A new raptorial dinosaur with exceptionally long feathering provides insights into dromaeosaurid flight performance

Abstract

Microraptorines are a group of predatory dromaeosaurid theropod dinosaurs with aerodynamic capacity. These close relatives of birds are essential for testing hypotheses explaining the origin and early evolution of avian flight. Here we describe a new 'four-winged' microraptorine, Changyuraptor yangi, from the Early Cretaceous Jehol Biota of China. With tail feathers that are nearly 30 cm long, roughly 30% the length of the skeleton, the new fossil possesses the longest known feathers for any non-avian dinosaur. Furthermore, it is the largest theropod with long, pennaceous feathers attached to the lower hind limbs (that is, 'hindwings'). The lengthy feathered tail of the new fossil provides insight into the flight performance of microraptorines and how they may have maintained aerial competency at larger body sizes. We demonstrate how the low-aspect-ratio tail of the new fossil would have acted as a pitch control structure reducing descent speed and thus playing a key role in landing.

Wings versus legs in the avianbauplan: Development and evolution of alternative locomotor strategies

“…Some theropods might have engaged their limbs simultaneously to flap‐run up slopes and/or jump and flap up to elevated surfaces (Earls ; Dial ), like extant developing birds. Other theropods—the “four‐winged dinosaurs”—might have used both sets of limbs to generate aerodynamic forces (Xu et al ; Alexander et al ; Han et al ). Either way, cooperative use of wings and legs may have been crucial to the early phases of flight evolution, with hindlimb support (1) compensating for incipient wings that produced only small amounts of aerodynamic force, (2) compensating for small pectoral muscles with limited power output, and/or (3) maintaining balance if the center of mass was posterior to the center of lift (due to longer tails and smaller flight apparatuses; Heers and Dial ).…”

A new microraptorine theropod from the Jehol Biota and growth in early dromaeosaurids

“…There is little data on how extinct theropods may have used their tails and such an analysis is beyond the scope of the current study. Without the caudal fan found in Microraptor , isolated tail feathers could not assist with flight in the ways currently modeled for that taxon or for Changyuraptor (Han et al,), but this does not rule out other functions for the rectrices in Wulong .…”

“…For the purposes of this description we accept a maximum age of 124.1 AE 0.3 Ma for the main fossil bed of the lower Yixian at Sihetun (Chang et al, 2009). The younger Jiufotang Formation was dated at the same site from which D2933 was recovered, the Shangheshou locality, which dates to 120.3 AE 0.7 Ma (He et al, 2004).…”

Rhetoric vs. reality: A commentary on “Bird Origins Anew” by A. Feduccia

“…Far from inaccessible, China is a cosmopolitan hub for biological research across a broad swath of scientific disciplines, and the discovery of China's diverse Mesozoic vertebrate faunas have drawn researchers from around the world to China at a much greater pace than at any time in its history. Consequently, we would suggest that these Chinese fossils actually are among the most intensely studied examples today, with many international teams having traveled to China to examine them first hand, to conduct field work in order to collect additional specimens, and to collaborate with Chinese institutions on the description of those fossils in international peer-reviewed journals (e.g., Zhou et al 2002, Clarke et al 2006, Lamanna et al 2006, Xu et al 2009a, 2014b, Zhang et al 2010, O'Connor et al 2013, Han et al 2014 Hou et al 1995, Lingham-Soliar et al 2007, and a previously unpublished photograph of a Chinese specimen is included in his recent opinion paper (provided to him by Zhonghe Zhou, Director of the Institute of Vertebrate Paleontology and Paleoanthropology; Feduccia 2013, figure 5). Thus, Chinese fossils can hardly be characterized as ''inaccessible'' and the individual fossils that convincingly support the dinosaurian ancestry of birds have received a great deal of international scrutiny over a relatively short period of time (i.e.…”

“…Feduccia (2013) contradicts himself by suggesting that dromaeosaurine dinosaurs that have been systematically placed as dinosaurs based on boney evidence for nearly 80 years, suddenly become birds with the discovery of their feathers. Every time microraptorine dromaeosaurs have been analyzed using all available character data (hundreds of scored characters) phylogenetic analysis yields a placement close to birds, within Paraves, but not as ''birds'' (e.g., Turner et al 2012, Xu et al 2012, Han et al 2014, Brusatte et al 2014. When only unfeathered raptors such as Velociraptor or Troodon were known, Feduccia denied any relevance of those fossils to bird origins (Feduccia 1999), but now that microraptorines are known to share derived characters with this taxon, those characters are ignored and the feathers present in the specimens are interpreted as evidence that they are birds.…”