Tuesday, July 5, 2016

Feathered Dinosaurs and Speculative Evolution Date Back Far, Far Earlier Than You Probably Think

This article covers three topics that may seem disparate, but are actually intertwined. These three topics are feathered non-avialan dinosaurs, the possibly non-avialan dinosaurian nature of Archaeopteryx, and speculative evolution. I will cover the early histories of all three topics, and show that all three actually date back far earlier than is commonly thought.

It is widely-known among paleontologists and paleontology aficionados that a close evolutionary relationship between birds and the, then-newly discovered, dinosaurs was proposed by English naturalist Thomas Henry Huxley (nicknamed "Darwin's Bulldog" due to his tenacious support of the latter's theory of evolution by natural selection) in the mid-19th century. No doubt bolstered by the discovery of a highly unusual animal in fossil form in Germany in 1861, just two years after the publication of Darwin's scientific manifesto, outlining his views on evolution, On the Origin of Species, which was christened Archaeopteryx lithographica, Huxley began to be struck by the staggering amount of similarities that existed between the two groups. The significance of Archaeopteryx was, of course, that its fossil appeared to preserve evidence that the animal was coated by a feathery plumage in life, while the skeleton displayed copious hallmarks of close affinity with members of the taxonomic Class Reptilia. If not for the presence of impressions indicative of the existence of a feathered integumentary system in the animal's fossil, it would undoubtedly have been classified as a small predatory dinosaur upon its discovery. It is quite telling that at least one specimen of Archaeopteryx was actually misidentified as a specimen of the contemporaneous small-bodied theropod dinosaur Compsognathus for many years. It is not for want of good reason that I make mention of Compsognathus at this juncture, for I will now initiate a discussion of this diminutive dinosaur, which, indeed, will allow me to segue into discussion of what constitutes the gist of this article.

While I mentioned at the start that Huxley's proposal that birds are descendants of dinosaurs is well-known among paleontologists and paleontology aficionados, there exists another contribution by Huxley to the then-nascent study of dinosaur paleontology that is much less widely-known, but nevertheless, the implications of which for the history of dinosaur paleontology are equally as staggering, if not more so. In the 19th century, Thomas Henry Huxley speculated that the aforementioned small theropod dinosaur Compsognathus might have been feathered, and reflected that, if it was, it would be difficult to decide whether it ought to be deemed a bird-like reptile or a reptile-like bird.

Yup. That's right. Indubitably talented researchers and paleo-artists such as Robert T. Bakker, Gregory S. Paul, Mike Hallett, and Sarah Landry might have speculated about and drawn feathered non-avian dinosaurs in the 1970s and 1980s, but by no means were they the first to do so. Unless a still earlier example is found, for now, that distinction goes to Huxley, who formulated the idea of a feathered Compsognathus more than a century prior to those aforementioned paleo-artists. But it wasn't just the concept of feathered non-avialan dinosaurs that dates back to far earlier than is conventionally assumed; so, too, does the concept of four-winged arboreal feathered reptiles lying close to the origin of birds, and, by extension, the field/genre of speculative evolution.

In 1915, American naturalist William Beebe wrote an article in the scientific journal Zoologica in which he proposed the possible existence of a highly bizarre animal that he termed the Tetrapteryx, so named due to the fact that it was a creature on the cusp between reptiles and birds, much like Archaeopteryx, albeit with one exquisite twist: it found  itself in possession of, not two, but four wings composed of feathers, a pair on the hind limbs, as well as on the front limbs. If this description is ringing a bell, there's a mighty good reason for that; the discovery of the four-winged dromaeosaurid theropod dinosaur Microraptor in 2003 showed that Beebe's speculative Tetrapteryx was presciently on-the-ball, and that it had been an unwise decision by mainstream science to shun his hypothesis for so long. Not only did Beebe successfully presage the discovery of a four-winged feathered dinosaur 88 years later, he even drew a picture of his speculative beast, which was published in his 1915 paper. If Beebe intended for his Tetrapteryx to be dinosaurian, which I cannot ascertain definitively from his writing, then his drawing would hold the distinction of being the first known depiction ever drawn of a feathered non-avialan dinosaur. But it doesn't even end there. There's more.

William Beebe's Tetrapteryx is undoubtedly a product of speculative evolution, thereby invalidating the commonly-held notion among those involved in the field that Dougal Dixon "created" the field of speculative evolution in 1981 with the publication of his book After Man: A Zoology of the Future. Even without mentioning Beebe's Tetrapteryx at all, the publication of Gerolf Steiner's book The Life and Times of the Rhinogrades in 1961, in which an entire speculative order of mammals, Rhinogradentia, was envisioned is undoubtedly a work of speculative evolution, and it was published 20 years before Dixon's book. So the notion that Dougal Dixon "created" speculative evolution in 1981 is already known to be false due to the 1961 introduction of the Rhinogradentia. The 1915 introduction of the Tetrapteryx merely serves to push it further back still by 46 years. Speculative evolution, just like feathered non-avialan dinosaurs, likewise dates back to far earlier than is often assumed.

As if that wasn't enough, there's still more. Even if Huxley might have speculated about the existence of feathered non-avialan dinosaurs in the 19th century, surely, it doesn't mean anything if no fossils of feathered non-avialan dinosaurs were known, right? Well, think again. First of all, as demonstrated by the successful prediction of the eventual discovery of Microraptor by the Tetrapteryx, speculation plays an important role in paleontology. There was also another case of a speculative anomalocarid presaging the eventual discovery of the fossil of a real one that resembled it greatly, and was, in fact, therefore named after the speculative creature. Even so, if it turns out that Archaeopteryx was, in fact, a non-avialan dinosaur, rather than a bird (as some paleontologists nowadays are starting to classify it as), then the first fossil of a feathered non-avialan dinosaur would have been unearthed back in 1861. But still, it wouldn't have been recognized as non-avialan until recently, right? Wrong. Back in 1935, a scientific paper appeared, written by Lowe et al., in which it is stated that the Archaeopteryx fossil shows almost no uniquely avian autapomorphies with the exception of its feathers, and that it could very well be regarded as an example of a small feathered non-avialan dinosaur. So if Lowe's views end up being vindicated by future science, then the first feathered non-avialan dinosaur to be discovered would have been discovered in 1861, and recognized for its non-avialan nature in 1935. The discoveries of feathered dinosaurs in China in the 1990s, widely hailed at the time, would no longer be so significant.

By no means do I intend to diminish the research and work of Bakker, Paul, Hallett, Landry, et al. with regard to their research into and artistic depictions of feathered non-avialan dinosaurs, and Dixon with regard to his research into and artistic depictions of speculatively-evolved animals. These people have made great strides in advancing the concept of feathered non-avialan dinosaurs and speculative evolution, respectively, and should be commended in the highest for their valiant efforts to advance these areas of science. However, it should not be forgotten that Thomas Henry Huxley proposed the possibility of feathered non-avialan dinosaurs in the mid-19th century, that William Beebe possibly drew the first depiction of a feathered dinosaur, as well as the first example of a creature of speculative evolution, in the early 20th century, and that Lowe et al. genuinely entertained the notion that Archaeopteryx was a non-avialan feathered dinosaur, also in the early 20th century. It would be wise to repeat the words of George Santayana, which ring as true for paleontology and zoology as for any other disciplines: "Those who cannot remember the past are condemned to repeat it." It is highly beneficial to the future of paleontology and zoology that Huxley, Beebe, and Lowe be given recognition for being the first to conceptualize feathered non-avialan dinosaurs, speculative evolution, and the possible non-avialan dinosaurian affinities of Archaeopteryx, respectively, the first two over a century ago, and the third over eighty years ago. Let's give these three great men their due so that we do not forget where our ideas came from, so that we can have a less nebulous idea of where to take them in the future.

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