User:Abyssal/Feathered Dragons Intro

Edward Hitchcock's 1836 monograph on fossil "bird" tracks reexamined

Carcharodontosaurus saharicus skull.

In the introduction to Feathered Dragons, Robert T. Bakker argues that the Reverend Edward Hitchcock was the first scientist to "explore the birdness of dinosaurs in all senses[.]" Bakker argues that three distinct issues regarding the origin of birds within the dinosauria are conflated by the popular media. The first is whether or not dinosaurs are birds in an evolutionary or taxonomic sense. The second is whether or not dinosaur "physiology, ecology, and behavior" resembled those of birds. The final issue, which Bakker argues that 20th and 21st century science has been neglecting, is how the more bird-like dinosaurs fit into the broader scheme of life throughout the history of planet earth. Bakker claims that greater degrees of scientific attention were bestowed upon the third of his issues in the 19th century. He argues for the distinctiveness of his three proposed central issues in the study of the dinosaur-bird transition on the basis of the widely divergent views of the early scientists who studied it. Bakker notes "It's possible to believe that birds are the descendants of dinosaurs and yet insist that most dinosaurs were cold-blooded 'good reptiles'." Bakker says that even some of the most prominent early advocates for a dinosaur-bird connection treated with scorn the idea of feathered dinosaurs with high metabolisms. By contrast, Sir Richard Owen advocated that dinosaurs had advanced physiologies, but "inexplicably" failed to see an evolutionary connection between birds and dinosaurs.

Bakker notes that references to early studies in the dinosaur bird connection frequently target his own 1975 Dinosaur Renaissance article or John Ostrom's 1973 paper on similarities between Archaeopteryx and theropods. Many regard the very first serious treatment of the connection between birds and dinosaurs to be an 1867 collaboration between John Phillips and Thomas Henry Huxley. However, Bakker treats research by Edward Hitchcock from 1836 to be the start of serious examination of a dinosaur-bird connection. Hitchcock researched fossil dinosaur footprints from the Connecticut Valley, which he interpreted as being left by birds. Treatment of Hitchcock's work has often had a disdainful, condescending tone regarding the misidentification of the Connecticut Valley tracks. Bakker criticized such an approach to Hitchcock's research and defended Hitchcock's interpretation as being sensible in the context of dinosaur paleontology at the time. Scientists contemporary to Hitchcock tended to reconstruct dinosaurs with flat-footed plantigrade feet like those of some mammals and modern reptiles. Hitchcock correctly recognized the trackmakers as having digitigrade ("tip-toe") gaits and a bird-like rather than lizard-like body plan.

Standard dinosaur reconstructions of the period were the products of "sophomoric" errors in anatomy and selective attention to features. For instance, the illium of Megalosaurus, while originally understood by William Buckland to be bird-like was misinterpreted by Sir Richard Owen and Georges Cuvier to be a coracoid (part of the shoulder). Similarly, another pelvic bone, the ischium, was misinterpreted as a clavicle (collar bone). These misinterpretations lead to reconstructions in the style of the famous Crystal Palace dinosaurs with quadrupedal body plans, lizard-like paws, and forelimbs more muscular than the hindlimbs. Bakker contrasts the "anatomical malpractice" of mainstream dinosaur science from the time with Hitchcock's more accurate knowledge of dinosaur gait, poture and foot anatomy. From the tracks alone, Hitchcock was able to infer the digital formulas of the trackmakers. He was also able to accurately infer an Early Jurassic age for the tracks. Although he had little in the way of actual bone to work with, what little he did have had bird-like characters like hollowness. One such specimen was recovered when a barrel of black powder was detonated to assist in making a well. The remains served as the type specimen of Anchisaurus colurus, a "gazelle sized" "prosauropod." Bakker expressed "awe" at the 1836 monograph Hitchcock published about the tracks, praising his reasoning abilities and declaring that the publication single-handedly made the study of fossil tracks "a robust discipline."

Hitchcock figured out that the trackmakers had digitigrade gaits by noting that few tracks left any impressions from the metatarsals, and these traces seemed to be left when the trackmaker "hunkered down." Hitchcock also notice that the rarity of foreprints meant that the trackmakers were bipeds. Further, the trackways were very narrow, as were the animal's metatarsals, which could be inferred from the narrow angle at which the toes diverged therefrom. Based on the time's flawed understanding of dinosaur anatomy, these features would have excluded them from candidates for the trackmakers. Other animals could be excluded from potential candidacy based on the inferred number of phalanges in the digits that Hitchcock deduced from the number of pads on the sole of the animal's foot. Since he knew that the pads would underlie joints between phalanges, Hithcock could count the number of bones without actually having access to body fossils. His method successfully determined the dinosaur phalangeal formula 2-3-4-5-0, even going so far as to estimate the correct number of phalanges in the hallux despite this digit not typically leaving traces with prints. The formula he uncovered excluded mammals, who have a 2-3-3-3-3 formula from being potential track makers. Crocodilians share the same formula, but the splayed limbs and plantigrade feet excluded them. Birds however fit every aspect of the track morphology, much more closely than the inaccurate contemporary dinosaur reconstructions.

Hitchcock also reconstructed the behavior of the trackmakers, observing that multiple trails occurred in parallel implying that the animals were traveling together in groups. Hitchcock drew from his inferences to paint "vivid word portraits of the Jurassic ecosystem: great flocks of giant ground birds contend[ing] for dominance with each other on the river-edge floodplains and along the wide banks of warm lakes." Hitchcock "struggled" to understand where his assumed avian trackmakers fit into the scheme of Divine Creation. Evolutionary ideas were being advocated by some scientists, but Hitchcock found such views strongly offensive on the grounds that they removed the supernatural from life's origins. Bakker describes Hitchcock's sentiments as "hat[r]ed" for the idea of "transmutation" its "impious materialism." In contrast to materialist understandings of the devlopment of life was a period religious interpretation of the fossil record called serial creation. Serial creation postulate a scale of nature ranking animal life from highest to lowest. This scale was topped by the mammals, who ranked over birds, reptiles, and amphibians in descending order. Serial creationists believed that the earth began in a molten state. As it cooled and, God specially created increasingly higher order animal groups. During the Carboniferous the hot wet planet was only suitable for amphibians and the most primitive reptiles. Gradually, God began replacing the preceding dominant and vertebrate class, going from birds to mammals, and then people. Each of these new dominant groups were designed to exploit progressively cooler drier habitats, with serial creationists seeing humans as intended to inhabit "a brisk, temperate climate, like that of Western Europe or New England." Hitchcock was a reluctant convert to this view of nature despite his revulsion for materialistic evolutionary ideas because he saw the Connecticut Valley "bird" tracks as being chronologically out of place for the serial creationist scheme. Hitchcock didn't believe that birds, as the second highest class, should have been created by God until the Cenozoic. However, his later writings show that Hitchcock became convinced of the existence of a ladder of progress within divine creation. Bakker praised the idea of serial creation as anticipating the broad trends paleontology would go on to discover in climatary and faunal changes across Laurasia, although noted that this was only true if the theological elements were removed from the narrative. Gradually Hitchcock began to notice that his alleged birds had very non-avian traits, including some resembling those of amphibians, mammals, and familiar modern reptiles like crocodillians and lizards. Some Anomoepus tracks from the Connecticut Valley deposits were accompanied by small five-fingered hand prints, with the inner three digits possessing claws. Since the mud should have preserved any traces of feathers, Hitchcock concluded that his birds had lacked feathers on the hand. Bakker notes that these hand prints resemble those belonging to the Late Jurassic Morrison ornithopods like Dryosaurus and Drinker. Other trackways preserved what seemed to be evidence for a bony tail. Hitchcock interpreted a depression left in the sediment between two Anomoepus tracks as having been left by a short muscular tail, although modern science has not confirmed that this is a tail trace. Trackways left by Grandipus sometimes preserved long, sinuous traces that do, however, seem to be tail marks. Despite the accumulation of traits contrary to bird anatomy, Hitchcock never could shake his interpretation of an avian nature for the tracks. But as more time went on his views of the Connecticut Valley trackmakers grew nuanced enough that he interpreted his birds as bearing features that blurred the distinctions between the traditional land vertebrate classes. Bakker describes Hitchcock's growing realization of the uniqueness of his trackmakers as having "exhilarated" him. Hitchcock's ideas paralleled conclusions reached by other life scientists of the time like Yale's W. D. Dana who saw the duck-billed platypus as blurring the boundries between mammals, reptiles and birds. Dana saw lungfish as combining the features of amphibians and fish, while dinosaurs had the gait and internal anatomy of mammals withe crocodillian jaws and tails. Despite the resemblance of these boundry crossing interpretations of various modern and fossil forms, Dana was also a serial creationist who saw them as representing the fullness of creation. He saw the Jurassic world as being too primitive for God to place the modern higher vertebrate classes at the apex of its ancient ecosystems but thought the conditions were right for a subclass of animals combining the traits of the higher and lower vertebrates groups.

Bakker praises the serial creationists as actually developing a more accurate narrative than the intellectual ancestors of evolutionism. He calls this "one of the greatest ironies of 19th century geology," pointing out that while young, Thomas Henry Huxley was critical of earth history models featuring progressive elements. Charles Lyell also reject the notion of progress in favor of cyclical interpretations of history, for instance he believed that extinct classes of animal could be ressurected when favorable environmental conditions returned to their habitats. The appearance of a directional trajectory for life's development Lyell attributed to poor sampling of the fossil record. He thought that at stages of history where only fossils of primitive mammals had bee found that larger more complex forms of the period may have just been confined to higher elevation regions not subject to the sedimentation processes that lead to fossil formation. Bakker criticized historians of science for being dismissive of the serial creationists since their discovery of increasingly numerous faunas and intermediates between the body plans of different classes provided the key evidence for evolution to gain an intellectual foothold in the scientific community. Bakker attributes the decline of serial creationism's intellectual prominence to two key developments. The first were the ever-increasing numbers of unique chronological separate faunas that strained the imagination for the number of divine interventions they would require. Bakker observed that although in 1851 Hitchcock advocated for six key Creations, within 20 years "the Jurassic alone was divided into a dozen faunal stages, and the entire Mesozoic required thirty or forty individual creation-interjections." The second major development Bakker sees as undermining the prominence of serial creation was the continual discovery of additional intermediate forms that continued to blur boundaries between Linnaean classes. Archeopteryx was one such form. Although Dana incorporated the discovery into his serial creation scheme, Darwin gave the find an "ecstatic" reception as Archeopteryx was the sort of perfect transitional form between reptiles and birds many creationists had dismissed as impossible.

Hitchcock's son was another creationist to embrace Archeopteryx. In 1864 Edward Junior updated his father's monograph on the Connecticut Valley tracks and compared Archeopteryx to his father's unorthodox "birds." He noted that Archeopteryx had the clawed reptilian hands reported from the fossil foreprint traces, as well as a bony tail that could have left an imprint in the sediment like his father had observed. The younger Hitchcock's synthesis of his father's work attributing the Connecticut Valley track fossils to the activities of claw-handed birds with long bony tails is regarded by Bakker as the first treatment of modern science's understanding of dinosaurs in print. Bakker agrees that all of the Connecticut Valley's theropod tracks could be though of in terms of variants on the Archaeopteryx body plan.

He encouraged future researchers to emulate Hitchcock's example by paying detailed attention to anatomy of their subjects and trying to establish their ecological context while imagining the forces that shaped their evolution throughout deep time. Bakker ends his review by attributing the success dinosaurs had in suppressing mammalian evolution to advantages lent to them by their bird-like body plans.

Other stuff

Early pioneer of the dinosaur-bird connection Robert T. Bakker has quipped that the feathery quills added to the Velociraptor for Jurassic Park III "looked like a roadrunner's toupee." However, he conceded that feathers are difficult subjects for computer animation and speculated that "Jurassic World"'s raptors would have more realistic thorough plumage.