Archaeopteryx a bird???

Dear All, Part of the problem with bird origins is that Archaeopteryx and modern birds may have descended from different groups of 'dinosaurs'. It may sound preposterous to suggest that Archaeopteryx is not a true 'bird', but it is being suggested and analyzed as a possibility by many different workers. Archaeopteryx seems to be closely related to dromaeosaurs, but this does not necessarily mean that modern birds (Neornithes) are that closely related to dromaeosaurs. Keep this in mind as the 'bird' origins debates continue, and it will probably help you sort through all the semantic confusion that this debate will continue to generate.

These workers rely on vague similarities. Whatever their conclusion may be, they would have to explain how feathers could have evolved at least twice, since Archaeopteryx has feathers that are indistinguishable from those of modern birds. Yes, it is preposterous to suggest that birds evolved from dinosaurs. It is even more preposterous to suggest that birds evolved more than once from different dinosaur groups. Scientists who make that sort of suggestion should have their heads examined for signs of incurable intoxication by cladism.

Not at all. What is the evidence for such a relationship? The semilunate is one bone in Archaeopteryx, 2 bones in dromaeosaurs. The bird fingers are 2-3-4 and the theropod fingers are 1-2-3. The Archaeopteryx and dromaeosaur wishbones and shoulder joints are structurally different. Archaeopteryx's 'coracoids meet the avian straplike scapula at a 90º angle, a condition unique to volant birds' (Feduccia 1996:81). The superficial similarities that were used to link birds and dinosaurs simply do not stand up to close scrutiny, even though they may fool those who rely on vague similarities: the cladists and their followers.

Of course modern birds are not closely related to dromaeosaurs. Modern birds are closely related to the sauriurine birds like Archaeopteryx. All birds, including Archaeopteryx, have the unique and complex synapomorphy of feathers, shared only by Longisquama, which is not classified as a bird but is most likely the closest known relative of birds, if not their direct ancestor.

Some cladists, since they are losing the debate, are now trying to redefine bird. They are clearly grasping at straws. Cladistics is, as Dodson (2000) points out, not even necessary in the formulation of the theory of a dinosaurian origin of birds since Ostrom and Huxley have no problem putting together cogent arguments in favor of that theory without employing cladistics. And it certainly isn't the final word in the bird origin debate. In fact, Ostrom was apparently flabbergasted that some cladists consider Mononykus a bird, when he writes ''Mononykus was not a bird, ...it clearly was a fleet-footed fossorial theropod.... Reasoning of such dubious quality demonstrates a fundamental flaw in the cladistic methodology.' (1997, 172)' (Feduccia 1996:90). If cladists claim that Mononykus is a bird and that Archaeopteryx is not a bird, then Ostrom is right! There is a fundamental flaw in cladistic methodology since Mononykus does not have a single uniquely avian character. Not one! If cladistic methodology can lead its practitioners to the conclusion that an animal without a single uniquely avian character is a bird and at the same time to the conclusion that Archaeopteryx, which has many uniquely avian characters (including feathers, reversed hallux, enlarged cerebellum, double-headed quadrate, avian palatine) is not a bird, then a reasonable person who is not hopelessly enamored with cladism may conclude that cladistic methodology is simply unreliable.

Some clarification may be needed. I do not imply that those who believe in a dinosaurian origin of birds are intoxicated by cladism since they may (or may not) be convinced by John Ostrom, who exployed classic comparative anatomy in concluding that birds are probably descended from a coelurosaur. Ostrom did not use cladistic analysis to arrive at his conclusion.

I only suggest that those who will ignore the many uniquely avian characters shared by Archaeopteryx and modern birds in order to suggest that Archaeopteryx may have arisen from a different group of dinosaurs than modern ornithurine birds should have their heads examined for possible incurable intoxication by cladism.

John, The most recent attempt to bring together various evidence (linking Archaeopteryx more closely with dromaeosaurs, while other maniraptor groups seem closer to modern birds) would probably be the paper by David Marjanovic of Austria. I don't have an exact citation handy, but it was published in the Dinosaur Society Quarterly Journal (volume 4, number 1?) early this year. It has some errors, but does make me wonder if we should continue to include Archaeopteryx in Class Aves if we don't also include some maniraptoran groups as well.

Count me out as part of the 'we' to which Kinman is referring.

Paraphrasing Storrs Olson, I can only hope to distance myself from those who will accept the likelihood of such nonsense.

Wow. You just destroyed all your credibility. Longisquama was a lizard that had highly modified scales, that, on an extremely cursory level, do resemble flight feathers, but upon an even slightly closer examination resolve into structures that cannot possibly sustain powered flight or gliding. Upon close examination, the structures in Longisquama do appear to have a hollow center shaft, but the rest of their structure is not fibrous, like a feather. The impressions in the fossil slab are of a structure that is fairly narrow for roughly 2 thirds of it's length, then gets wider as it curves backwards. There is a center shaft (apparently hollow) on this structure, with grooves departing from the shaft at fairly regular intervals. These grooves are too large, by far, to be the interlocking fibers (or gaps between them) that comprise flight feathers. Nor do they appear to be possible clumping together of these fibers (because of mud or whatever getting into them as the creature lay dead or dying) they are far too regularly spaced for that. They simply appear to be grooves in an otherwise relatively solid structure. Like the hollow shaft, these grooves could have assisted in reducing the weight of the structure, not because it was important for flight, but because (like feathers) these things appear to have only attached to the animals skin! If they were solid structures they'd need to be light in weight for this alone. So they do appear to have a very few features in common with feathers, (central hollow shaft, general light-weight construction, cutaneous attachment) but they are not feathers.

Even if they could support some kind of flight and were a bird ancestor, you'd have to create (and support) 'special explanation's for how ALL other bird features came into existence from an animal that just doesn't appear to be in a position to provide them, while there is another group of animals that to appear to at least have a common ancestor. The toughest thing by far would be to explain how the 'flight feathers' appear to have 'migrated' from the creatures back to the arms in a process that still allowed for some sort of flight.

Also, flight feathers need to very broad along virtually their entire length and they need to be straight. The structures on Longisquama are relatively narrow for most of their length, then curve backwards before they become broad. Additionally, they never become asymmetrical in the way that flight feathers must be. Even more to the point, the most distal flight feathers must point outward and away from the animal; in Longisquama, the most distal part of the structure points backwards.

You'd also have to explain how these structures, which appear to be attached only to the skin along the animal's back, with no underlying structure to provide additional support, could have supported the weight of the entire animal during either gliding or powered flight! All other extant or extinct known gliders or flyers use their limbs as a support for the flight structure.

Perhaps the dinosaur to bird theory of bird origins is incorrect. But it has far more facts that fit the bill, than the Longisquama to bird explanation. It also has fewer glaring paradoxes and requires far fewer 'special explanations'

Not to disagree with your general assessment, but the flying snakes (Chyrsopelea sp.) don't use their limbs to support their glides...

Philip Bowles

Ooops! HOWEVER this still supports my point (and thank you) - because their gliding surface is their entire body, surely a bony structure that lends vital support to it's function as an air foil. In Longisquama, the 'foil' is attached at various single points only to the creature's skin - there's no evidence to show otherwise. Surely this could not support the weight of the creature during any type of flight, it seems pretty certain you need the assistance of a major bodily structural support to assist in supporting an airfoil that must in turn support the entire creture in mid-air.

Paul, Excellent post. I would only add that Longisquama might not be a lizard (i.e., a lepidosauromorph). The best current assessment seems to make it a primitive archosauromorph, somewhere within in the prolacertiform radiation.

Longisquama has feathers. No lizard has feathers.

The antorbital fenestra would make it an archosaur. The feathers and the furcula (which is nearly indistinguishable from those of Archaeopteryx) would make it the closest known relative of birds. No dinosaur has a furcula that is this similar to a bird's and no dinosaur has anything remotely resembling feathers.

This is merely an assertion, Cal. Please support it with some facts.

Even given that these structures are feathers (which they aren't) that ould be a grand total of two features that it has in common with birds. But since these things are demonstrably NOT feathers that leaves only one common feature. Now explain why the nearly 200 features that 'bird-like' dinosaurs have in common with birds are NOT indicative of a relationship and explain how so many nearly identical features evolved indepentdantly. (Hint: Convergent evolution does not work this way)

You are merely ignoring painfully abundant evidence here. There is more and more evidence every year (heck - every *month*) to show that some dinosaurs probably had feathers.