
strong evidence that the lungs were so shallow). On the other hand turtles and
chameleons also have similar livers, unlike most reptiles in which the liver
is more posterior (see Duncker in Avian Form & Function 1). It is completely
different from crocodilians, in which the liver is very large, fills the body
cavity from top to bottom, and is much deeper than the pubes. There is no way
that the possible little liver of Scipionyx could operate as a piston to
ventilate the lungs. 

Rahona also tells us about theropod respiration. For years critics of a dino-
bird link have gone on and on about the lack of a hypopubic cup - seen in
Archaeopteryx and other early birds -  on the pubic boot of any theropod. In
particular, Ruben et al last year cited the absence of the cup in theropods as
evidence against their having a preavian respiratory complex. Yet Rahona has
the cup. 

Here's the funny part. Obviously, if Rahona really is a winged sickle clawed
beast, then it is very strong evidence that birds are dinosaurs. So much so
that people like Feduccia, Martin and Ruben are denying it is a winged form at
all. They assert that the avian wing bones do not belong to the dinosaurian
hindquarters. This is not unreasonable. But, the pubis has the avian hypopubic
cup, plus distinctive ischial processes seen in early birds. Hey fellas, if
hypopubic cups and Archaeopteryx- like ischial processes are avian characters
like you have been saying, then what are they doing on a mere dinosaur? Of
course these characters are as dinosaurian as they are avian, in that
dinosaurs are birds. 

While discussing Scipionyx, it is not an advanced, bird-like form related to
dromaeosaurs or troodonts, because the tall quadrate, L-shaped quadratojugal,
shoulder girdle, wrist, pubis and tail are all of the standard theropod rather
than near avian theropod grade. 

GSPaul