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

2004 in the small tyrannosauroid Dilong (Xu et al. 2004). Skin impressions from the jaw and tail reveal the animal was covered in feathers lacking a central shaft, much like downy feathers exhibited in modern birds. Such feathers would be useless for flight, but it is possible they were helpful in insulation or display. In 2012, the significantly larger Yutyrannus was found in Lower Cretaceous deposits in Liaoning, China (Xu et al. 2012). The body of Yutyrannus was covered in large, filamentous feathers up to 200 mm long. Feathers are known from the neck, arms, feet, pelvis, and tail, and may have played a role in thermal regulation (Fig. 7). It is worth noting that the larger tyrannosaurids, such as Tyrannosaurus , are known to have been scaly in some places where feathers are present in Yutyrannus , perhaps indicating that feathers were lost as members of the group reached massive body sizes (Bell et al. 2017). At nearly 9 meters long, Yutyrannus is the largest known dinosaur with direct evidence of feathers. Ornithomimosaurs are slender, bipedal theropods known for their long limbs, necks, and toothless beaks, and their superficial similarity to ostriches. When Ornithomimus was named in 1890, it was thought to have been entirely covered in scales until specimens with feathers were first discovered in 1995 (but not recognized as feathers until over a decade later). The feathered specimens include juveniles and adults, which indicates that the animal possessed feathers throughout its life. However, only the adults seem to have possessed pennaceous feathers on the arms, which may suggest that they were display structures (Zelenitsky et al. 2012). Others argue against the arm feathers being pennaceous, citing the similarities of the preserved Ornithomimus feathers to those of cassowaries (Foth et al. 2014). It is worth noting that the juvenile specimen bore feather impressions preserved in sandstone, previously thought to be impossible. This suggests feathers may be found in other fossils with more careful excavation (Zelenitsky et al. 2012). A specimen discovered in 2015 was found to have feathers of a similar structure and distribution as an ostrich (van der Reest et al. 2016). The massive Deinocheirus , long known only as a pair of gigantic front limbs, underwent a revision in 2014 when additional specimens were described, from which a near-complete skeleton could be reconstructed. In addition to revealing some very peculiar and unforeseen anatomical traits, the last two vertebrae are fused to form a pygostyle, indicating Deinocheirus , as well as other ornithomimosaurs, likely had a tail fan (Lee et al. 2014b). Alvarezsaurids were small, specialized theropods with distinctive, highly reduced forelimbs and hands. Some species only had one claw, though two tiny claws are also present in Shuvuuia . Shuvuuia was found surrounded by structures resembling the central shaft of modern bird feathers. As noted before, these structures possess β-keratins, but not α-keratins, just as in modern feathers (Schweitzer et al., 1999). Oviraptorosaurs are best known by their undeserved moniker “egg thieves.” Their beaked skulls were short and superficially similar to that of a parrot. Many species of oviraptorosaur have been found with pygostyles (Fig. 8), the first evidence of such being found in Nomingia in 2000 (Barsbold et al. 2000). Since then, species such as Citipati and Conchoraptor have been found with pygostyles (Persons IV et al. 2013). Direct evidence of feathers has been McLain et al. ◀ Feathered dinosaurs reconsidered ▶ 2018 ICC 476 Figure 7. Integumentary structures surrounding the tail of Yutyrannus huali . Image cropped and brightened from original photo by ★ Kumiko ★ . CC BY-SA 2.0. Figure 8. Left lateral view of the pygostyle of the oviraptorid Nomingia gobiensis. Scale bar 10 cm. Image modified from Barsblod et al. 2000, obtained via Wikimedia Commons. CC BY 2.0.