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The following errors, omissions and other mistakes are present in Ruben et al
Science 278:1193-1368. 

It is important to understand that Ruben et al have not actually seen any of
the Sinosauropteryx specimens, they are making guesses based on photos of
just one specimen, photos that fail to show its 3-D complexity. In Fig. 5A
they use a low resolution, out of focus photo to contend that there is a
semi-circular anterior border to the abdominal cavity. There is no such
thing. Examination of higher quality, larger format photos on the cover of
the April 97 Audubon (counterslab) and Nov 14 97 Science (main slab) and the
March 97 Episode (both slabs) show that much of the supposed border of the
abdominal cavity is really an irregular break in the sediment! This is
especially obvious in the superbly detailed Audubon photo, where the shallow
rim of a large, semi-circular, light colored break under the spinal column is
clearly delineated both by cast shadows, and obvious breakage of the ribs at
that location, the rest of the ribs are complete. Ruben et al saw this photo
since they cited it in their paper, yet they make no mention of the damage
(either they missed it, or thought it unimportant). Yet  their arrow points
to this break as the septum - i.e. they misidentify sediment damage as soft
tissue anatomy.  On the main slab there also appears to be small,
subrectangular break in the sediment projecting ventrally from the larger
area, perhaps parallaling a rib. If so, then this break forms more of the
border of the supposed abdominal cavity. Also, on the mainslab, a small part
of the dark area extends more anteriorly than they indicate, resulting in a
more pointed apex to the dark region than the nice gentle curve they
indicate. The rest of the "abdominal cavity" just consists of vague,
irregular, darkish stains with no particular pattern to them. Who knows what
they represent. Perhaps thoroughly degraded abdominal tissue flattened to
paper thinness, it will require careful examination and analysis of the
specimen to determine so or otherwise, there may never be definitive results.
The claim that the specimen shows a croc-like separation between the lung and
belly cavities via a septum is absurd, it shows nothing of the sort. 
      Severely crushed specimens are always badly damaged and can be very
difficult to correctly interpret under the best of circumstances. Yet Ruben
et al treat the flattened dinosaur - whose soft tissues are less well
preserved than your well run over roadkill - as though it is one of their
high tech CT scans of a carefully pickled carcasse. The damage to the ribcage
area in the Sinosauropteryx specimen probably occurred when the slab was
first split. This kind of damage is very common, yet can be hidden in 2-D
photos unless the lighting happens to be at a low enough angle, and coming
from the right direction, so the shallow topography is not washed out. Any
person working with such photos should be very careful to watch out for and
not be mislead by such obvious pitfalls. As it is, Ruben et al violated all
of the necessary protocals.   
     Basic rule of paleontology. It's always a good idea to actually SEE THE
SPECIMEN, or at least have excellent stereo photos and/or a detailed
description, before making dramatic claims concerning same in a major science

According to Ruben et al birds "lack a crocodilelike or mammallike
thoracic-abdominal subdivision (septum) of the visceral cavity". Duncker
(1979) states that in "all birds the coelum (body cavity) is subdivided in a
manner rather similar to reptiles and especially crocodiles" (he also notes
the differences), and "ventrally the pleural (lung) cavity is bounded by the
horizontal septum" (illustrated in Fig. 2.13). Schmidt-Nielsen (1972) states
that "a membranous structure.....is located along the ventral surface of the
lungs. This membrane arches slightly up into the lungs" (as shown by Fig.
25). Interestingly, the septum is attached to the ribs via muscles. The
septum is pierced by the bronchai leading to ventro-posterior air-sacs. Ergo,
the presence of a septum does not interfer with the evolution of abdominal

Ruben et al assert that birds use a very large sternum articulated via
ossified sternal ribs with the ribs to ventilate the large abdominal
air-sacs. This is partly true, yet misleading because it applies to flying
birds in which in flight ventilation rates are extraordinarily high, and the
super sternum anchors enlarged flight muscles. Theropods did not fly, and
their aerobic capacity was probably more similar to ground birds like the
kiwi, which Ruben et al ignore. In the kiwi there are no extensive abdominal
air-sacs, and the sternum is very short. Alas, so little work has been done
on respiration in these birds, but it is clear that the sternum ventialtes
only the antero-ventral most air-sacs. The majority of air-sac ventilation is
via simple rib action. 

Ruben et al contend that theropods lacked the adaptations needed to operate
an air-sac complex. Au contraire. It is important to understand that the
avian complex did not spring into being fully developed, it developed
gradually in their theropod ancestors. It started with elongation and
increased mobility (via well developed double heads of the posterior ribs in
ceratosaurs. This trend increased in avetheropods, in which the anterior
chest ribs also shortened, showing that ventilation was shifting from the
lung itself to bellows action air-sacs. Ruben et al state that theropods
"lacked an expansive sternum". In the real world that most of us live in,
large ossified sternal plates - at least as large as those of kiwis - were
described and figured in dromaeosaurs and oviraptors by Barsbold in 1983, and
have been discussed and figured in many other publications! In an odd way
this denial makes sense, in that Ruben et al 1997b use an out of date
cross-section of the ribcage of a dromaeosaur - based on incomplete
disarticulated remains - in a futile effort to deny/ignore the evidence
provided by complete ribcages, that these near birds have large sternal
plates. These big sternal plates articulated with the coracoids via a
transverely long hinge joint which allowed to sterna to help ventilate the
antero-ventral air-sacs. Ruben et al also ignore the ossified dromaeosaur
sternal ribs published by Ostrom in 1969. They fail to mention the ossified
uncinate processes present on the fighting Velociraptor. Why do not Ruben et
al make any mention of the work by Britt (1994) or Reid (1996) showing that
the pneumatic vertebrae of theropods are strongly indicative of the presence
of pulmonary air-sacs? Fact is that advanced theropods had the most bird-like
trunks of any tetrapods. 

It is equally important to understand that theropods have none of the
adapations associated with the crocodilian piston action respiratory complex.
In the latter the pubes are short (only one tenth trunk length, so they are
not "elongate" as Ruben et al claim), transverely broad (maximum
breadth/height ratio ~0.6) plates, separate along most of their length, and
they are MOBILE! The last is a bizarre adaptation that is critical to the
function of the liver pump, in which the shovel shaped pubes help move the
mass of the broad abdominal cavity during the breath cycle. In theropods the
pubes are very long (about a third trunk length), transversely narrow (ratio
~0.25), cojoined along most of their length, and immobile as in birds and
everything else. Fig 4 in Ruben et al is very misleading, because the extreme
difference in pubis structure between the dinosaurs and crocs is obscured by
comparing the posterior view of the croc to the lateral view of the dinosaur
pubes, and failing to show the dinosaur pubes in posterior or anterior view.
 There is not the slightest reason to think that theropod pubes anchored a
liver pump system. 

In crocodilians there is a well developed, rib free, broad lumbar region.
This is critical in order to allow the abdomen to expand and contract as the
liver-piston works. We mammals have a plump lumbar region for a broadly
similar reason. Theropods not only lack a lumbar region, the posterior ribs
are elongated as in birds, and the belly was narrow and deep. Lacking either
a broad lumbar region to allow strong abdominal movement, or mobile, shovel
pubes to help move the belly, the idea that an abdominal mass dominated
system could operate in theropods is absurd. Crocs have long, narrow,
flattened, flexible trunks with hyperelongated transverse processes on the
vertebrae. Theropods, including birds, have short, deep, rigid trunks with
normal transverse processes. You can hardly get a ribcage less similar to
those of crocs than those of theropods. 

In Ruben et al the pubes of Archaeopteryx are shown nearly horizontal. They
state that the pubis has "occasionally" been restored more vertically. Again
this is most misleading. There is no Archaeopteryx specimen that shows a
subhorizontal pubis. In the London specimen the pubes are completely and
entirely disarticulated from the ilia. In the Berlin specimen the pubis is
retroverted about 45 degrees, not horizontal as Ruben et al imply. I used to
illustrate the urvogel's pubis at 45 degrees, but all four other specimens
consistently show the pubis nearly vertical. This includes the newest
specimen, in which there is no evidence that the pubis is in any way
displaced from the ilium. So the pubis was subvertical and its distal end was
anterior to the tip of the ischium, like it or not. It is the Ruben et al
reconstruction that is the now rare and obsolete Heilmann version, the modern
consensus of the great majority of modern researchers is that the protobird's
pubis was subvertical. Actually, it is in dromaeosaurs that the pubes are
strongly retroverted (Barsbold 1983). 

It is also worth noting that the sternal plates in Archaeopteryx were
actually quite large, because there is a large gap between the coracoids and
the first gastralia. It's just that only the anterior part of the plates
ossified, a situation similar to some ratites. Because they sternum
articulated with the coracoids via a hinge araangement, the sternum could
help ventilate the more antero-ventral air-sacs. 

Ruben et al are also internally inconsistent and illogical. They cite the
presence of gastralia in theropods as evidence that they had a croc-like
respiratory system, yet conclude that early birds with well developed
gastralia had air-sacs. They contend that early birds were not endotherms,
yet they argue that they had air-sac ventilation. Of course, functioning
air-sacs would not be present unless the aerobic exercise capacity was
elevated above the reptile level (a few reptiles seem to have air-sacs, but
there is no evidence that they help ventilate the lungs). It is known that
the early birds were fully insulated with feathers. This would only be true
of the birds were endotherms that generated the majority of their body heat
internally. It is also becoming increasingly apparent that small theropods
were feather insulated endotherms. Indeed, if and when it is shown that the
hollow bristles adorning Sinosauropteryx and Mononykus are made of feather
type keration then the house of cards called the antidinosaur hypothesis of
bird origins will be run over by a truck. 

I suggest to all that they compare the paraoccipital process of Archaeopteryx
(Fig. 6 stereo views in Whetstone 1983) to that of Dromaeosaurus (Figs. 1,3,9
in Colbert & Russell 1969). They share a distinctive structure not observed
in other tetrapods. This is because the urvogel is a diminutive, flying
dromaeosaur. It is now known that the egg microstructure of ovirpators is the
same as that of ratites. It is careful methodical comparisons of this sort -
not superficial appraisals of photos or inherently ambiguous assumptions
about finger counts in bird embyros - that reveal the reality of bird

Reading Ruben et al reminded me of watching one of those old Twilight Zone
episodes. You know, the one in which reality was distorted all out of
recognition? Well, they were all like that.  But in this case there is no
evidence of any kind that any dinosaur had a croc-like respiratory complex,
there is a lot of evidence that they did not. Here is a more plausible
scenario. The presence of a septum in crocs and birds suggests that this is
the general archosaur condition. Therefore, a weakly developed abdominal pump
system may have been present in basal archosaurs. This was taken to an
extreme in crocodilians which adapt the liver as a powerful pump. In
tridactyl footed theropods this system was suppressed as air-sac ventilation
gradually developed in order to overcome the aerobic limitations inherent to
septate lungs. As this occurred, the septum migrated dorsally as the lungs
reduced in size, and air-sacs expanded posteriorly through the septum. The
system was probably weakly developed in Coelophysis, intermediate in
Sinosauropteryx, better developed in Archaeopteryx, and about as well
developed in dromaeosaurs as in kiwis. Only as flight evolved to high levels
in the Cretaceous did volant birds evolve a hyperenlarged sternum in order to
support enormous flight muscles, and help ventilate oversized abdominal

Yet again an attempt to refute the dino-bird link fails completely. The
evolution of the theropod-bird respiratory complex is strong evidence in
favor of an ancestor-descendent relationship. 


Barsbold R 1983 Joint Soviet-Mongolian Palaeont. Exp. 19:1
Britt B 1994 J. Vert Paleont 14(3) 18A
Colbert E & Russell D 1969 Amer Mus Novitates 2380:1
Duncker H 1979 39 in King A & McLelland J, Form & Function in 
 Birds I
Ostrom J 1969 Bull Peabody Mus Nat Hist 30:1 
Reid R 1996 BYU Geol Studies 41:25
Ruben J et al 1997b 505 in Farlow J & Brett-Surman M, The 
 Complete Dinosaur
Schmidt-Nielsen K 1972 How Animals Work 
Whetstone K 1983 J. Vert Paleo 2:439 (the text is largely incorrect)