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Anatomy and Systematics of the Confuciusornithidae &Lpar

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Anatomy and Systematics of the Confuciusornithidae &Lpar Reviews EDITED BY REBECCA L. HOLBERTON Thefollowing critiques express the opinions of the individual evaluators regarding the strengths, weaknesses,and value of thebooks they reviem As such,the appraisals are subjective assessments anddo not necessarilyreflect the opinions of theeditors or anyofficial policy of theAmerican Ornithologists'Union. The Auk 117(3):836-839, 2000 Anatomy and Systematicsof the Confuciusorni- papermay be interpretedto the contrary,so to this thidae (Theropoda: Aves) from the Late Mesozoic reviewer the issue remains unresolved. of NortheasternChina.--L. M. Chiappe, S. Ji, Q. Ji, Most of this publicationconsists of descriptive and M. A. Norell. 1999. Bulletin of the American Mu- anatomy,which had been treatedin at least eight seum of Natural History, Volume 242. 89 pp. ISSN shorterpapers on Confuciusornisby other authors. In- 0003-0090.Paper, $8.60.--Only a few yearsago, the stead of summarizing this literature, however, fossilrecord for the earliestknown period in theevo- Chiappeet al. haveselectively chosen from it various lution of birds was depressinglymeager. From the pointsof whichto be critical,even when the view in lateJurassic Archaeopteryx to the lateCretaceous Hes- questionmay not be the mostcurrent. Such selectiv- perornisand Ichthyornis,only scrappyavian remains ity, apartfrom being disingenuous, detracts from the were known. This changeddramatically with the usefulness of the work as a whole, which cannot be discoveryof birds in early Cretaceouslake deposits relied upon to supercedethe earlier literature.For in Spain and particularlyin northeasternChina's example,Hou et al. (1999)are citedonly to saythat LiaoningProvince, where thousands of fossilshave Chiappeet al. were"unable to examinethe recently been recovered,including several different kinds of describedConfuciusornis dui." Yet,nowhere is it men- birds. Incredible as it once would have seemed, one tionedthat the main importanceof this specimenis that it preservesthe hornyrhamphotheca. Likewise, of theseearly Cretaceousbirds, Confuciusornissanc- Chiappeet al. sparenothing to reproduceand criti- tus,is now known from hundredsof specimens. cize an outdatedreconstruction by Hou et al. (1996), The work reviewed here has the superficialap- madewhen only a few incompletespecimens of Con- pearanceof a monographictreatment of Confuciusor-fuciusornis existed, but they neverallude to the pre- his and its relatives.Unfortunately, it is not. The au- posterousreconstruction on the cover of Scientific thors, steeped in cladistic fundamentalism,have Americanthat accompaniedan articleby Padianand beenamong the moreinsistent proponents of the or- Chiappe (1998)in which Confuciusornisis depicted igin of birds from theropoddinosaurs, with its at- like somemedieval rendition of a dyspepticphoenix tendantcorollaries, such as the originof flight from that had just dismountedfrom a horse. the groundup. The presentwork appearsto be but It had previouslybeen determined that the skullof an attemptto put a dinosaurian"spin" on the still- Confuciusornisexhibits the primitive diapsidcondi- emerginginterpretations of the significanceof Con- tion and, in a separatesection on kinesis (pp. 72-75), fuciusornis. Chiappeet al. arguethat the skullwas akinetic. Food Mostof the specimensfrom the Liaoningdeposits processingby a toothlessbird with an akineticskull were collected,and to someextent prepared, not by would be highly problematic,so a more detailed scientists,but by thoseintent on sellingthe speci- study of the wealth of specimenspotentially avail- mens,so that the possibilityof artificial "enhance- ablewill morelikely showthat the skull wasin fact ment"of fossilsis ratherhigh. Indeed, Chiappe et al. kinetic. (p. 68, figures 60 to 63) note several specimensof No onehad detecteduncinate processes on theribs Confuciusorniswith partsglued on from otherindi- in anyof the specimensof Confuciusornishitherto ex- vidualsor with structuresthat havebeen sculpted amined. Nor do these processesoccur in Archaeo- out of matrix with a binder.It has also been sug- pteryxor othervery early birds. Supposeduncinate gestedthat the otherwiseinexplicable proximal hu- processeshave recently been reportedin late Creta- meral foramen of Confuciusornisis an artifact. Al- ceoustheropods, however (Clark et al. 1999).If they thoughChiappe et al. denythis, information in their are invariably absentin late Jurassicand early Cre- 836 July2000] Reviews 837 taceousbirds, it would suggestto any reasonable of the outermostprimary feathers.Regrettably, in personthat the structuresare unlikelyto be homo- noneof their photographsare all of the elementsof logousbetween birds and dinosaurs.Therefore, for the hand of Confuciusornisclearly displayed,and advocatesof the theropodorigin of birds, it would thereis no interpretivediagram of the hand. be desirableto find uncinateprocesses in early birds Vazquez(1992) identified a number of specializa- or to wishtheir absenceaway. Chiappe et al. do both. tions of the wrist in all modern birds that he consid- They illustrate(figure 34) what they claim to be un- ered to be necessaryfor flappingflight. He suggest- cinateprocesses articulating with six ribs in only a ed that the wrist in Archaeopteryx"was probablyin- singlespecimen of Confuciusornis,from which they capableof executingthe kinematicsof modernavian go on to speculate"that their absencein otherbasal poweredflight." Becausethis hasbeen seized upon birds... may be due to preservationalfactors or on- as supportingthe "ground up" theory of the origin togeneticdevelopment" (pp. 32-33). This goesbe- of flight, what bearingdoes the morphologyof the yondspecial pleading, because the authorscould not wrist of Confuciusornishave on thisquestion? Chiap- possiblybelieve that this would explainthe absence peet al. do not cite Vazquezand do not addressthis of uncinateprocesses in all of the specimensof Ar- issue.They describe the ulnare (which nowhere is la- chaeopteryxor in any of the hundredsof otherspec- beled in their illustrations)as much smaller than the imens of Confuciusornis. radiale, a condition unlike modern birds. Another As shown(fig. 34), the so-calleduncinate process- importantdifference is that the alular metacarpalis esoriginate only on theposterior six ribs, whereas at notfused to themajor metacarpal, and the major and least two strong ribs anterior to thesedo not have minor metacarpalsare not fused distally. Therefore, processes,which would be unlike any known bird. it seemssafe to saythat Confuciusornisdid not have Also, "the uncinate processesare long and extend all of the adaptationsof the modernavian wrist. over nearly two subsequentribs" (p. 32), an utterly One aspectof its wrist must havebeen as well de- unheardof condition.And judgingfrom the illustra- velopedas in modernbirds, however,as inadver- tion, some of the ribs must have had two tmcinate tently demonstratedin figure70, which showsa re- processes,which is evenmore implausible.Clearly, constructedskeleton of Confuciusorniswith the shad- thesecannot be uncinateprocesses and are probably ed outline of the body and wings. Here the hand is displacedgastralia or ribs that havebeen misrepre- shownextending down at an angleof about45 ø from sentedto servea larger purpose. the horizontal.In this position,had the bird beenter- The furcula of Confuciusornisis large and robust restrial, as the authors would prefer, its long pri- and the scapula and coracoid are fused; "conse- maries would have been pressed down and bent quently,the acrocoracoidprocess is not developed" againstthe surfaceof the ground. Instead,the pri- (p. 29). Therefore,the shouldergirdle is more like mariesare shownprojecting straight back, horizon- that of Archaeopteryxthan that of modernbirds. The tally, as thoughthey were comingoff the ulna per- sternumis a large ossifiedplate but lacksan ossified haps. Thus, it can be seenthat with its very long carina. From this osteologicalevidence, it is clear wing, whetherit cameto rest on the groundor on a that the supracoracoideusmuscle was not function- tree limb, Confuciusornishad to be able to flex the ing as a dorsalelevator in Confuciusornis.The lack of wrist to the samedegree as in modernbirds to keep an acrocoracoidprocess and other adaptationsfor its primariesclear of the substrate. the supracoracoideusto functionas a dorsalelevator The pelvishas the avian retropubicconstruction, were among the main evidenceused by Ostrom but with the primitivecondition of havingthe pubes (1976) and othersto argue that Archaeopteryxwas at fused distally. The tarsometatarsusis short and best a poor flier or even a "pre-flight" stagein the squat,much shorterthan the tibiotarsusor femur, evolutionof avian flight. Chiappeet al. do not men- which is very unlike any truly terrestriallyadapted tion any of this in connectionwith Confuciusornis,birds and militatesagainst any interpretationof this however. bird being at all cursorial. The humerusis robust,with a very largepectoral Perhapsthe mostspectacular aspects of Confucius- crest.It is slightly longerthan the radius and ulna, ornis are revealedby the preservationof feathers and the hand is muchlonger than either the forearm with the skeleton.These indicate that the wing was or the humerus.Chiappe et al. (p. 33) considerthis extremelylong and pointed,with the primarieshav- to be "clearlyprimitive" but do notexplain their rea- ing veryasymmetrical vanes. There was, however, no soning. alula on the outer digit, whereasthe alula has been Thehand consists of threedigits, the outerand in- argued
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