This commentary begins with three questions, but don't panic, because these are easy ones; in fact, I answer them for you.
Question #1: Are birds descended from dinosaurs? Answer: It's not yet known.
Question #2: If they are, does it mean that they are dinosaurs? Answer: Of course not. A bird is a bird, and a dinosaur is a dinosaur.
Question #3: Were there feathered dinosaurs? Answer: No. There may have been feathered animals that otherwise resembled reptiles, but if they had feathers (a classic hallmark of birds), how could they have been "dinosaurs?"
In Asteroid Asininity, I alluded to the unpleasant penchant that many scientists have for speaking on purely conjectural matters as if their views had won universal acceptance; this practice is also apparent in regard to the issue of how birds relate to the extinct therapods, viz., carnivorous dinosaurs. According to the online University of California Museum of Paleontology:
"The oldest known fossil unambiguously identified as a bird is still the dinosaur-like [the italics are mine] Archaeopteryx, from the Solnhofen Limestone of the Upper Jurassic of Germany. However, it was not the only bird of the time. Very recently, another bird of almost the same age was discovered in northeastern China, and named Confuciusornis; Confuciusornis resembles Archaeopteryx in having wing claws, but unlike Archaeopteryx and like modern birds, Confuciusornis lacked teeth…."
A second u.r.l. from Berkeley reads thus:
"Archaeopteryx is considered by many to be the first bird, being of about 150 million years of age. It is actually intermediate between the birds that we see flying around in our backyards and the predatory dinosaurs like Deinonychus…. [i.e., dromæosaurs]"
A third u.r.l., from the same site, tells the visitor:
"According to current thinking, birds are hypothesized to have shared a common ancestor with the dromaeosaurs sometime in the Jurassic period; Dromaeosauridae is thus termed the sister group of the clade Aves (which includes all birds). It may even be that the ancestry of birds lies within this group, which would make them dromaeosaurs too…."
A different site posits that "Protoavis [which means "first bird"] predates Archaeopteryx by 75 million years pushing the origin of birds to the Late Triassic and is considered the oldest known bird (Chatterjee 1999)." The site also depicts a "Life restoration of Protoavis," and informs us that "the presence of feathers is inferred from quill knobs. (Chatterjee 1999)" The ubiquitous "Wikipedia" relates that dromæosaurs appeared in the second epoch of the Jurassic period, 176-161 million years ago, and disappeared some 100 million later. One source, which I consulted no more than a few years ago—I don't remember now what it was—says matter-of-factly that palæontologists now believe that birds hail from the dromæosaurs and that archæopteryx was an evolutionary dead end! Another forgotten font of knowledge concurs that birds sprang from dromæosaurs, but asserts that archæopteryx is considered to be neither a transition fossil nor a dead end, but merely a juvenile cœlophysis mistaken for a separate species.
What, then, have we learned of avian lineage from these sources that set the record straight so authoritatively, three of which actually are from the same museum but presumably of various authorship? We have learned that the earliest bird was archæopteryx; that the earliest bird was protoavis; that palæontologists deem archæopteryx a dead end; that palæontologists deem archæopteryx not even a valid species; that birds descend from, yet have a common ancestry with, dromæosaurs, which originated at least 11 million years before the younger candidate for the title of "first bird" and at least 50 after the older; that dromæosaurs yet existed at a time when, as fossils show, their descendants the birds were well-established; that a bird of "almost the same age as" archæopteryx differed significantly from its near-contemporary; and that birds may qualify as dromæosaurs, and thus as reptiles.
Naturally, none of what I've said here proves that birds are not the progeny of dinosaurs; I, also, even as a child, noticed that the latter bear in some ways (e.g., the bipedal posture of the therapods) greater (though perhaps superficial) similarity to the former than to modern reptiles. It only shows that this debate, like that over whether human action causes "global warming," is far from over. What I read while growing up merely stated that archæopteryx was a link between birds and reptiles, not necessarily dinosaurs; this seems a much safer position to take. What's the point of speculating as to whether a sparrow can call a deinonychus "Grampa," when we don't even know how long ago the earliest true birds lived?
