A Jurassic avialan dinosaur from China resolves the early phylogenetic history of birds

Abstract

The recent discovery of small paravian theropod dinosaurs with well-preserved feathers in the Middle-Late Jurassic Tiaojishan Formation of Liaoning Province (northeastern China) has challenged the pivotal position of Archaeopteryx, regarded from its discovery to be the most basal bird. Removing Archaeopteryx from the base of Avialae to nest within Deinonychosauria implies that typical bird flight, powered by the forelimbs only, either evolved at least twice, or was subsequently lost or modified in some deinonychosaurians. Here we describe the complete skeleton of a new paravian from the Tiaojishan Formation of Liaoning Province, China. Including this new taxon in a comprehensive phylogenetic analysis for basal Paraves does the following: (1) it recovers it as the basal-most avialan; (2) it confirms the avialan status of Archaeopteryx; (3) it places Troodontidae as the sister-group to Avialae; (4) it supports a single origin of powered flight within Paraves; and (5) it implies that the early diversification of Paraves and Avialae took place in the Middle-Late Jurassic period.

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

“…The rostral ramus of the maxilla is relatively short in Anchiornis huxleyi ( fig. 5), less than one-third the length of the antorbital fossa, which is the also the case in other Jianchang paravians, troodontids, and some dromaeosaurids such as Microraptor and Bambiraptor (Burnham et al, 2000;Xu et al, 2011;Godefroit et al, 2013aGodefroit et al, , 2013bPei et al, 2014). In avialans, derived dromaeosaurids, and some more-basal coelurosaurians, the rostral process of the maxilla is much longer, at more than two-thirds the length of the antorbital fenestra (e.g., Chiappe et al, 1999;Mayr et al, 2005Mayr et al, , 2007Turner et al, 2012).…”

“…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).…”

“…In addition to many fossil mammals (Meng et al, 2006;Luo et al, 2007aLuo et al, , 2007bLuo et al, , 2011Zhou et al, 2013), pterosaurs (Ji and Yuan, 2002;Lü et al, 2009), salamandroids (Gao and Shubin, 2012) and insects (Ren et al, 2010), discoveries of feathered dinosaurs in Jianchang County have considerably improved our understanding of the evolution and paleobiology of the Paraves (Xu et al, , 2011Zheng et al, 2009;Longrich et al, 2012;Godefroit et al, 2013aGodefroit et al, , 2013b. Fossil deposits in the Tiaojishan Formation in Jianchang County have been dated to ~160 million years ago (Wang et al, 2013), thus, Late Jurassic (Oxfordian) in age (Cohen et al, 2013).…”

“…These deposits have furnished the most abundant collection of Jurassic paravians in the world. Fossils discovered in these deposits include multiple specimens of Anchiornis huxleyi, Xiaotingia zhengi, Aurornis xui, and Eosinopteryx brevipenna (Xu et al, , 2011Hu et al, 2009;Zheng et al, 2009;Godefroit et al, 2013aGodefroit et al, , 2013b.…”

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

“…is a logically distinct question from the evolutionary relationships of birds (Makovicky and Dyke 2001). Inferences of phylogeny in extinct Dinosauria are based on extensive morphological character data (current theropod datasets include 850þ characters; Choiniere et al 2010, Xu et al 2011, Turner et al 2012, Agnolín and Novas 2013, Godefroit et al 2013, Brusatte et al 2014. Contemporary systematists do not propose relationships based on plausibility of functional scenarios.…”