Responses to dinosaur-lung claims

Jeff Poling

John Ruben, Terry Jones, Nicholas Geist and W. Jaap Hillenius published an article in the November 14, 1997, issue of Science titled "Lung Structure and Ventilation in Theropod Dinosaurs and Early Birds." The abstract of the article reads:

Reptiles and birds possess septate lungs rather than the alveolar-style lungs of mammals. The morphology of the unmodified, bellowslike septate lung restricts the maximum rates of respiratory gas exchange. Among taxa possessing septate lungs, only the modified avian flow-through lung is capable of the oxygen-carbon dioxide exchange rates that are typical of active endotherms. Paleontological and neontological evidence indicates that theropod dinosaurs possessed unmodified, bellowslike septate lungs that were ventilated with a crocodilelike hepatic-piston diaphragm. The earliest birds (Archaeopteryx and enantiornithes) also possessed unmofied septate lungs but lacked a hepatic-piston diaphragm mechanism. These data are consistent with an ectothermic status for theropod dinosaurs and early birds (John Ruben, Terry Jones, Nicholas Geist and W. Jaap Hillenius, "Lung Structure and Ventilation in Theropod Dinosaurs and Early Birds," Science 278 (14 November 1997): 1267.)

Ruben et al also conclude that because of the above, the dinosaurian origin of birds is "problematic" (Ibid., 1269).

The authors relied in part on controversial interpretations of various Archaeopteryx specimens and photographs of one of the Sinosauropteryx specimens to reach their conclusions (Ibid., 1268, 1269).

I leave it to the reader to track down and read the article itself. What follows are counter-arguments and criticisms of the paper.

From: GSP1954@aol.com (Gregory Paul)

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 paralleling 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 carcass. 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 protocols.

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 journal.

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 interfere with the evolution of abdominal air-sacs.

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, little work has been done on respiration in these birds, but it is clear that the sternum ventilates 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 the 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 adaptations 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 keratin 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 descent.

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 air-sacs.

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)

From: jonest@ava.bcc.orst.edu (Terry D. Jones)

We urge that readers of the dino-list regard GSP's recent novella ("theropod lung unreality") with the skepticism it deserves. All of the objections/issues raised by him (as well as others) were easily dealt with in the course of peer-review before the paper appeared in the 14 November Science. Thus, for example:

1. "The dorsal 'imperfection' in the otherwise domelike outline of the anterior portion of the abdominal compartment (see especially the Bejing slab)" -- This imperfection actually represents an artifact (actually a gouge on the Bejing slab and a corresponding raised area on the Nanjing counter slab) created by local disruption of the otherwise mostly regular plane in which the specimen was split. Thus, the apparently "missing" portion of the border of the dome-shaped liver is probably contained within the small raised area on the Nanjing counter slab. Additionally, note that fairly distinct remnants of fecal material can be seen in both slabs of the cloacal region of this individual-- further evidence that the darkened region of this specimen's trunk probably reflects the outline of the abdominal cavity subdivision with a fairly high degree of fidelity. Members of the "dream team" (all of whom had the opportunity to study these specimens under 'scopes) have corroborated all of these observations. It is also important that dinolist readers realize that at least two distinct individuals of Sinosauropteryx (one's not published) exhibit similar diaphragm-related partitioning of the visceral cavity.

2. "(i) Mobility of the crocodilian pubis and (ii) variation in pelvic girdle proportions between theropods and crocodilians"-- (i) Mobility -- unlike the theropod pubis, the croc pelvis is somewhat mobile (it doesn't participate in formation of the acetabulum). However, during diaphragmatic muscle contraction, the crocodilian pubis is functionally just as rigid as the pubis of theropod dinosaurs. This is because a stout ligament runs between the ischium and pubis and quite effectively prevents any anterior excursion of the pubic bones. The need for posterior mobility of the croc pubis is probably related to the combination of the forward projecting nature of the elongated pubis and the lateral undulatory motion utlized by these animal's during swimming/walking. Alternately, theropods probably maintained a fair amount of trunk rigidity during locomotion and required no pubic mobility. (ii) Variation in croc/theropod pelvic girdle proportions -- remember, we specifically mention that the key here is the pubis in all hepatic-piston breathers must be "...at least as long as the liver is deep..." in order to properly accommodate the ventral diaphragmatic muscles (which insert on the ventral aspect of the liver). Thus, the fact that the pubis in a markedly dorsoventrally flattened animal (i.e., crocs) is relatively shorter than the pubis in a markedly laterally-compressed group (theropods) is irrelevant.

We could go on to refute the rest of GSP's objections but, at this point, it seems unnecessary.

From: luisrey@ndirect.co.uk (Luis Rey)

We urge that readers of the dino-list regard GSP's recent novella ("theropod lung unreality") with the skepticism it deserves. All of the objections/issues raised by him (as well as others) were raised and easily dealt with in the course of peer-review before the paper appeared in the 14 November Science.

Gosh... these people must be desperate. Not only CAN'T they prove any of their own points but still are also clinging to their own falsehoods and mistakes.

I was there when Luis Chiappe rose his voice accusing them of using an outdated and badly reconstructed Archaeopteryx pelvis to make their point and the only answer he could get from them was embarrassed silence. I also can testify that all the argument of the collagen fibres in Sinosauropteryx came tumbling down not only as Philip Currie was demonstrating the hollowness of the 'spiny' structures, but right from the moment Jones and Ruben were showing slides of the real collagen fibres (that looked like fuzzy 'fur' and were patently some other kind of tissue that had nothing to do with Sinosauropteryx proto-feather structures). I know, this must look like a reiterative post over things that have already been said, but...as I said in a post before: when some people don't want to see what is in front of them, there is no hope that they will ever see it.

P.S. There will be even more surprises with respect of air sacs in theropods in the very near future.

From: luisrey@ndirect.co.uk (Luis Rey)

I have decided to answer Terry Jones latest arguments about the SVP discussion in public, to see if it is useful and fuels some more debate.

What *evidence* did Chiappe give that convinced you that our reconstruction was wrong? As I remember, my answer was not "embarrassed silence." What I said was that some people we talked to at the meetings said our reconstruction may be *slightly* exaggerated, but that the pubis of Archaeopteryx was not vertical; it extended *well* beyond the posterior end of the ilium and ischium.

Well, you were the experts and the people speaking in authoritative terms in a public meeting. If you haven't sorted out all the details properly how would you expect credibility?

>I also can testify that all the argument of the collagen fibres in
>Sinosauropteryx came tumbling down not only as Philip Currie was

Again, what *evidence* did Phil Curry give? As I remember, Larry Martin stood up and explained that these were not hollow structures, but were, in all likelihood, scales. Remember that 4 members of the "dream team" that studied the specimens in great detail agreed that there was no feather structure. By the way, although my name and Ruben's where on the abstract, it was Nick Geist who gave that presentation.

The micro-photographs that Phil Currie exhibited showed clearly that they were hollow structures. So now you go for the 'scale' thing. Well I admit that that sounds much more reasonable than trying to convince us that they were collagen fibers... because they are NOT! And it can be deduced just by sight. The collagen fibers you showed in your slides were nothing similar to the rather 'thick' (compared to the collagen fibers) structures >covering< Sinosauropteryx and that can easily be isolated one by one. This has nothing to do with (again) the furry/fuzzy integument formed by the mass of collagen fibers. Besides: Sinosauropteryx structures can be seen on top of the skin not underneath it. Patches of skin are perfectly discernible, and the structures are on top of these. If you accept the 'scale' status of Sinosauropteryx structures then we go directly for the proto-feather possibility and above all the fact that such 'scaly' coverage can very well be, in fact, insulatory. A good chemical analysis will help I'm sure. On the other hand you still haven't answered or showed convincingly that GSPaul arguments about theropod lungs are false or not good enough... At least I can say that they are better that trying to give Sinosauropteryx an 'aquatic theropod status'. Air sacs will convince you at the end.

Note: as regular readers of my site already know, personal communication with one of the dream team members, Alan Brush, indicates that, unless he's changed his position, he did not conclude "that there was no feather structure" as claimed by Jones. He concluded that the "fuzz" of Sinosauropteryx is unlike modern feather morphology. That's different from concluding no feather structure at all. Indeed, Brush explicitly states that electron microscopy is still needed to determine whether the fibers have or lack any featherlike structure or attributes, modern or not. -- ed.

From: GSP1954@aol.com (Gregory Paul)

Still waiting for Rod Serling to show up. This, because the posts by Jones et al replying to my post on the Ruben et al paper in the Nov 14 Science was itself peculiar.

It seems that Jones etc. agree with my observation that there is breakage on the main slab of the type Sinosauropteryx. This is astonishing, especially because they made no mention of this in Ruben et al. In fact, in their Fig. 5A they show the tip of the topmost arrow ending exactly at the edge of the breakage, leading to the impression that this is part of the supposed arc of the septum. It is not! There is no way to tell what the shape of the dark area is in this area, because we cannot see it (more prep work would be useful). That the breakage was never mentioned in their paper, and an arrow points to the break as a border, is deeply unsettling to say the least.

Jones et al then go on to assert that the breakage in the type does not really matter because it "is important that dinolist readers realize that at least two distinct individuals of Sinosauropteryx (one's not published) exhibit similar diaphragm-related partitioning of the visceral cavity". They also state that "members of the 'dream team' (all of whom had the opportunity to study these specimens under 'scopes) have corroborated all of these obsevations". This appears to be in their tradition of A) commenting on specimens they have not seen, B) making claims they cannot verify, C) implying that other agree when they may not. I've received messages from two people -- one a member of the "dream team" -- who have seen all three specimens and carefully examined them, and in no way do they corroborate the observations of Ruben et al. Larry Martin probably does, but do Jones etc. have endorsements from others dream team and others who have seen the specimens? I saw a slide of the second Sinosauropteryx during Phil Currie's talk at SVP -- one person who does not agree with their observations -- and there was no trace of a septum. This is fact. All the Sinosauropteryx specimens will soon be described properly and carefully. Do not count on the claims by the Oregon State group being verified.

Jones et al. try to defend their characterization of crocodilian pubes as being "elongate". For the record, in Ruben et al. they state that "the distinctive crocodilian pubis is robust and elongate (at least as long as the liver is deep), much like the pubis in theropod dinosaurs (Fig. 4)". Lots of problems here. First, I suggest all those interested refer to their Figs. 3&4. The pubes are not "at least as long as the liver is deep", the bone is only about 60% as long as the liver is deep! The Twilight Zone theme creeps in again as one wonders, don't they look at their own figures? In other crocodilian specimens the pubis seems to be even shorter (only 30% liver depth in H Duncker 1978). Now, Webster's defines elongate as "stretched out" or "long in proportion to width". Croc pubes are only about one tenth as long as the trunk, and when articulated together are broader than they are long! I am hard pressed to come up with archosaurs with pubes as short as those of crocodilians, only a few "thecodonts" are similar. Most archosaur pubes are more elongate. Fact, crocodilian pubes are not elongate.

What are elongate -- to an extreme among archosaurs -- are the pubes of theropods and birds. In theropods avian and non the pubes are fully one quarter to one third trunk length, and when articulated together are three or four times as long as they are wide. Now THAT'S elongate!

It cannot be overemphasized how extremely different crocodilian and theropod pubes are. In anterior view the latter become even narrower distally, and the pubic boot when present faces entirely laterally and does not participate in supporting the abdomen. In crocodilians the pubes become much broader distally, because they form shovel shaped plates that help support the belly. To see just how different they are compare Fig. 4A (croc pubis) in Ruben et al. to Fig. 2d (theropod pubis) in F Nova & P Puerta (Nature 387:390 1997). Of course, Ruben et al did not bother to illustrate croc and theropod pubes in functionally equivalent, anterior views, doing so would have revealed the profound difference.

Because the theropod pubic boot faces entirely laterally, and the pubis is so narrow transversely, it is not at all clear how the could support massive, anteriorly directed respiratory muscles, as do the transverely broad pubes of crocodilians. In addition to that, some theropods do not even have a pubic boot! This includes primitive Triassic Coelophysis and near avian, Cretaceous troodonts. The pubic boots of Archaeopteryx and some early birds are much larger than those of some theropods -- and are just as ill suited for supporting respiratory muscles. There is no evidence that the pubes of theropods had anything to do with a liver-pump system.

On a related issue, Hou et al (1996 Science 274:1164) claim that "uncinate processes hinging on the ribcage are found in all ornithurine birds", and cite Ruben as asserting that the early birds that lack these processes would not be able to ventilate the abdominal air-sacs. As a result, early birds could not be endotherms. Today, at the Smithsonian, I checked a number of ribcages of screamers, which are peculiar relatives of ducks. Not a trace of uncinate processes in any of them. Even rummaged through the box bottoms just to be sure. Emus do not have them either. Well, one really big adult did have one very short (about 7 mm) projection that was doing the best it could to be an uncinate process. So, both flightless and flying birds do not need to have ossified uncinate processes in order to ventilate their air-sacs, and be endotherms. It is possible that uncinate processes have more to do with bracing the ribcage than with respiration, the problem is poorly understood. As for early birds without uncinate processes, they were heavily insulated with body feathers. No small ectotherm is insulated, it prevents them from readily absorbing the large amounts of environmental heat they require. Only endotherms (i.e., vertebrates with [metabolic rates] high enough to produce the majority of their body heat internally) that need to retain their internally generated heat are insulated. This is all so obvious, yet we actually have people arguing that feathered, flying birds had reptile-like energetics. How very perplexing! Rather disturbing too.

About feathers, kiwis have very long head feathers that consist mainly of a simple shaft that looks just like cat whiskers. Probably serve similar purposes. Looked at vulture heads, their heads have a thin fuzz of simple fur-like feathers. Except for being thin, it looks like the bristles that adorn Sinosauropteryx bodies, arms and legs.

From: Stanley Friesen <sarima@ix.netcom.com>

Actually, I find the article on post-cranial pneumaticity in dinosaurs in the Currie & Padian Encyclopedia to effectively falsify everything Ruben et alii say. That article alone is worth one third the price of the book (it an expensive book).

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.

This is very interesting, and fits in well with the pneumaticity article. The earliest evidence for pneumaticity in basal theropods is in the anterior dorsals and posterior cervicals - that is it indicates *thoracic* air-sacs. Evidence for abdominal air-sacs is not found except in highly derived ceolurosaurian lineages (birds, oviraptosaurs and so on).