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Kurochkin 2006 critique

Kurochkin, 2006. Parallel Evolution of Theropod Dinosaurs and Birds. Entomological Review, Vol. 86, Suppl. 1, pp. S45?S58.

Kurochkin's latest (2006) paper is an interesting entry into the BAND camp. In a way, it is the antithesis of MANIAC (Maniraptorans Are Not In Actuality Coelurosaurs) as endorsed by Feduccia, Martin and Czerkas. Instead, Kurochkin believes Archaeopteryx and enantiornithines are coelurosaurian dinosaurs, while confuciusornithids, Protoavis and euornithines are descended from a more basal archosauromorph.
As could be expected, Kurochkin rejects cladistics. He cites Dodson (2000), with such wonderful rationales as "parsimony (economy), contradicts the essence of the evolutionary process in nature, because evolution is wasteful in every respect." Er, if this were true, morphology wouldn't reflect phylogeny at all. Also presented are falsehoods like "Cladistists exclude stratigraphy, embryology, physiology, ecology, and biogeography from consideration and take into account only formalized morphological characters, irrespective of space and time;."
On the plus side, Kurochkin recognizes theropods have numerous birdlike characters and correctly understands the BAD viewpoint for the most part. He lists some of the problems BADists have with BANDists, but waves them away by referencing his own 2001 paper and Feduccia's (1999) fossil bird book. The later certainly doesn't address the problems satisfactorily, though I haven't read Kurochkin (2001), so can't comment further on this matter. He does seem to think the contradictory conclusions of various BAD cladograms (e.g. the varying sister taxa of birds) somehow weaken the BAD hypothesis, which doesn't follow from logic. Also, I'm not sure where Kurochkin has been in the last few decades, but he says "At the same time, theropods are referred to as nonavian theropods. This implies (but has never been said) that birds (= Avialae) are avian theropods, feathered dinosaurs, or living dinosaurs (Gauthier and Gall, 2001)." Surely the 'birds are dinosaurs' slogan has been widespread, enough to inspire DML threads by those annoyed by it.

Kurochkin notes the numerous feathered coelurosaurs now known, also crediting Early Jurassic theropods, pterosaurs and Psittacosaurus with sufficiently similar structures (the former is based on Gierlinski's (1996) tracks which preserve vegetation mats, not feathers). He suggests that because filamentous integument was so widespread, it should not be assumed to be homologous in coelurosaurs and birds. What he ignores is the detailed similarity between microraptorian and ornithurine stage III feathers, for instance. Even if Psittacosaurus' quills and pterofuzz are homologous to feathers, they lack barbs and a central rachis, making them stage I in Brush's scheme.

The author correctly notes some characters are convergently present in ornithurines and some maniraptoran lineages, such as oviraptorids' double-headed quadrate and Nomingia's pygostyle. Yet these and other attempts to dehomologize characters (uncinate processes, opisthopuby) aren't defended rationally. The fact structures serve different purposes in different taxa does not mean they lack homology, nor does differing morphology indicate lack of homology. As an obvious example, whale tails have a different purpose and morphology than cow tails, yet both are homologous.

Both of these paragraphs illustrate a fallacy of Kurochkin's- that if a structure is found to be homoplasious in two taxa, its homology in a third taxon can be safely doubted. So because pygostyles developed in Nomingia and ornithurines convergently, it's easier to assume the pygostyles of enantiornithines and ornithurines are convergent. Yet evolutionary lineages are independent of one another, and no character is a priori immune to homoplasy.

Kurochkin discusses the I-II-III II-III-IV disparity between basal theropods and neornithines, and notes that digital frameshifts have been shown to occur in living taxa. He then falls into the classic BAND trap of naive falsification (Makovicky and Dyke, 2001)- "The supporters of the dinosaurian hypothesis for the origin of birds believe that this is an open question that requires further examination. However, the recognition of distinctions between theropods and birds in the manual formula alone conflicts with the sisterly or ancestor?descendant relations of these groups." And even more explicitly- "To conclude the consideration of the major characters shared by theropod dinosaurs, Archaeopteryx, and birds, note that, as relationships are estimated, cladistics do not take into account differences; nonetheless, we believe that they may be of primary significance for this purpose. Such differences unequivocally indicate the absence of direct relationships of living ornithurine birds with predatory dinosaurs." Kurochkin states the ornithurine tarsometatarsus could not evolve from an arctometatarsus, but no BADist claims it did. Oddly, he says heterocoelous vertebrae cannot evolve from opisthocoelous ones, though several enantiornithines have partial heterocoely, as do some deinonychosaurs. Even stranger, he seems to think birds' single oviduct couldn't evolve from one of a theropod's two oviducts, but as far as I can tell amniotes primitively have two oviducts. So unless birds aren't amniotes, they had to lose an oviduct somewhere. Finally, he believes theropods had a diaphragm giving them a fundamentally different respiratory mechanic than birds, despite the numerous objections raised by Paul et al. (immobile pubis, etc.) and fundamentally birdlike thoracic morphology of maniraptorans including enantiornithines (airsacs, uncinate processes, large sterna, ossified sternal ribs, etc.).

Kurochkin's cladogram is-
However, his phylogram shows Vorona being derived from enantiornithines. It also indicates he views Wyleyia, Horezmavis, Gargantuavis, patagopterygids and kuzholiids as ornithurines.

Discussing Archaeopteryx, Kurochkin correctly notes most of its birdlike characters have been found in other theropods, though many of his examples are subtly flawed. For instance, he states one such character is "the double-condyled quadrate (although it is single-condyled in Archaeopteryx and Enantiornithes, while in Ornithurae it is double-condyled)." In actuality, most coelurosaurs (including tyrannosaurids, caenagnathoids, troodontids and Archaeopteryx) have a surface on the quadrate which contacts the braincase. Most basal euornithines are similar, an in fact the only taxa with a distinct double-condyled morphology are Shuvuuia, Confuciusornis, Enaliornis and many neoavians. Euornithines with basically single-headed quadrates include Archaeorhynchus, Patagopteryx, Yixianornis, Apsaravis, Potamornis, Hesperornis, Ichthyornis, paleognaths and galloanserines. Another example- "the fusion of the proximal tarsals with the tibia and fibula, at least in adults (they fuse in the majority of adult theropods; however, in ornithurine birds, the fibula does not participate in this fusion)." These do not in fact fuse in most adult theropods. Nor do most enantiornithines leave their distal tarsals unfused, contra Kurochkin. He goes on to list several characters more recently proposed to unite Archaeopteryx with birds (external naris extends far posteriorly, few caudal vertebrae, reduced postacetabular process, etc.), but confusingly says "The artificiality of placing Archaeopteryx close to Ornithurae based on such characters does not need any proof." Well Kurochkin, yes it does. Finally, Kurochkin lists 16 "derived" characters Archaeopteryx shares with theropods but not with ornithurines. Symplesiomorphies, of course (how can he possibly think the presence of an ectopterygoid or long pubic symphysis is DERIVED within Reptilia?!). Taking each in turn-
(1) Wide dorsal end of the lacrymal. Also in Archaeorhynchus.
(2) The anteriorly directed medial condyle of the ventral portion of the quadrate. Also in Confuciusornis and Hesperornis.
(3) The presence of the ectopterygoid. Also in Confuciusornis.
(4) Uniform width of the body of the scapula throughout its extent. Also in Confuciusornis and Hesperornis. Absent in enantiornithines.
(5) Flat subquadrate coracoid. Absent in enantiornithines.
(6) Special tubercle located cranioventral to the glenoid on the coracoid. Also in Patagopteryx and Hesperornis. Modified into the acrocoracoid in enantiornithines, as in confuciusornithids and ornithurines.
(7) The projection of the plane of the proximal head of the humerus is directed perpendicular to the distal head. Also in Confuciusornis. Absent in Neuquenornis and many theropods.
(8) The forearm is shorter than the manus and humerus. Also in confuciusornithids, Hongshanornis, Yixianornis. Absent in many enantiornithines.
(9) Digits IV and V of the manus are reduced. Only absent in ornithuromorphs according to Kurochkin due to his disbelief in the frameshift.
(10) The semilunate carpal is articulated with metacarpals 1 and 2. Ditto.
(11) The ungual phalanges of the manus are large, with large tubercles for the insertion of flexor tendons. Also in confuciusornithids. Absent in enantiornithines.
(12) Development of the lesser trochanter in the proximal part of the femur. Absent in enantiornithines.
(13) Long preacetabular part of the ilium compared to the short postacetabular part. Also in Confuciusornis, Archaeorhynchus, and Patagopteryx. Absent in Aberratiodontus.
(14) Development of a peduncle on the ilium for the articulation with the pubis. Also in Confuciusornis, Archaeorhynchus, Patagopteryx, Apsaravis, Gansus, Ichthyornis and Iaceornis.
(15) Split of the caudal end of the ischium. Absent in enantiornithines.
(16) The pubis has a large symphysis. Also in confuciusornithids, Archaeorhynchus, Hongshanornis, Yanornis and Yixianornis.
Remember that in Kurochkin's view, confuciusornithids are on the bird branch while enantiornithines are on the theropod branch. So of the 14 non frameshift-influenced "theropod" characters above, confuciusornithids have nine. At least some enantiornithines lack nine of them. Of the remaining five "ornithurine" characters, four are missing in at least basal euornithines. The remaining character involves the ectopterygoid's absence, which has not been verified in any ornithurine more basal than Hesperornis. If confuciusornithids (as basal birds) have most theropod synapomorphies, why not just have birds derive from theropods? And if enantiornithines can lose theropod synapomorphies, why not let birds lose them as well?

Kurochkin believes many flight-related characters in enantiornithines and ornithurines arose through convergence, a conclusion I'm increasingly agreeing with as taxa like Hongshanornis and Archaeorhynchus are described. This does not mean every ornithothoracine character is convergent however. Kurochkin uses symplesiomorphies to group enantiornithines with Archaeopteryx instead-
1. "the quadrate has a laterocaudal condyle;" Seen in all Mesozoic theropods, including Confuciusornis and Hesperornis.
2. "the quadratojugal and quadrate are articulated by the adjacent joint (Martin and Zhou, 1997);" As in Confuciusornis and Hesperornis. How else would they articulate?
3. "the distal head of the femur has a lateral crest;" Absent in Archaeopteryx (Chiappe, 2002).
4. "the proximal ends of the metatarsals are arranged tightly to form an integral transverse row." I honestly don't understand this character, though it seems to be a standard in the sauriurine lists. All theropod metatarsals are tightly arranged in a mesotarsal manner. Perhaps he means metatarsal III is not displaced plantarily or that there is no intercotylar eminence, but this is true of Archaeorhynchus too, not to mention confuciusornithids. Indeed, there's really no metatarsal feature Archaeopteryx and enantiornithines share to the exclusion of confuciusornithids.
Finally, Kurochkin mentions the LAGs found in enantiornithines, and indeterminate growth of the latter(?) and Archaeopteryx. Both are archosaurian plesiomorphies that cannot support Sauriurae however. As no valid characters support Sauriurae, the ornithothoracine characters which are seen even in basal enantiornithines and euornithines (pygostyle, strut-like coracoid, trochanteric crest, etc.) may be used to construct the phylogeny. Interestingly, the addition of basal euornithines has lowered the support for Ornithothoraces in Clarke's matrix recently (Zhou and Zhang, 2005, 2006), but that groups confuciusornithids and enantiornithines together, in contrast to Kurochkin's phylogeny.

Kurochkin places confuciusornithids on the ornithurine line in his phylogeny, seemingly due mostly to the absence of LAGs. As seen above, it would make much more sense for him to place them in his theropod lineage.

Kurochkin lists 18 characters for his Ornithurae (= Ornithuromorpha or Euornithes; excludes confuciusornithids and Protoavis). Of them, several are missing in basal taxa such as Archaeorhynchus and Hongshanornis (heterocoelous cervical vertebrae; at least ten sacral vertebrae; gastralia reduced; elongate sternum; pubis parallel to ilium; intercotylar eminence on metatarsus; metatarsal III plantarily displaced; completely fused metatarsus), while others are present in some enantiornithines (more than nine cervical vertebrae; elongate sternum; capital groove on humerus; broad flat manual phalanx II-1; distal tarsals fused to metatarsus; metatarsals completely fused).

Interestingly (and disasterously), Kurochkin concludes with Protoavis. He places this taxon as the basalmost of his bird lineage, basal to confuciusornithids and ornithurines. This is based on several characters-
1. heterocoelous cervical vertebrae. If taken to mean completely heterocoelous vertebrae (as to distinguish neornithines from enantiornithines), absent in Confuciusornis, Archaeorhynchus, Yixianornis, Gansus and Ichthyornis.
2. voluminous tropibasal braincase. I don't know what tropibasal means, though no non-ornithurine Mesozoic bird braincases besides Archaeopteryx have ever been measured volumetrically.
3. reduced postorbital. Absent in Confuciusornis.
4. closed temporal fenestrae. Absent in Confuciusornis, correlated with previous character.
5. narrow elongated coracoid. Also in enantiornithines
6. mobile articulation of the scapula to the coracoid through a fossa in the coracoid and a prominence on the scapula. Absent in confuciusornithids.
7. deep renal depressions on the internal surface of the ilium and sacrum. Absent in Confuciusornis, Patagopteryx, Yixianornis, Apsaravis, hesperornithines and Ichthyornis.
8. fusion between both ends of the third and fourth metacarpals. Absent in confuciusornithids, Archaeorhynchus and Hongshanornis.
9. plantar shift of the third metatarsal in the proximal part of the foot. Absent in confuciusornithids, Archaeorhynchus and Patagopteryx.
It's amazing this escaped Kurochkin's notice (even accepting Protoavis as a distinct taxon instead of a chimaera). The near complete lack of these characters in confuciusornithids should suggest Protoavis is more closely related to ornithurines, or that it developed the characters convergently with ornithurines. Indeed, the renal fossa is a much better example of homplasy than anything Kurochkin listed for theropods vs. birds. Not only does Confuciusornis lack it, but _all known non-neornithine birds_ do too, when they can be examined. The absence of heterocoelous cervicals, a renal fossa, distal metacarpal fusion and a plantarily displaced metatarsal III in basal ornithurines invalidates their use as synapomorphies for Protoavis + Ornithurae. This leaves the scapulocoracoid joint, strut-like coracoid, enlarged braincase and reduced postorbital as potentially valid synapomorphies, though enantiornithines share the second and possibly third, while the third and fourth are unconfirmed in basal ornithurines. Also notable is that Protoavis has a few of Kurochkin's supposed theropod characters- anteriorly directed medial quadrate condyle, lesser trochanter on femur, pubic peduncle on ilium.
Kurochkin claims "Late Triassic Protoavis is a headache for the proponents of the dinosaurian hypothesis of the origin of birds. If its characters were introduced in a cladistic matrix, all cladograms of sister relationships of theropods and birds would be destroyed, while the Late Jurassic dating for the deviation of birds from the dinosaurian stem would be rejected; the same is true of the differentiation of the basic theropod families, which would be shifted to the Late Triassic. This is probably the main reason why the majority of supporters of sister relationships between birds and theropods omit Protoavis from their considerations." No, the main reason is that the remains are identical to coelophysoid and pterosauromorph (Atanassov, 2002) elements, while the cervicals are similar to drepanosaurids'. Besides being a chimaera, many details described and illustrated by Chatterjee are not recognizable in the fossils (Witmer, 2001). For instance, the metacarpus Kurochkin uses to propose a character uniting Protoavis with ornithurines is actually a pterosauromorph metatarsus. While the cervicals he uses are extremely similar to contemporary drepanosaurids. Admittedly, the apparently reduced postorbital and bone resembling a euornithine coracoid are intriguing. But a massive reanalysis involving comparison with various Triassic vertebrate elements is needed before we'll know which, if any, material belongs to a distinct taxon, let alone a bird.

On the one hand, Kurochkin appears to have a much better grasp of BAD than Feduccia, Martin or Czerkas. Yet he is just as guilty of naive falsification and magically knowing which characters are free of homoplasy and thus important for phylogeny. Also similar to Martin is the presence of large amounts of phylogenetic contradictions which remain undiscussed. Martin (2004) proposed Protoavis as a basal bird, ignoring the fact it possessed his supposed theropod characters, lacked characters he claimed to be primitive for birds, and lacked characters he claimed (the supposedly more basal) Longisquama shared with birds. Equivalently, Kurochkin proposes confuciusornithids as basal birds, ignoring the fact they possess most of his supposed theropod characters, and lack characters he claimed (the supposedly more basal) Protoavis shares with birds. Kurochin's theropod + Archaeopteryx characters are mostly present in confuciusornithids, and mostlyly absent in enantiornithines, with several seen in basal euornithines. Just what's to be expected if the standard topology were true. Kurochkin's sauriurine characters are few and symplesiomorphic, as Martin's and Feduccia's have always been. Kurochkin's placement of confuciusornithids as more closely related to ornithurines than enantiornithines contradicts nearly all of his own characters, let alone those of Clarke, Chiappe and others. His placement of Protoavis in this position is weakened by the absence of half the states in basal ornithurines and the presence of a few theropod characters in it. Kurochkin's general point that avian convergence is rampant in coelurosaurs is quite valid, though his functional/morphological method of showing this is unsound. Similarily, he's right that Archaeopteryx is not necessarily more birdlike than some traditionally more basal coelurosaurs, but his utterly random rejection of the birdlike characters it DOES have only hurts his argument. And while many ornithothoracine characters may have been convergent in derived enantiornithines and euornithines, it's the basal members of these clades lacking the characters which shows this is true, not homoplasy of the character in outgroups or differing morphologies in the ingroups. The methodological and logical problems noted above prevent Kurochkin's model from being a likely alternative to BAD.

Mickey Mortimer