The Proceedings of the Eighth International Conference on Creationism (2018)

and theropods, such as the contemporary Compsognathus . Despite recognizing the strong parallels between the two groups, Heilmann refused to conclude that birds evolved from dinosaurs due to one missing piece of evidence he considered critical: dinosaurs did not possess clavicles, much less a furcula (the set of fused clavicles in birds commonly referred to as the “wishbone”). Heilmann concluded that birds must have an ancestor within Pseudosuchia, which contained specimens known to have clavicles. In 1924, the theropod Oviraptor was discovered in Mongolia by Henry Fairfield Osborn. This specimen possesses a furcula, but it was misidentified in the original paper (Barsbold 1983; Osborn 1924). Just over a decade later, the Lower Jurassic theropod Segisaurus was found with an unmistakable clavicle, which under later review was found to be a furcula (Carrano et al. 2005). Heilmann’s view on the origins of birds was generally accepted through the 1950s. In 1964, paleontologist John Ostrom discovered Deinonychus , a new species of dromaeosaurid – a small theropod with a large, sickle-shaped “killing claw” on the second toe. Through the early 1900s, dinosaurs were predominantly portrayed as sluggish, reptilian ectotherms. Deinonychus, however, was clearly an active and agile predator (Ostrom 1969). In addition to this, Ostrom (1974) noticed many similarities between the forelimbs of Deinonychus and Archaeopteryx (Fig. 2). In fact, Deinonychus shows numerous striking skeletal similarities to Archaeopteryx. For instance, Deinonychus had features that most theropods known at the time did not, such as a birdlike hip structure with a retroverted pubic bone (vertical, according to Senter et al. (2012)), a semilunate carpal bone (a wrist joint that allows birds and other maniraptorans to fold their hand against the forearm) much like that of Archaeopteryx, and likely feathers (several other fossil dinosaurs in the same family have been found with feathers) (Kane et al. 2016). Earlier restorations of Archaeopteryx depicted it with a fully reversed hallux like a modern perching bird (Morell 1993), but newer specimens with less distortion have confirmed toe positions in Archaeopteryx to be the same as in deinonychosaurs (Fowler et al. 2011; Mayr et al. 2007; Mayr and Peters 2007), although there are dissenters to this opinion (Feduccia 2007; Feduccia et al. 2007). 2. What Is a Feather? Many creationists, and some evolutionists, have been hesitant to call the fuzzy structures present in many dinosaur fossils “feathers”. Some have suspected that the structures are actually degraded dermal collagen tissue (e.g., Feduccia et al. 2005; Lingham- Soliar et al. 2007), whereas others recognize them as “dino fuzz”, an indeterminate form of integument unrelated to feathers. Microscopic examination of the filaments in Sinosauropteryx suggest that they were hollow, similar to feathers (and very different from mammalian hair). Further analysis has revealed preserved melanosomes in the structures, suggesting they are not collagen, as collagen does not contain pigment (Longrich 2002). Additionally, chemical analysis of similar structures in the alvarezsauroid theropod Shuvuuia has revealed the presence of β-keratins, but no α-keratins. β-keratins are only produced by the epidermal cells of non-avian reptiles and birds, and feathers are the only structures known that consist entirely of β-keratin (Schweitzer et al. 1999). There have been claims that feather impressions have been carved onto some fossils, even Archaeopteryx (Halstead 1987; Hoyle and Wickramasinghe 1986; Hoyle et al. 1985a; Hoyle et al. 1985b; Hoyle et al. 1985c; Spetner et al. 1988; Trop 1983). Most of the Chinese specimens have feathers preserved as carbonaceous films, which means that they could not have been simply carved. The London Archaeopteryx specimen (the neotype) has been studied under scanning electron microscopy and UV light photography, and the authors demonstrated that the feather imprints were genuine (Charig et al. 1986). Additionally, the Thermopolis Archaeopteryx specimen has been studied under synchrotron rapid scanning X-ray fluorescence, which revealed that portions of the feathers were not impressions but actual body fossil remains with distinct chemical signatures (Bergmann et al. 2010). Xu and Guo (2009) define modern feathers as “complex integumentary appendages formed by hierarchical branches of rachis, barbs, and barbules which are composed of Φ-keratins and grow from a follicle”. However, we cannot automatically assume that the spectrum of feather types present today (and there are many) encompasses all feather types that have ever existed. To distinguish some feather-like fossils in the fossil record from modern feathers, some evolutionists have used the term “protofeather”, but this implies that these structures are ancestral to modern feathers. Xu and Guo (2009) described eight different feather morphotypes that they noted in fossils of non-avian dinosaurs, including “basal” avialans (Fig. 3). Some of these morphologies are bizarre when compared to modern feather types (especially morphotypes 2, 5, and 8, which are B, E, and H in Figure 5), which has led some researchers to suspect that they might be influenced by taphonomic processes (e.g., Benton et al. 2008). For instance, contact with water causes a loss of morphological information resulting in feathers taking on a filamentous morphology (Kundrát 2004). A major taphonomic influence on feather preservation in fossils is compaction. Foth (2012) conducted an actualistic experiment where he flattened a cadaver of a Carduelis spinus (European siskin) in a printing press to simulate the compaction of many non- avian theropods in the Jehol Beds of China. The flattened feathers appear filamentous like in non-avian dinosaur fossils, which means that the original feather morphology is essentially unrecognizable. Additionally, some feather barbs appear to have stuck together because of the discharge of body fluids during compaction, which results in artificial “fused” structures. Taphonomic considerations combined with observations of modern avian plumage lead Foth (2012) to conclude that morphotypes 2, 5, and 8 (Fig. 3B, 3E, and 3H) are probably not real feather types, but taphonomically-altered more normal feather types. A recent discovery has given paleontologists new insight into ancient feather types: a portion of a feathered tail trapped in amber (Xing et al. 2016). Although it was difficult to clearly visualize the morphologies of the caudal vertebrae, Xing et al. (2016) concluded that the tail belonged to a non-avialan coelurosaur because of the vertebral profiles and estimated length. The amber exquisitely preserved some feathers which showed a previously unknown morphology of barbules branching not only within individual barbs, but also from the rachis, which appears to have been flexible. These feathers could not have been used for flight, but may have been used in display or insulation. McLain et al. ◀ Feathered dinosaurs reconsidered ▶ 2018 ICC 473