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On the Alleged Dinosaurian
Ancestry of Birds

he recent discoveries of Protarchaeopteryx robusta and Caudipteryx zoui are being hailed as conclusive proof that birds evolved from theropod dinosaurs.^[1]  According to Kevin Padian, an expert in the field and a long-time proponent of the dinosaur theory, these finds “should lay to rest any remaining doubts that birds evolved from small coelurosaurian dinosaurs.”^[2]  This confidence has understandably taken root in the popular press, where one writer described the dinosaur-bird link as “now pretty close to rock solid.”^[3]  The purpose of this article is to explain why the case for dinosaurian ancestry of birds is far from closed.

Some Background

The idea that birds descended from dinosaurs was first suggested by Thomas Huxley in 1868 on the basis of skeletal similarities between Archaeopteryx lithographica and Compsognathus longipes, a chicken-size coelurosaur recovered from the same formation as Archaeopteryx. ^[4]  Of course, Compsognathus itself could not qualify as an ancestor for Archaeopteryx because it was “too late in time (as a direct contemporary of Archaeopteryx) and too specialized in the reduction of the manus to two digits.”^[5]  Nevertheless, Compsognathus was considered illustrative of the kind of creature from which Archaeopteryx evolved.  It was believed that the features shared by the two species had been inherited from a common dinosaur ancestor that was more like Compsognathus than Archaeopteryx.

A number of experts (e.g., Seely and Vogt) resisted Huxley’s theory, arguing that the similarities between Compsognathus and Archaeopteryx were probably the result of convergent evolution rather than common descent from an earlier dinosaur.^[6]  As a result, Huxley’s views never gained general acceptance.^[7]  In 1913 Robert Broom described Euparkeria, a small, 230-million-year old thecodont, and argued that it was the common ancestor of both theropod dinosaurs and birds.  This made theropods an evolutionary side branch having nothing to do with the origin of birds.  Following the publication in 1926 of Gerhard Heilmann’s classic, The Origin of Birds, the thecodont (as opposed to theropod) ancestry of birds became a matter of textbook orthodoxy for the next fifty years.^[8]

The theropod theory of bird origins was revived in the mid-1970s through a series of papers by John Ostrom.  He detailed a number of similarities between Archaeopteryx and theropods, focusing especially on Deinonychus antirrhopus, a lightly built, 110-million-year old dromaeosaurid that he discovered in 1964.^[9]  Subsequent cladistic analysis supported and refined Ostrom’s claim by identifying dromaeosaurids as the group that shared the greatest number of derived characters with Archaeopteryx. ^[10]

By the mid-1990s, Ostrom’s theory had become “practically dogma among vertebrate paleontologists.”^[11]  Thus, even before the recent finds, one was assured: “Birds are dinosaurs.  And not all dinosaurs have gone extinct; one group, the birds, survives.  What did dinosaur meat taste like? A trip to Kentucky Fried Dinosaur, or a mouthful of Dinosaur McNuggets can answer that question!”^[12]  With the report of Protarchaeopteryx and Caudipteryx, the “theropodists” have openly declared victory.

Recent Finds (Round 1)

The discoveries of Protarchaeopteryx and Caudipteryx were preceded by the discovery of Sinosauropteryx prima, a small theropod, similar to Compsognathus, that had short, fibrous structures along its spine and on other parts of its body.^[13]  There were early rumors that the structures were downy feathers, but that turned out not to be the case.^[14]  However, the belief that these filaments were holdover "protofeathers" is still very much alive.^[15]

The holotype for Sinosauropteryx was found by farmer Li Yin Fang in June 1996 in the Yixian Formation in Liaoning Province (a far northeastern province of China).^[16]  Mr. Li sold the fossil to a dealer who sent it to Ji Qiang, the director of the National Geological Museum in Beijing.  The mirror-image counterslab found its way, presumably through the same dealer, to Chen Pei-ji of the Nanjing Institute of Geology, as did another nearly complete specimen of the same creature.^[17]

The following summer, farmers working for Ji Qiang in the Yixian Formation found three turkey-size fossils that had well-preserved evidence of true feathers.  Ji Qiang and his colleague, Ji Shu-An, originally concluded that the fossils represented a single species, which they thought bore a striking resemblance to Archaeopteryx. They dubbed the creature Protarchaeopteryx robusta and published a brief report describing it as a new genus of Archaeopterygidae.  It was not until they examined the specimens with Philip Currie in the fall of 1997 that they concluded the fossils represented two quite different species and that neither was as similar to Archaeopteryx as they had first thought.  They named the second species Caudipteryx zoui. ^[18]

The plumage on Protarchaeopteryx and Caudipteryx is said to be identical to feathers on modern birds, but neither is believed to have been capable of flight because they had relatively short forelimbs (wings) and symmetrically-shaped feathers like those seen in flightless birds today.^[19]  Proponents of the theropod theory consider them to be dinosaurs rather than birds “because they lack a number of features seen in Archaeopteryx and more advanced birds.”^[20]

The significance of these fossils depends largely on whether they are feathered dinosaurs or flightless birds.  To call them feathered dinosaurs is to claim that they did not descend from birds.  If that is correct, it means, from an evolutionist perspective, either that they shared a feathered ancestor with birds or that feathers evolved more than once.  The latter option is considered unlikely because feathers are such complex structures.^[21]  So if these creatures are feathered dinosaurs, the favored conclusion of evolutionists is that they descended from the same feathered ancestor as birds, an ancestor that also would be classified as a dinosaur.

If, on the other hand, Protarchaeopteryx and Caudipteryx are flightless birds, they would provide little, if any, new ammunition for the theropod theory.  The fact they resemble coelurosaurs in a number of features would be consistent with theropod ancestry, but they offer at best a marginal advance of the similarity argument provided by Archaeopteryx, which argument has failed to convince a minority of experts (who have attributed the similarities to convergent evolution).  As flightless birds, they would not have come by their feathers independently of the avian lineage, and thus their existence would not imply the existence of a feathered, pre-bird ancestor.

Dinosaurs or Birds?

Some extinct birds, such as Archaeopteryx, shared quite a few features with some theropods.  That raises the question of how one can determine whether a creature is a bird that resembles a dinosaur or a dinosaur that resembles a bird.  Feathers had long been accepted as a distinctively avian characteristic because they had never been found on any creature, living or extinct, that was not a bird.^[22]  The presence of feathers marked a creature as a bird, but one is now told that this is an invalid criterion and that Protarchaeopteryx and Caudipteryx were dinosaurs despite the fact they possessed feathers.^[23]

Before it can be concluded that feathers do not prove avian rank, they must be found on a creature that clearly is not a bird.  The evidence for the creature’s non-avian status must be compelling enough to overcome the presumption of avian status created by the presence of feathers.  Only then can one be confident that the diagnostic role assigned to feathers was erroneous.  If, for example, someone claimed to have found hair on a reptile, it would need to be established that the creature was indeed a reptile, rather than a previously unknown mammal, before hair was jettisoned as a uniquely mammalian trait.^[24]

The claim that Protarchaeopteryx and Caudipteryx were dinosaurs rather than birds is made with a certainty far exceeding the evidence.  Larry Martin and Alan Feduccia, two experts on bird evolution, and John Ruben, a zoophysiologist, are all convinced these creatures were flightless descendants of earlier flying birds and were more "advanced" than Archaeopteryx. ^[25]  The dating is certainly consistent with that view, as the new fossils are believed to be some 25 million years younger than Archaeopteryx (see note 16).

Ji et al. excluded Caudipteryx from Avialae because it reportedly lacked the following features shared by members of that clade (which features are defined as "derived" based on comparisons of Velociraptorinae, Archaeopteryx, and some more modern birds): (1) quadratojugal joined to the quadrate by a ligament, (2) quadratojugal-squamosal contact absent, and (3) obturator process of the ischium reduced or absent.^[26]  Yet, the interpretation of each of these features is open to question.

One expert has stated that he was unable to find evidence in Caudipteryx of suturing between the quadratojugal and quadrate (which suggests they were joined by a ligament).  The quadratojugal appeared to him to be nearly identical to that of Archaeopteryx. He also believes that Ji et al. probably had the ischium upside down and consequently misconstrued the ischial process as a ventral rather than a dorsal structure.^[27]  If that is correct, the ischial process supports rather than opposes avian status.

Such disagreements among experts reveal that fossil interpretation is more subjective than is commonly appreciated.  As J. M. Clark noted in his review of H.P. Schultze and L. Trueb, eds., Origins of the Higher Groups of Tetrapods, (Ithaca, NY: Cornell University Press, 1991), “the book again and again demonstrates that similarity lies in the eye of the beholder, and that the particular hypothesis being advocated strongly colors perceptions of morphological resemblance.”^[28]  Given that a “feathered dinosaur” is the holy grail of theropod advocates, there is certainly reason for caution regarding the theropodists’ disputed interpretations of these fossils.  After all, it was zeal for the theropod hypothesis that prompted the premature characterization of the fibrous structures on Sinosauropteryx as “downy feathers.”^[29]

As for the claim that the quadratojugal of Caudipteryx contacted the squamosal, the squamosal was apparently not preserved.  It is not mentioned in the description of the skull and is not shown in the relevant diagram.  The fact Ji et al. state that “[t]he tall quadratojugal seems to have contacted the squamosal” suggests strongly that this is a matter of inference rather than observation (emphasis supplied).^[30]

Even if these features were correctly diagnosed by Ji et al. that would not mean Caudipteryx was a dinosaur.  Putting aside the matter of feathers, Caudipteryx has a number of characters that point to its avian status.  Ji et al. include one such character in their phylogenetic matrix,^[31] but other experts believe there are more.  They cite such things as the shortened tail with distal fusion, the reduced fibula, the ventral occiput, the long premaxilla relative to the maxilla, the reduced and edentulous (toothless) maxilla, the edentulous dentary, the small, moveable head of the quadrate, the absence of a pubic foot, and the rounded, ball-like head of the femur.^[32]

When Caudipteryx was first reported, all theropods were considered “irredeemable carnivores.”^[33]  Caudipteryx, on the other hand, was apparently an herbivore.  Not only were its maxilla and dentary edentulous, but both specimens of the creature included large masses of gastroliths (“gizzard stones”), which are used for grinding plant matter.^[34]  Because herbivory and gastroliths were both known in Avialae but neither was known in any of the scores of theropod genera,^[35] their presence in Caudipteryx seemed suggestive of avian status.  Gastroliths have since been reported in an ornithomimid species from the Upper Cretaceous, so this particular argument for avian status is no longer available.^[36]

It is difficult to accept that the long hand-feathers of Caudipteryx evolved within (nonavian) Maniraptora.  The strong, grasping hands of maniraptorans were an essential part of their weaponry,^[37] but the well-formed feathers attached to Caudipteryx’s middle finger would prevent the hand from being used as a grasping organ.  What possible selective advantage could be bestowed on a cursorial predator by the development of hand-feathers that disable the function of one of its primary weapons?

The anticipated retort that the loss of use caused by the development of hand-feathers coincided with and perhaps drove the shift to herbivory does not address the real problem.  One still must explain how the survival advantage of developing hand-feathers on a maniraptoran would exceed the survival disadvantage from the concurrent impairment of the grasping function.  A shift to an herbivorous diet may well reduce the degree of disadvantage resulting from impairment of the hand, but unless the feathers provided a net advantage to survival at each step in their development, they would never become established in the population.

If, on the other hand, Caudipteryx was a secondarily flightless bird, there is no need to conjure up an explanation of how long hand-feathers on a maniraptoran could provide a net survival advantage.  Those feathers would be vestigial flight structures.^[38]

Ji et al. considered Protarchaeopteryx to be more “primitive” than Caudipteryx because it reportedly lacked the following “derived” features shared by Caudipteryx and Archaeopteryx: (1) frontal process of premaxilla relatively long to very long, and (2) teeth with unserrated crowns.^[39]  But again, other experts were unable to confirm these features in the fossils.  Moreover, these experts found additional characters, such as the absence of a pubic foot, which point to Protarchaeopteryx’s avian status.^[40]

Apart from the alleged serrations, the short, bulbous maxillary and dentary teeth of Protarchaeopteryx look remarkably like those of Archaeopteryx, complete with waisted crowns.^[41]  Perhaps this is one of the features that led Ji Qiang and Ji Shu-An to conclude originally that Protarchaeopteryx bore a striking resemblance to Archaeopteryx. Velociraptorine teeth, on the other hand, are laterally compressed so as to be bladelike (as are the teeth of all dromaeosaurids).^[42]

Even if serrations are present, it is clear from the report that they are quite unlike the serrations in dromaeosaurids.  Ji et al. state there were 35-50 serrations per 5 mm, but the number of serrations in dromaeosaurids is only 16-18 per 5 mm.^[43]  The serrations, therefore, do not support the contention that these teeth were inherited from the ancestor of dromaeosaurids.  Protarchaeopteryx’s teeth look nothing like those of dromaeosaurids.

Ji et al. acknowledged that in one feature Protarchaeopteryx and Caudipteryx were more like modern birds than was Archaeopteryx (see note 31).  This means, according to the proposed phylogenetic positioning of Protarchaeopteryx, that this feature was either (a) developed in Protarchaeopteryx after it split from the lineage leading to dromaeosaurids or (b) was lost in the dromaeosaurid lineage after Protarchaeopteryx split (since it is not present in Dromaeosauridae).  (The same holds for each of the derived avian features suggested by other experts.)

If option (a) is correct, then Caudipteryx did not inherit this feature from a common ancestor with Protarchaeopteryx. That means the feature evolved independently in both Protarchaeopteryx and Caudipteryx. It then evolved independently a third time within Avialae at some point after Archaeopteryx (since it is a derived avian character not present in Archaeopteryx).  If the feature is so advantageous that it evolved these three separate times, it seems most unlikely that it would have been lost in the lineage leading to Archaeopteryx. If, however, Protarchaeopteryx and Caudipteryx were secondarily flightless birds, then the feature need have evolved only once after Archaeopteryx.

If option (b) is correct, then Caudipteryx could have inherited this feature from a common ancestor with Protarchaeopteryx. If so, then the feature evolved independently only one other time, within Avialae at some point after Archaeopteryx. That scenario, however, raises the question of why a feature so advantageous that it evolved on both sides of Archaeopteryx would have been lost in both the dromaeosaurid lineage and in the lineage leading to Archaeopteryx. Again, if Protarchaeopteryx and Caudipteryx were secondarily flightless birds, this difficulty is removed.

The proposed positioning of Protarchaeopteryx and Caudipteryx on the phylogenetic tree also implies that feathers were a universal feature of dromaeosaurids.^[44]  Yet, no dromaeosaurid has been found with any evidence of feathers.  The recently reported dromaeosaurid Sinornithosaurus shows evidence of filaments, which some theropod advocates have hastily characterized as “protofeathers” and “downy feathers,”^[45] but in the words of Storrs L. Olson, Curator of Birds at the Smithsonian Institution, this “is little more than wishful thinking that has been presented as fact.” ^[46]  Apparently the Sinosauropteryx affair has done little to instill caution in the theropod faithful.

The absence of feathers on dromaeosaurids is admittedly negative evidence, but one wonders if feathers are as difficult to preserve as is often speculated.  Feather impressions are visible on all seven of the Archaeopteryx specimens, whereas an ossified sternum was preserved in only one.^[47]  Feathers were also found with Confuciusornis, Ambiortus, Noguerornis, and numerous other fossil birds, not to mention the only known specimens of Protarchaeopteryx and Caudipteryx. ^[48]  If dromaeosaurids did have feathers, it is most unfortunate for the theropod position that no trace of them was preserved on any of the more than 20 individual creatures that have been unearthed.^[49]

There are thus ample grounds for believing that Protarchaeopteryx and Caudipteryx are extinct birds rather than dinosaurs.  The rush to a contrary judgment has more to do with a prior commitment to theropod ancestry than with the weight of the evidence.  These creatures have been pronounced dinosaurs because that is what many people want them to be.

Recent Finds (Round 2)

Since the discovery of Protarchaeopteryx and Caudipteryx, two filament-bearing dinosaurs from the Yixian Formation in China (middle Early Cretaceous) have been reported in the formal scientific literature: a quite fragmentary seven-foot-long therizinosaur dubbed Beipiaosaurus inexpectus ^[50] and an eagle-size dromaeosaurid (mentioned above) dubbed Sinornithosaurus millenii. ^[51]  Theropod advocates suggest that these filaments represent an early stage in the development of feathers and thus link theropods to avian ancestry, but this is pure speculation.  As Dr. Olson put it in his recent open letter, “[t]he statement [in Sloan 1999] that ‘hollow, hairlike structures characterize protofeathers’ is nonsense considering that protofeathers exist only as a theoretical construct, so that the internal structure of one is even more hypothetical.”^[52]

Moreover, if the filaments on the Yixian fossils existed as external structures on the living animals, rather than being the result of a peculiar (perhaps Yixian specific) breakdown of tissue in the course of fossilization, then these filamentous structures either existed throughout Coelurosauria or evolved more than once (since they are present in the compsognathid Sinosauropteryx).  If they existed throughout Coelurosauria, it is hard to imagine why they are not present in such exquisitely preserved coelurosaurs as Compsognathus longipes and Scipionyx samniticus. And if, contrary to the claim of Xing et al. (1999a), therizinosaurs (such as Beipiaosaurus) are not nested within Coelurosauria (see the discussion of therizinosaurs in subsection 2 below), then the filamentous structures are even more widely distributed.  This makes it an even greater mystery why they have not shown up elsewhere.  Of course, one can wave the wand of “convergent evolution” and have filamentous structures evolve independently as often as needed, but this rapidly begins to look contrived.

The theropod faithful, undaunted by these issues, claim (in the recent exhibit at National Geographic Society) “there is strong evidence that a wide variety of carnivorous dinosaurs had feathers” and depict Deinonychus and baby tyrannosaurs as having feathers.  Dr. Olson labels the claim “spurious” and says the depictions are “simply imaginary and [have] no place outside of science fiction.”^[53]

An interesting aspect of Sinornithosaurus is that, in numerous features, it is allegedly the most birdlike of all nonavian theropods.  Since it is the oldest known dromaeosaurid, predating Deinonychus by some 14 million years, one is left to wonder why certain birdlike features are absent in Deinonychus, only to be reappear in dromaeosaurids some 75 million years later (see note 73).  It seems ad hoc to claim that avian features first provided a selective advantage for dromaeosaurids (resulting in Sinornithosaurus), then nonavian features provided a selective advantage (resulting in Deinonychus), and then avian features once again provided a selective advantage (resulting in the birdlike dromaeosaurids of the Late Cretaceous).

Another “feathered theropod,” dubbed Archaeoraptor liaoningensis, has been reported in the popular press^[54] but has not yet been published in a formal scientific journal.  Though bold claims were made for this fossil, Larry Martin says it “is one of the worst preserved specimens in a long line of poorly preserved specimens.” It is what is facetiously referred to as “paleontological road kill,” a specimen so compressed that interpretation will be extremely difficult.  To make matters worse, it now appears that the fossil is a composite of two separate creatures.  Someone added to the specimen a tail from a dromaeosaurid!^[54A]  As for the claim of feathers, neither Martin, who has seen photographs of the specimen, nor a University of Kansas colleague of his, who viewed the actual fossil, was able to identify any feather impressions.^[55]

Some Issues Beyond the Recent Finds

1. Protoavis texensis. In 1983, Sankar Chatterjee, a paleontologist at Texas Tech University, discovered some fossil bones in a small mudstone block dating to 225 million years ago.  In 1985, after six months of carefully preparing the material, he realized he had discovered two individuals of a previously unknown species.  The larger specimen, the holotype, was about the size of a pheasant, making it comparable to the largest Archaeopteryx specimen.  The smaller specimen, believed to be a juvenile, was about half that size, making it comparable to the smallest Archaeopteryx specimen.  Since then, Chatterjee has collected 31 isolated postcranial elements, which have been referred to this species.^[56]  “Nearly every skeletal element is represented among these specimens.”^[57]

The species, later dubbed Protoavis texensis, predates Archaeopteryx by about 75 million years and, as described by Chatterjee, is more like modern birds than is Archaeopteryx. It has a V-shaped furcula, a keeled sternum, quill knobs in the hand for attachment of flight feathers, birdlike cervical vertebrae, and a birdlike skull, pelvis and pectoral apparatus.  As Feduccia admits, “The features Chatterjee illustrates are without question quite birdlike, and an early bird from the late Triassic is certainly possible.”^[58]

Regarding Protavis’s flight capability, Chatterjee writes:

Protoavis shows many derived features associated with flapping flight that are not encountered in Archaeopteryx. Of particular importance are the keeled sternum, hypocleidium-bearing furcula, strutlike coracoid, large flight muscles, and triosseal canal for the supracoracoideus tendon (fig. 4.4).  The glenoid cavity faces dorsolaterally, which permits unrestricted movements of the humerus in all directions.  The humerus is an exceptionally strong bone and shows all the bumps and ridges for the attachment of flight muscles.  The specialized linkage system of elbow and wrist joints would stiffen the entire extended wing into a plane to resist twisting when exposed to air pressure during flight.  The presence of feathers is inferred indirectly from the development of quill knobs in the hand.  The furcula and keeled sternum must have accommodated large flight muscles.  The flexible furcula would act as a spring between the shoulder joints during the flight strokes.  The presence of a triosseal canal suggests that the supracoracoideus muscle must have functioned effectively as a wing elevator and that the animal could possibly take off from the ground.  The enlargement and partial fusion of pelvic bones, a relatively short horizontal femur with antitrochanter articulation, and mesotarsal ankle joint all may indicate that the hindlimb was modified as a landing gear.^[59]

Given that the prevailing view of bird origins (the theropod theory) was developed with the assumption that Archaeopteryx was a very early bird and that birds therefore arose in the Middle to early Late Jurassic, the reaction to Protoavis texensis was predictable.^[60]  The discovery touched off what Feduccia describes as “a tremendously bitter and acrimonious controversy ”that was laced “with sharp personal attacks.”^[61]  Chatterjee’s published descriptions of the material seem to have mollified his opponents, but his interpretations continue to meet resistance.  His find is slighted by such remarks as: “The material has become a paleontological Rorschach test of one’s training, theoretical bias, and predisposition.”^[62]

Another method used to dismiss Protoavis is to claim that any conclusions about it are premature until “the paleontological community has had adequate opportunity to evaluate the Protoavis material” so as to “test the original observations and conclusions, and to draw their own.” One is told that until then “all claims [about Protoavis] must be treated tentatively, especially in view of the paradoxes it presents” (emphasis supplied).^[63]  This rule obviously has been suspended in the case of the so-called “feathered theropods,” but in any event, one should not get the impression that Chatterjee is alone in his assessment.  As Lawrence Witmer recently pointed out, “such esteemed paleornithologists as Evgeny Kurochkin and D. Stephen Peters have regarded Protoavis as a bird in their published accounts of early avian evolution.”^[64]  Likewise, Chatterjee reports, “Many experts on fossil birds came to our museum and confirmed my belief that the newly found material exhibited a suite of distinct avian traits.”^[65]

It is noteworthy in this context that several researchers have reported probable bird tracks from the Late Triassic to Early Jurassic.  In 1974 Ellenberger presented as avian a variety of Late Triassic-Early Jurassic footprints from Africa, and in 1992 Lockley et al. reported on Early Jurassic birdlike tracks from northern Africa and North America.^[66]  In 1993 Weems and Kimmel described tracks from a Protoavis-like bird from the Late Triassic of Virginia.^[67]

Advocates of theropod ancestry admit that “these footprints deserve serious consideration,” but they are unwilling to consider them avian in the absence of “reliable osteological evidence before the Late Jurassic” (emphasis supplied).^[68]  So rather than see these footprints as supporting Chatterjee’s interpretation of the Protoavis material by showing the presence of birds in the Late Triassic or Early Jurassic, skepticism about Chatterjee’s interpretation, which is spawned in part by the implications of that interpretation, is used to deny the significance of the footprints.

A Late Triassic bird that is more modern than Archaeopteryx puts a fatal strain on the theropod theory.  It pushes the origin of birds back at least to the Middle Triassic, before the time of Eoraptor, the earliest known dinosaur.^[69]  Coelurosaurs and dromaeosaurids, those dinosaurs believed to be anatomically similar to birds, first appear some 80 and 105 million years, respectively, after the Middle Triassic (see note 73).  To maintain the theropod theory in the face of this, its proponents must claim not only that dinosaurs existed in the Middle Triassic but that by that time they had also diversified into the various theropod clades and had evolved into birds, all without leaving a trace! As Witmer concedes, if that were so, “we should reasonably expect to find Triassic representatives of the ornithomimid, tyrannosaurid, troodontid, and dromaeosaurid clades, among others.”^[70]

Of course, if dinosaurs are eliminated as ancestral candidates, something else will be put in their place.  Evolution abhors ancestral vacuums.  It will, however, be a powerful demonstration of how deceiving cladistic analysis can be.  The fact two groups of creatures uniquely share similarities need not mean that they inherited those similarities from a common ancestor.  The similarities may be due to convergent evolution, to creative design, or to some combination of the two.

2. Too late.  Accepting Archaeopteryx as the earliest known bird by no means solves the timing problem posed by the theropod theory of origins.  Since Archaeopteryx dates to the Late Jurassic, some 150 million years ago, birds presumably originated quite a bit earlier.  Even advocates of theropod ancestry place the rise of birds in the Middle to early Late Jurassic.^[71]  This means that the alleged dinosaur ancestor must have existed by at least the Middle Jurassic.^[72]  The problem is that no dinosaur with particularly avian affinities is known before the Late Jurassic, and those with the most birdlike characteristics do not appear until much later.^[73]  This pattern has led some experts to suggest the possibility that coelurosaurs were derived from primitive birds (archaeopterygids)!^[74]

The recent claim that an Early Jurassic jaw fragment (with two teeth) is that of a therizinosauroid (and thus that of a coelurosaur) does not solve this problem.^[75]  First, the specimen is too fragmentary to permit a confident diagnosis.  Convergence is believed to be “very common,”^[76] so the most one can say is that this jaw fragment is consistent with that of a therizinosaur.

Second, since this jaw fragment allegedly predates the next oldest therizinosaur by some 94 million years, even if one assumes it belonged to a creature in the therizinosaur lineage, it would be a leap to conclude that such an ancient ancestor possessed the essential features of the later forms.  Nothing in evolutionary theory excludes the possibility that the jaw features developed in the lineage before those features by which the group is included within Coelurosauria.  So until coelurosaurian features are documented in such early members of the lineage, their presence remains an assumption.

Third, it is not at all clear that even the later therizinosaurs should be included in Coelurosauria.  Fastovsky and Weishampel report that segnosaurs (see note 75) “have been likened to an offspring of a menage a trois involving a theropod, a prosauropod, and an ornithischian.”^[77]  It is therefore no surprise that experts have variously allied them with prosauropods, ornithischians, and sauropodomorphs.  Though some have recently allied them with “the large, strange, and poorly understood theropod Therizinosaurus,” thus placing them within Theropoda, Fastovsky and Weishampel caution, “Only time and more fossils will unravel the true affinities of these strange animals.”^[78]

Finally, even if therizinosaurs deserve to be included within Coelurosauria, coelurosaurs below Maniraptora are not particularly strong candidates for avian ancestors.  This is evident from the fact that, though coelurosaurs have long been known, the theropod theory of ancestry did not take hold until the mid-1970s, after the discovery of the dromaeosaurid Deinonychus. Only in Maniraptora did the number of avian features reach the “critical mass” necessary to persuade a majority that they were not the result of convergence (see note 6).

The Middle Jurassic teeth that have been tentatively identified as dromaeosaurid fail to solve this timing problem for some of the same reasons.^[79]  Even if the teeth had clear dromaeosaurid morphology, it would be impossible to know whether they actually belonged to a dromaeosaurid.  To draw that conclusion, one would have to assume that no other creature had the same type teeth.  And even if one assumes the teeth belonged to a creature in the dromaeosaurid lineage, one could not know whether such an ancient representative possessed the avian features present in those forms dated some 50 million years later.

Padian and Chiappe seem to think the issue of timing has only to do with the late appearance of dromaeosaurids relative to birds, their putative “sister group” (i.e., the group believed to be most closely related).  They frame the problem this way:

A difficulty regarded as insurmountable by opponents of the theropod origin of birds (e.g., Feduccia, 1996) is the presumption that the taxa identified as closest to Archaeopteryx among theropod—the dromaeosaurids—do not appear in the fossil record until Albian-Aptian times (perhaps 110 million years ago: Deinonychus, Cloverly Formation, Wyoming), whereas Archaeopteryx comes from Late Jurassic (Tithonian) times (about 150 million years ago).^[80]

But this ignores the important point that the known dinosaurs from the assumed ancestral time lack the characteristics that are used to unite birds and dinosaurs.^[81]  In other words, the problem is not simply that the putative sister groups (dromaeosaurids and birds) appear with such a large stagger, but also that no dinosaur old enough to qualify as an ancestor of birds has the particularly birdlike traits on which the claim of dinosaurian ancestry is based.

In the end, the response to this and all timing objections is an appeal to the inadequacy of the fossil record.  One must believe that, in the case of birdlike dinosaurs, the vagaries of fossilization and discovery have conspired to create a false picture.^[82]  Yet, as Feduccia points out, “we have a wonderfully preserved array of fossil reptiles from the Triassic, Jurassic, and Cretaceous periods.”^[83]  Benton lists from the Jurassic and Cretaceous some 98 families of terrestrial reptiles, 49 families of terrestrial mammals, and 29 families of birds.^[84]  This translates into hundreds of genera and thousands of species.  One cannot, of course, disprove a negative, but the evidence seems sufficient to create, within an evolutionist framework, a presumption that the hypothesized ancestral theropods did not exist at the required time.

As for the late appearance of dromaeosaurids, Padian and Chiappe admit it is “puzzling,” but they deny its significance on the basis that the Mesozoic fossil record frequently contains large disjunctions in the appearance of sister groups.  They state:

For example, although stegosaurs and ankylosaurs are regarded as sister taxa that must have diverged by the late Early Jurassic, stegosaurs are not known before the Bathonian-Callovian (approximately 170 mya), whereas before the 1980s, ankylosaurs were not known before the Aptian-Albian (approximately 110 mya; Weishampel, et al., 1990).  The situation is not unique to dinosaurs.  No one doubts today that marsupials and placentals are sister taxa within mammals, and monotremes are their sister taxon.  Hence, the split between therians (marsupials + placentals) and monotremes must have taken place before the first recognizable marsupials and placentals evolved.  However, the first marsupials and placentals are known from Early Cretaceous times (approximately 100 mya), whereas until recently, monotremes were not known until the Oligocene (approximately 20 mya), a disjunction of 80 million years—over twice that between Archaeopteryx and Deinonychus (Carroll, 1988)!^[85]

Padian and Chiappe are saying to their evolutionist opponents that since they accept other disjunctions in the appearance of sister groups, it is inconsistent for them to complain about this one.  This, of course, has nothing to do with the merits of the complaint, with whether the disjunction is relevant to the claim of ancestry.  (Indeed, Padian and Chiappe acknowledge its probative value when they say the absence of earlier dromaeosaurids is “puzzling,” i.e., difficult to explain.  Witmer describes the problem as “vexing.”^[86]) It is, rather, an attempt to bar certain parties, in this case evolutionists, from raising the issue.  In law, this is known as an estoppel argument.

This argument loses its force when directed against those who do not accept megaevolution.  They cannot be charged with inconsistency in raising the complaint.  Such critics agree it is “puzzling” for sister taxa to appear 40 million years apart and believe such stratigraphic disjunctions indicate that the groups have been misconstrued as sister taxa.^[87]

Padian and Chiappe apparently recognize the weakness of simply declaring the late appearance of dromaeosaurids to be irrelevant, so they argue in the alternative that small maniraptorans are in fact known from the Late Jurassic.^[88]  But this is not helpful, since birds are classified as maniraptorans and the bones in question (a distal radius and a femur) were described as possibly belonging to a bird (see note 73).  So Padian and Chiappe are left to weakly claim: “These bones unfortunately could not be identified to the generic level but nonetheless indicated that if they are not bones of birds, then they are certainly those of their sister taxon, the dromaeosaurids” (emphasis supplied).^[89]  If the stratigraphic disjunction between birds and dromaeosaurids is a genuine nonissue, one wonders why these experts are willing to stretch so far to find a Jurassic dromaeosaurid.

3. Too specialized.  In all the talk about shared anatomical traits and “sister groups,” it is easy to lose sight of the fact that, even if they were old enough, all known coelurosaurs are too specialized to have been actual ancestors of birds.  In other words, they have features believed to have arisen in their lineage after it split from the lineage leading to birds, which features disqualify them as actual ancestors.  Thus, after explaining that Compsognathus could not be ancestral to Archaeopteryx because of its date and its specialization, Carroll says, “No other adequately known theropod appears to be an appropriate ancestor.”^[90]

Even dromaeosaurids are not claimed to be suitable ancestors of birds but merely the best approximation, based on speculation from cladistic analysis, of what the hypothetical bird ancestor would look like.^[91]  It is admitted that “in some characters, such as the stiffened tail, dromaeosaurids are too specialized to have been good ancestors for birds.”^[92]  Indeed, the smallest known dromaeosaurid (other than the eagle-size Sinornithosaurus, for which no weight estimate is available) is estimated to have weighed 66 pounds, compared to a mere one pound for the largest Archaeopteryx specimen (see notes 4 and 9).

One can include among these characters the most conspicuous feature of dromaeosaurids: the large, raptorial claw on the second toe of the hind foot.  This feature almost certainly was not present in the alleged common ancestor of birds and dromaeosaurids, as it is not present in Archaeopteryx, the basal bird, or in any of the other early birds (including Protarchaeopteryx and Caudipteryx).  It is a specialization that moves dromaeosaurids away from the actual avian lineage.

It is thus difficult to understand how the presence of such a claw in Rahonavis ostromi can be considered “a pretty clear link to its dinosaur origins.”^[93]  Given that birds are believed to be monophyletic and that the raptorial claw is not present in the basal members of the group, the appearance of the feature in more derived birds must, from an evolutionist perspective, be due to convergent evolution (as is believed to have occurred in troodontids).^[94]  It thus does nothing to link birds to dinosaurs.

The alternative is to claim that the claw is the primitive condition in Avialae.  Without even considering Protoavis, that would require one to hypothesize an undetected lineage of sickle-clawed birds extending some 85 million years, from before Archaeopteryx to the time of Rahonavis. Moreover, if sickle claws are a primitive avian feature, then their absence in Protarchaeopteryx and Caudipteryx reinforces the conclusion that these creatures are birds rather than dinosaurs.  Theropod advocates will not look favorably on that implication.

4. Similarities overstated.  It is not widely known at the popular level, but many of the key characters seen as uniting birds and theropods are disputed.  According to Feduccia, these include:

the nature of the pelvis (Martin 1991; Tarsitano 1991), the homology of the digits (Hinchliffe and Hecht 1984; Hinchliffe 1985; Martin 1991; Tarsitano 1991), the nature of the teeth (Martin, Stewart, and Whetstone 1980); Martin 1991), the hallux (Tarsitano and Hecht, 1980; Martin 1991; Feduccia 1993a), the ascending process of the astragalus (Martin, Stewart, and Whetstone 1980; Martin 1991; also see McGowan 1984, 1985 and reply by Martin and Stewart 1985), the pubis (Martin 1983a, 1983b, 1991; Tarsitano 1991; also see Wellnhofer 1985), and even the supposed unique semilunate carpal thought to be shared by Deinonychus and Archaeopteryx (and modern birds) (Martin 1991; Tarsitano 1991).^[95]

Since the hypothesized relationship of theropods to birds is based on the similarity of certain features, uncertainty about that similarity casts doubt on the hypothesis.  There is obviously more art in the interpretation of these fossils than popular presentations would lead one to believe.

5. Lung questions.  John Ruben, an expert in respiratory physiology, concluded from an examination of Sinosauropteryx “that theropods had the same kind of compartmentalization of lungs, liver, and intestines that you would find in a crocodile”—and not a bird.^[96]  The thoracic cavity and the abdominal cavity of theropods appear to have been completely separated from each other by the diaphragm, whereas birds have no such separation.  In living crocodilians, the function of this separation is to provide an airtight seal between the cavities.  Air is drawn into the bellows-type lungs by contraction of the diaphragmatic muscles which creates negative pressure in the thoracic cavity.

One reason this is significant is that, as Ruben argues, “a transition from a crocodilian to a bird lung would be impossible, because the transitional animal would have a life-threatening hernia or hole in its diaphragm.” According to Ruben, this means that if there is a relationship between dinosaurs and birds, “it’s not the linear relationship you see in the museum displays.”^[97]

These results were confirmed by the subsequent work of Ruben’s team on the maniraptoran Scipionyx samniticus. ^[98]  This unique specimen, which has the best preserved fossil organs of any dinosaur ever found, revealed under ultraviolet light the arrangement of some of its internal organs.  As Ruben stated in an interview, “It seems clear that a bird’s radically different system of breathing, in which air is continuously drawn through its lungs, could not have evolved from the hepatic-piston system we see in this theropod dinosaur.”^[99]

Regarding the conclusions of Ruben’s team, Larry Martin has stated, “There’s actually no way they could be wrong about this.  The Scipionyx specimen has the best preservation ever seen.  It’s one of the biggest discoveries of this decade.  It tells us more about dinosaurs than any other specimen.  The positions of the dinosaur’s windpipe and colon serve as independent checks that the animal did not have a bird’s breathing apparatus.”^[100]

In fact, it is impossible to imagine any animal whose lungs could have given rise to those in birds.  “No lung in any other vertebrate species is known which in any way approaches the avian system.”^[101]  Denton’s amazement regarding the avian lung is apparent:

Just how such a different respiratory system could have evolved gradually from the standard vertebrate design without some sort of direction is, again, very difficult to envisage, especially bearing in mind that the maintenance of respiratory function is absolutely vital to the life of the organism.  Moreover, the unique function and form of the avian lung necessitates a number of additional unique adaptations during avian development.  As H. R. Dunker, one of the world’s authorities in this field, explains, because first, the avian lung is fixed rigidly to the body wall and cannot therefore expand in volume and, second, because the small diameter of the lung capillaries and the resulting high surface tension of any liquid within them, the avian lung cannot be inflated out of a collapsed state as happens in all other vertebrates after birth.  In birds, aeration of the lung must occur gradually and starts three to four days before hatching with a filling of the main bronchi, air sacs, and parabronchi with air.  Only after the main air ducts are already filled with air does the final development of the lung, and particularly the growth of the air capillary network, take place.  The air capillaries are never collapsed as are the alveoli of other vertebrate species; rather, as they grow into the lung tissue, the parabronchi are from the beginning open tubes filled with either air or fluid.^[102]

In Denton’s opinion, “The avian lung brings us very close to answering Darwin’s challenge: ‘If it could be demonstrated that any complex organ existed, which could not possibly have been formed by numerous, successive, slight modifications, my theory would absolutely break down.’”^[103]

6. Flight question.  A corollary of the theropod theory of bird origins is that flight evolved from the ground up (cursorial theory) rather than from the trees down (arboreal theory).  There is, however, no plausible explanation for how this could have occurred.  The difficulty is so great that Chatterjee, who supports theropod ancestry, suggested recently that some theropods may have been tree climbers.^[104]  If they were, they apparently left no evidence of that ability.  According to Fastovsky and Weishampel:

It has been argued that perhaps the earliest birds scaled trees, and from that position learned to fly.  There is, however, no evidence for an arboreal proto-bird, no evidence for climbing adaptations, and no evidence in the skeleton of any nonavian theropod for arboreal habits.^[105]

The cursorial theory of flight origin was first proposed by Samuel Williston in 1879.  He simply raised the idea that flight could have evolved through a series of steps (running, leaping, jumping from heights, and finally soaring) without addressing any of the details of how that might have happened.  The following year, O. C. Marsh proposed an arboreal theory of flight origin, and this theory has since held sway with the majority of evolutionists.  The cursorial theory has, however, had several periods of revival.^[106]

In 1907 and 1923, Franz Baron Nopcsa elaborated on Williston’s claim by suggesting that wings would develop to increase the speed of an animal as it ran along the ground.  “Nopsca’s ideas on the origin of flight were severely criticized by other workers because the use of wings to increase running speed has no living analogs and because outstretched wings would increase drag (Heilmann 1926; Ostrom 1974; Bock 1986).”^[107]  Feduccia labels the theory an “aerodynamic absurdity.”^[108]

Roughly fifty years later, John Ostrom proposed a new version of the cursorial theory.  He suggested that wings developed from arms used to catch insects.  The “[f]eathers were first present as insulators and later became elongated fly swatters.”^[109]  This “insect net” theory was heavily criticized on four major grounds, and in 1983 Ostrom rejected his own hypothesis.^[110]

The latest attempt to explain a cursorial origin of flight is the “fluttering model” of Caple, Balda, and Willis published in 1983.

In this theory, the avian feathered wing and concomitant flapping evolved in creatures with bipedal cursorial habit to control body orientation during leaping and in landing.  Feathered wings and flapping, argue the authors, would increase the distance of the leap and therefore the running creature’s ability to capture insect prey. . . . For them, the most appropriate selection pressure for the enhancement of wings is stability while running at high speed, perhaps to escape predation.^[111]

Like its predecessors, this theory has faced a barrage of criticism.^[112]  For example, Jeremy Rayner has calculated that the hypothesized proavian would suffer a 30-40 percent drop in running speed as it leaped into the air, which creates a serious problem in terms of attaining any type of flight.  He concludes:

The first “flights” of a fluttering proto-flapper would have been at low speeds, where the energetic demands of flight are at their most extreme (Clark, 1977), and the wingbeat cycle is at its most complex.  The fluttering model fails because it takes no account of the extreme morphological, physiological and behavioural specializations required for flight.^[113]

Thus, Chatterjee is compelled to admit that “[t]he cursorial theory, even in its modified form, is biomechanically untenable.”^[114]  Fastovsky and Weishampel, who also favor the theropod theory, likewise acknowledge:

Fundamentally, however, it has proven nearly insurmountable to ‘design’ a cursorial theropod that developed flight by running along the ground.  Functional morphologists—that is, scientists who study the function of particular anatomical structures—have been unable to satisfactorily model the running-to-flight transition in early birds.^[115]

It is also significant, from an evolutionist perspective, that there are no contemporary examples of cursorial bipeds that use forelimbs for stability.  As Walter Bock states:

I know of no small tetrapods about the size of Archaeopteryx that are primarily terrestrial (e.g., not flying-running forms, or secondarily flightless or degenerate flying forms) and use their forelimbs for balance during fast running or during a leap.  And I know of none using the forelimbs as flapping structures to provide forward thrust to increase the length of its leap.^[116]

In fact, kangaroos, which share several functional traits with theropods (obligate bipedality, cursorial posture, short forelimbs, long tail) and thus offer a modern analog for testing the theory, do not extend their forelimbs during jumping.  Rather, the limbs play a passive role.  “To minimize drag force, they are kept in a folded position in a strictly sagittal plane during takeoff, midway through the leap, and during landing.”^[117]  The use of the forelimbs in these animals does not mimic a rudimentary flight stroke.

Conclusion

The idea that birds evolved from dinosaurs remains at best a highly speculative hypothesis.  One suspects its popularity has less to do with the evidence for theropod ancestry than with the Darwinian aversion to ancestral vacuums.  When paleontologist Hans-Dieter Sues says, “Only dinosaurs are anatomically suited to be the precursors of birds,”^[118] he is saying that, when it comes to bird origins, it is dinosaurs or nothing.  Since evolutionists are convinced that every taxon arose from some other, “nothing” is not an option.  This philosophical predisposition induces them to read lineages into ambiguous data.  They compound that error by confusing these interpretive constructs with fact.

One can state the matter no more forcefully than did Storrs Olson in his November 1, 1999 letter to the most prominent scientist at the National Geographic Society.  He concluded with the following:

The idea of feathered dinosaurs and the theropod origin of birds is being actively promulgated by a cadre of zealous scientists in concert with certain editors at Nature and National Geographic who themselves have become outspoken and highly biased proselytizers of the faith.  Truth and careful scientific weighing of evidence have been among the first casualties of their program, which is now fast becoming one of the grander scientific hoaxes of our age – the paleontological equivalent of cold fusion.  If Sloan’s article is not the crescendo of this fantasia, it is difficult to imagine to what heights it can next be taken.  But it is certain that when the folly has run its course and has been fully exposed, National Geographic will unfortunately play a prominent but unenviable role in the book that summarizes the whole sorry episode.

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Endnotes

[1] These finds are reported in Ji et al. (1998) and, at a more popular level, in Ackerman (1998).  “Theropod dinosaurs” refers to a wide variety of bipedal, carnivorous dinosaurs.  Many of the features that distinguish them from other dinosaurs occur in the legs, feet, and hands.  Fastovsky and Weishampel (1996), 261, 271-272.  In the Linnaean system of classification, theropods are those creatures in the Class Reptilia, Subclass Diapsida, Infraclass Archosauromorpha, Superorder Archosauria, Order Saurischia, Suborder Theropoda.  Carroll (1988), 615-621.  In cladistic classification, “theropod dinosaurs” are those creatures in the clades Reptilia, Diapsida, Archosauromorpha, Archosauria, Ornithodira, Dinosauria, Saurischia, and Theropoda.  Fastovsky and Weishampel (1996), 86-89, 271-273.  For a brief note on the classification differences, see Glut (1997), 18.  Conventional dating is assumed arguendo throughout the paper. [RETURN TO TEXT]

[2] Padian (1998), 730.  Coelurosauria is a subset of Theropoda. In the Linnaean system of classification, theropods were traditionally divided into the Infraorders Carnosauria and Coelurosauria. These taxa have been abandoned in that system because the features once thought to distinguish the two groups were found to be combined in a number of genera. Carroll (1988), 290, 621. Coelurosauria as a clade designation includes compsognathids and the clade Maniraptora. Coelurosaurs are distinguished from other theropods by their expanded circular orbit, semilunate carpal in the wrist, short ischium, heightened ascending process of the astragalus, and reduction of the transverse processes of the tail vertebrae. Fastovsky and Weishampel (1996), 274-275; see also, Padian (1997), 550. [RETURN TO TEXT]

[3] Lemonick (1998), 83. [RETURN TO TEXT]

[4] Feduccia (1996), 28, 52. Compsognathus was considerably larger than Archaeopteryx, its estimated weight being six to seven pounds compared to about one pound for Archaeopteryx. Carroll (1988), 291; Carroll (1997), 314. The estimated weight for the smallest Archaeopteryx specimen is a mere 7-9 ounces. Swartz (1998), 356. “By comparison with the Solnhofen Archaeopteryx, which is the largest example, the others in size, are as follows: Solnhofen 100 percent, London 90 percent, Maxberg 87 percent, Berlin 77 percent, Archaeopteryx bavarica 66 percent, and Eichstatt 50 percent.” Feduccia (1996), 35. The latest Archaeopteryx specimen was described by Wellnhofer in 1993. He considered it sufficiently different from the others in the relative length of its tibiae and hind legs to be named a new species, Archaeopteryx bavarica. Feduccia (1996), 32. [RETURN TO TEXT]

[5] Carroll (1988), 340. Though Compsognathus is accepted as a contemporary of Archaeopteryx, the precise location at which the holotype was found is unknown. It was collected in the late 1850s, apparently by physician and amateur fossil collector Dr. Oberndorfer. John Ostrom and Peter Wellnhofer attempted to determine the precise source of the fossil “but were only able to conclude that it came from lithographic facies of the Solnhofen Limestone, probably from the Riedenburg-Kelheim area.” Glut (1997), 307. [RETURN TO TEXT]

[6] Feduccia (1996), 55, 67. Those convinced that the similarities between dinosaurs and birds were the result of convergence include Mudge (1879), Dollo (1882, 1883), Dames (1884), Parker (1887), Furbringer (1888), Osborn (1900), Broom (1913), Heilmann (1926), Simpson (1946), de Beer (1954), and Romer (1966). Feduccia (1996), 67. [RETURN TO TEXT]

[7] Padian and Chiappe (1997), 73. [RETURN TO TEXT]

[8] Feduccia (1996), 55. [RETURN TO TEXT]

[9] Padian and Chiappe (1997), 73; Feduccia (1996), 66. Dromaeosauridae is a Family in the Suborder Theropoda. Carroll (1988), 621. Prior to the recent discovery of Sinornithosaurus millenii, Dromaeosauridae was divided into two Subfamilies: Velociraptorinae and Dromaeosaurinae. Velociraptorinae includes the genera Deinonychus, Saurornitholestes, and Velociraptor. Dromaeosaurus is the only “unquestionable” genus in Dromaeosaurinae, but Adasaurus has been referred to it. Currie, (1997b), 194. Sinornithosaurus millenii was placed within Dromaeosauridae but not within either of the existing Subfamilies. Xing et al. (1999b). With the possible exception of Sinornithosaurus millenii, the live weight of dromaeosaurids ranged from 66 to 176 pounds, and most of them were six to ten feet in length. They are distinctive in the possession of a highly mobile hand-wrist complex, unique caudal vertebral adaptations, and a large, sickle-like claw on their feet. Ostrom (1990), 269-271; Currie (1997b), 194-195. The holotype of Sinornithosaurus millenii is eagle size (Sloan [1999], 102), but one wonders whether that specimen had reached full adulthood. [RETURN TO TEXT]

[10] The most influential of these analyses was Gauthier (1986). See also, Holtz (1994). Cladistic analysis (also called phylogenetic systematics and Hennigian systematics), which has gained prominence in the last twenty years, is the classification of creatures into subsets on the basis of characters (recognizable attributes) they uniquely share. Such characters are regarded as having been inherited from a common ancestor who possessed them. It differs from the methodology of “evolutionary systematics” in its exclusive focus on shared, derived characters. Evolutionary systematics employs “an eclectic spectrum of evidence from all lines of biological information to establish relations. Such lines of evidence might derive from a blend of such disciplines as comparative anatomy and embryology, functional anatomy and biomechanics, biochemistry, physiology, and behavior.” Feduccia (1996), 56. [RETURN TO TEXT]

[11] Feduccia (1996), 66. [RETURN TO TEXT]

[12] Fastovsky & Weishampel (1996), 321. [RETURN TO TEXT]

[13] Chen et al. (1998), 150. [RETURN TO TEXT]

[14] In October 1996, Philip Currie said of the filaments, “They look so much like the feather impressions seen in the bird fossils at the same site that you can’t come to any conclusion other than the fact that you’re dealing with feathers.” He then equivocated with, “Now, they may not be feathers. They may be featherlike scales, they may be hair, they may be something else. Until the detailed work is done on it, you can’t really tell. But the bottom line is that, now, I don’t think there is any question that these dinosaurs had insulation of some kind, and in all probability it was feathers.” Monastersky (1996). See also, Gibbons (1996a) and Gibbons (1997a). It was reported in May 1997, however, that “[a]n international team of researchers that examined the Chinese fossil now concludes that the fibrous structures are not feathers.” Monastersky (1997). See also, Gibbons (1997c). [RETURN TO TEXT]

[15] In addition to Monastersky (1997) and Gibbons (1997c), see, Chen et al. (1998), 152; Padian and Chiappe (1998a), 45; Ackerman (1998), 78; Norell (1998), 33. [RETURN TO TEXT]

[16] The consensus is that these fossil beds are younger than the Solnhofen Limestones in which Archaeopteryx was found, but there has been disagreement over how much younger. An argon-argon analysis yielded a date of about 121 mya, but radiometric dates of 137 - 142 mya have also been reported. Gibbons (1996b), 1083; Anonymous (1997), 21. As of June 1998, ranges of 135 - 120 mya and 145 - 125 mya were being quoted. E.g., Gibbons (1998), 2051; Monastersky (1998), 404. Norell used an estimated date of 135 - 122 mya. Norell (1998), 33. Ackerman said the beds have “not yet [been] conclusively dated but [are] probably more than 120 million years old—the Early Cretaceous period.” Ackerman (1998), 86. Others were content to speak simply of an “Early Cretaceous age.” E.g., Chen et al. (1998), 147. The most recent, and purportedly definitive, dating effort yielded a middle Early Cretaceous date of 124 mya. Swisher et al. (1999). [RETURN TO TEXT]

[17] Ackerman (1998), 76-77, 86; Monastersky (1996); Gibbons (1996a), 720. [RETURN TO TEXT]

[18] The circumstances of the discoveries can be gleaned from Gibbons (1998); Ackerman (1998), 86-89, 95; and Unwin (1998), 120. The original article on these finds was Ji and Ji (1997). (This journal is in Chinese, but the translation of the title is provided in Chen et al. [1998], 152.) [RETURN TO TEXT]

[19] Mark Norell says of the feathers, “They are just like feathers on modern birds.” Gibbons (1998). According to Philip Currie, "The plumage on the new Chinese dinosaurs . . . is identical to bird feathers." Monastersky (1998). Kevin Padian agrees that the feathers on Archaeopteryx “are not much different qualitatively” than the feathers on these specimens. Padian (1998), 730. Regarding their presumed inability to fly, see, Monastersky (1998); Chen et al. (1998), 151-152. One detects, however, some equivocation on the flightlessness of Protarchaeopteryx. Thus, Ackerman reports that Protarchaeopteryx “probably could not have achieved true powered flight” (emphasis supplied). Ackerman (1998), 90. According to Feduccia, Protarchaeopteryx is within the range of living volant birds (reliable source). [RETURN TO TEXT]

[20] Monastersky (1998) (reporting the comment of Mark Norell). [RETURN TO TEXT]

[21] After describing briefly the complexity of feathers, Fastovsky and Weishampel state, “The importance of all this in an evolutionary sense is that feathers evolved (or originated) only once. After all, what are the chances of so complex a structure’s having evolved more than once? Using parsimony, we must conclude that feathers evolved only one time.” Fastovsky and Weishampel (1996), 294. Peter Wellnhofer agrees it is unlikely that a feature as unusual as feathers evolved twice. Gibbons (1996a). [RETURN TO TEXT]

[22] Fastovsky and Weishampel (1996), 294, 304. [RETURN TO TEXT]

[23] Padian (1998), 729. [RETURN TO TEXT]

[24] Carroll states, “Hair is a uniquely mammalian tissue that is not directly homologous with any derivative of the skin present in other amniotes.” Carroll (1988), 411. [RETURN TO TEXT]

[25] Gibbons (1998); Monastersky (1998); Ruben’s opinion based on a reliable source. All three have examined the fossils. [RETURN TO TEXT]

[26] Ji et al. (1998), 759 (and the supplementary information made available on Nature’s web site <http://www.nature.com>). [RETURN TO TEXT]

[27] Personal communication. [RETURN TO TEXT]

[28] Clark (1992) (cited in Feduccia [1996], 59). [RETURN TO TEXT]

[29] Theropod bias was also evident in Padian and Chiappe (1998a). A subsequent letter by the original describers of Confuciusornis (Feduccia, Martin, Zhou, and Hou) charged that the cover illustration of Confuciusornis made it look more dinosaurian than it was. They wrote, “Although Confuciusornis is a primitive, sauriurine bird, in life it would have appeared very much like a normal perching bird, such as a small crow, not a feathered dinosaur. The cover illustration has nothing to do with Confuciusornis.” Feduccia et al. (1998). [RETURN TO TEXT]

[30] Ji et al. (1998), 754. [RETURN TO TEXT]

[31] According to the matrix provided as supplementary information on Nature’s web site <http://www.nature.com.>, Protarchaeopteryx and Caudipteryx shared the derived avian feature of a radial shaft to ulnar shaft ratio that was smaller than 0.70 (character 49), whereas Archaeopteryx did not. [RETURN TO TEXT]

[32] Personal communication. [RETURN TO TEXT]

[33] Fastovsky and Weishampel (1996), 261, 284-287. [RETURN TO TEXT]

[34] See, Ji et al. (1998), 759. Fastovsky and Weishampel define a gastrolith as a “[s]moothly polished stone in the stomach, used for grinding plant matter.” Fastovsky and Weishampel (1996), 435. Masses of gastroliths similar to those in Caudipteryx have been found in moas, a group of extinct, leaf-eating birds in New Zealand. Feduccia (1996), 5, 281-283. [RETURN TO TEXT]

[35] Gastroliths were known in some birds, crocodilians, sauropodomorphs, and psittacosaurs. Fastovsky and Weishampel (1996), 125, 182 (n. 6), 254-255. [RETURN TO TEXT]

[36] Kobayashi et al. (1999). The authors reason from phylogenetic analysis that herbivory evolved independently in the ornithomimid species and in Caudipteryx. [RETURN TO TEXT]

[37] Fastovsky and Weishampel (1996), 282-283. [RETURN TO TEXT]

[38] Another possibility, open to creationists, is that (at least some) land birds were descendants of an originally created kind whose members were given feathers for some purpose(s) other than flight (perhaps for one or more of the purposes theropodists use in arguing that feathers evolved, e.g., insulation, camouflage, or display). [RETURN TO TEXT]

[39] Ji et al. (1998), 759 (and the supplementary information made available on Nature’s web site <http://www.nature.com>). Ji et al. do not claim that Protarchaeopteryx had an obturator process or that its quadratojugal contacted the squamosal. These features admittedly could not be determined. [RETURN TO TEXT]

[40] Personal communication. [RETURN TO TEXT]

[41] Ji et al. (1998), 753, 755; compare drawing at Feduccia (1996), 80. [RETURN TO TEXT]

[42] Ostrom (1990), 270-271. [RETURN TO TEXT]

[43] Ji et al. (1998), 753; Feduccia (1996), 80. The chart in Feduccia (from Chatterjee) lists Deinonychus and Dromaeosaurus. Since Currie does not include the number of serrations among the dental distinctions between velociraptorines and dromaeosaurines, they presumably do not vary significantly in that regard. Currie (1997b), 195. [RETURN TO TEXT]

[44] Padian (1998), 729. [RETURN TO TEXT]

[45] Sloan (1999), 103, 105. [RETURN TO TEXT]

[46] Olson (1999). [RETURN TO TEXT]

[47] Feduccia (1996), 24-35. [RETURN TO TEXT]

[48] Regarding Confuciusornis, Ambiortus, and Noguerornis, see, Feduccia (1996), 139-145. [RETURN TO TEXT]

[49] Ostrom (1990), 270. [RETURN TO TEXT]

[50] Xing et al. (1999a). [RETURN TO TEXT]

[51] Xing et al. (1999b). [RETURN TO TEXT]

[52] Olson (1999). [RETURN TO TEXT]

[53] Ibid. [RETURN TO TEXT]

[54] Sloan (1999). [RETURN TO TEXT]

[54A] Monastersky (2000); Kurtenbach (2000); Friend (2000). [RETURN TO TEXT]

[55] Monastersky (1999). [RETURN TO TEXT]

[56] Chatterjee (1997), 33-38. On the sizes of the Archaeopteryx specimens, see also note 4. [RETURN TO TEXT]

[57] Chatterjee (1997), 38. [RETURN TO TEXT]

[58] Feduccia (1996), 38. For firsthand descriptions, see Chatterjee (1991), (1995), (1997). [RETURN TO TEXT]

[59] Chatterjee (1997), 79-80. [RETURN TO TEXT]

[60] In a bit of an overstatement, Padian and Chiappe claim “it has become nearly universally accepted that birds evolved from small carnivorous dinosaurs most closely related to DROMAEOSAURIDS, probably sometime in the Middle to early Late Jurassic.” Padian and Chiappe (1997), 71. Elsewhere they write, “The reported find [of Protoavis], deep in the Late Triassic, was stratigraphically unexpected given the consilience between the order of the bird-theropod cladogram (e.g. Gauthier, 1986) and the sequence of appearance of these taxa, which suggested that the origin of birds was in the Late (or perhaps Middle) Jurassic (Padian, 1985; Gauthier, 1986).” Padian and Chiappe (1998b), 12-13. [RETURN TO TEXT]

[61] Feduccia (1996), 38. [RETURN TO TEXT]

[62] Padian and Chiappe (1998b), 13. [RETURN TO TEXT]

[63] Ibid. [RETURN TO TEXT]

[64] Chatterjee (1997), x. [RETURN TO TEXT]

[65] Chatterjee (1997), 37. [RETURN TO TEXT]

[66] Chiappe (1995), 349. See, Ellenberger (1974) and Lockley et al. (1992). [RETURN TO TEXT]

[67] Chatterjee (1997), 137. See, Weems and Kimmel (1993). [RETURN TO TEXT]

[68] Chiappe (1995), 349 (referring to Ellenberger [1974] and Lockley et al. [1992]). [RETURN TO TEXT]

[69] Fastovsky and Weishampel (1996), 365. There is some question, however, whether Eoraptor is a dinosaur. If not, then the earliest known dinosaur is Herrerasaurus, also from the Late Triassic of Argentina. Feduccia (1996), 90. The Middle Triassic date is calculated from the fact the origin of birds is believed by theropod advocates to have preceded Archaeopteryx by some 10-15 million years (see note 71). Since Protoavis is more derived, it would require even more time to evolve. [RETURN TO TEXT]

[70] Chatterjee (1997), x. One can only marvel at Currie’s faith in the theropod theory. He writes, “If birds were present during the Late Triassic, then theropods are less likely to have been ancestral to birds” (emphasis supplied). Currie (1997a), 231. [RETURN TO TEXT]

[71] Padian and Chiappe (1997), 71. Others (without regard to Protoavis) claim that birds may have arisen as early as the Middle Triassic. Feduccia (1996), 90. [RETURN TO TEXT]

[72] Ostrom states it this way: “The evidence strongly indicates a close phyletic relationship between dromaeosaurids and primitive birds, and one could argue that an (as yet unknown) Early or Mid-Jurassic dromaeosaurid was ancestral to archaeopterygians and later birds.” Ostrom (1990), 276. [RETURN TO TEXT]

[73] The earliest known coelurosaurs, Compsognathus, Coelurus, and Ornitholestes, are all from the Late Jurassic. The earliest known dromaeosaurid, Sinornithosaurus, is from the middle Early Cretaceous, some 25 million years later. Xing et al. (1999b). Deinonychus, the next oldest dromaeosaurid, is from the late Early Cretaceous. With the exception of Sinornithosaurus, the most birdlike dromaeosaurids are from the Late Cretaceous, some 75 million years after Deinonychus. Feduccia (1996), 90; Padian and Chiappe (1997), 78; Hutchinson and Padian (1997), 132; Benton, (1993), 699, 702. A distal radius and femur from the Late Jurassic were re-identified by Jensen and Padian in 1989 as belonging to the clade Maniraptora, but no determination was made whether they were from a dromaeosaurid or a bird. Jensen and Padian (1989). Some teeth from Japan that have been attributed to Dromaeosauridae may be older than Deinonychus, but the dating is disputed. Some “dromaeosaurid/troodontid-type” teeth from the late Middle Jurassic of England have also been noted (see discussion in text). Benton (1993), 702. [RETURN TO TEXT]

[74] Fallow (1997), 108-110; Feduccia (1996), 90. [RETURN TO TEXT]

[75] Zhao and Xu (1998). According to one recent classification, Therizinosauroidea is a superfamily consisting of the families Alxasauridae (consisting of the genus Alxasaurus) and Therizinosauridae (consisting of the genera Enigmosaurus, Erlikosaurus, Nanshiungosaurus, Segnosaurus, and Therizinosaurus). Glut (1997), 55-56. The genera Alxasaurus, Enigmosaurus, Erlikosaurus, Nanshiungosaurus, and Segnosaurus are also known as Segnosauria. Fastovsky and Weishampel (1996), 226-227. [RETURN TO TEXT]

[76] “[B]iologists working with both modern and extinct groups argue that convergence is very common.” Carroll (1988), 8. A classic example is Thylacinus, a marsupial “wolf,” and the placental canids. Carroll says, “The general body form [of Thylacinus] as well as details of the dentition provide a strikingly close parallel with the placental canids” (emphasis supplied). Carroll (1988), 435. [RETURN TO TEXT]

[77] Fastovsky and Weishampel (1996), 226. [RETURN TO TEXT]

[78] Fastovsky and Weishampel (1996), 228. See also, Glut (1997), 55. The recently discovered Beipiaosaurus inexpectus has been interpreted as a primitive therizinosaur. Xing et al. (1999a); Sloan (1999), 103, 106. The authors believe it has features that show therizinosaurs to be coelurosaurian theropods. [RETURN TO TEXT]

[79] Zhao and Xu state, “Isolated teeth tentatively identified as dromaeosaurid have been found in Middle Jurassic deposits” (emphasis supplied). Zhao and Xu (1998), 235. Benton refers to teeth from the late Middle Jurassic as “dromaeosaurid/troodontid-type.” Benton (1993), 702. [RETURN TO TEXT]

[80] Padian and Chiappe (1998), 14. Padian and Chiappe would now view Caudipteryx as the “sister group” of birds, but as previously discussed, Caudipteryx is probably a flightless bird. [RETURN TO TEXT]

[81] Feduccia (1996), 90. He writes: “First, the timing is off. Archaeopteryx occurs in the late Jurassic, some 150 million years ago, and presumably birds originated much earlier, say, possibly medial to late Triassic. However, the earliest dinosaurs, Eoraptor (if it is a dinosaur) and Herrerasaurus [cites omitted], both from the late Triassic of Argentina, lack the synapomorphies that are used to unite birds and dinosaurs” (emphasis supplied). The same holds for Middle Jurassic dinosaurs. [RETURN TO TEXT]

[82] The desperation is palpable in the claim that the middle Early Cretaceous Yixian Formation is a “refugium for relicts,” a pocket of evolutionary holdovers, none of which left evidence of its existence during the preceding ages. Zhexi (1999). Zhexi understates the difficulty of his position by suggesting that the “ghost lineages” of the Yixian “relicts” extend back to the Late Jurassic (some 25 million years). Without even considering Protoavis, to qualify as ancestors of birds the “ghost lineages” of the Yixian theropods would need to extend back at least to the Middle Jurassic, another 25 million years (see notes 61 and 62). [RETURN TO TEXT]

[83] Feduccia (1996), 56. [RETURN TO TEXT]

[84] Benton (1993), 681-711, 717-734, 739-768. [RETURN TO TEXT]

[85] Padian and Chiappe (1997), 78. [RETURN TO TEXT]

[86] Chatterjee (1997), x. [RETURN TO TEXT]

[87] Of course, creationists have their own problems regarding the fossil record, but explaining how evolutionary lineages could exist for tens of millions of years without leaving a clear trace is not one of them. [RETURN TO TEXT]

[88] Padian and Chiappe (1997), 78. [RETURN TO TEXT]

[89] Ibid. [RETURN TO TEXT]

[90] Carroll (1988), 340. [RETURN TO TEXT]

[91] Chatterjee (1997), 7-8. He writes, “The common ancestor of birds and dromaeosaurs has yet to be found in the fossil record. However, we can speculate from cladistic analysis that this hypothetical bird ancestor would be very similar to dromaeosaurs in general morphology.” He concludes, “Dromaeosaurs are currently the best approximation of the hypothetical bird ancestor and serve as a model when tracing avian ancestry.” [RETURN TO TEXT]

[92] Currie (1997b), 195. [RETURN TO TEXT]

[93] Zimmer (1998), 32 (quoting Catherine Forster). She told the Associated Press, “This animal gives powerful new evidence to support the theory that birds descended from dinosaurs,” and said it may be “the strongest last nails in the coffin” for those who doubt that birds evolved from dinosaurs. Anonymous (1998). Rahonavis dates from 65-75 million years ago. [RETURN TO TEXT]

[94] Fastovsky and Weishampel (1996), 278-279. [RETURN TO TEXT]

[95] Feduccia (1996), 68. The specifics are elaborated upon at pp. 68-81. For a response from theropod advocates, see Padian and Chiappe (1997), 73-78. Suffice to say that neither side is persuaded. The debate about digital homology has received a fair amount of attention. Opponents of theropod origins argue on the basis of embryological developmental patterns that the three digits of the avian hand are II-III-IV, whereas it is agreed that the digits of the theropod hand are I-II-III. If this is correct, the three digits are not a shared feature inherited from a common ancestor and thus argue against theropod ancestry. See, Burke and Feduccia (1997); Padian and Chiappe (1998b), 7-8. [RETURN TO TEXT]

[96] Gibbons (1997b), 1230. [RETURN TO TEXT]

[97] Ibid. [RETURN TO TEXT]

[98] Ruben et al. (1999). [RETURN TO TEXT]

[99] Browne (1999). [RETURN TO TEXT]

[100] Ibid. [RETURN TO TEXT]

[101] Denton (1998), 361. Padian and Chiappe state that bird lungs “are extremely complex and are unlike the lungs of any living animal.” Padian and Chiappe (1998a), 43. Pough et al. say, "The respiratory system of birds is unique among living vertebrates." Pough et al. (1989), 621. [RETURN TO TEXT]

[102] Denton (1998), 361. [RETURN TO TEXT]

[103] Denton (1998), 361-362. [RETURN TO TEXT]

[104] Chatterjee (1997), 161-184. [RETURN TO TEXT]

[105] Fastovsky and Weishampel (1996), 313. [RETURN TO TEXT]

[106] Feduccia (1996), 97; Chatterjee (1997), 151. [RETURN TO TEXT]

[107] Chatterjee (1997), 151-152. Burgers and Chiappe have recently argued that Archaeopteryx could have gained the velocity necessary to take off from the ground by flapping its wings as it ran. Burgers and Chiappe (1999). The validity of their analysis remains to be seen, but in any event, it assumes the presence of Archaeopteryx-type wings to generate the hypothesized forward thrust. It thus does not seem useful in explaining how such wings developed in the first place. [RETURN TO TEXT]

[108] Feduccia (1996), 98. [RETURN TO TEXT]

[109] Chatterjee (1997), 153. See also Feduccia (1996), 98-101. [RETURN TO TEXT]

[110] Chatterjee (1997), 153; Feduccia (1996), 101. Though Ostrom had abandoned the theory by 1983, he apparently did not formally publish that opinion until 1986. [RETURN TO TEXT]

[111] Feduccia (1996), 102. Chatterjee describes the theory this way:

According to these authors, the proavians might have used their jaws to catch prey but employed their wings as bilateral stabilizers during a jump into the air. Caple and colleagues maintained that the rudimentary wings of proavians were effective for balance while running, jumping, and turning, until they were able to take off at high speed. They speculated that, when the proavians extended their forelimbs, minute increments of lift made it easier to jump further and capture more prey. The motion of the forelimbs for stabilization, according to them, would mimic the flight stroke of a bird. Eventually, the proavians evolved larger airfoils that enabled them to obtain even greater lift. Also, as lift increased it aided in landings. Therefore, the proavians could slow down and direct their landings. As a result, power flight evolved. Chatterjee (1997), 153-154.

This theory has recently been modified by assuming that the hypothesized cursorial ancestors of birds specialized in pouncing on their prey from elevated sites. Garner et al. (1999); Taylor (1999). So instead of leaping on prey from trees, which they could not climb, they supposedly leaped on prey from other structures that they could climb. Of course, one can only speculate about the terrain in which these alleged avian ancestors hunted, but even if there were a sufficient number of elevated sites that were frequented by prey, the tail and sickle claws of dromaeosaurids seem ill suited for climbing of any kind. It also seems unlikely that a predator apparently built for running would catch its prey by waiting for it on a perch. And certainly an enhanced pouncing ability cannot account for the presence of alleged “protofeathers” (the filamentous structures) on the seven-foot-long Beipiaosaurus. In addition, if one accepts Caudipteryx as a nonavian theropod, as do Garner et al., the fact it was an herbivore rather than a leaping predator presents an additional problem. Taylor’s attempt to counter this with the assertion that Caudipteryx was an insectivore (Taylor [1999], 32) is hindered by the fact the only other theropod found with gastroliths was almost certainly an herbivore. Kobayashi et al. (1999). [RETURN TO TEXT]

[112] Included in this list of critics are Jerison, Rayner, Bock, Martin, Feduccia, Norberg, and Pennycuick. Chatterjee (1997), 155. [RETURN TO TEXT]

[113] Rayner (1988), 278. [RETURN TO TEXT]

[114] Chatterjee (1997), 155. [RETURN TO TEXT]

[115] Fastovsky and Weishampel, 313. [RETURN TO TEXT]

[116] Bock (1986), 68. [RETURN TO TEXT]

[117] Chatterjee (1997), 155. [RETURN TO TEXT]

[118] Ackerman (1998), 96. [RETURN TO TEXT]

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