[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

Critique of a critique



Hi everyone.  While looking through BioOne, I chanced upon a review of Chiappe et al.'s Confuciusornithidae monograph written by Storrs Olson.  I was kindly given a copy of Chiappe et al. by coauthor Mark Norell and I find many of Olson's critiques unfair and biased, which is why I'm writing this defense.
"The authors, steeped in cladistic fundamentalism, have been among the more insistent proponents of the origin of birds from theropod dinosaurs, with its attendant corollaries, such as the origin of flight from the ground up."
Here again, we see the common misconception that if birds are dinosaurs, flight must have evolved from the ground.  This ignores the possibility of small arboreal theropods, realized in recent years with the discovery of Rahonavis and Microraptor.
"It has also been suggested that the otherwise inexplicable proximal humeral foramen of Confuciusornis is an artifact. Although Chiappe et al. deny this, information in their paper may be interpreted to the contrary, so to this reviewer the issue remains unresolved."
Chiappe et al. state "...many of the specimens studied here have been carefully prepared, and there is little doubt this foramen was a true feature of Confuciusornis sanctus." and, "Of these, specimens .....(specimen numbers)...... were fully prepared at the American Museum of Natural History and are the nucleus of this study."  If the AMNH can't prepare a specimen accurately, who can?  I see nothing in Chiappe et al. that could be interpreted as supporting an unnatural origin for the humeral foramen and no reason to doubt its existance.
"Instead of summarizing this literature, however, Chiappe et al. have selectively chosen from it various points of which to be critical, even when the view in question may not be the most current. Such selectivity, apart from being disingenuous, detracts from the usefulness of the work as a whole, which cannot be relied upon to supercede the earlier literature. For example, Hou et al. (1999) are cited only to say that Chiappe et al. were “unable to examine the recently described Confuciusornis dui. Yet, nowhere is it mentioned that the main importance of this specimen is that it preserves the horny rhamphotheca."
I know of nothing in Chiappe et al. which conflicts with recent work, when that work is correct.  Olson's example is not valid, as the main importance of C. dui was to establish confuciusornithids had a complete diapsid temporal arrangement.  Chiappe et al. discuss the presumed presence of a horny rhampotheca (pg. 18, 50).  While I would have enjoyed discussion of C. dui, the species was described the year Chiappe et al. was published.
"Food processing by a toothless bird with an akinetic skull would be highly problematic, so a more detailed study of the wealth of specimens potentially available will more likely show that the skull was in fact kinetic."
This is highly unlikely due to several features Chiappe et al. describe (premaxillae firmly attached to frontals; jugal high anteriorly; jugal-postorbital suture; quadratojugal-squamosal suture; jugal anchored to palatine by ectopterygoid?).
"They illustrate (figure 34) what they claim to be uncinate processes articulating with six ribs in only a single specimen of Confuciusornis, from which they go on to speculate “that their absence in other basal birds may be due to preservational factors or ontogenetic development” (pp. 32–33). This goes beyond special pleading, because the authors could not possibly believe that this would explain the absence of uncinate processes in all of the specimens of Archaeopteryx or in any of the hundreds of other specimens of Confuciusornis."
Olson obviously didn't read the paper clearly enough, as the authors clearly state "Remnants of uncinate processes or their caudodorsally oriented molds are also visible in several other specimens (eg., GMV-2130, GMV-2146, and GMV-2147)."  In fact, these can be seen in figure 28 (GMV-2130) and figure 31 (GMV-2147).
Regarding the statement preservational factors could not be responsible, I wrote the following a while back-
How many dromaeosaurid specimens have uncinate processes preserved?  One (the fighting specimen of Velociraptor).  And how many oviraptorid specimens?  Two (IGM 100/979 and IGM 199/1002).  It may seem there are a ton of enantiornithine specimens out there with obviously absent uncinates, but despite the number of named species, very few good specimens exist.  Most well-preserved enantiornithines (Concornis, Eoalulavis, Spanish nestling, Sinornis, Cathayornis, Neuquenornis, Boluochia, Longchengornis, Cathayornis? caudatus, Cuspirostrisornis, Largirostrornis) have only a few scattered ribs preserved at most (or are broken in that area, like Sinornis) and often preserve small structures that could easily be uncinates, although they could just as easily be sternal ribs or dorsal rib fragments.  The same is true of Changchengornis, which preserves two fragments that may be uncinates, but might not be as well.  The only specimen you might be able to make a case for is Iberomesornis, which has an articulated ribcage on its left side.  This specimen is clearly juvenile however, due to the unfused metatarsus and sacrum, etc., which could be a plausible reason for the apparant lack of ossified uncinates.
"One aspect of its wrist must have been as well developed as in modern birds, however, as inadvertently demonstrated in figure 70, which shows a reconstructed skeleton of Confuciusornis with the shaded outline of the body and wings. Here the hand is shown extending down at an angle of about 45° from the horizontal. In this position, had the bird been terrestrial, as the authors would prefer, its long primaries would have been pressed down and bent against the surface of the ground. Instead, the primaries are shown projecting straight back, horizontally, as though they were coming off the ulna perhaps."
Untrue.  Tracing the primaries back to the forelimb clearly shows they would have attached to the manus in figure 70.
"The pelvis has the avian retropubic construction, ..."
Just a question: Is the term "retropubic" used in relation to bird pelves?  I always thought it was opisthopubic.  A Google search for retropubic only brings up medical references.  It looks to me like an attempt to make birds seem less dinosaurian....
"That Changchengornis is a valid genus is highly doubtful. ... What is apparent is that it has the same wing shape, the same two elongated rectrices, the same distinctive shape of the humerus, and the same overall proportions of the wing and leg as Confuciusornis."
Chiappe et al. find twelve differences between the genera.  These are not variable within Confuciusornis specimens and appear valid.  The many similarities simply support placing the two in the same family, as Chiappe et al. have done.
"At one point (p. 67), Chiappe et al. say of Changchengornis that “the phalangeal formula of the foot is typical of theropod dinosaurs: 2-3-4-5-x ” Who do they expect to impress with this choice tidbit? It happens to be true, but it is also true that the same phalangeal formula is found in Confuciusornis (p. 47) and is the typical and primitive condition found in almost all birds. Such gratuitous statements are characteristic of the propagandizing that the theropod proponents of avian origin seem to think is necessary to bolster their hypothesis."
A might harsh, don't you think? Perhaps Olson is annoyed at the 2-3-3-3-3 formula of Megalancosaurus or the 2-3-4-5-2 formula of Cosesaurus. ;-)
"In the same vein, Chiappe et al. refer to the digits of the hand in the Confuciusornithidae with the theropodan formula of I, II, III, whereas it has been repeatedly shown (Holmgren 1955, Hinchliffe 1985, Burke and Feduccia, 1997) and conceded (Wagner and Gauthier 1999) that the digits of the hand in birds are II, III, IV. Because this is such compelling evidence against the theropod origin of birds, it is hardly any wonder that Chiappe et al. cannot bring themselves to use the correct formula."
Or perhaps good genetic evidence shows frameshafts can occur and change which digits appear to be developed....  Just because the digits of neornithines are 2-3-4 doesn't mean they always were.
In all fairness, Olson does mention some actual problems with the paper (lack of behavioral analysis or biomechanical considerations, few reconstructions and measurement tables), but the positives far outweigh the negatives.
"Thus, if Chiappe et al. actually understand the true significance of Confuciusornis, then they have done their best to prevent it from being revealed. Their paper will stand as an exemplar of manipulation of information to conform to preconceived ideas, but it is otherwise insufficiently credible or comprehensive to constitute a lasting addition to knowledge."
Ouch.  I completely disagree.  This monograph is the best available for a non-ornithurine pygostylian.  A very detailed description compliments extensive photographs.  Such a document is sorely needed in a time when complete basal pygostylians are mentioned briefly in Science/Nature or described in Chinese.
 
Olson's review can be read here-
http://www.bioone.org/bioone/?request=get-document&issn=0004-8038&volume=117&issue=03&page=0836
 
Mickey Mortimer