New specimen of Archaeopteryx provides insights into the evolution of pennaceous feathers

Abstract

Discoveries of bird-like theropod dinosaurs and basal avialans in recent decades have helped to put the iconic 'Urvogel' Archaeopteryx into context and have yielded important new data on the origin and early evolution of feathers. However, the biological context under which pennaceous feathers evolved is still debated. Here we describe a new specimen of Archaeopteryx with extensive feather preservation, not only on the wings and tail, but also on the body and legs. The new specimen shows that the entire body was covered in pennaceous feathers, and that the hindlimbs had long, symmetrical feathers along the tibiotarsus but short feathers on the tarsometatarsus. Furthermore, the wing plumage demonstrates that several recent interpretations are problematic. An analysis of the phylogenetic distribution of pennaceous feathers on the tail, hindlimb and arms of advanced maniraptorans and basal avialans strongly indicates that these structures evolved in a functional context other than flight, most probably in relation to display, as suggested by some previous studies. Pennaceous feathers thus represented an exaptation and were later, in several lineages and following different patterns, recruited for aerodynamic functions. This indicates that the origin of flight in avialans was more complex than previously thought and might have involved several convergent achievements of aerial abilities.

New Specimens ofAnchiornis huxleyi(Theropoda: Paraves) from the Late Jurassic of Northeastern China

“…The quadratojugal process is slender and short, and confluent with the ventral margin of the suborbital process, as in Xiaotingia and Microraptor, but not as well developed as in anatomically derived dromaeosaurids such as Tsaagan (Xu, 2002;Norell et al, 2006;Xu et al, 2011). In contrast to Archaeopteryx (Foth et al, 2014;Rauhut, 2014) and Microraptor (Pei et al, 2014), but as in other theropods, there is a rounded margin between the quadratojugal process and the postorbital process, showing no incision. Unlike many deinonychosaurians (e.g., Norell et al, 2006;Tsuihiji et al, 2014), the quadratojugal process of the jugal of BMNHC PH804 is rodlike and lacks a notch.…”

“…The dentary teeth of Anchiornis have a similar shape and size as the corresponding maxillary teeth, with constrictions between the roots and tooth crowns, as in other maniraptorans. As in Archaeopteryx, but differing from troodontids, interdental plates are present along the medial side of the dentary toothrow in PKUP V1068 (Xu, 2002;Averianov and Sues, 2007;Foth et al, 2014).…”

“…As in Xiaotingia, Archaeopteryx, and Caudipteryx, the anterior surface of the nasal process is straight and confluent with the premaxillary body (Ji et al, 1998;Zhou et al, 2000;Mayr et al, 2005;Xu et a., 2011), which is in contrast to other nonavian paravians and Sapeornis, where the nasal process is curved and forms an angle with the anterior surface of the premaxilla body (e.g., Barsbold and Osmólska, 1999;Xu et al, 1999;Zhou and Zhang, 2003). The internarial bar of PKUP V1068 is dorsoventrally flat, as in troodontids and Archaeopteryx (Makovicky et al, 2003;Norell et al, 2009;Foth et al, 2014). The subnarial process of PKUP V1068 is short and slender in lateral view.…”

“…Later discoveries of closely related paravians further cloud the phylogenetic position of Anchiornis huxleyi as well as other paravians (Xu et al, 2011;Tuner et al, 2012;Agnolín and Novas, 2013;Godefroit et al, 2013aGodefroit et al, , 2013bFoth et al, 2014;Brusatte et al, 2014). Yet, despite its importance and being known from a large number of specimens, the morphology of this taxon has only been described briefly Hu et al, 2009;Li et al, 2010;Zheng et al, 2014).…”

As a toxin dies a prion comes to life: A tentative natural history of the [Het-s] prion

“…31 Yet, the use of the term, in a number of recent high-profile publications on evolution illustrates its lasting potency. [32][33][34][35] We feel that [Het-s] is an interesting example of exaptation in which the process can be understood at the molecular level and pinned down to a single point mutation. In addition, the [Het-s] case is characterized by the coincidence of loss-offunction and neofunctionalization (neofunctionalization here corresponds to acquisition of the incompatibility function which confers a benefit in restricting various forms of parasitism).…”